JMC : The Physical System of St. Thomas / by G.M. Cornoldi, S.J.


IT is a fixed principle in St. Thomas's physical system that the agent and the patient must be conjoined, and therefore that action at an absolute distance is impossible and absurd: but the agent may be substantially distant from the patient, if the two are conjoined by virtue of a medium. The Scholastics, therefore, said that the immediatio suppositi is not always necessary, the immediatio virtutis being sufficient in finite causes. "However great the virtue of the agent may be," says St. Thomas, "it cannot act on anything distant, except through a medium,"{1} and because the virtue of God is not really distinguishable from His essence, the holy Doctor adds that, "To act immediately on all things belongs to the most great virtue of God. Wherefore nothing is so distant that God is not in it." And he exemplifies this with regard to finite agents by saying that he who operates, being absent, is not the proximate cause of the thing done, but its remote cause, as the sun's virtue is first impressed on a body conjoined to it, and so on successively; which virtue, as Avicenna says, is its light, by which it acts on inferior things. There is more sense in this than in the sayings of modern scientists, who talk about ethereal atoms very far apart, and oscillations of light parallel to each other, so that the ethereal atoms never can meet; while the sun nevertheless communicates its virtue by atomic ethereal motion to all things, and by illuminating, fructifies them.

When we consider the facts of nature, we always find valid arguments for a general induction that created causes never operate at a distance: and philosophical reasoning makes us draw the same conclusion. For if we admit that a substance can operate on another, in spite of an absolute void between, we must admit an effect without a cause. In fact, if there are two substances, A and V, separated by an absolute void, and A is to operate a change, X, on V, between these there must be a virtue, a force, a cause, productive of that change. Now this virtue and the substance whence it proceeds are either conjoined or not conjoined. If they are conjoined, A must be in true contact with V, and that upsets the hypothesis of absolute distance. If they are not conjoined, that virtue must either depend on another substance, to which it was transmitted from A, or it must subsist of itself. In the former case the hypothesis of action absolutely at a distance would vanish: in the second we should be affirming what is contrary to nature. Substance alone can subsist of itself. Every virtue or force or quality or accident must be inherent in a substance as in its proper subject. Therefore that virtue or force of A cannot detach itself and fly alone to Y; but, in order to arrive there, must be consigned, so to speak, first to B, then from B to C, and from C to D, and from D to E, and so on, through a series of intermediate substances, till it comes to that which is in immediate contact with V, like the mechanical movement communicated from the first to the last in a series of balls apart from each other. Hence the Scholastic principle, that the operator and the thing operated on must be conjoined, either immediatione suppositi or immediatione virtutis.

The illustrious Cardinal Toledo says in his Commentaries on Aristotle: "Substance that moves anything or is the cause of some change therein, is twofold, viz., either mediate and remote, or immediate and proximate. It is immediate when there is no mover between it and the thing that it moves, as fire burns the wood to which it is conjoined. It is mediate when between it and the thing that it moves there is some other substance, as fire warms distant objects through the medium of air. . . . Moreover, when any substance operates between, and thereby produces an effect at a distance, that effect is not always the same in the medium and in the distant object. Fire, through the medium of glass, liquifies wax, not the glass: and the reason is, that one and the same accident received in various subjects produces in them different effects according to their various dispositions; and thus heat makes one subject white, another black. . . . Therefore, though the same accident be received in the medium and in the remote object, the effect in them is not always equal. . . ." Hence we may lay down this first conclusion, that if there is not some immediate mover, no true change can take place. This is an axiom of the Peripatetics. In fact it is inconceivable that one substance could produce a change in another without it, either immediately or through the medium of something else: for the operation and the being are conjoined, and therefore where a substance is not, its operation will not be. Thus, when a substance does not operate on another at a distance by communicating its own operation to a medium, it cannot by any means be found operating in that substance. Hence theologians validly argue that God is present everywhere, precisely because He operates everywhere. . . . And now let us lay down a second conclusion, that the proximate mover and the moved are always together, and immediately together. For though the former is far off in its suppositum, its virtue is always immediate. And thus we must understand Aristotle to mean that no change, of any sort, can take place unless the mover and the moved are together. We must not suppose him to have believed that all the movers are contemporaneous."{2}

