To each according to his contribution was a concept espoused by many members of the socialist and labor movement. Examples of this can be found from Ferdinand Lassalle's and Eugen Dühring's statements to Leon Trotsky's writings. However, it was Vladimir Lenin, inspired by Marx's writing on the subject in his Critique of the Gotha Programme, who claimed the principle to be a fundamental element of socialism within Marxist theory.[3]