This chapter offers an overview of the notion of computation with a particular focus on how it applies in perceptual theory. It aims to show that the incompatibility is only apparent by suggesting that the two theories are in tension only with a semantic way of individuating computation. The chapter presents a first take on the notion of computation and explains why, when this notion is applied to understanding perception, it would seem to produce a theory that is at odds with both ecology and disjunctivism. It argues that there is a syntactic way of understanding classical computation that dispels the incompatibility, but it also shows that we have little reason to accept Classicism when it comes to perception. The chapter introduces two non-classical and non-semantic ways of understanding computation – minimalism and functionalism. It concludes by discussing how these theories relate to the common idea in cognitive science that computation is fundamentally a matter of information processing.