1. Moral Philosophy is the science of the moral order, or of the right and wrong of human acts. It is called Ethics from the Greek word êthê which, like the Latin word mores, signifies morals. Since its object is not merely speculative knowledge, but the true direction of human acts, Ethics is also styled Practical Philosophy.
2. Ethics, we say, directs human acts. However, not all the acts of a man are called human acts, but only such as are under the control of his free will. Whatever he does necessarily -- i. e., whatever he cannot help doing -- results from the physical laws of nature, and, as such, is willed and directed by the Author of nature. For instance, a man may fall like a stone, or grow like a plant, or perceive a sound like a brute animal, without any power on his part to prevent himself from falling or growing or hearing, if the required conditions are present. These are acts of the man, but they are not acts of what is distinctively human -- namely, his intellect and his will. The term human act is restricted in philosophy to those acts which a man does knowingly and willingly -- which he has the power either to do or not to do.
3. To be qualified for the direction of human acts, Philosophy must derive its conclusions by reasoning from first principles; it must take into account the nature of man, and The natures of all the causes that influence human action. Much of this we have considered in Metaphysics, or Mental Philosophy. Ethics is thus founded on Metaphysics: Moral Philosophy assumes as its principles the conclusions established in Mental Philosophy.
4. To explain the object of Moral Philosophy, which we have declared to be the true direction of human acts, we shall treat in Book I. of the direction of human acts in general; in Book II., of the special duties and rights of men viewed as individuals; and, in Book III., of the rights and duties of men viewed as members of society.
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