This chapter discusses the philosophical importance of Lenin's thought. It reevaluates Lenin's philosophical legacy by examining his major and perhaps most controversial philosophical work, Materialism and Empiriocriticism. A sympathetic yet critical assessment of the work offered in this chapter reveals important details about Lenin's version of Marxism, bringing into light his contributions to philosophical thought, such as the defense of materialism against idealism, the rigorous advocacy of dialectical approach to reality, and the ability to identify and, to some extent, overcome problems of previous philosophy, particularly positivism. The chapter also reconstructs the historical context in which Lenin's book was written and discusses the political and social situation to which it responds.