Principles of Natural Theology / by George Hayward Joyce, S.J.

Chapter III. Proofs of God's Existence (i. Metaphysical proofs).

  1. The Cosmological Argument (God as the First Cause).
  2. The Argument from Contingency (God as Necessary Being).
  3. The Argument from Motion (God as the Prime Mover).
  4. The Henological Argument (God as the One and the Perfect).

We treat in this chapter of the proofs of God's existence derived from efficient causation, from contingent being, from motion, and from the multiplicity and limitation of finite things. Among the many arguments by which our conclusion may be established these have an indisputable right to priority. They are in the strictest sense metaphysical demonstrations. They rest directly on primary principles of reason, so that it is impossible to reject them without at the same time calling in question the validity of human reason itself. Furthermore, in them our appeal is not to the witness afforded by physical law, nor to the nature of man as a moral agent, but simply to the nature of finite being as such. Any finite substance whatever is capable of furnishing the data for the reasoning. Natural Theology, viewed as a science, is, as we saw in chap. i., § 2, a part of metaphysics. It follows that the demonstrations on which it rests. must be metaphysical. The physical and moral proofs to be considered in the two following chapters are subsidiary in character. Those with which we are here concerned form the essential basis of the whole treatise. It must not, however, be imagined that the physical and moral arguments, because subordinate to the metaphysical, are therefore devoid of importance. Natural Theology cannot afford to overlook them. It is manifest that, where the same conclusion can be reached by very different paths, some minds will be more influenced by one argument, others by another. And it is often the case that reasoning which can be variously illustrated from the field of experience is more efficacious to convince the understanding than such as is immediately based on first principles.

I. The cosmological argument. In this first proof we shew that it is necessary to admit the existence of a first cause of all finite things, and that this cause is intelligent and personal. We are here, be it noted, concerned with efficient causation, an efficient cause being that whose action makes the thing what it is. The point is of importance as the term 'first cause' may be employed in another sense. When, e.g., the materialist says that no other first cause of the universe need be postulated save ether,{1} he is in fact asserting that a material cause is sufficient, and that we may dispense with efficient causes altogether. We must, further, by way of preliminary, call attention to another distinction, this time among efficient causes themselves, viz., that between a cause in fieri and a cause in esse. A cause in fieri is the cause of the thing's becoming what it is: a cause in esse is one whose action sustains the thing in being. If a smith forges a horse-shoe, he is only a causein fieri of the shape given to the iron. That shape persists after his action has ceased. So, too, a builder is a cause in fieri of the house which he builds. In both these cases the substances employed act as causes in esse as regards the continued existence of the effect produced. Iron, in virtue of its natural rigidity, retains in being the shape which it has once received: and, similarly, the materials employed in building retain in being the order and arrangement which constitute them into a house. It may, perhaps, be asked whether in these examples we are dealing with efficient causation. Can iron be said to be an efficient cause of the conservation of the shape, as the smith is the efficient cause of its origination? Do the building materials really exercise an efficient causality in regard of the permanence of the structure? Reflection will shew that the question must be answered in the affirmative. Inasmuch as the persistence in being of the accident supposes a continuous exercise of conservation on the part of the substance, it stands to the latter in the relation of effect to cause.{2}

There are, however, certain effects which require the continued action of the same cause which first produced them. In this case we have a cause which is at one and the same time a cause in fieri and in esse. Thus not only does a candle produce light in a room in the first instance, but its continued presence is necessary if the illumination is to continue. If it is removed, the light forthwith ceases. Again, a liquid receives its shape from the vessel in which it is contained; but were the pressure of the containing sides withdrawn, it would not retain its form for an instant. Similarly, a certain measure of heat was needed that the icecap, which once covered northern Europe, should melt, and the soil become capable of supporting vegetation. But the same cause must remain in operation if the effect is to continue. If ever the temperature of these regions should sink to its former level, Europe would again become icebound. In all these cases we have causes in fieri et in esse .

It must not be imagined that we wish to maintain that the cause in fieri is altogether unconnected with the being of the thing which it produces. Becoming is the passage from potential to actual being. The cause which affects the transition -- the process of change from the potential to the actual -- is indirectly the cause of being also. But its direct effect is limited to the process: and the cause of the thing's continuance in being must be sought elsewhere.

In the present proof we are concerned only with causes in esse: the question of becoming -- of the origination of things -- does not come under consideration.

The preliminaries of our argument are, however, not yet complete. Besides the vital distinction which we have just noticed, two philosophical principles bearing on causation claim our attention.

It must be observed, first, that an effect properly so called demands the actual operation of the cause of which it is the effect, and ceases with the cessation of that action. The horse-shoe, it is true, continues to be, long after the smith has ceased to act; but this is simply because it is not the effect of his action as regards being, but only as regards beeoming. Had he stopped work during the process of becoming, that process would have ceased likewise. Precisely the same is true as regards the cause in esse. Were the substance iron to lose those natural qualities of rigidity, etc., which conserve the shape once given to it, that shape would disappear. This truth was expressed in the saying, Cessante causa cessat effectus{3}

The other point which calls for notice is this: that whatever demands a cause in fieri demands also a cause in esse. It is absolutely impossible that a thing, which requires a cause to bring it into being, should remain in existence independently of a cause in esse retaining it in being. At first sight this truth may present some difficulty. We are accustomed to regard substances as enjoying an absolutely independent existence in their own right and apart from any conserving force, so soon as the process of becoming is complete. When the bird develops from the egg, or the oaktree from the acorn, or when a human being, complete as a member of the species, though as yet far from full maturity, is produced by generation, we readily recognize that the transition from potentiality to actuality demanded a causein fieri; but the idea that the completed entity needs to be sustained by a cause of its being strikes us as strange. Yet it may easily be shewn that so it is. For to what is the existence which the thing possesses due? This existence requires, we admit, a cause to bring it into being, and can only be explained by reference to this efficient cause. But viewed as a fully constituted and enduring substance, it does not depend upon the cause in fieri. That cause, as has been pointed out, only effects the process of becoming. Moreover, it is no longer operative: and what is no longer operative cannot be now exercising causality. But, most assuredly, the persisting existence calls for explanation no less than does the original passage into existence. The nature is not the sufficient reason of its own reality in the full sense of the term. That which even for a single instant is the sufficient reason of its own existence is self-existent. But a nature which is capable of self-existence needs not to wait for the action of an efficient cause in order to exist; it must have existed from all eternity. Probably most people imagine that, once constituted, the substance can somehow conserve itself unless brought into contact with hostile agencies which are too powerful for it. Yet to say that a thing conserves itself is to say that its persistence through each successive moment is to be attributed to its own existing nature. But the existing nature is the precise thing which we are seeking to explain. We are thus driven by sheer logical necessity to admit that the finite substances of this world, inasmuch as they require a cause in fieri, depend for their present actual existence upon a cause in esse, even though that cause is not an object of sensible experience.

We pointed out just now, in regard to the shape of the horse-shoe, that were the iron to lose the qualities which are the cause in esse of that shape, it would cease to be. Its permanence in being, as well as its origination, demand a cause: and the permanent existence being a present effect must be due to the operation of a present cause. What is true of the accident is no less true of the substance. The blacksmith and the horse, as well as the shape of the horse-shoe, need a cause in esse. The greater difficulty which we experience in grasping this truth where substances are concerned is due to the fact that sense does not assist us to realize the dependence of substances, as it does the dependence of accidents. But the verdict of reason is conclusive.

Nor can the materialist invalidate this argument by contending that the elementary constituents of which, e.g., the man or the horse are formed, when once they have received the requisite collocation, will retain it much as the building materials secure the permanence of the house when once built.{4} Such an objection supposes that man is not an independent being at all: that he is merely an accidental arrangement of atoms: that he possesses no more true unity than does a house. This is in open contradiction with the facts. Man acts as a single whole. Whether there is question of thought or feeling or of external activity, it is the man as such, not the individual particle, who is the true agent. That which acts as a unit is a unit. Man, in other words, is a single substance -- a reality of a higher order than the material constituents which go to form his body. A fortiori the efficient cause which sustains him in being is of a higher order than they.

It appears, then, that all those things which experience makes known to us, substances and accidents alike, are dependent on an efficient cause without whose action they could not continue in being. Just as the building of a house would be at a standstill, if the builder ceased to work, so the builder himself would cease to exist if the cause in esse on which he depends were not to exert its causality. What that cause is does not here concern us. It is enough to note that we are speaking of an efficient cause, not a material or a formal cause, and with a cause which is actually hic et nunc operative in regard of its effect. We are now in a position to consider the argument by which the existence of God as the First Cause is established : --

We see all around us things, both substances and accidents, coming into being through the action of efficient causes. Reason assures us that what commences to exist through the operation of a cause is similarly dependent on a cause for the continuance of its existence: that it can never be the sufficient reason for its own being. The cause which is actually operative in regard of the effect in which we are interested, may itself depend for its existence on a higher cause, and this on another, and so on. Thus, in the example which we have already employed, the form of the horseshoe is the immediate effect of quantitative extension combined with certain qualitative properties such as rigidity, etc.: quantity and the properties in question are the effect of the substantial nature of iron: and, finally, the substance itself supposes an efficient cause. But it is impossible that a series of causes, of which each is dependent for its being on the cause above it, should be infinite. It follows that we must admit the existence of a first cause, itself uncaused and self-existent. This first cause can be none other than God: for (as will be shewn) a self-existent being is, of necessity, infinitely perfect, immaterial and intelligent.

