This chapter reviews how the early post-Kantians perceived the need of reforming Kant’s Critique in order to complete the philosophical revolution it had initiated. In 1785, Jacobi had brought Spinoza to the discussion, claiming that his monism undermined human freedom and personality. He further claimed that this monism was the logical conclusion of all philosophy. The post-Kantians’ task was thus threefold: (1) to demonstrate that personalism is consistent which monism, which they in principle accepted as the necessary standpoint of reason; (2) to show that Kant’s idealism could be the basis for the desired personalism; and (3) to overcome what they took to be the formalism of Kant’s system that stood in the way of it. All this came down to ridding the system of its presumed unknown “thing-in-itself” while finding a principle that would unify it internally, not just by means of external reflection. Fichte had attempted this with his “I.” Even more important, however, was his analysis of feeling, which he considered the concrete counterpart of the “I” and which, as in the feeling of guilt, brought reason and nature together. This was the synthesis that the post-Kantian idealists explored in their different ways.