Edit. Routledge & Kegan Paul Ltd., 1957 London. Tercera edición revisada. 8ºM (22x15cm) 391 págs. Tela editorial con sobrecubierta. Cubierta deslucida, algo rozada con lomo soleado. Muy buen estado general. «This is a work of great interest and significance, stimulating and suggestive throughout, though in some portions extremely irritating… Dr. Popper’s virtues are manifold. He has a scrupulous conscience about exact references… He has a great fertility of ideas. Almost every sentence gives us something to think about. (Professor G.C. Field in Philosophy)»