While modern ethics is essentially concerned with which actions are right or wrong, ancient Greco-Romans conceived of ethics as the much broader inquiry into how to live a happy life – the pursuit of which they deemed to be a human being’s most important endeavor. But, a happy life can be pursued in different ways, depending on which concept of eudaimonia – the flourishing life – one adopts.

Though a flourishing life was the common goal, the major Hellenistic schools of philosophy differed on how to achieve such a life.

Ethics is one of the classical branches of philosophy, with the other ones being: aesthetics (concerned with beauty and art), epistemology (the study of how we know things), logic (dedicated to understanding reason), and metaphysics (to comprehend the nature of the world).

How to Be a Stoic: Using Ancient Philosophy to Live a Modern Life
Massimo Pigliucci