The center of Epictetus's philosophy is a single distinction he returned to constantly, between what is up to us and what is not. Judgment, desire, aversion, and one's own choices belong to the first category and are, in his view, entirely within a person's control. The body, possessions, reputation, and the actions of other people belong to the second and are not, however much effort a person spends trying to manage them. Suffering, on this account, comes not from external events themselves but from judging them as good or bad and then striving to control what cannot be controlled. A person who confines their concern to the first category, Epictetus argued, achieves a freedom that no external power, not even enslavement, can touch, a claim that carried particular weight coming from a man who had once been literally unfree. This teaching was not offered as abstract theory but as a discipline to be practiced through constant self examination, and the Enchiridion reads accordingly as a manual of short, practical instructions rather than a systematic treatise. The emperor Marcus Aurelius, writing his own private notebook a generation later, drew directly on this framework, and the same distinction between the controllable and the uncontrollable remains the core exercise recommended in modern therapeutic approaches descended from Stoic practice.