According to Fichte, Kant’s greatest merit was in his discovery and establishment of Transcendental Idealism (whereby the emphasis is on Idealism). … In other words, Kant elucidated that the idea determines the object and not that the object determines the idea (unlike the assumption of the British Empiricism). Our knowledge does not derive from the external world, but no doubt being related to the external world, our knowledge possesses the universal and necessary validity (as the criterion of its truth) by means of our reason (our mind or consciousness).

In other words, Kant “divorced” the pursuit of knowledge (=philosophy) from its immersion in the external world (nature) and brought philosophy back to the inquiry into the Self itself or consciousness.