In the mysterious leap from the body to the mind, and vice versa, psychoanalytic writing encounters the same problem that is at the very heart of the conscious/unconscious dichotomy. This dilemma enters into all attempts to describe what supposedly happens along the interface between the two divergent registers at the moment of change from one to the other.

Monique David-Ménard argues in Hysteria from Freud to Lacan that Freud's attempt to bridge this gap was an epistemological failure because he was a 'prisoner of physiology' and hence had to resort to the notion of a 'substance' as the active principle: the 'mystery of conversion' remained just that. She tries to avoid this pitfall by ascribing the changes taking