This essay is intended to be a systematic exposition and critique of Daniel Dennett's general views. It is divided into three main sections. In section 1 we raise the question of the nature of a plausible scientific psychology, and suggest that the question of whether folk psychology will serve as an adequate scientific psychology is of special relevance in a discussion of Dennett. We then characterize folk psychology briefly. We suggest that Dennett's views have undergone at least one major change, and proceed to discuss both his earlier and his later views. In section 2 we suggest that Dennett is correctly perceived as an instrumentalist in his earlier works. We think that Dennett later abandons this position because of general worries about instrumentalism and, more importantly, because Dennett became convinced that an instrumentalist conception of folk psychology will not enable us to vindicate the notions of personhood, moral agency, and responsibility. This left Dennett with a dilemma. On the one hand, he does not think that beliefs, etc., will turn out to be genuine scientific posits. On the other hand, he thinks that moral agency would be impossible if we could not treat beliefs, etc. as causally efficacious in some suitable sense. In section 3 we discuss Dennett's resolution of this dilemma. The key to his current view, we suggest, is the illata-abstracta distinction. Dennett holds that both illata and abstracta are real and have causal powers, even though only illata are genuine scientific posits. He suggests that beliefs etc. are abstracta, and are the subject matter of what he calls 'intentional system theory'. The subject matter of another theory, what Dennett calls 'subpersonal cognitive psychology', are illata, which are subpersonal intentional states. The important point is that this distinction lets Dennett have it both ways: (i) Since beliefs are mere abstracta, we need not commit ourselves to the thesis that beliefs will turn out to be posits of an adequate scientific psychology. (ii) Since beliefs have causal power, we are assured of moral and rational agency. We shall argue that Dennett's current view is untenable. If we are right in our arguments, then Dennett's program to produce a scientifically plausible psychology, one that will turn out to vindicate folk psychology (in some suitable sense), is a failure. It fails in the following important ways: (i) What Dennett sketches - intentional system theory cum subpersonal cognitive psychology - is not a plausible scientific psychology. (ii) As a consequence, Dennett also fails to provide a satisfactory foundation for moral and rational agency.