Aristotle, Nicomachean Ethics
H. Rackham, Ed.

Happiness, therefore, being found to be something final and self-sufficient, is the End at which all actions aim. [9]

To say however that the Supreme Good is happiness will probably appear a truism; we still require a more explicit account of what constitutes happiness. [10] Perhaps then we may arrive at this by ascertaining what is man's function. For the goodness or efficiency of a flute-player or sculptor or craftsman of any sort, and in general of anybody who has some function or business to perform, is thought to reside in that function; and similarly it may be held that the good of man resides in the function of man, if he has a function. [11]

Are we then to suppose that, while the carpenter and the shoemaker have definite functions or businesses belonging to them, man as such has none, and is not designed by nature to fulfil any function? Must we not rather assume that, just as the eye, the hand, the foot and each of the various members of the body manifestly has a certain function of its own, so a human being also has a certain function over and above all the functions of his particular members? [12] What then precisely can this function be? The mere act of living appears to be shared even by plants, whereas we are looking for the function peculiar to man;