Abstract
When reflecting on the conditions of a happy human life, Plato and Aristotle agree that we can only understand what happiness is if we tackle the relation between the ergon or proper function of man and the virtue that makes the performance of that function to be good. That´s why both philosophers arrive at the conclusion that eudaimonia is an activity of reason, and even more, an excellent and perfect activity of reason, which shows how Plato and Aristotle are heirs to Socratic Ethics and Epistemology, extending, as well, an invitation to take care for the soul and live and examined and rational life, that is, the happy life.