This last life is the peculiar work or province of man.

For our purpose, we must consider man, not merely as possessing, but as actually exercising and putting in action, these mental capacities.

Moreover, when we talk generally of the work or province of an artist, we always tacitly imply a complete and excellent artist in his own craft: and so likewise when we speak of the work of a man, we mean that work as performed by a complete and competent man.

Since the work of man, therefore, consists in the active exercise of the mental capacities, conformably to reason, the supreme good of man will consist in performing this work with excellence or virtue.

Herein he will obtain happiness, if we assume continuance throughout a full period of life: one day or a short time is not sufficient for happiness (VII.).
Aristotle thus lays down the outline of man's supreme Good or Happiness: which he declares to be the beginning or principle [Greek: archae] of his deductions, and to be obtained in the best way that the subject admits.