Kant employs the term ‘aesthetic’ first in his Critique of Pure Reason as a means of clarifying the general conditions of experience. He develops the notion of a ‘transcendental aesthetic’ to indicate an a priori dimension of experience. There is on the one hand experience that relates specifically to our interaction with the world via our sensible organs. This is linked to the traditional Ancient Greek meaning of the term ‘aesthetic’ as relating to the senses. There is on the other hand a plane of experience that exceeds the senses. The ‘transcendental aesthetic’ has its basis not in sense as such, or in any relation to the external world, but in terms of the appearance of things to the native grounds of consciousness. It refers to the sensing of a level of generality that is unconditioned by the senses. It is an interior plane of sensation that involves the appearance of the a priori as the fundamental capacity for space-time consciousness/experience.
Key here is that the transcendental is general. It relates to no specific, contingent form of experience, but to experience generally. It is not something that is generalised from experience, or that results from experience, but rather something that shapes our capacity to experience anything whatsoever. In this sense, the transcendental character of experience cannot be based in experience per se, but pertains instead to its underlying conditions. Yet at the same time, this other, inner realm must also appear. It must somehow be represented – here not by ordinary sensibility, but instead at some meta-sensible level. This is the paradoxical conception of the ‘transcendental aesthetic’, which at once both distances the a prior character of space time consciousness from sense, but also acknowledges that it must somehow be presented to us.
As I have explained, Kant clarifies that he is employing the term ‘aesthetic’ in its traditional sense of pertaining to the senses. He distinguishes this from the modern German sense of the aesthetic as pertaining to the ‘critique of taste’ (CPR, p.60). Subsequently, in the Critique of Judgement, Kant will discover means of mediating between these two meanings, and specifically of demonstrating the transcendental character of the experience of the beautiful, which emerges not as a consequence of experience per se, but from an internal free play of the faculties of imagination and understanding. This complicates any initial sense that Kant moves from a general to a more specific and restricted use of the term. It is tempting to suggest, for instance, that the ‘transcendental aesthetic’ relates to the conditions of all consciousness, whereas the later aesthetic of the sublime and beautiful relates to a specialised form of experience separate from properly epistemological and ethical concerns. The other possibility, however, is that the two senses closely correspond. Both are concerned with the mysteries of an internal plane of appearance and intuition that establishes the core frame of human identity and freedom. From this perspective, the aesthetic of the Critique of Judgement is a more focused examination of the transcendental aesthetic of the Critique of Pure Reason. And if Kant would like to restrict the implications of the former, it is because they so deeply affect the conception of the latter. The the two notions of the aesthetic are less neatly distinct than intimately entangled.