Cognitivism argues that psychology studies behavior to infer unobservable theoretical constructs, such as `belief,' that summarize and explain empirical observations and predict new phenomena. Here, Fodor tries to provide a scientific account of commonsense belief/desire psychology by defending a representational theory of mind. Assuming that there is no alternative to the vocabulary of commonsense psychological explanation, he proposes that we have an infinite set of mental symbols at our disposal and that a propositional attitude is equivalent to a symbol's occurring and its functioning in a particular causal role. Underlying his account is the view that mental processes will turn out to be physical processes. Highly recommended for philosophers of mind and cognitive psychologists.