Historical novel of the 20-ies of the XIX century is based on a new philosophy of history dealing with the problems of the meaning of history, its laws, the main directions of human development and historical knowledge. An important moment in the new philosophy of history is the principle of unity. History is perceived as a single process. The change of epochs is the sequence of stages of a single evolution. Each epoch is prepared by previous development and is the cause of the following stages. All historical epochs are bound by this law of unity, and many processes that remain incomprehensible to contemporaries have found their meaning for descendants. Conversely, many modern events can only be understood with regard to previous events. This is the so-called principle of "history lessons". These ideas formed the basis for the works of Walter Scott, Alfred de Vigny, Alexander Dumas and other authors of historical novels. The article analyzes the works of Vico, Herder, Guizot, Thierry, Cousin, Michelet and the influence that French romantic historiography had on the historical novel.