Full Idea
Thinking, then, is something other than perceiving, and its two kinds are held to be imagination and supposition.
Gist of Idea
Thinking is not perceiving, but takes the form of imagination and speculation
Source
Aristotle (De Anima [c.329 BCE], 427b28)
Book Reference
Aristotle: 'De Anima (On the Soul)', ed/tr. Lawson-Tancred,H.C. [Penguin 1986], p.198