Lev Tikhomirov (1852–1923) was one of the active members of the narodnichestvo movement. From 1879 he was a member of the Executive Committee of “Narodnaya Volya” party. After the assassination of Alexander II by the members of “Narodnaya Volya” and defeat of the party, he went abroad, where, together with P. Lavrov, he edited the "Journal of Narodnaya Volya”. In 1888, in Paris, his pamphlet Why I Ceased to Be a Revolutionary was published, where he criticized the revolutionary path of development. In the meantime Tikhomirov send a petition to Alexander III, in which he expressed remorse for his previous activities and requested permission to return to Russia (which was granted). In monarchist Russian Tikhomirov became one of the leading writers of the conservative camp, and from 1909 to 1913 headed the newspaper “Moscow News”. Being an author of historical and philosophical works and memories, for decades he was considered a renegade who betrayed a revolutionary struggle. In recent years works of Tikhomirov as a monarchist started to arouse a significant interest. However, only the study of all the major events of his life and philosophical evolution can reveal the originality of Tikhomirov’s views as revolutionary and as conservative. These events are reflected in his diary. Tikhomirov kept the diary for over 30 years. Shortly before his death he gave it to the Rumyantsev Museum, where they are preserved today. However, Tikhomirov’s diary virtually unknown to the public.