Reinhold's Letters on the Kantian Philosophy is arguably the most influential work ever written concerning Kant. On the basis of the stunning success of the Letters, Reinhold was appointed professor of philosophy at Jena, and his engaging lectures quickly drew unprecedented crowds. Overnight, his teaching turned the small university town into the center of the next generation of German thought and the first professional home of the German Idealists: Fichte, Schelling, and Hegel. It also helped to attract to Jena an extraordinary constellation of writers, including Schiller, Hölderlin, Novalis, and Friedrich Schlegel, who all began to focus on Kant and to react to him in terms of the way that the Critical system was initially presented by Reinhold.

Reinhold's success had its preconditions in Kant's difficulties. When the first edition of the Critique of Pure Reason appeared in 1781, Mendelssohn and Goethe found it impenetrable in form, and the first reviewers harshly criticized its idealist content. In 1783 Kant issued a shorter account of his Critical philosophy in the Prolegomena, but this work is so condensed and so riddled with touchy reactions to criticisms that it did little to improve the early reputation of the Critique.