There is no one kind of thing that we 'perceive' but many different kinds, the number being reducible if at all by scientific investigation and not by philosophy: pens are in many ways though not in all ways unlike rainbows, which are in many ways though not in all ways unlike after-images, which in turn are in many ways but not in all ways unlike pictures on the cinema-screen--and so on.

Sense and Sensibilia (ed. 1964)