Full Idea
To experience pleasure or pain is to be active with the perceptive mean in relation to good or bad as such.
Gist of Idea
Pleasure and pain are perceptions of things as good or bad
Source
Aristotle (De Anima [c.329 BCE], 431a10)
Book Reference
Aristotle: 'De Anima (On the Soul)', ed/tr. Lawson-Tancred,H.C. [Penguin 1986], p.208
A Reaction
A bizarre view which is interesting, but strikes me as wrong. We are drawn towards pleasure, but judgement can pull us away again, and 'good' is in the judgement, not in the feeling.