A year before his death, B.F. Skinner wrote that "There are two unavoidable gaps in any behavioral account: one between the stimulating action of the environment and the response of the organism and one between consequences and the resulting change in behavior. Only brain science can fill those gaps. In doing so, it completes the account; it does not give a different account of the same thing." This declaration ended the epoch of radical behaviorism to the extent that it was based on the doctrine of the "empty organism," the doctrine that a behavioral science must be constructed purely on its...