Full Idea
The sceptics say there are three movements of the soul: presentation, impulse and assent. …And action requires two things: a presentation of something to which one has an affinity, and an impulse toward what is presented as an object of affinity.
Gist of Idea
Action needs an affinity for a presentation, and an impulse toward the affinity
Source
Plutarch (74: Reply to Colotes [c.85], 1122c)
Book Reference
'The Stoics Reader', ed/tr. Inwood,B/Gerson,L.P. [Hackett 2008], p.37
A Reaction
Not much reasoning involved in this account, which the sceptics say is compatible with suspension of judgement.