Kant-the five senses and noumena From Terry Pinkard's book: German Philosophy 1760-1860
The distinction between “things-in-themselves” and “noumena” is tricky. The former are the things that are the unknowable sources of our sensible intuitions; the latter are concepts of the world as intelligible to reason alone, apart from any experience, and a rerepresentations of certain “wholes” or supersensible objects that traditional metaphysics thought could be grasped by reason alone. As such, noumena function as limiting concepts, as reminders and cautions about the impossibility of extending rational accounts of the world in ways that contradict the conditions under which those accounts can be given.