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.
(1.) Character, good or bad, is produced by what Aristotle calls “habituation,” that is, it is the result of the repeated doing of acts which have a similar or common quality. Such repetition acting upon natural aptitudes or propensities gradually fixes them in one or other of two opposite directions, giving them a bias towards good or evil. Hence the several acts which determine goodness or badness of character must be done in a certain way, and thus the formation of good character requires discipline and direction from without. Not that the agent himself contributes nothing to the formation of his character, but that at first he needs guidance. The point is not so much that the process cannot be safely left to Nature, but that it cannot be entrusted to merely intellectual instruction. The process is one of assimilation, largely by imitation and under direction and control. The result is a growing understanding of what is done, a choice of it for its own sake, a fixity and steadiness of purpose. Right acts and feelings become, through habit, easier and more pleasant, and the doing of them a “second nature.” The agent acquires the power of doing them freely, willingly, more and more “of himself.”