These familiar considerations do not, indeed, decide the issue between the rival theories of psychology, but they serve to suggest that our introspective psychology has been too easily satisfied in the conception of its specific problem or subject-matter. As a matter of fact, the work that has been done in the name of psychology has been peculiarly barren of results, so far as a consciousness _an sich_ is concerned, although it has led to a wealth of material pertaining to adaptive behavior. Its solid achievements lie in the domain, not of consciousness, but of instinctive, habitual, and intelligent adaptation. It teaches us little that has to do unequivocally with consciousness as distinct from things, but it teaches us much concerning stimulus and response, attention and habit, conflict and adjustment. The doctrine that psychology is a science of behavior is justified at least to the extent that it emphasizes a factor, the importance of which introspectionism has consistently refused to recognize. Whatever conclusion we may ultimately reach regarding the nature of consciousness, the whole drift of psychological and biological investigation seems to indicate that an adequate conception of consciousness and of the distinctive problem of psychology can be attained only on the basis of a painstaking reflection on the facts of behavior. I It is evident that the attempt to ascertain the nature of consciousness and of psychology from the standpoint of behavior is committed to the assumption that the behavior in question is of a distinctive kind. The justification of this assumption will enable us to formulate the definitions which we seek. Discussions of conscious behavior ordinarily emphasize the similarity between conscious and reflex behavior rather than the difference. An attitude of expectancy, for example, is usually conceived as a sort of temporary reflex. Certain nervous connections are organized for the occasion, so that, when a given stimulus arrives, it will induce its appropriate response. This situation is best exemplified, perhaps, in simple reaction-experiments, in which the subject makes a certain predetermined response upon presentation of the stimulus. The process is supposed to be of the reflex type throughout, the only difference being that ordinary reflexes are relatively permanent and unvarying, whereas a prearranged response to a stimulus has to do with a reflex that is made to order so as to meet the exigencies of the moment.