Aristotle contends that in perception the sense organ is “made like” its object, but only “in a certain way.” Much controversy has surrounded these remarks, primarily about how to understand being “made like.” One camp has understood this to require literal exemplification, such that the sense organs manifest the sensible qualities of their objects. Others have understood likeness to require no physical alteration at all in the sense organs.I accept as a starting point in this paper that understanding perceptual likeness (...) in terms of exemplification is a non-starter. By doing so, however, I also reject the easiest and most direct understanding of what it means for the sense organs to be “made like” their objects. Others who have shared this assumption have suggested that likeness consists in “isomorphism.” Unfortunately, they have not adequately explicated how this notion is to be understood, with the result that Aristotle’s theory of perception remains crucially underdeveloped. I argue that the key is to understand the form of isomorphism at work in Aristotle’s account of thinking. (shrink)