Kant and Arthur Schopenhauer (1788-1860) are two key influences.
Kant proposes that the mind organizes experience but, as noted above, his system raises the problem of the noumenon or the thing-in-itself:
concepts transform intuition and thereby determine t้he way things appear to us
but they do not have access to things as they are in themselves behind appearances.
Much post- Kantian philosophy tries to overcome this divide, and various attempts are made to reconcile or equate the two realms.
Hegel offers one reply, as we have seen, and Schopenhauer provides another