DESPITE ITS WIDE INFLUENCE, THE POLITICAL THOUGHT OF KARL POPPER has received, until recently, remarkably little systematic attention from academic political theorists. Hailed by Isaiah Berlin as the most formidable of Marxism's living critics and reviled by Marxists as a prominent luminary of that White Emigration whose pernicious influence is mainly responsible for the ideological rejuvenation of a moribund reactionary culture, canonized as a prophet of freedom and enterprise and lumped together with such despised conservatives as Oakeshott, Namier and Butterfield as one of those who want only ‘to keep that dear old T-model on the road by dint of a little piecemeal engineering’, Popper incontestably has been a storm centre of several major ideological controversies. Equally, Popper's dissident reinterpretations of the thought of Plato and Hegel, like his defence of value-freedom and methodological individualism in the social sciences, have generated massive and subtly ramified literatures, while the form of critical rationalism which has been developed by some of his disciples has been seen, both by its proponents and by its enemies, as the foremost contribution to the contemporary struggle against irrationalism.