Full Idea
It is from his choosing that we judge what sort of person someone is; that is, what that for whose sake he does something is, not what he does.
Gist of Idea
We judge character not by their actions, but by their reasons for actions
Source
Aristotle (Eudemian Ethics [c.333 BCE], 1228a03)
Book Reference
Aristotle: 'Eudemian Ethics I,II and VIII', ed/tr. Woods,Michael [OUP 1992], p.34
A Reaction
Not entirely true. It can be sufficient to reveal their character that a person does some particular thing, as novelists know. When Hud parks his car in her flowerbed, we don't need to enquire about his reason. But see 1228a16!