Immanuel Kant

A distinction between phenomena and noumena - phenomena being that which can be experienced, and noumena being things that are beyond the possibility of experience - things in themselves. Nothing can be truly experienced or else you would experience the noumena itself. The phenomena is only the representation of the object/noumena that a person receives through their sensibilities. The phenomena is a representation of an object not the object itself, nothing more. Kant then discussed and expanded on the faculties of experience we have, and thus was able to come up with a system of metaphysics that applied to the world as we perceive it.