In the philosophy of perception, critical realism is the theory that some of our sense-data (for example, those of primary qualities) can and do accurately represent external objects, properties, and events, while other of our sense-data (for example, those of secondary qualities and perceptual illusions) do not accurately represent any external objects, properties, and events. Put simply, critical realism highlights a mind-dependent aspect of the world that reaches to understand (and comes to an understanding of) the mind-independent world.
According to Locke, some sense-data, namely the sense-data of secondary qualities, do not represent anything in the external world, even if they are caused by external qualities (primary qualities). Thus it is natural to adopt a theory of critical realism.
By its talk of sense-data and representation, this theory depends on or presupposes the truth of representationalism. If critical realism is correct, then representationalism would have to be a correct theory of perception.
The American critical realist movement was a response both to direct realism, as well as to idealism and pragmatism. In very broad terms, American critical realism was a form of representative realism, in which there are objects that stand as mediators between independent real objects and perceivers. A prominent developer of American critical realism is Roy Wood Sellars, father of Wilfrid Sellars.
One innovation was that these mediators aren't ideas (British empiricism), but properties, essences, or "character complexes."