W. Sady’s book Struktura rewolucji relatywistycznej i kwantowej w fizyce [The Structure of the Relativist and Quantum Revolutions in Physics] is discussed. In his analysis of the history of physics of XIX and early XX centuries the Author argues, contrary to Kuhn, that grand discoveries result as conclusions from certain assumptions and suitably selected pieces of background knowledge. I point to major Sady’s inspirations — Wittgenstein, Wiśniewski and Fleck — and the kinship of his account to hinge epistemology and my sandwich theory of knowledge. His view on the social nature of knowledge and the role of mathematics is commented upon. In conclusion I suggest that the tension between Sady’s antirealism and traditional truth requirement for knowledge can be resolved by a suitable modification of Ajdukiewicz’s radical conventionalism.