Kant's Neglected Alternative and the Unavoidable Need for the Transcendental Deduction

The problem of Kant's Neglected Alternative is that while his Aesthetic provides an argument that space and time are empirically real - in applying to all appearances - its argument seems to fall short of the conclusion that space and time are transcendentally ideal, in not applying to any things in themselves. By considering an overlooked passage in which Kant explains why his Transcendental Deduction is 'unavoidably necessary', I argue that it is not solely in his Aesthetic but more so in his Deduction where he intends to provide his argument for the transcendental ideality of space and time. His Deduction shows that space and time do not have a valid application to any things in themselves by arguing that the categories do have a valid application to everything in space and time, but that the categories do not have a valid application to any things in themselves.