Freud defines the notion of drive as a barrier concept between psychic and physical and sets up their first links based on the model of anxiety. He distinguishes physical sexuality from psychic sexuality. For him, the expression of physical anxiety could be the result of an insufficient link between physical and psychic, thus involving the differentiation between two forms of neurosis; actual neurosis and psychoneurosis. In the first theory of drives, the ego gets its development through a specific psychic action which allows the emergency of narcissism following the evolution of auto-erotism based on the somatic. So the ego becomes also psychosexual obtaining its independency towards its bodily origins and functions. Freud kept up thinking about the physical origins till the end of his work and within the second drive theory.