Male pubescent sexual theories (P.S.T.) are characterized on the one hand, by being rooted in the first orgasmic experiences, wherein the release of excitation, of sperm and of germinal cells are condensed; and on the other hand, by their evolution towards different theories about fluids, one of which is economical. This transformation is followed here in an adult patient. The opposite path leads us to hypothesize that Freud’s economical theory could be derived from these pubescent sexual theories.