The doctrine of free will supposes that human behavior is the result of rational deliberation and conscious choice. Two recently formulated doctrines—psychoanalysis and behaviorism—that disavow free will for rather different reasons, disagree about what should be put in its place. Cognitive science, the modern study of the mind, offers yet another view on where our behavior comes from and what has to be done to effectively modify it. At stake in all this are matters absolutely central to our understanding of what it is to be human: to think, to feel and to act. The basic question seems to be: What are the causes of our behavior? Other questions arise immediately: Are we, or can we be, consciously aware of these causes? If not, why not? If so, how, and to what avail? The debates among proponents of the various views just noted are more than dry academic affairs; each view suggests a rather different approach to the treatment of people with clinical disorders. This chapter will consider first, and rather briefly, the nature of cognitive therapy and then the emergence and evolution of cognitive science. We will see that the two domains have converged on similar views of cognition and that fruitful collaboration is beginning.