sentences:  Lenin, Tschernow and Basarov confront the views of Ludwig Feuerbach, Joseph Dietzgen and Friedrich Engels and comment on the criterion of practice in epistemology.Lenin seeks to define "matter" and "experience" and addresses the questions of causality and necessity in nature as well as "freedom and necessity" and the "principle of the economy of thought".Lenin deals with left and right Kant criticism, with the philosophy of immanence, Bogdanov's empiri-monism, and the critique of Hermann von Helmholtz on the "theory of symbols."