Provisional Definition.-The place for an accurate definition of a subject is at the end of an inquiry rather than at the beginning, but a brief definition will serve to mark out the field. Ethics is the science that deals with conduct, in so far as this is considered as right or wrong, good or bad. A single term for conduct so considered is "moral conduct," or the "moral life." Another way of stating the same thing is to say that Ethics aims to give a systematic account of our judgments about conduct, in so far as these estimate it from the standpoint of right or wrong, good or bad. Ethical and Moral.-The terms "ethics" and "ethical" are derived from a Greek word ethos which originally meant customs, usages, especially those belonging to some group as distinguished from another, and later came to mean disposition, character. They are thus like the Latin word "moral," from mores, or the German sittlich, from Sitten. As we shall see, it was in customs, "ethos," "mores," that the moral or ethical began to appear. For customs were not merely habitual ways of acting; they were ways approved by the group or society. To act contrary to the customs of the group brought severe disapproval. This might not be formulated in precisely our terms-right and wrong, good and bad, -but the attitude was the same in essence. The terms ethical and moral as applied to the conduct of to-day imply of course a far more complex and advanced type of life than the old words "ethos" and "mores," just as economics deals with a more complex problem than "the management of a household," but the terms have a distinct value if they suggest the way in which the moral life had its beginning. Two Aspects of Conduct.-To give a scientific account of judgments about conduct, means to find the principles which are the basis of these judgments. Conduct or the moral life has two obvious aspects. On the one hand it is a life of purpose. It implies thought and feeling, ideals and motives, valuation and choice. These are processes to be studied by psychological methods. On the other hand, conduct has its outward side. It has relations to nature, and especially to human society. Moral life is called out or stimulated by certain necessities of individual and social existence. As Protagoras put it, in mythical form, the gods gave men a sense of justice and of reverence, in order to enable them to unite for mutual preservation. And in turn the moral life aims to modify or transform both natural and social environments, to build a "kingdom of man" which shall be also an ideal social order-a "kingdom of God." These relations to nature and society are studied by the biological and social sciences. Sociology, economics, politics, law, and jurisprudence deal particularly with this aspect of conduct. Ethics must employ their methods and results for this aspect of its problem, as it employs psychology for the examination of conduct on its inner side.