This article presents an initial approach to the philosophical problems at the ground of the discussion between Jacobi and Fichte at the end of the nineteenth century. I begin with a discussion of Jacobi's criticism against Fichte. I analyse both Jacobi's conception of Fichte's philosophy as nihilism and Jacobi's idea of the relationship between reason and nature. I then present the different answers Fichte offers in 1799, 1804, 1807 and 1812-13. As a conclusion I present some considerations about the modern idea of freedom and autonomy of reason as it can be founded in Fichte's philosophy.