The following essay tries to explain the concept of Dianoematics in Gueroult’s thinking. The core of this theory is constituted by the original solution of the problem concerning the relationship between truth and reality, philosophy and history. Gueroult refuses any kind of philosophy of history and tries to justify the manifold of philosophical systems present in history as conceptual creations with eternal validity. Therefore, he distinguishes the reality of common experience from the superior reality of the philosophical systems and proposes a new kind of method for the history of philosophy.