It will be observed that the key-stone of the argument is to be found in the assertion that an infinite series of efficient causes in esse, each essentially dependent on the actual operation of the cause above it, is impossible. The truth of this is evident. If no member of the series possesses being otherwise than in virtue of the actual present operation of a higher cause, it follows that in default of a first cause there can be no secondary causes in existence.{5}

It is manifest that the reasoning which we have employed is quite independent of the vexed question whether an infinite series of causes in fieri operating successively is possible. We do not base our proof on the alleged impossibility of an infinite number. Our argument is not that the world must have been created, inasmuch as, had it existed from all eternity, we should be forced to admit an infinite succession of causes and effects. In the last two or three centuries, it is true, the proof has not infrequently been presented in that form: and we shall return to the point very shortly. Here it is sufficient to note that such is not the true scope of the traditional argument for the necessity of a first cause. Even though it should be true that reason cannot demonstrate that an infinite number of successive causes in fieri is repugnant, our proof that there must be a first cause actually operative in giving existence to all things which depend on efficient causation retains its full force.

An illustration may serve to make this point clearer. The movement of a clock's hands is caused immediately by wheels, of which there may be more or fewer, but which are ultimately dependent, as regards their action, on the spring. If there be no spring to start the motion not a wheel will move. Unless there be a cause which Originates the movement, none will ever take place.

Nothing is gained by supposing the wheels multiplied to infinity. An infinity of subordinate agents is as incapable of initiating action as is one alone. But the same reasoning will not prove that the number of times which the clock has been wound up is necessarily limited. It is a matter of indifference to the actual working of the clock whether this number be finite or infinite. The movement of the hands has no essential dependence on past windings. We may imagine, if we will, that these form an infinite series, and have gone on through infinite time. Whatever supposition we make regarding them, the causes on which the movement of the hands, as a present fact, essentially depends, must be finite in number, and the first of them -- that to which the others are subordinate -- must be an originating principle of activity.{6}

St. Thomas Aquinas supplies us with a similar example.{7} When a carpenter is at work, the series of efficient causes on which his work depends is necessarily limited. The final effect, e.g., the fastening of a nail is caused by a hammer: the hammer is moved by his arm: and the motion of his arm is determined by the motor-impulses communicated from the nerve-centres of the brain. Unless the subordinate causes were limited in number, and were connected with a starting-point of motion, the hammer must remain inert: and the nail will never be driven in. If the series be supposed infinite, no work will ever take place. But if there is question of causes on which the work is not essentially dependent, we cannot draw the same conclusion. We may suppose the carpenter to have broken an infinite number of hammers, and as often to have replaced the broken tool by a fresh one. There is nothing in such a supposition which excludes the driving home of the nail.{8}

It should be noticed that from the fact that substances require a cause in esse we cannot forthwith draw the conclusion that their existence is immediately due to God's causal action. The argument throws no light on the question whether He is an immediate or a remote cause. So far as it is concerned the immediate cause of material substances might be a subordinate agency. Indeed, at one time it was held by a certain school of philosophers that each natural species postulated such a cause, the causa totius speciei -- a theory now almost forgotten. We merely argue that whether the series of causes be long or short, it must ultimately rest on the action of a First Cause.

It is sometimes urged that the proof which we have given fails to shew us that the cause is intelligent and personal: and that, this being so, it does not establish the existence of God at all.{9} To this it may be replied that, in the nature of the case, the consideration of the properties of the First Cause must follow after the proof that such a Cause exists: the two points cannot be taken together. Only when the existence of a self-existent being has been demonstrated, can we proceed to the discussion of His attributes. To shew that He is a Person possessed of intelligence and free-will is logically complementary to the demonstration which we have given. This complement, it is true, is sometimes taken for granted: since it is felt that the main issue has been decided, when the existence of a First Efficient Cause has been made good. Still, it is reasonable enough that some treatment of the point should be required here. There are two ways in which the conclusion may be reached. We may argue a priori from the essential attributes of a self-existent being: or we may adopt the a posteriori method, and reason from the perfections found in the effects to those which must belong to the cause. In this chapter we shall employ the latter proof. The former will be made good later, when we shall shew in a series of detailed arguments that to the self-existent being belong all those attributes which reason assigns to a Personal God. Here we shall merely indicate the general line of this demonstration.

It will appear that the self-existent nature must, as self-existent, be infinite, possessing or, rather, itself being the plenitude of all perfection. Both intelligence and volition must, therefore, be of the number of its attributes. Moreover, there cannot be such a thing as a nature apart from the individual subject (or subjects) to which it is referred: the ultimate subject alike of predication and action is the individual. It follows that in God there must be personality in the strict sense of the term. For by the term 'person' is signified nothing else than an individual endowed with intelligence and will.

Such in bare outline is the first of the two proofs which we have mentioned. Its various parts will receive full treatment in the course of the work. But in view of our statement that any finite thing would serve as a basis of our whole argument, it seemed desirable to indicate at least in general how, when once the existence of the First Cause is proved, it may be shewn on a priori grounds that that cause is none other than a personal God.

The a posteriori proof is of a less abstract character and presents little difficulty. It may be briefly stated as follows: An effect cannot contain any perfection which is not found in its cause: and among the effects produced by the First Cause are immaterial beings possessed of intelligence and free-will; it follows that the First Cause must Himself be an immaterial being, intelligent and free. The statement that every perfection belonging to the effect must be found in the cause is an immediate deduction from the principle of contradiction. A cause is that which makes its effect to be what it is -- which gives to it that actuality or perfection in respect of which it is termed its cause. If it does not itself possess that actuality, it cannot confer it on another. None can communicate what it has not got. To hold the contrary is to assert that nonentity can produce being: and this is equivalently to deny the principle of contradiction.

It is perfectly true that everyday experience seems to bring us across many cases in which a cause certainly does not contain the perfection which it appears to confer. An engine-driver turns a handle and thereby gives motion to the locomotive; but he has no motion himself save that which the locomotive may be giving him. And countless other examples occur to the mind. How then is it possible, it may be asked, to lay down the principle as a general truth? We will endeavour to deal shortly but sufficiently with the difficulty. In the first place it is necessary to distinguish the causa per se from the causa per accidens. A cause per se is a cause which contains in itself the explanation of the effect. Thus a seal is the cause per se of the impression which it leaves on the wax: a father is the cause per se of the human nature in his son. Such alone are causes properly so called: and our principle has reference alone to these. A causeper accidens is an agent whose action allows the true causes to exercise their causal efficacy. The engine driver is a cause per accidens in regard to the motion of the train. His action allows the steam to produce its due effect on the machine which he directs. It is clear that the cause per accidens is only termed a cause by analogy, and that it is very far from being a cause in the full and adequate sense of the word. It does not really make the thing to be what it is. Further, it is by no means necessary that the perfection which the cause per se communicates to its effect should exist in it alter the same manner in which it exists in the effect. The carpenter is the cause per se of the table which he makes: the sculptor the cause of the statue. In a true sense they possess the perfections which they confer. The sculptor could not transform the rude block of marble into a statue, unless the form to be communicated to it existed in his mind: and the same is true of the more modest achievement of the carpenter. In these cases the perfection conferred belongs to the physical order, whereas in the efficient cause it exists in the order of thought. But this latter mode of existence, it must be noted, is not the less perfect, but the more perfect of the two. It is spiritual, not material.

We have already referred to the fact that some writers give the argument for a First Cause in a very different form. The series of causes which they consider does not consist of such as are essentially dependent, one on another, for the actual exercise of causality, but of such as succeed each other in time. The universe in which we live, they say, is one in which all things owe their origin to a cause. The son takes his being from his father, the oak-tree from the acorn, etc., etc. However far back we go, the same must hold good. Now a series which stretches back to eternity is, they urge, an impossibility. The world certainly began, and, therefore, must have had a first cause to give it being. And this first cause must have been a Creator.

It is in this form that the argument is commonly criticized by its assailants. Yet the demonstration as given by the great Scholastic philosophers has nothing whatever to do with these successive causes in fieri, but is wholly concerned with causes on which the effect is actually hic et nunc dependent. Indeed, St. Thomas Aquinas in more than one of his works is insistent in affirming that we cannot prove by reason that the world has not existed from eternity. We can shew that it was created, he contends, by many lines of proof; but we cannot prove that God could not, had He so wished, have created it from all eternity. That He did not do so is known to us by revelation. It cannot be established by philosophical demonstration.{10}

It would carry us beyond our limits to enter at any length into the question of the abstract possibility of creation ab aeterno. But it may be said that, philosophically, there does not appear to be greater impossibility involved in the notion of an infinite series in the past, than in that of an infinite series in the future. All those who believe in the immortality of the soul admit the latter notion: holding, as they must, that the series of our intellectual acts will endure for all eternity. In both cases the series is innumerable. It lies outside the category of number; for number is multitude measurable in units (multitudo mensurata per unum). Such a series is a multitude, but a multitude to which no measure is applicable. Our difficulty in grasping the notion lies partly in our failure to distinguish the two ideas of multitude and number. It is objected that the future series, when computed from the present, never reaches infinity. Whatever point it may have reached in future time, the series is finite. But to this it may be replied that, similarly, whatever point we take in past time, the series between now and then is finite. Just as we cannot actually reach infinity in the future, so, no matter how far back we go in thought, we cannot indicate a point at which the series between that moment and the present is not a finite series. The two cases are absolutely parallel. If we admit that there will be an infinite series in one direction, it seems necessary to allow the abstract possibility of such a series in the other. The same difficulty is sometimes urged in another form. If the world had no beginning, it is said, it is hard to see how we could ever have reached the present point. We should be supposing that a journey ex hypothesi infinite had nevertheless arrived at its term. But to this it is replied that in judging of the possibility of traversing any distance, we must count from point to point. If the distance between the terminus a quo and the terminus ad quem is infinite, then, manifestly, starting from the former we shall never reach the latter. But if there is no terminus a quo no reason can be assigned why in an infinite progress we should not pass any given terminus ad quem. As soon as we fix on a terminus a quo in our series, no matter how remote, the distance between then and now is a limited distance, and can in consequence be traversed.{11} Notice must also be taken of an argument not infrequently found in recent Scholastic works, that an infinite series in the past is impossible, because it is a contradiction in terms to suppose that the infinite can be increased. That which can be increased is not infinite. Yet the series of causes in fieri is constantly receiving increments. This reasoning we believe to be quite unsound. It is, of course, impossible that the infinite can be increased, if by the infinite is signified the fulness of all being,the sum of all reality. But we are here using the term in a wholly different sense, viz., to signify a series of units which had no beginning. To say that such a series is incapable of increase is the merest assumption. The syllogism, in fact, has four terms, and would seem to be a pure sophism.{12}

Before bringing our treatment of the argument for a First Cause to a close, it will be well to consider a criticism of it from the empiricist standpoint. J. S. Mill has devoted a chapter in his Three Essays on Religion to the subject,{13} and there contends that it is valueless as a proof of God's existence. He maintains that the evidence at our disposal does not enable us to conclude to any other ultimate causes than matter and force.

