It is no secret that Fichte believed that the only legitimate starting point for any philosophical system worthy of the name was the standpoint of subjectivity itself, what Fichte called “I-hood [Ichheit]. Knowing this, it is easy to see why Fichte was suspicious of any and all attempts to establish a philosophical system on a contrary foundation, that is to say, on concept of objectivity, or ‘nature’. What should come as a surprise then is that no sooner than Fichte had articulated his system of philosophical science – his Wissenschaftslehre – and had won followers to his system that the very same followers attempted to derive a new philosophical system that was to be no less scientific than Fichte’s own but that would begin not with the concept of the I at is foundation but with that of nature. Instead of the subject as prius we have the object as origin. For, at least in its inception, Naturephilosophie was intended not as a substitute for Fichte’s Wissenschaftslehre but as its logical culmination. Just as Kant’s transcendental idealism was presented not as a rival science to Newton’s Principia but as its condition of possibility, so too was Schelling’s Naturephilosophie presented as an exploration of the conditions of the possibility of Fichte’s Science of Knowledge.
Why, then, did Fichte reject the very notion of a Naturephilosophie out of hand? An answer should begin by contemplating the following possible explanatory reasons:
i) nature is not an independent concept but is only thinkable in relation to an I
ii) this relation of nature to the I is one of metaphysical subordination even though these concepts are equally and mutually foundational from a logical point of view
iii) nature has no external check on which it could exert its free activity; freedom needs an ‘outside’; but pure objectivity has no ‘beyond’.
iv) if nature itself is free then the function of the summons becomes superfluous (because the latter only works if a level of uncertainty is involved; my ability to do otherwise is conditioned by my ability to apply different concepts to the same particular including myself. My rational faculties only become transparent to themselves when they are stirred to activity without being caused to any particular activity. In this way, the summons operates on analogy with the feeling of beauty in Kant and Schiller. Notice how both aesthetic experience and the summons involve a surrender to the object which one cognizes as autonomous.)