Last week in Lenin in a Year, we delved into an important text that Lenin wrote amidst the 1905 Revolution: Two Tactics of the Social-Democracy in the Democratic Revolution. The revolution, however, went down to defeat. In the wake of the counter-revolution, all kinds of pessimism and mysticism swept Russia. These moods even infected layers of the Bolsheviks, reflected in attempts to revise Marxist philosophy. This week we republish Alan Woods’ excellent introduction to Lenin’s 1908 work, Materialism and Empirio-criticism, in which Lenin launched a strident defence of dialectical materialism.