  From Plato until Kant, Nativism was supposed to serve Realism.  Whatever the vision of reality was – Forms for Plato, matter and mind for Descartes, etc. – our grasp of that reality was possible because we were provided with a map to that reality before we set out. Kant rejects the Realist aspirations of this tradition. For him, we can never understand the ultimate nature of things as they are in themselves. Our theoretical knowledge can only go as deep as the structure we impose. The only necessity we can grasp is the one we have spontaneously made.