September 19, 2026

What Actually Exists

Of time, the past and the future subsist, but only the present exists.

Chrysippus led the Stoic school in Athens during the third century BCE, and as its most prolific writer he worked out the fine details of Stoic physics that Zeno and Cleanthes had only sketched. Here he addresses the nature of time itself, arguing that strictly speaking only the present moment has real existence, while the past has already slipped away and the future has not yet arrived to be real at all. For the Stoics this was never just abstract physics: if the present is the only stretch of time that actually exists, then it is also the only stretch of time in which a person can actually act. The tradition treats this as a daily discipline, not a theory, training attention to land on the task at hand rather than drifting into replaying yesterday or rehearsing tomorrow. Neither the past nor the future can be touched or changed from where you now stand.

A principle of Stoicism: Confine Yourself to the Present →