Philosophy in the Soviet Union was officially confined to Marxist–Leninist thinking, which theoretically was the basis of objective and ultimate philosophical truth. During the 1920s and 1930s, other tendencies of Russian thought were repressed (many philosophers emigrated, others were expelled). Joseph Stalin enacted a decree in 1931 identifying dialectical materialism with Marxism–Leninism, making it the official philosophy which would be enforced in all Communist states and, through the Comintern, in most Communist parties. Following the traditional use in the Second International, opponents would be labeled as "revisionists". From the beginning of Bolshevik regime, the aim of official Soviet philosophy (which was taught as an obligatory subject for every course), was the theoretical justification of Communist ideas. For this reason, "Sovietologists", among whom the most famous were Józef Maria Bocheński, professor of philosophy at the Pontifical University of Saint Thomas Aquinas and Gustav Wetter, have often claimed Soviet philosophy was close to nothing but dogma. Since the 1917 October Revolution, it was marked by both philosophical and political struggles, which call into question any monolithic reading. Evald Vasilevich Ilyenkov was one of the main philosophers of the 1960s, who revisited the 1920s debate between "mechanicists" and "dialecticians" in Leninist Dialectics and Metaphysics of Positivism (1979). During the 1960s and 1970s Western philosophies including analytical philosophy and logical positivism began to make a mark in Soviet thought. Philosophical and political struggles in the Soviet Union Dialectical materialism was initially expounded by Karl Marx and Friedrich Engels; one of the early works on the subject is Engel's 1878 polemic Anti-Dühring. It was elaborated by Vladimir Lenin in Materialism and Empirio-criticism (1908) around three axes: the "materialist inversion" of Hegelian dialectics; the historicity of ethical principles ordered to class struggle; and the convergence of "laws of evolution" in physics (Helmholtz), biology (Darwin) and political economy (Marx). Lenin hence took position between a historicist Marxism (Labriola) and a determinist Marxism, close to what was later called "social Darwinism" (Kautsky). Lenin's most important philosophical rival was Alexander Bogdanov (1873–1928), who tried to synthesize Marxism with the philosophies of Ernst Mach, Wilhelm Ostwald, and Richard Avenarius (which were harshly criticized in Lenin's Materialism and Empiriocriticism). Bodganov wrote a treatise on "tectology" and was one of the founders of Proletkult after the First World War. Following the 1917 October Revolution, Soviet philosophy divided itself between "dialecticians" (Deborin) and "mechanists" (Bukharin, who would detail Stalin's thesis upheld in 1924