Read the following passage and reflect on the questions below
This complete solution of the Humean problem, though coming out contrary to the surmise of the originator, thus restores to the pure concepts of the understanding their a priori origin, and to the universal laws of nature their validity as laws of the understanding, but in such a way that it restricts their use to experience only, because their possibility is founded solely in the relation of the understanding to experience: not, however, in such a way that they are derived from experience, but that experience is derived from them, a completely reversed type of connection that never occurred to Hume.
From this now flows the following result of all the foregoing investigations: “All synthetic a priori principles are nothing more than principles of possible experience,” and can never be related to things in themselves, but only to appearances as objects of experience. Therefore both pure mathematics and pure natural science can never refer to anything more than mere appearances, and they can only represent either that which makes experience in general possible, or that which, being derived from these principles, must always be able to be represented in some possible experience or other.
64-65