Former Roman slave turned Stoic teacher (~50-135 CE). Most famous for the dichotomy of control and for grounding Stoic ethics in everyday practice (recorded by his pupil Arrian in the Discourses and Enchiridion).
Key tenets
Dichotomy of control: some things are up to us (judgements, desires, aversions); others are not — distinguishing them is freedom.
Suffering comes not from events but from our judgements about events.
The will is sovereign and cannot be coerced from outside.
Philosophy is training, not theory — practice daily.
Of one thing beware, O Man; See what is the price at which you sell your will. If you do nothing else, do not sell your will cheap.