In this paper, I provide a history of Kant's extensive experimentation with the doctrine of the schematism. I claim that diverse interpretations of schemata—as syntheses or intuitions; as attributable to the imagination or to the understanding; even as wholly incomprehensible—mark specific stages in Kant's own thought, and that the changes in the doctrine reflect changes in the very idea of transcendental philosophy. Ultimately, I argue that the instability here lies at the heart of Kant's critical project: the schematism plays an (...) essential role in securing its most basic presupposition, but it is difficult to account for within that project. This is a problem that Kant recognizes and grapples with directly, without completely resolving it to his own satisfaction. (shrink)