This thesis has two purposes. The first is to offer a critique of existing accounts of knowledge in contemporary capitalism. On the one hand, knowledge-based models of new growth theory are criticised for privileging some aspects of knowledge whilst endogenising it on the basis of a neoclassical framing; many restrictions are placed upon knowledge, in general, and its utilisation and diffusion, in particular. On the other hand, the bold argument of cognitive capitalism theory, that contemporary capitalism is undergoing a transition to a new stage of capitalism and therefore Marx’s value theory has lost its validity, is shown to be based on flawed understandings of value theory. Externalities play essential roles in both new growth theory and cognitive capitalism theory, each being a theory of use value, although there is no place for externalities as such in Marx’s value theory. Especially, for cognitive capitalism theory, unpaid life activities are seen to contribute significantly to production, with surplus being appropriated by capital as rent, which can and should be re-appropriated as basic income. The latter is, however, understood in cognitive capitalism theory as factor remuneration derived from the production of surplus products and, in this respect, it has an affinity with neoclassical economics despite its purported commitment to Marx’s method. The second purpose is to incorporate the role of knowledge into Marx’s value theory in a consistent and coherent manner. Criticising the two contending approaches in the South Korean controversy on the value and price of information commodities, this thesis puts forward an alternative based on a structural distinction between knowledge and commodities. It is demonstrated that knowledge affects the determination of the productivity and complexity of (collective) commodity-producing labour within and across sectors, respectively, and therefore takes part in the determination of the value of commodities. This social process of virtual multiplication of labour is a relatively abstract formulation of the role of knowledge in contemporary capitalism, but it also provides a logical foundation upon which more concrete and complex, and constructive, theories of knowledge can be built.