"There is," he says, "in Nature a permanent element and a changeable: the changes are always the effect of previous changes: the permanent existences, so far as we know, are not effects at all. . . . That which in an object begins to exist is that in it which belongs to the changeable element in Nature: the outward form and the properties depending on mechanical or chemical combinations of its component parts. There is in every object another and a permanent element, viz., the specific elementary substance or substances of which it consists, and their inherent properties. These are not known to us as beginning to exist: within the range of human knowledge they had no beginning, consequently no cause." As regards the changes which take place in nature, these, he holds, are adequately accounted for by force. While in regard to the reasoning by which the existence of the human soul is made the basis of argument for an intelligent and personal Cause, he says: "The notion seems to be that no causes can give rise to products of a more precious and elevated kind than themselves. But this is at variance with the analogies of Nature. How vastly nobler and more precious, for instance, are the higher vegetables and animals than the soil and manure out of which and by the properties of which they are raised up." In view of what has already been said in this section, little need be added to shew that these criticisms are devoid of philosophical value, and fail to touch the argument. We have already adverted to the absurdity of regarding the specific types of nature as mere combinations of chemical elements without unity of their own. An animal is more than the simple aggregate of its material constituents. There is in it a principle of unity, the source of its characteristic attributes, constituting it as a single substance, a special type of perfection. It is for the philosopher to provide some explanation of these substantial perfections which are the true units of the natural order. They must, as we have maintained, be referred to the operation of an efficient cause. Otherwise their existence is inexplicable. It is assuredly no explanation whatever to say, as does Mill, that they are adequately accounted for by their material constituents as affected by 'force' -- a notion which he does not attempt to explain, but which is apparently understood as a principle of local motion operating blindly, and directed to no particular end. Moreover, it is to be observed that Mill does not dispense with the notion of a self-existent first cause. He merely asserts that matter will serve the purpose, whereas, as we have contended above, it may be demonstrated a priori that self-existent being is, as such, infinite in perfection, immaterial and intelligent. Mill does not deal with this difficulty at all. Had he been aware of it, he could hardly have assumed without proof the possibility of self-existent matter. He does, however, touch upon the a posteriori argument from the existence of the human soul, saying that he regards it as invalid, since experience seems to shew that effects can be more perfect than their causes. We have already pointed out that this is tantamount to saying that being can spring out of nonentity: and that in the numerous cases in which the effect appears at first sight to surpass the cause, this is only because the cause which we are contemplating is either a partial cause or a mere causa per accidens. It is utterly impossible that an effect can ever surpass its total cause. Thus, to employ Mill's own illustration, the soil and manure are not the total cause of the plants and animals into which their constituent elements may eventually enter. The perfection of the total effect is attributable in a far higher degree to the efficient than to the material cause.

It is further to be observed that, as Mill was considering the argument in the form in which it regards, not causes in esse, but successive causes in fieri, it was imperative that he should face the question whether an infinite series of changes succeeding each other in time, such as is involved in his supposition of self-existent matter and force, is or is not a contradiction in terms. Yet not a single word is said on this essential point. He had not even taken the trouble to make himself acquainted with the argument which he undertook to refute.

2. The argument Irom contingency. The argument from contingency is closely related to that from efficient causation. It is indeed more accurately described as the same proof viewed under a new aspect and treated in a different manner than as an independent demonstration. Yet among Scholastic writers the custom has grown up of presenting the two forms of the argument separately. And as the conceptions employed are not the same, this course has much to recommend it. By a contingent being is signified one which need not exist. It may be, but it also may not be: existence is in no sense one of its essential predicates. It stands in direct opposition to necessary being -- being, that is, which is incapable of not existing. Actual existence belongs to the nature of necessary being, just as to be three-sided belongs to the nature of a triangle. It is one of its essential attributes. Such a being must be either self-existent, or (if the supposition be admitted for a moment) some self-existent being must be determined by nature to its production. With this brief explanation of terms we may state the proof as follows: --

Experience shews us that contingent beings exist. We see things come into existence and pass out of it. Animals and plants have their period of life and then die. Inanimate substances enter into composition, forming a new substance with properties different from those of its constituents: and after a time the compound is again resolved into its original elements. Now the existence of contingent beings involves the existence of necessary being, and is inexplicable without it. Therefore a necessary being exists: and this necessary being can be none other than a personal God.

Such in briefest outline is the argument. The value of the conclusion depends, it is evident, on the statement that the existence of contingent being involves that of necessary being. If this can be established the proof holds good. There is no occasion for us to shew that necessary being can only be realized in a personal God: for here the same reasoning may be employed which we used to complete the cosmological argument.

Since contingent being may either exist or not exist, it is evident that it does not account for its own existence. It is not the sufficient reason for that existence. Were it so, it would be impossible for it not to exist: in other words, it would not be contingent. Consequently we must seek an explanation for it elsewhere: some sufficient reason for it there must needs be. If a thing be not self-existent, its existence must be due to a cause external to itself. The conclusion is the same, even if we suppose a contingent being to have existed from all eternity. Once admit that a thing is capable of non-existence, and it follows of necessity that it owes its existence to something else: and this in the last resort must be necessary being.{14}

It may, perhaps, be objected that even a materialist or a pantheist would go as far with us as this, and would be prepared to own the existence of necessary being: that the real question at issue is what that necessary being is. The materialist will urge that, though the individual substances are contingent, yet the whole vast series of such substances, taken in its entirety, should be regarded as necessary: or he will contend that the material substratum, which is common to all, is the necessary being whose existence has been established. The pantheist will maintain that the necessary being is in fact the Absolute, of which contingent beings are but manifestations: and that this is very different from a personal God. We shall deal with each of these points.

It may be easily shewn that no series of contingent beings, even were it infinite as regards time or spatial extension, could ever constitute a necessary being. If each individual member of a collective whole is such that it cannot account for its own existence, the same must be said of the whole collection, no matter how immense it may be. Inasmuch as it does not contain within itself any sufficient reason for its existence, it cannot be self-existent. To put the matter in a somewhat more technical form: contingency is an attribute belonging to the essential nature of the object of which it is affirmed: and such attributes are predicable, not merely of individuals, but of the whole body. Since individual men are rational in virtue of their essential nature, it follows that rationality is rightly predicated of a collective body of men. It has been aptly said that we might as well say that, although one idiot is not reasonable, a million idiots would suffice to form a reasonable being, as to maintain that an infinite number of contingent substances would constitute necessary being. Or to employ another illustration: those who contend that while the existence of each substance in a collection is contingent, the collection as a whole may be necessary, are asking us to believe that although each link in a suspended chain is prevented from falling simply because it is attached to the one above it, yet if only the chain be long enough, it will, taken as a whole, need no support, but will hang loose in the air suspended from nothing. It is, of course, true that there are some attributes which, though they are predicated of the several parts, cannot be affirmed of the whole. But these are those which relate to the thing in its quantitative aspect. We cannot conclude, because A, B and C, taken separately, each weigh an ounce, that therefore the three together will weigh the same amount. It is needless to say that contingency has no connection with quantity.

Can it be maintained that matter, understanding that term in the sense of the material substratum common to natural substances, is necessary being? We have seen that Mill entertained this idea. And we imagine that many materialists take the same view. Yet such a supposition involves us in numerous impossibilities. Matter, it is plain, is capable of receiving perfections which are not among its essential attributes. It becomes man: or gold: or a flower: and in each of these substances is endowed with distinctive properties. They are not essential to it; for what is essential to a nature is inseparable from it: the nature is never found without it. Whence then do they come? We answer that since they are not essential, there is no avoiding the conclusion that they are due to the operation of an external cause. We are here brought across a metaphysical principle of primary importance, viz., that whenever two things essentially distinct the one from the other are found in union, this must be due to the operation of an efficient cause other than the things themselves.{15} A little reflection will shew that this is a necessary and self-evident truth. To affirm the opposite would be to assert that something could take place without a sufficient reason. If A and B, things essentially distinct, are found united, the reason cannot be found in A. For A is the sufficient reason only for itself and its own essential attributes. For the same reason it cannot be found in B. No cause, for instance, is needed to explain why a triangle should have three angles. The attribute of having three angles results immediately from its essence as a plane figure bounded by three straight lines. If it had not three angles, it would both be and not be a triangle. But if there is question of a wooden triangle, we have a right to say that a cause is requisite to explain this union. Wood is not triangular per se: nor is a triangle per se wooden. The composition of diverse elements of necessity supposes the operation of an efficient cause other than the elements themselves. Now no agent can exist capable of conferring perfections upon necessary being. For that agent, since it is other than necessary being, must be a contingent being. But whatever contingent beings possess they owe in the last resort to necessary being. They have nothing which is not already found in it: they can add nothing to it. It follows that matter, the common substratum, which is a mere recipient for perfections, is not necessary being.

