The works of Karl Leonhard Reinhold (1757–1823) were a major factor in the development of post-Kantian philosophy, yet his exact contribution is still under discussion. This book investigates how Reinhold’s background in Enlightenment influenced his reception of Kant‌’s critical philosophy. From his pre-Kantian efforts up to the point where he began distancing himself from the master, Reinhold’s own philosophical development takes center stage. This development, rather than critical philosophy, was the main ingredient of Reinhold’s contribution to post-Kantian philosophy.