Understand
An impression (phantasia) is the raw, automatic mental event that happens the moment something registers: a sudden noise, a critical email, a stranger’s rude comment. You don’t choose to have it; it just arrives. Assent (synkatathesis) is the separate, voluntary act of endorsing a judgment about that impression, deciding, in effect, “yes, this is exactly as alarming/insulting/catastrophic as it first seemed.”
The Stoics located their entire practice in the narrow gap between those two moments. You can’t stop an impression from occurring. You can, with practice, notice it before automatically assenting to the judgment riding along with it.
Examine
Why this distinction matters
This is arguably the mechanism underneath the Dichotomy of Control rather than a separate idea next to it. The dichotomy says your judgments are up to you; impressions and assent explain how that’s true, by describing the actual two-step process (impression, then assent) where a judgment gets formed, and identifying the second step as the one you actually have leverage over.
Epictetus makes the point directly and often. One of the most quoted lines from the Enchiridion is really a compressed statement of this exact idea:
Primary source
Men are disturbed not by the things which happen, but by their opinions about the things.
The event (a noise, a comment, a setback) is the impression. “This is disastrous” is the opinion, formed by assent. Epictetus’s claim is that the second thing, not the first, is what actually produces distress, and the second thing is the one within your power to examine before accepting it.
The mechanism, in more detail
Stoic and Stoic-adjacent sources describe roughly three stages: an impression strikes you; your mind spontaneously proposes a judgment about it (“this is bad,” “this is dangerous,” “this person is my enemy”); and you either assent to that judgment or withhold assent and examine it further. Later Stoics, particularly in Epictetus’s teaching as recorded by Arrian, treat “examining impressions” (sometimes rendered dokimasia) as a skill that improves with deliberate practice, closer to a trained reflex than a one-time insight.
This is also where the Stoic theory of emotion connects in: on the Stoic account, a destructive passion (excessive fear, anger, grief) isn’t a raw impression, it’s what results once a faulty judgment about an impression has already been assented to. See Stoic Emotions for the fuller picture.
A modern example
Your phone buzzes with a short, blunt reply from a colleague. The impression arrives instantly: a flash of “they’re annoyed with me” or “I did something wrong.” That flash is not yet a judgment you’ve endorsed, it’s raw material. Assenting to it without examination might mean spending the next hour anxious and rehearsing apologies. Withholding assent means noticing the impression, then asking whether the evidence actually supports “they’re annoyed with me” or whether it’s equally consistent with “they’re busy and wrote quickly.” The message hasn’t changed. What’s changed is whether you accepted the first interpretation your mind offered you.
Common misunderstanding: examining an impression before assenting to it is not the same as suppressing or denying the impression itself. The Stoics didn’t claim you can stop the initial flash of alarm, insult, or fear from occurring, only that you can pause before treating your first interpretation of it as automatically correct.
Practice
- Notice the impression as it arrives, name it plainly: “I’m having the thought that X.”
- Ask what judgment is riding along with it, usually an unstated claim like “this is terrible” or “this means something bad about me.”
- Ask whether that judgment is actually supported, or whether it’s just the first interpretation your mind offered.
- Choose deliberately whether to assent to it, revise it, or set it aside, rather than reacting as if it were simply true.
Primary sources
- Epictetus, Enchiridion, Chapter 5