It may perhaps be urged that the reasoning just employed is open to a serious objection: since, granted the existence of a plurality of necessary beings, there does not appear to be the same difficulty in the hypothesis that one such being may receive perfections from another. This objection will receive its full answer, when in a later chapter we establish the essential uniqueness of necessary being, shewing that in the very nature of things it can be but one. Here it must be sufficient to point out that no metaphysician of real weight regards the supposition of a plurality of necessary beings as other than a paradox. All have recognized that the self-existent can be one only.

Equally invalid is the pantheist contention that contingent beings are merely modes of the one and all-inclusive Absolute: that they are manifestations of necessary being, and not entities possessed of a distinct though dependent existence. Here we may make appeal to the argument which we have just employed in regard of material substances. The contingent beings of experience are constantly undergoing changes and acquiring new perfections. This alone establishes that they are not modes of necessary being. A sheer contradiction is involved in the supposition that an agent exists, which can confer perfections on necessary being. Yet the acquisition of a perfection apart from an agent is, as we have seen, a metaphysical impossibility. We may, too, reach the same conclusion by another path. We have stated in the argument to the First Cause that it might be proved that the self-existent being -- and this concept includes necessary being as well as the First Cause -- is infinite in perfection. From this, as we shall also shew, it follows that He is immutable. But that which is immutable cannot be identical with the transitory contingent beings of experience.

3. The argument from motion.{16} As the cosmological argument is founded on finite substances statically regarded, so the argument from motion is based on them in their dynamical aspect. Of the five metaphysical proofs which St. Thomas gives, he assigns to this the first place, as being the simplest and easiest to grasp. Latterly it has suffered an eclipse owing to a belief that it depends upon a principle which physical science has shewn to be untenable. As a matter of fact, the prejudice against it is due, as we shall see, not to any of the results which physical science has achieved in recent times, but to an erroneous philosophy of motion, introduced by Descartes, which has widely affected current modes of thought. A careful consideration of the proof will shew its apodictic character. It is securely based on those fundamental first principles, which no physical discoveries can invalidate.

The term 'motion,' as here used, is not, it should be noted, restricted in its significance to local motion. This is but one of several distinct kinds of motion. By motion (kinêsis) is signified the process by which a potency is realized. It may be defined as the energetic and therefore incomplete actualization of a potency belonging to some form of being. The end towards which the process tends may be a new quality: or an increased quantity: or, again, a specific nature as is the case in the development of a seed or an embryo. Among the various kinds of motion which experience makes known to us local movement holds an important place. By reason of its universality it forces itself more than any other upon our attention: for physical change of every kind involves local movement at least in the constituent parts of the thing changed. Viewed, however, precisely in its aspect as change, it is similar to those other kinds of motion which we have just mentioned. It is a process by which a natural potency is realized. To be in a given place is the actualization of a natural potency of a material body -- an actualization requisite for its complete determination. It is, it is true, an extrinsic, not an intrinsic determination; but one which is none the less essentially requisite if the substance is to take place as an integral unit in nature. Certain special difficulties connected with this form of change we reserve for treatment in a separate note.

Before proceeding to our proof we must state with some degree of philosophical accuracy what motion is.

Motion is not a form of being. It is something very different, namely, the transition from one form of being to another. This is well illustrated in the case of a chemical compound. When, e.g., hydrogen and oxygen are brought together, and combine as water, the process of change begins and ends with definite forms of being. But in none of the intermediate stages have we a natural entity capable of subsistence. Sometimes it is true the process of actualization may be arrested, as in the case of a fertilized cell. But the result is not a natural entity -- a complete unit in the order of nature: it is a frustrated beginning of such a unit -- not a being properly so called, but a might-have-been. Aristotle's insight was too sure for him to reckon motion as a mode of being. It is not found among the nine categories into which he distributed the accidental perfections of substance. For it is becoming, not being -- fieri not esse.

Motion possesses certain special characteristics which should be most carefully observed. First, it is always on the road to realization. So long as the process endures the potency is still passing into act: it is not completely actualized. Strange as it may appear, motion, as such, never attains full actualization: for when it has reached its term, it has, as motion, already ceased to be.{17} Secondly, it is divisible in infinitum. Each part, however minute, being just as truly motion as is the whole. Yet these parts are all different one from another: and, what is more, they are not interchangeable. They occur in a definite order, all the previous portions being neeessary in any given process of change that the one next in order may take place.{18}

These facts regarding motion bring us to a conclusion of the highest importance. It is this. All motion demands the continuous operation of a causein fieri producing it: without such an influx of causality motion is impossible. At every stage of a movement, and at every fraction of every stage, there is the emergence of something new. There is the continuous passage from being potentially in movement to being actually in movement: and, as we have just noted, each part of a movement differs from every other part, the previous portions being a necessary condition to the production of the later ones. This continuous production of new reality postulates a sufficient reason: and this can only be the actual and constant operation of an efficient cause. In other words motion is not a stable entity which can be produced once and for all, and then only needs to be conserved in being by a cause in esse. It demands a cause in fieri -- a cause continuously productive of a new effect. This truth was expressed by the Schoolmen in the saying, Quidquid movetur ab alio movetur, 'Whatever is in motion is being moved by something other than itself.' The immediate agent of motion need not indeed be external to the substance in which the motion takes place; but it must at least be external to the part which is the immediate subject of change. If a thing is destitute of a particular form of being, it cannot be itself the source from which it receives the actualizing process by which that form of being is attained. Nemo dat quod non habet.{19}

The principle we have enunciated (Quidquid movetur ab alio movetur) does not of course deny the essential difference between those recipients of motion which possess active powers of their own and those which are devoid of any such endowment. It is plain that the 'motion' of a growing tree is very different from that which the hand communicates to the pen which it is guiding. In the former case the subject of motion receives from the superior agent the ultimate complement of active powers really internal to it, in default of which these powers would remain inert. In the latter case the subject acts instrumentally, i.e., its motion is not determined by its own powers but by an efficient cause.

We are now in a position to propose our argument:

The existence of motion in the world is undeniable. It meets us on every side. Now it is a certain and evident truth that whatever is in motion is being actually moved by an agent other than itself. The effect now coming into being demands the actual and present efficiency of a cause.

If this efficiency requires motion in the agent itself, the principle which we have invoked compels us to admit that this change in its turn must be due to the actual efficiency of another agent, and so on. But however many of these antecedent agents we suppose, we must of necessity come to a first of the series -- an agent which has the power to produce motion without any change taking place in itself -- a primus motor immobilis.

Were there no prime mover, but only a series of secondary agents, there could be no motion. For a secondary agent cannot of itself pass from potency to act. Its activity from moment to moment is due to the influx of a higher cause. If then the higher causes are themselves one and all secondary, and there be no prime mover, the sufficient reason for its own action, no motion will ever arise. To use an illustration already employed, to maintain that a series of secondary agents can produce motion without the influx of a prime mover is comparable to saying that no spring is needed to account for the movement of a clock's hands: that a series of wheels, if only it be long enough, affords an adequate explanation.

Yet here there is a difficulty to be met. It is maintained by some that the notion of an immutable mover, a cause which produces its effects without undergoing any change in so doing is self-contradictory: that causation necessarily involves a transition in the agent. The production of an effect, it is urged, is an activity: and an activity implies a change -- the actualization of potency. The objection was, in fact, raised by Kant. He reckons it as one of the antinomies of the human reason that, on the one hand, it leads us to refer finite existences to an Infinite Cause, and, on the other, compels us to admit that every change supposes a previous change in endless regress so as to exclude the supposition of ever arriving at an Infinite First Cause.{20} Now it is, of course, true that the causes of which we have experience, can only produce an effect in virtue of a change realized in themselves. But so far is this from being involved in the essential notion of causality, that it is due to the fact that finite agents are not causes in the full sense of the word. They have the potency of becoming causes, but that potency is incompletely actualized. An internal complement is needed before they are fully constituted in the actuality which will render them the sufficient reason of a given effect. But where the Infinite Being is concerned this is not so. Inasmuch as He is infinite, there can be no question of His reception of any complement to His actuality. He possesses in Himself the full actuality requisite for causal efficiency from all eternity. Moreover, as He is not a necessary agent but endowed with freedom, His effects proceed from Him at such time as He has from eternity determined. The full discussion of this point must wait for a later chapter (chap. xiv., § 3) since it presupposes the treatment of the Divine infinitude, of the Divine free-will, and of creation. But what we have here said will suffice to shew that the notion of the Unmoved Mover, the changeless cause -- a concept which the sheer necessity of reason compels us to accept -- involves no contradiction, but is verified in the Infinite Being, God.

Note on local motion. (a) The Cartesian philosophy of motion. We have contended in the previous paragraphs that local motion, viewed philosophically, is, like other forms of change, a transition by which the object moved acquires the actualization of a natural potency. A body, in order to be an integral part of nature, must be in some place. But it has always the potency of being in another place than this: in other words, it may be moved to a new place. When this is done, it acquires a new actuality: and in so doing loses the determination which it now possesses, inasmuch as the same potency cannot be simultaneously actualized in different ways. Thus just as the change by which the fertilized cell becomes the fully developed animal is a process of fieri resulting in a new substantial esse, so too local motion is no less truly a fieri resulting in a new accidental esse.

