Definition
An impression — phantasia in Greek — is any appearance that arises in the mind: a perception, a thought, an emotional reaction, a judgment about what is happening. Impressions occur automatically. A loud noise, an insult, or a setback each produces an impression before any deliberate thought.
Stoicism makes a sharp distinction between the impression itself and what one does with it. The impression is not in our power; whether we accept it as accurate is.
Why it matters
How it works
Epictetus advised that when a troubling impression arrives, one should address it directly: say that it is an impression and not at all the thing it claims to be. This names the appearance as merely an appearance and opens space to evaluate it.
The trained mind then asks whether the impression concerns something in its power, and whether the judgment embedded in it is accurate. Only after this examination does it grant or withhold assent.