At the end of 1922 Lenin was prompted by a sudden deterioration of his health to write his political testament. In it he declared that although Nikolai Bukharin was "the biggest and most valuable theoretician of the party," nevertheless "his theoretical views can only with the greatest doubt be regarded as fully Marxist, for there is something scholastic in him (he has never learned, and I think has never fully understood dialectics)."i Stephen E. Cohen's recent study2 has provided a comprehensive history of Bukharin's political career, making it appropriate now to explore the meaning of Lenin's comment and thus to assess the significance of Bukharin as a Marxist theorist. In the present essay, following Lenin's criticism, an effort will be made to interpret Bukharin's major theoretical writings from a methodological point of view. This approach, beginning with a brief exposition of Lenin's own use of the dialectical method, will make it possible to compare the works of the two men on several common themes and thus to determine the theoretical and practical origins of their differences. According to Lenin both the material world and all social existence are characterized by dialectical contradictions. "The identity of opposites," he wrote in his Philosophical Notebooks, "... is the recognition (discovery) of the contradictory, mutually exclusive, opposite tendencies in all phenomena ..."" While Lenin suggested that the concept of the identity of opposites expressed "the essence of dialectics,"4 in his investigation of any concrete social totality he invariably undertook a much more subtle and far-reaching study than this summary phrase might suggest. At a time when most other prominent Marxists, including Kautsky, Luxemburg, and Plekhanov, oriented their theoretical writings mainly on the principal contradiction of capitalist society that between the proletariat and the bourgeoisie, as social classes Lenin held that society could only be properly understood as a complex of heterogeneous relations. The principal contradiction, in other words, only assumed practical political significance through a careful analysis of its numerous specific and particular manifestations. As Lenin remarked: "Dialectics calls for a many-sided investigation into a given social phenomenon in its development, and [only then] for the external and seeming to be reduced to the fundamental motive forces, to the development of the class struggle. "5 To focus attention exclusively upon the principal contradiction was, in Lenin's