Karl Leonhard Reinhold (1757-1823), Austrian philosopher and first occupant of the chair on Critical Philosophy established at the University of Jena in 1787, first achieved fame as a proponent of popular Enlightenment and as an early and effective popularizer of the Kantian philosophy. During his period at the University of Jena (1787-94), Reinhold proclaimed the need for a more “scientific” and systematic presentation of the Critical philosophy, one based upon a single, self-evident first principle. In an effort to satisfy this need, he expounded his own “Elementary Philosophy” in a series of influential works between 1789 and 1791. Though Reinhold's Elementary Philosophy was much criticized, his call for a more coherent and systematic exposition of transcendental idealism exercised a profound influence upon the subsequent development of post-Kantian idealism and spurred others (such as J. G. Fichte) to seek a philosophical first principle even more “fundamental” than Reinhold's own “Principle of Consciousness.” After moving to the University of Kiel, Reinhold became an adherent, first of Fichte's Wissenschaftslehre and then of C. G. Bardili's “rational realism,” before finally proposing a novel “linguistic” approach to philosophical problems.

http://plato.stanford.edu/entries/karl-reinhold/
http://de.wikipedia.org/wiki/Carl_Leonhard_Reinhold