Hayek's theory of knowledge is his greatest achievement, and offers insights that should be utilised by both right and left, but he failed to apply them to one of the central aspects of the modern era - the way science and technology are utilised in increasingly perverse ways by a deregulated neo-liberal market economy, which if not checked will have devastating consequences for the biosphere and the survival of the human species. It is an example of how his market fundamentalism blinds him to conclusions to which his own analysis of markets should have led him. If he had followed the logic of his own argument, he might have arrived at a rather different view of the appropriate balance between the state and the market, and provided a more searching account of the nature and limits of government action, or as Keynes would have put it, between the agenda and the non-agenda of government. The resources for doing so are there within Hayek's thought, which remains a seminal contribution to modern social theory, but he chose not to develop his ideas in this direction because of his ideological commitment to market fundamentalism. That should not prevent others from doing so. It is increasingly urgent that we should.