That this, the Aristotelian account of local motion, is not the point of view commonly adopted in modern physics will be patent to all. That view is derived from Descartes -- a man whose genius was most conspicuous in his achievements as a mathematician, and who treats the subject exclusively from the mathematical point of view. Descartes denied the existence of any but local motion, believing that all change might be sufficiently explained by it.{21} For a mathematician other kinds of motion have in fact little interest. He teaches that when God created the universe, He established in it a dertain amount of movement: that this movement is still conserved in it by Him, passing from body to body, but remaining identically the same.{22} Moreover he maintains that from the immutability of God we can conclude that if motion is once communicated to a body, it will remain in it unless some external force intervenes to stay it.{23} Hence, though he styles motion a mode of corporeal substance, it is clear that in his system they are distinct realities, motion being something new added to the fully constituted substance. As a metaphysical theory these views are quite untenable. (1) Motion is not a new reality added to a fully actualized entity. It is, in all its forms, in this no less than in the others, a passage to complete actualization. The mere fact of change shews that complete determination is not yet obtained. (2) Further, he considers motion, not as does the metaphysician, in regard to being, but in regard to rest, this being the point of view most suitable for the mathematician. For his purpose the terminus a quo and the terminus ad quem are both regarded under this aspect. The state of rest, however, of the terminus a quo is manifestly inferior to the process of change: since a mere potency is inferior to that potency as already on the road to actualization. Hence it is not surprising that he should treat motion as something additional to the constituted substance. The metaphysician, on the other hand, necessarily treats motion in its relation to being, since metaphysics is the science of being. And for this very reason it is impossible for him to restrict his consideration of it to a single kind of motion. His theory must be valid for all species, for the motion by which an acorn becomes an oak, no less than for the passage of a stone through the air. And, viewed in relation to being, motion is essentially the transition from potency to act, the terminus ad quem being the perfected act. (3) Again, the mathematician may for practical purposes regard motion as a state. Philosophically the concepts of movement and of a state are mutually exclusive. A state is a condition of stable being, while motion is a condition involving continuous transition. (4) Once more, the idea of motion as a thing which passes from body to body is a philosophical absurdity. One moving body can start movement in another; but movement is not an entity which can travel from subject to subject. Hence although the Cartesian views may be perfectly compatible with the calculations of physicists, if introduced into metaphysics, they are prolific of the gravest errors. We have judged it necessary to touch upon them here, since they still enter largely into philosophical thought. Yet they are wholly incompatible with the metaphysical principles which we are maintaming: and unless the mind is disabused of them, it is impossible for it to appreciate the cogency of the present proof.{24}

(b) The principle 'Quidquid movetur, etc.,' and Newton's first law. The difficulties bequeathed to us by the Cartesian philosophy are not the only ones in our path. The assertion that motion depends on the continuous operation of an efficient cause other than the actual subject of motion, seems at first sight to conflict with Newton's first law. This assures us that a body in a state of motion persists in that state unless it is subjected to the action of some external force. Is not this equivalent to saying that no agency is needed for the continuance of a motion once originated -- that a body once started will go on of itself? Moreover there are certain facts of experience which appear to lend colour to this view. When a billiard-ball is travelling over the table, or a stone has been flung through the air, where is there any external agency at work? Is not the force initially communicated the adequate explanation of the subsequent movement? Do we not render a full account both of the motion of the ball and its eventual rest, by saying that in virtue of the blow given by the cue it would go on indefinitely, were it not gradually stopped by the friction of the table and the resistance of the atmosphere.

Reflection will, however, shew us that, though appearances seem unfavourable to our contention, there is no escape from the conclusion that the motion of the ball involves the continued application of an external force: that apart from the operation of such an agency we are involved in a series of impossibilities. For if the efficient cause of the motion is not external, two hypotheses are possible. The sufficient cause of the effect is either to be found in the moving body itself, or in its past motion. We shall examine both alternatives: and it will appear that both must be rejected.

We take, first, the explanation which would attribute the effect to the past motion of the body. We are dealing, it must be remembered, with actual motion. For this actual effect we require an actually operative cause. The past motion of the body has ceased to exist. What is no longer existing cannot be actually operative. The past motion was needed that the body might reach the spot where it now is; but in this its office ,was exhausted. It has now ceased to be, and is totally incapable of producing the new effect which is at each successive instant coming into being.

If the other alternative be adopted, the result is no more satisfactory. Here, when it is said that the ball accounts for its own movement, it cannot be meant that the reason why it moves is that it is in motion. This is simply to say that it moves because it does move -- an assertion which will not carry us far. The statement, however, may be taken in another sense. It has been held by a certain number of recent Scholastic writers that when movement is initiated, the cause which puts the body in motion communicates to it a new quality, which, so long as it endures is productive of local movement. This quality they term impetus or impulsus: and the degree in which it is communicated is, it is held, in proportion to the efficiency of the originating cause. When theimpetus is exhausted the motion ceases. This theory is defended among others by Fr. T. Pesch, S.J., and Fr. Garrigou-Lagrange, O.P. Difficulties of a grave character, however, may be urged against it: (1) Unless we are prepared to deny all validity to the first law of motion, we must admit that if a body is once set in motion, this movement would never cease, were it not for the action of impeding forces: as regards duration it would be infinite. Yet a corporeal quality which is a principle of movement without end appears to involve a sheer contradiction. An accident is necessarily proportioned to the substance which it qualifies and in which it inheres. But according to this hypothesis, a finite substance is the subject of a quality, which in one respect, at least, is infinite. (2) Further, even if this be supposed possible, another difficulty presents itself. The inherent impetus must constantly produce new effects: for, as we have pointed out, the parts of any given motion differ one from another, occurring, as they do, in a definite order, the previous stages being prerequisites to the production of each subsequent one. But it is manifest that the same quality cannot be continuously modifying its efficiency unless it is undergoing change itself. We have, in fact, merely shifted the difficulty from the motion to the alleged quality which produces it. We must provide an explanation for the change in the quality. (3) Again: theimpetus, if it exist, is actually operative, and in consequence not indeterminate but fully determined. Yet we are required to regard this fully determined quality as being a principle of motion which is indifferently of any velocity and of any direction. According to the laws of motion a body in constrained motion will leave its path and fly off at a tangent at whatever point of its course the constraint is removed. Now there is no need that the constraint should be due to a single force acting from one centre. Successive forces may have been brought to bear upon the body from widely different quarters. But, if we accept the theory in question, it is reserved for the last of all to determine the velocity and the direction of the effects of every one. Such a result seems wholly irreconcilable with reason.

We are driven then to the conclusion that all motion requires the continuous action of an external force to explain its persistence: and that without such agency the motion must cease. Reason compels us to admit that Aristotle and his Scholastic disciples were not deceived when they laid down the principle that whatever is in motion is being moved by something other than itself -- Quidquid movetur ab alio movetur. Nor does this involve any contradiction with Newton's first law of motion. Newton, indeed, says that a body in motion will continue to move uniformly in a straight line, unless acted upon by external forces. But we need not understand him to deny that the uniform movement itself is due to an agency acting ab extra; but merely that it is produced by an agency belonging to that category of agents which he denominates "external forces." We shall point out in a moment how entirely the agency, for which we are contending, differs from these forces whose action in each case is of necessity confined to a particular direction and velocity.

There is, however, a point which calls for previous consideration. The doctrine that every change in the direction or velocity of motion is due to an external force takes it for granted that whenever a plurality of forces is brought to bear upon a moving body, their effects will coalesce into a single motion. This, of course, is the case, as experience abundantly shews. But the fact is one involving important deductions. For it is philosophically certain that where many agents combine in the accomplishment of a work which has a true unity of its own, the work must be attributed to a single principal agent who has employed the more immediate agents instrumentally -- unless, indeed, the unity be a mere matter of chance. The agents would not be at one in the production of the result, were they not subordinate to a single directive cause.{25} Thus when the united labours of bricklayers, carpenters, and masons, etc., etc., result in a house -- an effect which, though not unum natura, is unum ordine -- we know from the unity of the work produced that their operative action was directed by a cause of a higher order. They are instruments, not prime agents. The prime agent, the principle of unity -- in this case the architect -- elevates the work of the immediate contributors to a higher plane, enabling them to produce something, which, without his action, was altogether beyond their powers. Now, when the effects of various moving forces combine in a single local motion, the unity is no matter of chance. Otherwise it would not occur in every such case. It is characteristic of casual results that they only happen in a very small minority of instances. The conclusion is inevitable that the agent which brings about the combination of the different effects, employs the contributory forces instrumentally. In other words, the phenomena of local motion reveal the existence of two orders of movers, Newton's external forces being the lower of the two.

The objective reality expressed by Newton's first law is, in fact, this equivalent conservation of every change, whether in the direction or the velocity of a movement, throughout all its subsequent parts. The law, as it stands, is, of course, incapable of experimental verification. No material body can be absolutely withdrawn from the action of all other forces except that which originated the movement. We can remove certain disturbing factors; but so long as our experiments are performed in this concrete world, it is idle to imagine that we can realize the conditions supposed in the terms of the law. Hence some writers have declared Newton's law to be an hypothesis suggested by the facts. It seems to us to be more accurately described as a logical abstraction based on a wide induction. For an induction of immense range assures us of the equivalent conservation of all the changes to which a movement may be subjected. And this, as we have said, is the objective fact to which the law gives expression. It follows that the first law as manifested in external phenomena provides the most cogent evidence for the truth of our thesis. We must either admit the existence of a higher mover or declare that the oneness of a work affords no proof that it is due to one agent: in other words, that multiplicity can be the source of unity.

We are now in a position to draw some conclusions as to the nature of this mover: though these will be of an extremely general character. It is manifestly a force which is not confined to any particularity of direction or velocity, but is of an altogether superior order to the mechanical forces which are the immediate agents of motion. These are instrumental in its regard. And as such, it must he carefully noted, they are not to be reckoned as mere occasional causes exerting no real efficacy of their own on the effect. The resulting motion is really produced by them: for in every case of instrumental causality the total effect is in the truest sense the work of the instrument as well as of the principal cause. The painting on the canvas proceeds in its totality alike from the directing mind of the artist and from the brush with its pigments. Although the finished work is primarily due to the intelligent principal cause, it is none the less produced in every detail by the instrument which he employs. Both causes are indispensable: for each has its own proper efficacy. The agency of both is requisite for the total result. The activity proper to the mechanical agents of motion is to determine the velocity and direction of the movement: and the total effect consists entirely of their contributions. But their efficiency is confined to the period of time and extent of space in which they are actually operative.

