Johann Gottlieb Fichte (May 19, 1762 - 1814) has significant importance as one of the progenitors of German idealism and as a follower of Kant.
Fichte believed that Kant was mistaken to argue for the existence of noumena, of things as they are, not just as they are perceived through the categories of human reason. Fichte saw the rigorous and systematic separation of "things as they are" (noumena) and things "as they appear to be" (phenomena) as an invitation to skepticism.
Rather than invite such skepticism, Fichte made the radical suggestion that we should throw out the notion that there is a noumenal world and instead accept the fact that consciousness is not grounded in a so called "real world." In fact, Fichte is famous for originating the argument that consciousness is not grounded in anything outside of itself. This notion eventually becomes the defining characteristic of German Idealism and is thus essential to understanding the philosophy of Hegel, and Arthur Schopenhauer, though they both reject Fichte's notion that human consciousness is itself sufficient ground for experience, and therefore postulate another "absolute" consciousness.