In this paper we present the links that need to be understood and worked out between the management philosophy of the leader and his unconscious processes. The theoretical framework is built on three basic concepts:. request, constraints and choice (variability of practices). The study of the variability of practices calls for other concepts such as the theories of use of the leader. Our contribution is to demonstrate that this concept (theories of use) omits certain dimensions of the subject and which we designate: implicit theory. In short, our study shows that any person, including a leader, has implicit theories and that the latter greatly influence the development of its theories of use; theories which he uses every day in the action for the govern of the business. The in-depth case study aims at supporting this contribution. The management philosophy of the leader is built on ideas, concepts, values, beliefs and convictions. However, these elements are organized and structured at various leveis, namely the cognitive elements, the ideas and the concepts; elements which are influenced by emotional dimensions. That is revealed through the in-depth analysis of a leader's case. In this article we analyze a case that shows the coherence of the management ideas/concepts and the links with the family· history of the leader and his unconscious life (implicit theory).