Imagine for yourself a character, a model personality, whose example you determine to follow, in private as well as in public.

The line expresses a practical Stoic exercise: deliberately choose an ideal of character—often embodied in a wise person or exemplar—and use it as a constant standard for conduct. By stressing “in private as well as in public,” it targets the gap between reputation and integrity, urging consistency when no audience is present. In Stoic ethics, virtue is the only true good, so the point is not to perform for praise but to train one’s judgments and habits toward courage, justice, self-control, and wisdom. The “model personality” functions as a moral compass and a tool for self-scrutiny: before acting, ask whether the chosen exemplar would approve.