Peter Munz begins his comparison of the two great twentieth-century philosophers by explaining that since the demise of positivism there have emerged, broadly speaking, two philosophical options: Wittgenstein and Popper. In Our Knowledge of the Growth of Knowledge, first published in 1985, he rejects Wittgenstein, and elaborates the potentially fruitful link between Popper's critical rationalism and Neo-Darwinism. Read in the light of the latter, Popper's philosophy leads to the transformation of Kant's Transcendental Idealism into 'Hypothetical Realism'.