Just as they themselves could never have passed from potency to act save through the agency of a higher mover, so the same agency is required for the actualization of the motion which they produced. As the writer, to whom I have acknowledged my obligations at the commencement of this proof, has well said: "The agency required is of a higher and more universal order than that to which mechanical forces belong. It transcends the possibility of measurement in terms of time and space. It is continuously at work in moving bodies, reducing or tending to reduce the manifold to unity, the variable to uniformity, and that which is liable to fail to indefectibility: in one word, reducing potentiality to act, and so establishing and crowning the results achieved by the agency of material things" (Month, CVIII. 434).

And here we may notice another point confirmatory, at least, of what has been said. Motion in a straight line and of uniform velocity is not the only kind of uniform motion. This is uniform motion in one dimension. Motion which is of two or of three dimensions may also be uniform. Thus we have uniform motion of two dimensions when the movement of a body round a point is such that equal areas are swept by the radius vector in equal times. No one questions that uniform motion of two dimensions demands an external agency for its realization. It seems difficult to explain why, if a regulating cause is requisite in the one case, it is not equally necessary in the other. Again: we are familiar with the phenomenon of uniform acceleration with regard to time. The motion of a falling body increases in arithmetical progression. Here, too, we postulate an external cause, without which the acceleration is declared to be inexplicable. But it may be questioned whether uniformity of velocity is really a whit more intelligible apart from the efficiency of an agent actually present than is uniformity of acceleration.{26}

When it has once been shewn that local motion is incomprehensible apart from actual efficiency exerted by an external cause, the chief difficulty in the way of our proof is removed. Common facts of everyday experience, such as the continued flight of a stone after it has left the hand, seemed incompatible with the principle Quidquid movetur at alio movetur, however weighty the metaphysical reasons which were urged on its behalf. We have seen that this is not so: and the full force of the reasoning must be admitted. Does the agent whose existence we have established require to be moved from potency to act? If so, we must suppose a higher cause to effect this. But the series of such agents must, as we saw, be limited. We are driven back upon a first agent, whose activity is uncaused -- the primus motor immobilis.

4. The henological argument. The henological argument is so called because in it we reason from multiplicity to unity (hen, unum): from goodness, truth, reality in the various forms in which experience makes them known to us, to a Being who is the Good, the True, the Real. Its scope is to shew that the limited and partial manifestations of these perfections compel us to admit the existence of a Being in whom they find their complete realization: that multiplicity and imperfection are wholly inexplicable apart from unity and perfection: and finally that the One and Perfect is, in fact, a Personal God.

For the understanding of the argument it is essential first to call attention to certain special characteristics of the perfections with which we are here concerned, viz., reality, goodness, truth, unity. Other attributes than these denote some particular generic or specific perfection within one of the ten categories: they express either the substantial nature of the subject, or some quantity, quality or relation, etc., etc., belonging to it. But the perfections of which we are speaking are applied in all the categories equally: nor is the application confined to any special part, be it genus or differentia of the nature. There is no nature and no part of any nature of which they may not be predicated. The animality and the rationality of Socrates are alike real: so too are his qualities, his quantity, etc., etc. In the same way goodness may be predicated of all these. Manhood is a good thing: so is strength: so too the size due to a human body: so also the relation of paternity. Again, one and all these things are capable of becoming the object of intellectual knowledge. They are therefore true. This peculiarity has, in the Scholastic philosophy, given to these attributes the name of transcendentals, inasmuch as they transcend the limits which restrict all other perfections to one or other of the great divisions of being. This terminology, which we shall employ throughout this work, should be carefully noted. For Kant gave to the word transcendental a new sense, entirely unconnected with its traditional signification: and since his time his use of the word has been adopted by all philosophical writers except those who adhere to the Scholastic system.

The transcendental character of these attributes carries with it two very important consequences. The first of these is that they do not connote any limitation or imperfection. An attribute, which of its essential nature is restricted to a particular mode of being, be it substance, or quality, or quantity, inevitably involves imperfection, because in virtue of this restriction it is essentially finite.{27} But when an attribute does not imply any one of the divisions of being, but transcends the limits which they impose, there is no reason why such a perfection should not be found in the Infinite Being Himself -- why it should not be predicable of God as well as of man. The second consequence is closely connected with the first. It is that these terms are analogous and not univocal. A generic or specific attribute is always univocal. It has the same signification in all the subjects of which it is predicated: the notion which it expresses is always identically the same. Thus the term 'animal ' denotes precisely the same characteristics, whether it is affirmed of a man or of an insect. So far as this term is applied to them, the differences of the two classes, however fundamental, do not come under consideration. Similarly 'spatial extension' has always the same meaning, the notion of extension as such prescinding from the question whether the extension be of one or two or three dimensions. It is otherwise as regards analogous terms. The notions which these signify are not identically, but proportionally (kat' analogian)the same. The goodness of a man is not identical with the goodness of a horse, nor can the two kinds of goodness be expressed by a concept which remains the same as applied to each of them. Yet there is a proportionate resemblance in the two cases. A good man and a good horse are each understood to have that which constitutes the perfection of their respective natures. In the one case the requisite qualities are moral: in the other physical. H ere we see how it is that the transcendental perfections can be affirmed of God. When from the goodness of the creature we conclude to the goodness of the Creator, we do not imply that the goodness is in all respects the same in the two cases. There is always analogy when we pass from the finite to the Infinite. Being or reality, goodness, truth, unity, are found in God, not in the same manner, but after an infinitely higher manner than they are found in the creature.

It seemed necessary to say at least thus much on this point at once. The further discussion of our analogical knowledge of God must be reserved for the chapter in which we treat at length of that subject (chap. viii.). There too we shall explain how it comes about that we are able by analogy to affirm of God certain other attributes (causality, will, intelligence, life) which are not themselves reckoned among the transcendentals. We may now pass to the consideration of the argument itself. It may be stated as follows : -- When one and the same perfection is found in different beings, it is impossible that they should possess it independently; all must have received it from one and the same source. And if the perfection in question is one, the idea of which connotes no imperfection, the source from which it is received is none other than the perfection itself, subsisting as an independent being. Now the things of our experience possess in common the perfections of being or reality, of goodness, of truth, and of unity: and these are perfections which involve no idea of imperfection. Hence we must admit the existence of the Real, the Good, the True, the One. Moreover, it may be shewn that these are not distinct the one from the other, but are one supreme and infinite Being.

It is manifest that each of the two assertions which form the major premiss of this argument call for proof: neither is immediately evident. On what grounds, first, is it declared that when the same attribute is found in a plurality of individuals, it is impossible that it can belong to each of them in its own right and in virtue of its being the particular thing which it is (per se et secundum quod ipsum): that even if there be but two such entities, either the one must have received the perfection from the other, or both must owe it to a cause belonging to a higher order: that the explanation of the manifold must necessarily be sought in the One?

We reply that this follows as a certain conclusion from a metaphysical principle which we have already had occasion to employ, viz., that wherever we have a union of diverse elements, that union postulates the action of a cause.{28} When we previously appealed to this principle, we were dealing with the case of the combination of different elements in a concrete thing. Here we are concerned with another kind of union -- that of separate individuals in a single class. It is undeniable that this is a true union of the diverse. The individuals, e.g., who form the class of men, are in virtue of their individuality utterly distinct. Yet their common nature makes them specifically (not numerically) one: and a series of propositions can be framed regarding the abstract subject Man, which are verified of every individual in the Class. We cannot explain this unity apart from a common cause. We cannot say that each member of the class is a man in virtue of his being himself, and because he is the individual which he is. Things are not united by the very thing through which they differ: the principle of diversity is not, and cannot be, the principle of unity. Individuality is the principle of diversity. It follows that the perfection held in common must have been received from another. And as diversity will never account for unity we are driven back at last to a single cause to which that common perfection must be referred. {29}

It might seem that we are drawing dangerously near the Platonic theory of ideas. Plato, as we know, held that wherever material objects exhibit similar properties and thus form a class, we must needs refer the common effect to a single cause, the source and origin of the properties in question: and that we are thus compelled to admit that there exists a world of immaterial essences, the archetypes and causes of all sensible objects, but belonging to a higher and supersensible plane of being. The theory involves many impossibilities. It is sufficient here to note that, as Aristotle points out, there can be no such thing as an immaterial essence of a material nature. Matter is part and parcel of the essence of such things. An immaterial essence of a horse or of a tree, subsisting as an individual thing, is a sheer contradiction in terms. Such natures can exist apart from matter as concepts of the mind: but not in rerum natura. Yet the Platonic theory supposes that the archetypes, which are the causes of the things of sense, are subsistent entities. Our argument, on the other hand, does not involve us in this absurdity. It does, it is true, conclude that when the same specific nature is found in many individuals, we must needs refer this similarity to a single cause. But we do not look for these causes in immaterial essences specifically the same as the material things themselves. We look for them, as will appear later, in a series of archetypal ideas in the Divine mind.

Transcendental perfections, however, stand on a different footing. Matter is no necessary part of their essence. 'Being' or 'goodness,' considered in their essential nature, involve no limit, no imperfection. The concept of goodness as such expresses goodness in an infinite degree. If we desire to conceive a finite and restricted goodness we must ourselves introduce the note of limit. It is true that, as we have experience only of finite things, our knowledge of goodness is necessarily of a goodness which is limited. But this does not affect the significance of the term. For the transcendentals are analogous: and hence the terms expressing them signify the perfection, but do not connote the particular mode in which it is found in this or that subject.

