One of Polanyi's most important contributions to critical social science was his insistence that land, labour, and money were fictitious commodities and that the liberal propensity to treat them as if they were real commodities was a major source of contradictions and crisis-tendencies in capitalist development -- so great that society would eventually fight back against the environmentally and socially destructive effects of such treatment. Polanyi wrote during the epoch of industrial and financial capitalism when land, labour, and capital were considered as the primary "factors of production". Contemporary capitalism is widely seen as a knowledge-based economy (or KBE), however, on the grounds that knowledge has become the most important factor of production and the key to economic competitiveness. This raises interesting questions as to whether knowledge is also a fictitious commodity, whether it has been disembedded from wider social relations and whether its disembedding and fictitious commodification also entail a "double movement". This chapter explores these questions and deploys the answers to interrogate Polanyi's analysis of the other fictitious commodities.