It has become almost a cliché to say that the most important explanatory posit today in cognitive research is the concept of representation. Like most clichés, it also happens to be true. Since the collapse of behaviorism in the 1950s, there has been no single theoretical construct that has played such a central role in the scientific disciplines of cognitive psychology, social psychology, linguistics, artificial intelligence, and the cognitive neurosciences. Of course, there have been many different types of representational theories. But all share the core assumption that mental processes involve content-bearing internal states and that a correct accounting of those processes must invoke structures that serve to stand for something else. The notion of mental representation is the corner-stone of what often gets referred to in Kuhnian terms as the “cognitive revolution” in psychology. But mental representation hasn't been important just to psychologists. Accompanying this trend in the sciences has been a corresponding focus on mental representation in the philosophy of mind. Much of this attention has focused upon the nature of commonsense notions of mental representation, like belief and desire, and how these can be part of a physical brain. More specifically, the central question has focused on the representational nature of beliefs – the fact that they have meaning and are essentially about various states of affairs.

Yet despite all of this attention (or perhaps because of it), there is nothing even remotely like a consensus on the nature of mental representation.