This chapter examines different aspects of cognitive studies before tackling the question of movement which seems to the true object of the physiology of the brain. Two principal concepts govern cognitive studies: conditioned reflexes and cognition. Mechanistic thinking from Descartes to current-day cognitivism is constituted, in fact, by a current of thought dating back to the seventeenth and eighteenth centuries which gave rise to reflex theory. Reflex theory is an integral part of neuroscience. Like the system of reflexes, Freud concluded, the psychical apparatus is also directional. Freud's psychical apparatus conformed, both in form and essence, to the Pavlovian theory of the nervous system. Sherrington succeeded in establishing the integrative properties of the central nervous system, whose intervention is commanded by the reflex on each occasion. By focusing on the formal and abstract properties of cognition, cognitive psychology leaves aside entirely the content of sensible knowledge, relegating it to the void of a subjectivity whose existence it refuses to accept.