This book addresses a part of a problem. The problem is to determine the architecture of cognition, that is, the basic structures and mechanisms underlying cognitive processing. This is a multidimensional problem insofar as there appear to be many distinct types of mechanisms that interact in diverse ways during cognitive processing. Thus, we have memory, attention, learning, sensation, perception, and who knows what else, interacting to produce behavior. As a case in point, consider a bit of linguistic behavior. To tell a friend that I think Greg won a stunning victory, I must evidently rely on various bits of information stored in my memory, including who my friends are, who Greg is, what he won, and what natural languages I share with my friend. I must sense and perceive that my friend is within hearing distance, how loud I need to speak, how loud I am speaking, and whether my friend is paying attention. I must avail myself of what I know about the language I share with my friend, along with innumerable principles about human folk psychology. This book does not address the full range of contemporary theorizing about cognitive architecture, but only a part. It addresses theories of cognitive architecture that hypothesize that there exist cognitive representations, then begins to explore the possible structure of these representations. One of the leading hypotheses concerning the structure of cognitive representations is that it is akin to that found in symbolic logic.