The Conimbrican{3} commentators of the Stagirite furnish us with another argument on the question, and one that is not to be despised. Every substance, they say, has a sphere of action, beyond which it cannot produce any sensible effect: but if it could operate from an absolute distance, it could also extend its virtue to any degree of remoteness. Therefore, operating at a truly absolute distance cannot be admitted. The minor proposition is certain: for supposing an operation at an absolute distance, the more or less of distance gives no reason for limiting the extent of the operating power. The precise words of the authors are as follows: "If a thing can, without a medium, operate on another at a distance, philosophers have no reason to say that every agent has its determined sphere of action: for the agent could not diffuse its action to any given distance, if its virtue did not pass through a medium in which it is gradually spent and weakened."{4}

It is not worth while to put forward other reasons. Common sense tells us that, as nothing can act before it exists, no cause can operate in a place where as yet it is not in any way, either by itself (immediatione suppositi) or by its virtue (immediatione virtutis): for that would imply an effect without a cause.

It will not be amiss to speak of some doctrines that were affirmed and are affirmed even now. Firstly then, it is false that the agent A can operate an effect on V without communicating its whole virtue to the medium. between, but only causing some change in the substance immediate to itself. This is evidently false, because in that case there would be, for a moment at least, action truly at a distance. Secondly, it is false that any medium whatsoever is sufficient between A and V, for the one to operate on the other. Not every substance is adapted to receive in the same way the qualities of another. We can see this in bodies that transmit badly either light or heat or electricity or magnetic virtue, and therefore are called, bad conductors. For if a medium is necessary to transport the action of A into V, an insufficient medium would mean action truly at a distance. Hence it follows, thirdly, that merely operating on anyhow, would not be sufficient. A must operate in a manner adapted for transmitting its action into V: for the change in V would equally be an effect without a cause, whether we supposed it to proceed from A without a medium, or whether we supposed it to be caused, by A with a medium, but without communicating anything proportionate to that change. Thus we find that many substances conduct certain operations of other substances well, others badly, as in the phenomena of light, heat, electricity and magnetism.

It is puerile to say that the absolute distance between the agent and the patient is too small to be worth considering: for action at an absolute distance is essentially repugnant to reason. The more and the less have no place in what concerns the essence of things.

This alone would show the falseness of the Mechanic and Dynamic systems, that oppose the Physical system: for they who profess them cannot avoid admitting action at a distance. With this criterion we can also refute certain modern doctrines that find support from the science of the day, such as modern magnetism and hypnotism: for the very singular phenomena put forward in support of these doctrines are attributed by some people not to good spirits, because that would be repugnant to the holiness of such, nor to evil spirits, lest consciences should be disturbed, but to the operations of nature. Now, in the first place, the human soul with its intellect and will cannot immediately join itself to the intellect and will of other human beings, nor to any external bodily thing. Secondly, to enter into communication with other men, it must compose sensible signs of its own acts, as, for instance, words or other external signs, and then the other people to whom the signs are directed, must have previously known the value of them: for otherwise they might feel the impressions, but would not understand the meaning of them. Moreover we should require some suitable medium for sending to others the signs of our thoughts and wishes; for otherwise we should have recourse to actio in distans, which we have shown to be absurd. To fall back on our ignorance about the reach of physical forces is not reasonable: and still less is it philosophical. True it is that we often do not know the value of those forces: but we certainly do know that they never can make an absurdity, and that it is an absurdity to suppose action at a distance, however small, -- as above shown.

{1} Summa, P. i. Q. viii. 1 ad 3.

{2} In VII. Phys., Q. 2.

{3} Coimbrian, antico Conimbrican.

{4} In VII. Phys., Q. i a. 2.

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