Reinhold's elucidation of the "Critique of pure reason" represents one of the first and most fortunate attempts to explain Kant's masterwork to a wider audience - and it is, at a time, its seminal interpretation from an idealistic point of view. This essay focuses on the main kantian doctrines on which Reinhold relied to elaborate his own "Elementarphilosophie". Although Reinhold made explicit that his first aim was a clarification of the kantian position, his result turned out to be actually the edification of an original and autonomous philosophical system. In order to make this passage clear, the essay identifies and analyzes Rheinold's readings of the transcendental "Aesthetics" and "Dialectics" of the first "Critique" as the two most important moments of the final divarication between the two authors. Here comes out most clearly how Reinhold's attempt to give a systematic structure to Kant's doctrines turned out to be a solution for what was in Reinhold's opinion the only relevant weakness of Kant's first "Critique". He actually pointed out its lack not only of a systematic form, but above all of a foundation on a first principle, which he then identified with the "Satz vom Bewußtsein". Such intervention opened the way to Fichte's idealistic interpretation of the transcendental philosophy.