The philosopher, as Aristotle is called by St Thomas Aquinas, was born in Stagira, northeast Greece, in 384 BCE, and was the most eminent of Plato's students. His father was doctor to King Amyntas of Macedon, and tradition has it that Aristotle later became the tutor of King Philip's son, the future Alexander the Great. Early on in the Nicomachean Ethics, one of his two major works on ethics, Aristotle says that his enquiry is “a sort of Politics”. Despite the lip service to kingship in his Nicomachean Ethics, the virtues Aristotle describes, especially the “nameless” ones, seem well suited to a democracy. Aristotle's interests in medicine and biology, no doubt gained from his father, lead him to compare the good human being with a doctor. The analogy had already been drawn by Protagoras, but whereas Protagoras held that whatever some person happens to think is good is good for that person, Aristotle has an objective account of happiness. What happiness is does not depend upon what anyone happens to think, although the good person will have the right view of what happiness is.

Aristotle has often been called a “eudaimonist” because he thinks that our ultimate goal in life is happiness: eudaimonia. The Greek word suggests that someone who is happy has a favourable guardian spirit (“daimōn”), and Aristotle discusses the question of how much of happiness is due to luck and how much is up to us.