Kant's Fracturing in Realness

Kant is trying to deal with this fracturing in realness that descartes has left, right? And the two sides, the inner subjective mind touching itself. How how do i get those together? cant comes up with a really radical proposal. He calls it a copernican revolution. It's as important as copernica's revolution of the external world. That's why many people who are realists in mathematics formally and explicitly label themselves as platonists.