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Wellsprings
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Impulse & Assent

ὁρμή / συγκατάθεσις

The Stoic anatomy of every action: an impression appears, reason says 'yes,' and that assent fires the impulse to act.

The Stoics, particularly Chrysippus and his school, developed a theory of action centered on two linked movements of the mind. When an impression (phantasia) strikes the mind—say, the sight of a poisonous snake—it naturally generates an impulse (hormē) toward response. But crucially, rational assent (synkatathesis) must follow. This voluntary endorsement by reason is what transforms a mere impulse into deliberate action. Without assent, even strong impressions fail to move a wise person to act foolishly.

This framework gave the Stoics a way to explain human agency and moral responsibility. A person confronted with danger or temptation experiences the initial impulse automatically, but assent remains within their control—a mental act they can withhold or grant. The wise person, according to Stoic teaching, learns to withhold assent from impressions that lead toward vice, thereby maintaining freedom and virtue even when circumstances are difficult.

Where this idea shows up

24 Greek sources

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