Aristotle, Nicomachean Ethics
H. Rackham, Ed.

we must therefore set aside the vital activity of nutrition and growth. Next in the scale will come some form of sentient life; but this too appears to be shared by horses, oxen, and animals generally. [13] There remains therefore what may be called the practical¹ life of the rational part of man. （This part has two divisions,² one rational as obedient to principle, the others possessing principle and exercising intelligence）. Rational life again has two meanings; let us assume that we are here concerned with the active exercise³ of the rational faculty, since this seems to be the more proper sense of the term. [14] If then the function of man is the active exercise of the soul's faculties⁴ in conformity with rational principle, or at all events not in dissociation from rational principle, and if we acknowledge the function of an individual and of a good individual of the same class （for instance, a harper and a good harper, and so generally with all classes） to be generically the same, the qualification of the latter's superiority in excellence being added to the function in his case （I mean that if the function of a harper is to play the harp, that of a good harper is to play the harp well）: if this is so, and if we declare that the function of man is a certain form of life, and define that form of life as the exercise of the soul's faculties and activities in association with rational principle, [15] and say that the function of a good man is to perform these activities well and rightly, and if a function is well performed when it is performed in accordance with its own proper excellence—from these premises it follows that the Good of man is the active exercise of his soul's faculties in conformity with excellence or virtue, or if there be several human excellences or virtues, in conformity with the best and most perfect among them. [16] Moreover, to be happy takes a complete lifetime; for one swallow does not make spring, nor does one fine day; and similarly one day or a brief period of happiness