In "History and Class Consciousness" (1923), György Lukács started from the theory of commodity fetishism for his development of reification (the psychological transformation of an abstraction into a concrete object) as the principal obstacle to class consciousness. About which Lukács said: "Just as the capitalist system continuously produces and reproduces itself economically on higher levels, the structure of reification progressively sinks more deeply, more fatefully, and more definitively into the consciousness of Man"—hence, commodification pervaded every conscious human activity, as the growth of capitalism commodified every sphere of human activity into a product that can be bought and sold in the market. (See: "Verdinglichung", Marx's theory of reification.)