The best proof that E. H. Carr has written a true ‘classic’ is that The Twenty Years' Crisis provides much food for thought even now when some of its alleged foundational verities have become problematic. Rather than being limited to a ‘realist’ understanding of politics pure and simple, the reader encounters an analysis that is much more subtle though much less scientific than later realist interpretations would suggest. True, the first chapter is entitled ‘The science of international politics’ but the discussion about ‘purpose’, Carr's invocation of Marx, and the intellectual history he paints with a broad brush, make it clear that it is not a conception of natural science that informs his inquiry. Besides, as with every classic, different readings are possible.