Kathēkon

The fitting act

A kathēkon is an action that fits one’s nature and circumstances — what it is reasonable to do, such as honoring parents or caring for one’s health. Cicero rendered it officium, duty. The Stoics distinguished the merely fitting act from the katorthōma, the perfectly right act done from a settled virtuous disposition: the good and the bad may both do their duty, but only the sage acts rightly through and through.