In order to understand the internal genesis and development of Plekhanov's epistemology, it is now necessary to show how his readings and reflections on previous philosophers' thought had influenced his own thinking. Since studying philosophy had always meant a great deal to Plekhanov, it is not surprising that he carried on philosophical studies all through his life. A contemporary stated that Plekhanov knew the classical materialists' and Hegel's works almost by heart.¹ His many notebooks, now kept in the">Dom PlekhanovaLibrary, provide us with a unique opportunity to read Plekhanov's own marginalia, thereby reconstructing his searching and conclusions.