The paper discusses Vladimir Solovyov’s philosophical concept of unity (fullness of knowledge) and the philosopher’s contribution to the formation of professional philosophy in Russia in the second half of the 19th century. We have analyzed the arguments of Solovyov’s master’s thesis, directed against the positivist programme of development of scientific knowledge. We have identified the issues associated with the development of science and humanities common for Solovyov and our time. We have examined the relationship of religious attitudes, philosophical and scientific knowledge. We have clarified the role of practical (moral) philosophy in the general conceptual context of Solovyov’s philosophy. We have detected the importance of Solovyov’s philosophy for the prospects of modern humanitarian knowledge. It is concluded that thanks to Solovyov’s philosophy the relation of philosophy, religion and science (positive knowledge) appears as a positive model for their possible interconnection. We have analyzed Solovyov’s attitude towards Nietzsche’s philosophy and towards the philosophy of Socrates and Plato, detailed in the “Life drama of Plato” and in his articles in the philosophical section of the Brockhaus and Efron dictionary.