Analogy: knowing how lungs work allows us to know what the air must be like for breathing, without the air being constituted by or an appearance of lung-function.

6. It is then partly because of the apparently rather special nature of these transcendental claims, that the suspicion arises that there will then turn out to be something distinctively Kantian about such arguments; for Kant made it the focus of his critical project to account for metaphysical knowledge of this sort, where transcendental idealism is then supposed to provide the answer to how such knowledge is possible. The idea, roughly speaking, is that it is too much for us to be able to know