From this we draw a weighty conclusion. The perfections of being, goodness and truth, as they are known to us in experience, must, as we have seen, be referred to a single cause of a higher order. Now, when we were considering material essences, we recognized that this immaterial higher cause could not be something of the same specific nature, since such a nature can only be found upon the plane of material existence. The higher cause which confers a material perfection must be of an altogether different kind. It must, indeed, somehow contain the perfection which it confers, or it could not give it. But, to employ Scholastic terms, it contains it eminently and not formally.{30} As regards transcendental perfections the case is otherwise. Goodness and reality are not perfections proper to a lower plane of being. Here there is no question of a cause which only contains the perfection which it gives, eminently. Goodness and reality will be found formally in the cause producing them. The cause of goodness will itself be good: the cause of reality will be real; though the mode in which these perfections belong to it will not be identical with, but analogous to, the same perfections as found in its effects.

We may go yet further. In the ultimate resort the cause must be the perfection itself as a subsistent entity. The cause of goodness will not be something which possesses goodness, but is not identical with goodness. It must be none other than subsistent Goodness. Were it otherwise, we should again be face to face with a thing composed of diverse elements, and be compelled to seek for the cause of the union. We should have to refer the goodness possessed by this thing to some higher cause which had conferred it: and thus we should at last be driven back to a cause identical with goodness. And the same reasons hold good of the other transcendentals.

But goodness itself -- absolute goodness -- is not goodness restricted to some particular mode. It is goodness in its fullness: in other words, infinite goodness. For we are ex hypothesi dealing with a goodness which has no cause higher than itself. But, as we have seen, wherever we find a limited perfection, that perfection involves the presence of two principles distinct from each other, the principle of perfection and the principle of limit. The entity is therefore composite, and is the result of causal efficiency. It follows of necessity that the goodness with which we are dealing knows no limits.

It only remains to point out that the Good, the Real, the True, the One, are but one supreme Being, whom we term God. Pure goodness, as we have seen, is absolutely simple and is uncaused. It is at the same time real. Hence it is not merely uncaused goodness, but uncaused being. It does not possess being; but it is being. It is therefore infinite being as well as infinite goodness. So, too, in regard to truth. The True is an absolutely simple and uncaused perfection. Moreover, like the Good, it is real: otherwise it would be nonentity. It, therefore, also is identical with uncaused and infinite being. And a precisely similar argument gives us the same conclusion regarding the other analogous perfections which we mentioned, Unity, Intelligence, Will. They are identical one with another, coalescing into one simple Being. But this Infinite Being, Who is at the same time Infinite Intelligence, Infinite Will and Infinite Goodness, is manifestly what we signify by the name God.{31}

{1} "We regard ether as the fundamental cause or agency in nature, and are not compelled to look for anything beyond it. As far as the arguments for a first cause goes, the first cause may be material " (The Existence of God, by J. McCabe, p.41).

{2} Between a substance and its accidents there is reciprocal causation in different orders of causality. While the substance is the efficient cause of the accident, the latter exercises formal causality in regard of the former, giving it an accidental determination which it would not otherwise possess. Reciprocal causation in the same order of causality would, of course, be a contradiction in terms. Aristotle takes note of reciprocal causality in Metaph. V., c. ii., 1013b9. See also St. Thomas in Metaph. V., lect. 2. 'Dicit quod etiam contingit.'

{3} "Omnis effectus dependet a sua causa, secundum quod est causa ejus. Sed considerandum est quod aliquod agens est causa sui effectus secundum fieri tantum, et non directe secundum esse ejus: quod quidem convenit et in artificialibus et in rebus naturali us. Aedificator enim est causa domus quantum ad ejus fieri, non autem directe quantum ad esse ejus. Manifestum est enim quod esse domus consequitur formam ejus: forma autem domus est compositio et ordo: quae quidem forma consequitur naturalem virtutem quarundam rerum. Aedificator facit domum adhibendo caementum, lapides et ligna, quae sunt susceptiva et conservativa talis compositionis et ordinis. Unde esse domus dependet ex naturis harum rerum, sicut fieri domus dependet ex actione aedificatoris. . . . Sicut igitur fieri rei non potest remanere cessante actione argentis quod est causa effectus secundum fieri: ita nec esse rei potest remanere, cessante actione agentis quod est causa effectus non solum secundum fieri, sed etiam secundum esse" (St. Thomas Aq., Summa Theol., I., q. 104, art. 1).

{4} It is hardly needful to point out that the building-materials need a causein esse just as does a man. But these materials, in virtue of their respective qualities, are able to act as a permanent cause of the organized arrangement in which the house, as such, consists.

{5} Dr. J. Caird urges the following strange objection to the cosmological argument: You cannot in a syllogistic demonstration put more into the conclusion than the premisses contain. Beginning with an infinite or absolute cause you might conclude to finite effects, but you cannot reverse the process " (Phil. ol Religion, p. 128). He seems to regard the finite causes of experience as actually constituting the premiss of the syllogism. As a matter of fact, the two premisses are self-evident propositions. The existence of a finite cause is simply that which enables us to apply our a priori reasoning to the world of fact, and conclude to the existence of a First Cause. This becomes perfectly clear when the argument is thrown into strict logical form, as follows: "Every causally produced substance demands a cause in esse: and this cause (if itself causally produced) demands a similar cause, and so on: But a series of causes, each of which is dependent for its existence on the one which precedes it in the series, is impossible apart from a self-existent first cause: Therefore every causally produced substance demands a self-existent First Cause: But there are such things as causally produced substances: Therefore a First Cause exists." The same sophistical objection occurs in Illingworth, Personality, Human and Divine, p. 92.

{6} The illustration is from Garrigou-Lagrange, Dieu, son existence et sa nature, § 10 (Paris, 1914).

{7} Summa Theol., I., q. 46, art. 2, ad 7.

{8} Aristotle establishes the necessity of admitting a first cause in connection with his statement that the science of metaphysics deals with primary principles. And it is noteworthy that he illustrates the impossibility of an infinite series by an example in which each cause is essentially dependent for its operation on the one immediate preceding. oute gar hôs ex hulês tode ek toude dunaton ienai eis apeiron . . . oute hothen hê archê tês kinêseôs, oion ton men anthrôpon hupo tou aeros kinêthênai, touton d' hupo tou hêliou, ton de hêlion hupo tou neikous, kai toutou mêden einai peras. (Metaph. II. c. ii.) St. Thomas comments as follows: "Secundo exemplificat in genere causae efficientis ; dicens quod nec possibile est ut causa quae dicitur unde principium motus in infinitum procedat: puta cum dicimus hominem moveri ad deponendum vestes ab aere calefacto, aerem vero calefieri a sole, solem vero moveri ab aliquo aijo, et hoc in infinitum."

{9} Cf. e.g., Martineau, SeaL of Authority in Religion, p. 312. "The theist deceives himself by secreting in his premisses more than he supposes them to contain, the additional element being no other than the conclusion itself: for whether he works from the principle of causality, or from the signs of a perfection higher than the realized world, he hides within them the assumption of living will, of supreme excellence, of eternal authority, which come out at last in concentrated form under the name God."

So, too, Mr. McTaggart, Some Dogmas of Religion, § 156, who adds strangely enough, "Thus the argument could not reach the desired conclusion without calling in the aid of the argument from design." Why it should be necessary to appeal to the argument from design does not appear.

{10} SummaTheol. I., q. 46, art. 2; Con. Gent., II., c. xxxviii; II. S., d.1, q. 1, art. 5; Opusc. 23 De aeternitate mundi.

{11} It is one thing to say that God might, had He willed, have created ab aeterno. It is another to say that the phenomena of experience must form an infinite series. The former statement is, as we have seen, defensible. For the latter no valid reason can be assigned. Yet where the authority of Kant holds sway, it is confidently asserted. Thus Professor Pringle-Pattison writes: "As Kant no less than Spinoza clearly saw, God cannot be reached at the farther end of any chain of phenomenal antecedents and consequents. To imagine that He could be reached in that way is to treat God and the divine action as a particular fact, one more phenomenon added to the series. But to talk of a first cause in that sense is a contradiction in terms: once embarked on the modal sequence, we are launched on an infinite regress" (Idea of God, p. 302).

{12} Cf. P. M. Périer, A propos du nombre infini, in the Revue pratique d'apologétique, Aug. 1919, p. 526.

{13} Three Essays on Religion, pp. 142-154.

{14} "I cannot see why it should be said, of three substances existing in time, that God did not need a Creator, but that a man and a pebble did" (McTaggart, Some Dogmas, etc., § 158). The question of time is here quite immaterial. The man and the pebble need a Creator because they are not the sufficient reason for their own existence; in default of certain definite conditions they cease to exist.

{15} Quae secundum se sunt diversa non conveniunt in aliquod unum nisi per aliquam causam adunantem ipsa." St. Thomas Aq., Summa Theol., I., q. 3, art. 7; Con. Gent., I., C. xviii., n. 4.

{16} In my treatment of this proof I am under great obligations to a short article by the late Fr. T. Rigby, S.J., "Aristotle and the First Law of Motion," which appeared in the Month (Oct. 1906), and to two letters addressed by the same writer to the Tablet (Nov. 10 and Dec. 1, 1906).

{17} Hence Aristotle defines motion as "the act of that which is potential inasmuch as it is potential " (hê tou dunamei ontos entelecheia hê toiouton). In other words, motion does not actuate the subject in respect of its potency to be at the term of its movement, seeing that this remains throughout to the end of movement unactuated; but in regard of the potency signified when we say that the thing is movable, i.e., capable of being subjected to motion.

{18} Motion, of course, like time, is continuous; it does not consist of discrete parts. It seems worth while to call attention to this in view of Mr. Bradley's attempt to shew that motion is self-contradictory, and therefore can only be appearance not reality (Appearance and Reality, c. v.). His chief argument is found in the contention that the unity of any motion demands that the time in which it takes place should be one. But, "no duration is single: the would-be unit falls asunder into endless plurality." The fallacy is patent. A given duration being continuous, does not 'fall asunder.' It is one.

