This article discusses Kant's transcendental idealism in relation to his perplexing use of ‘body’ and related terms in Prolegomena §13. Here Kant admits the existence of bodies external to us, although unknown as what they might be in themselves. It is argued that we need to distinguish between a phenomenal and a noumenal use of ‘body’ to make sense of Kant's argument. The most important recent discussions of this passage, i.e., Prauss, Langton and Bird, are presented and shown to suffer (...) from both systematic and exegetical shortcomings. The article is a contribution to understanding the nature of Kant's transcendental idealism, defending the view, especially against Prauss and Bird, that Kant is committed to the existence of things in themselves. (shrink)