Aristotle (384 BC – 322 BC)

Involving both the genus and the difference, definitions are propositions about the fundamental nature of a subject. For Aristotle, propositions are true if there is an agreement with the reality they represent. The truth can be reached by means of the logic syllogism, the laws of contradiction, and that of excluded middle. Disrespect for these laws would result in the uniformity of all assertions and in apathy concerning one’s conduct. Aristotle regards ethics as Man’s effort to identify his chief end. In fact, the world as a whole (whose ground consists of its concrete objects) is a constant transformation of matter toward an end. Man reaches his purpose or happiness by developing the learned faculty of controlling his irrational side through reason. The “autonomy of will” thus attained allows for voluntary actions, whose causes lie within Man himself.