{19} In regard to the principle Quidquid movetur ab alio movetur, Aristotle's teaching in Physics, III., c. iii., is in the highest degree illuminating. He there points out that when the mover energizes as such -- when it is actually exercising its efficient powers -- its action is simply the motion effected in the moving body. The process of change (kinêsis) taking place in the subject of motion may in fact be viewed under two aspects. On the one hand, it is the action of the mover received by the patient. On the other, it is the actuation of the potentiality of the movable subject. In relation to the mover it is actio: in relation to the movable body it is passio. He says: "We have now solved the difficulty, and shewn that motion is in the thing moved. For it is the act of this latter effected by the agency of the mover. And the act of the mover is not something other than it. For it must of necessity be the act of both. For the mover (kinêtikon) is so termed by reason of an active power which it possesses: and it is said to be 'moving' (kinoun), because it exercises that power. But it exercises it in the thing moved. So that the act of both is one and the same. Just as the difference between one and two is the same as that between two and one, and uphill and downhill are the same reality.

{20} Mr. McTaggart states the objection with great confidence: 'An event happens, and makes the state of the universe different from what it had been before. The cause is said to be God's timeless nature. That nature is the same, however, both before and after the event. . . . Then there is nothing in that nature which accounts for the change; and it cannot be the cause. If while the so-called cause remains the same, the effect varies, it is clear that the variation of the effect -- that is, the event is uncaused. . . . The position we are discussing maintains that God is changeless and a cause. . . . This means that a cause may be what our reason says it cannot be" (Some Dogmas of Religion, § 159).

{21} Principia, II. 24.

{22} Ibid. n. 42.

{23} Ibid. n. 37.

{24} There is another point on which the modern conception of motion differs from the Aristotelian, to which it may be well to call attention. In modern mechanics motion is viewed purely as relative to a closed system, understanding by that term a system of bodies and forces so ordered that it may be considered as an integral whole, prescinding from all forces external to it. In regard to any particular body which appears to be in motion it remains an open question, whether its movement is real or only apparent. All that matters is its change of position relative to the other members of the system. Viewed absolutely it may be undergoing no transference in space. It may, therefore, be objected that we are reasoning at cross purposes, since the Aristotelian assumes that a given motion is a veritable transition from point to point in space, whereas the modern scientist neither can nor does affirm anything of the kind. The difficulty, however, does not really affect the value of our argument, since relative motion necessarily involves absolute motion. If a body A, which is moving relatively to the other members of the system to which it belongs, is, absolutely speaking, stationary in space, it follows that the rest of the system is moving with real motion. There cannot be relative movement without absolute movement somewhere. The Aristotelian is indifferent on which side the real movement is found. He sees that there is motion in the universe. This is sufficient for his purpose. From this he will demonstrate the existence of the motor immobilis. Moreover, there are many cases of local motion in which we can discard the whole question of absolute position in space, such, for example, as the motion which takes place when a man moves his limbs in walking. And, further, as we have pointed out already, the argument is based not on the phenomenon of local movement as such, but on the fact of motus in its widest sense, including change in all its different species.

Latterly, however, the doctrine of relative motion has been made the basis of a more fundamental objection. Einstein contends that the very conception of absolute motion is a chimera: that the terms motion and rest are significative simply of certain relations between bodies as observed. According to him, the motion which we believe ourselves to perceive in a body, is no positive determination inherent in that object, but consists solely in the relations between it and ourselves as observers, and is dependent on the subjective conditions of observation. We note once more that this theory treats of local motion alone in abstraction from all other kinds of motus, and that it does so entirely from the abstract standpoint of the mathematician to the exclusion of all other aspects of reality. The metaphysician, on the other hand, views the motion of a billiard-ball, not simply in its spatial relations, but as a new fieri resulting from the action of an efficient cause -- as a new actuation of a subject previously in potentia, and, further, as manifesting the characteristics common to change as such. When thus considered the plausibility of Einstein's theory disappears.

{25} Ex multis enim non fit coordinatio nisi per aliquem ordinantem: nisi fortasse multa casualiter in idem concurrant (St. Tbomas Aq. Dc Pol., q. 3, art. 6).

{26} [For my opponent] the quantity of movement would appear to be indistinguishable from the momentum of the body in motion, it follows from this that uniformity in the quantum of motion can have no other meaning for him tban uniform velocity. A truer conception, as I think, would identify quantity of motion with momentum of movement -- a thing altogether independent of the mass in motion. It is a conccption, which opens our eyes at once to the absurdity of measuring motion round a point by units of motion towards a point, the latter being of one dimension only, while the former is manifestly of two. It reveals the true conditions of uniformity in each of the three orders of motion. In the measure of motions towards a fixed point the only variable is the distance covered by the moving body in a unit of time, i.e., the measure of its velocity. Therefore uniform motion, in this order, means uniform velocity. But the measure of a turning movement should be a unit of revolution, in which two variable factors are involved; and all that is required for the maintenance of uniformity in this second kind of motion is that these factors should vary inversely. Such is the case when the law of equal areas swept by the radius vector in equal times is seen to hold. Thus movement in a circle, or in an ellipse, or in a parabola, can be just as uniform as motion in a straight line. If the one needs no external agency to keep it uniform, neither should the other.

But is uniform motion towards a fixed point a proof of actual external agency? Most decidedly, yes; for there is nothing, either in the moving body, or in its past movement, to account for any further realization of uniformity as time goes on. Assuredly agency is as much needed to keep movement straight as to confine it to any other orderly course. The moving body cannot choose its own course. Its past movements are no longer in existence, and therefore cannot be the agency we require. In fact, all that can be affirmed of movement is that it has been, or that it will be never that it is. How, then, can it be either an agent or its agency? It seems to me that, on this point, modern science has something to learn from the Aristotelian physics. Aristotle knew better than to put motion in his list of Categories of Being (Fr. T. Rigby, S.J., in the Tablet, Nov. 10, 1906, Vol. CVIII., p. 739).

{27} It may here be noted that the term 'substance' has not precisely the same signification when applied to God and when applied to creatures. In both it significs a nature possessed of existence on its own account (per se). But the sense in which this is said of God is not identical with that in which it is affirmed of creatures. God exists on His own account as being Self-existent: created substances as being natures which are capable of receiving existence as independent realities, and not as mere accidental determinations. The two ideas are radically different. Hence God is not included in the Aristotelian category of substance. The beings which fall within the category form a class, the generic term being affirmed of all alike in precisely the same sense. The Infinite cannot belong to the same class as finite creatures: and when we term Him a Substance, we do not attribute to Him a limited and restricted mode of being. See St. Thomas Aq., I. Sent., d. 8, q. 4, art. 2.

{28} Supra.

{29} Cf. St. Thomas Aq., Summa Theol., I., q. 65, art. I. "Si diversa in aliquo uniuntur, necesse est hujus unionis causam esse aliquam: non enim diversa secundum se uniuntur. Et ideo est quod, quandocunque in diversis invenitur aliquod unum, oportet quod illud unum ab aliqua una causa recipiant. . . . Hoc autem quod est esse communiter invenitur in omnibus rebus quantuncumque diversis. Necesse est ergo esse unum essendi principium a quo esse habeant."

De Pot., q. 3, art. 5: "Oportet si aliquid unum in pluribus invenitur quod ab aliqua una causa in illis causetur: non enim potest esse quod illud commune utrique ex seipso conveniat, cum utrumque secundum quod ipsum est ab altero distinguatur: et diversitas causarum diversos effectus producit. Cum ergo esse inveniatur omnibus rebus commune, quae, secundum illud quod sunt, ad invicem distinctae sunt, oportet quod de necessitate eis non ex seipsis sed ab aliqua una causa esse attribuatur."

{30} A thing is said to contain a perfection formally, when the perfection in question is found in it with the same essential characteristics, which are expressed in its definition. It contains it eminently when the perfection exists in it in an altogether higher manner, in such wise that the same definition is not verified in the two cases.

{31} St. Thomas in the Summa states the henological argument in a somewhat different form. We find, he says, that in the world of experience some things possess more, some less of goodness, truth, unity and being. But we cannot speak of more or less of any perfection unless that perfection is, somewhere or other, realized in its fullness: and as thus completely realized it must be the cause of all its inferior exemplifications. It follows that being exists in absolute perfection, and as the cause of all finite things. The assertion here made that being is found in a diversity of grades is established from the correspondence of being with the attributes of goodness, unity, etc. The measure in which a substance possesses these attributes is the measure of its being. Unity will serve as an illustration. Substances, it is evident, exhibit this attribute in very different degrees. An organized animal is more perfectly one than a plant, which can often be multiplied by mere division: and a plant is a truer unit than a fragment of some inanimate substance. Man, on the other hand, in virtue of his self-consciousness, is more perfectly one than any of the lower animals. A pure spirit is a more perfect unity than man. The more fully a thing is a unit, existing in and for itself, the greater is the degree in which it possesses substantial being. Only the individual substance is properly said to be (infra): and our argument shews that this substantial being is realized in many different grades. Moreover, these grades demand the existence of a highest grade in which the perfection is fully realized. Were there not such a supreme realization the terms more or less would be meaningless The various manifestations can only be grouped together as possessing a common nature, if there is an ultimate norm to which the several individuals approach more or less closely. This may be exemplified in the case of a circle. We should have no right to group circles together in a class and call them by a common name, did not the circles which we draw, approach, however imperfectly, to an ideal type, which the mind can apprehend, though concrete matter does not admit of its perfect realization. What has been said in the text will shew why the argument enables us to conclude to the real existence of the supreme degree of being, goodness, etc., though only to the ideal existence of those inferior perfections, which demand material embodiment. The argument was derived by the Schoolmen from St. Augustine. He thus establishes the existence of God in De Civ. Dei viii c.6. P.L. 41, col. 231. Cf. De Div. Qq., lxxxiii., q. 45; De Doct. Christ., c. 38; De Trin. V., c. 10, n. 11. The proof in this form is generally called the argument from the degrees of being.

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