Kant's account of mathematics has been one of the most debated topics in the recent literature. It amounts to a complicated matter Kant bequeathed to philosophy. Since Kant's time, several philosophers have been trying to disentangle the Kantian claims on the nature of mathematical sciences. The issue of the synthetic a priori is the stumbling block, insofar as it grounds the general structure of Kant's portrait of human knowledge. Different proposals critics have put forward so far incline to overestimate logical or geometrical reasons in the attempt at fi nding out why Kant considered mathematics and geometry as synthetic a priori sciences. Conversely, this book aims at taking transcendental facets of critical project seriously. An epistemological analysis of the role of the notion of synthetic a priori is the principle clue. The outcome might sound a bit heterodox but aims at giving Kant his due.