Аннотация:The article investigates political and legal views on the separation of powers theory, its commencement, development and adoption of the classical shape. Prior to the well-known classical doctrine the separation of powers theory underwent some evolutionary changes. But for relying on the inheritance of the ancient and medieval thinkers, this theory wouldnt have such a firm basis. The article focuses on the views of the founder of the theory, Charles de Montesquieu, analyzes some works of his successors and opponents, and suggests periodization of the theory.