The aristotelian principle purports to be a basic principle of human motivation, one that describes a strong, and not easily counterbalanced, tendency or desire. The principle states that “other things equal, human beings enjoy the exercise of their realized capacities (their innate or trained abilities), and this enjoyment increases the more the capacity is realized, or the greater its complexity” (TJ 374). To illustrate with Rawls’s own example: if people can play both chess and checkers, they will tend to prefer the former over the latter, since chess is a more complex game, one that draws on a wider range of abilities. The Aristotelian principle also has a companion effect. “As we witness the exercise of well-trained abilities by others, these displays are enjoyed by us and arouse a desire that we should be able to do the same things ourselves” (TJ 375–376). Rawls introduces the Aristotelian principle and its companion effect in part iii of TJ. The principle and its companion effect, he claims, add content to the formal deinition of a person’s good, help to account for our considered judgments of value, and contribute to the stability of a well-ordered society.

Since the Aristotelian principle purports to be a basic principle of human motivation, the question of its justiication, Rawls claims, does not arise.