This paper offers an analysis of Fichte’s reception of Kant’s idea of transcendental philosophy focussing on the influence of this idea on the development of Fichte’s Doctrine of Science (Wissenschaftslehre). It is argued that the Kantian idea of transcendental philosophy proposes a concept of philosophy that in fact corresponds with Fichte’s concept of philosophy as Wissenschaftslehre, i.e. philosophy as unity of gnoseology and metaphysics. Furthermore, it is shown that Fichte’s reception and interpretation of Kant occurs in the line of a critical prolongation of the transcendental perspective; and that the horizon of thought within which Fichte reads and accepts the novelty of Kant’s philosophy is opened thanks to the postulation of the primacy of practical reason, i.e., the recognition of the central role of freedom in critical philosophy. Accordingly, the Doctrine of Science represents neither an overcoming nor an alternative to transcendental philosophy. The Doctrine of science must be understood rather as transcendental philosophy completely systematized and clarified in its intrinsic principles.