Prosdiairesis

The external, foreign element that interferes with human actions and contributes to their outcome, without originating from one's own intention.

Prosdiairesis (from pros = toward/in addition, and diairesis = distinction) is Epictetus's term for the external component of an action: outside circumstances, other people, chance, and the givens of nature. While prohairesis denotes the individual's rational power of choice, prosdiairesis encompasses everything that lies outside one's own control yet still bears on the outcome of an action. This distinction is central to Epictetus's ethics: moral excellence depends on prohairesis alone, not on success, which is also shaped by prosdiairesis.