Synkatathesis

The conscious assent of the rational will to an impression; the decisive act by which the Stoic recognizes a phantasia as true and relevant to action.

Synkatathesis is neither automatic nor compelled — it is the locus of Stoic freedom. Every impression (phantasia) presents itself to consciousness, but synkatathesis, the assent, is an active act of will. When assent is withheld or consciously refused (epoché), the impression remains without effect. This is the core of the Stoic self-understanding: it is not impressions that control us, but our assent or dissent.