Philosophy of Neo-Kantism, differing from Kantism in modifying the a priori and rejecting the thing in itself.
Lange thus transmuted inconsistent Kantism into a consistent Neo-Kantism, consisting of these reformed positions: (1) we start with sensations in a priori forms; (2) all things known from these data are mental phenomena of experience; (3) everything beyond is idea, without any corresponding reality being knowable.
To Kantism itself a consistency, which, however, has only succeeded in producing a new.
Having, however, made a deduction, which is at all events consistent, that on Kantian assumptions all we know is mental phenomena, Lange proceeded to reduce the rest of Kantism to consistency.
It is most important also to notice that Kantism denies, but science asserts, the logical power of reason to infer actual things beyond experience.
Hence the doctrine of Kant, that Nature as known to science is phenomena, means one thing in Kantism and another thing in science.