‘Without a revolutionary theory, there can be no revolutionary movement.’ — Lenin V.I. Lenin (1870–1924) took forward Marxist theory and practice in critical areas. Imperialism, the Highest Stage of Capitalism (1916) opened the strategic path for the revolutions of the twentieth century. The State and Revolution (1917) explained the necessity for the seizure of state power by the proletariat and for the replacement of the old state by a new state apparatus dominated by the proletariat. Two Tactics of Social Democracy in the Democratic Revolution (1905) pioneered the new strategic perspective of dovetailing the bourgeois-democratic revolution with the socialist revolution under the leadership of the working class. An equally important and crucial contribution by Lenin was his theory of organisation. Organisation, for Lenin, was not a technical question or a tactical issue. Organisation was integral to revolutionary theory. What is to be Done? (written in 1901 and published in 1902) elaborates on how an appropriate organisation alone can translate revolutionary theory into a revolutionary movement. Prakash Karat’s Introduction explains the main arguments of Lenin’s thick pamphlet — his critique of an over-reliance on spontaneity in the working class struggles, which marks out the terrain of Economism; his elaboration of the idea of democratic centralism in party organisation; his idea of the vanguard, a party consisting of an advanced detachment of the working class. What is to be Done? is a core text that every student of Marxism and revolution must study.