Definition
In Stoic philosophy, virtue is excellence of character: a stable disposition to think and act in accordance with reason and nature. The Stoics organized virtue into four cardinal forms, namely wisdom, courage, justice, and temperance, and held that the four are deeply unified, since each requires the others to be exercised well.
Virtue is not a list of rules but a quality of the agent. It describes how a person reasons, chooses, and responds, rather than which outcomes they happen to secure.
Why it matters
How it works
For the Stoics, virtue arises from correct judgment. When a person reliably reads situations well, distinguishing what is good, bad, or indifferent, their actions follow as a natural expression of that understanding. Vice, by contrast, is rooted in mistaken belief about value.
Virtue is also practical. It shows up in concrete moments: holding to a commitment under pressure, treating others fairly when it costs something, declining an easy excess. Each of the four cardinal virtues addresses a different domain of life, but all of them express the same underlying soundness of reason.