The Transcendental Aesthetic is concerned with sensibility, and thus with objects in so far as they are sensed (the Greek root ‘aesthesis’ denotes the capacity for sense perception). Its focus, however, is principally on space and time, regarding which its first central claim is that space and time provide the sensible form of experience, and on that account play a fundamental role in making objects possible. This sets space and time apart from other elements in sense experience. Kant formulates this claim in thoroughly technical terms: space and time are said to be ‘pure a priori intuitions’ ‘forms of intuition’ and ‘forms of appearance’. The second central claim of the Aesthetic is that space and time are not features of absolute reality but only ‘forms of sensibility’, elements of our subjective cognitive constitution, and that everything that has spatial or temporal properties - all the objects of our experience - are mere appearances as opposed to things in themselves. This, the first of Kant’s two promised proofs of transcendental idealism, will be discussed in the next chapter.