The main factor which determines success or failure in human life is the acquisition of certain powers, for Happiness is just the exercise or putting forth of these in actual living, everything else is secondary and subordinate. These powers arise from the due development of certain natural aptitudes which belong (in various degrees) to human nature as such and therefore to all normal human beings. In their developed form they are known as virtues (the Greek means simply "goodnesses," "perfections," "excellences," or "fitnesses"), some of them are physical, but others are psychical, and among the latter some, and these distinctively or peculiarly human, are "rational," _i e_, presuppose the possession and exercise of mind or intelligence. These last fall into two groups, which Aristotle distinguishes as Goodnesses of Intellect and Goodnesses of Character. They have in common that they all excite in us admiration and praise of their possessors, and that they are not natural endowments, but acquired characteristics But they differ in important ways. (1) the former are excellences or developed powers of the reason as such--of that in us which sees and formulates laws, rules, regularities systems, and is content in the vision of them, while the latter involve a submission or obedience to such rules of something in us which is in itself capricious and irregular, but capable of regulation, viz our instincts and feelings, (2) the former are acquired by study and instruction, the latter by discipline. The latter constitute "character," each of them as a "moral virtue" (literally "a goodness of character"), and upon them primarily depends the realisation of happiness. This is the case at least for the great majority of men, and for all men their possession is an indispensable basis of the best, _i e_, the most desirable life. They form the chief or central subject-matter of the _Ethics_.

Perhaps the truest way of conceiving Aristotle's meaning here is to regard a moral virtue as a form of obedience to a maxim or rule of conduct accepted by the agent as valid for a class of recurrent situations in human life. Such obedience requires knowledge of the rule and acceptance of it _as the rule_ of the agent's own actions, but not necessarily knowledge of its ground or of its systematic connexion with other similarly known and similarly accepted rules (It may be remarked that the Greek word usually translated "reason," means in almost all cases in the _Ethics_ such a rule, and not the faculty which apprehends, formulates, considers them).

The "moral virtues and vices" make up what we call character, and the important questions arise: (1) What is character? and (2) How is it formed? (for character in this sense is not a natural endowment; it is formed or produced). Aristotle deals with these questions in the reverse order. His answers are peculiar and distinctive--not that they are absolutely novel (for they are anticipated in Plato), but that by him they are for the first time distinctly and clearly formulated.