Abstract
This article challenges three widespread assumptions about Kant’s argument for the antithesis of the Second Antinomy. The first assumption is that this argument consists of an argument for the claim that “[no] composite thing in the world consists of simple parts”, and a logically independent argument for the claim that “nothing simple exists anywhere in the world”. The second assumption is that when Kant argues that “[no] composite thing in the world consists of simple parts”, he is making a claim about the mereological structure of spatially extended things in particular, as opposed to a claim about the mereological structure of things in general. And the third assumption is that Kant’s argument for this part of the antithesis is based on a claim about the relationship between the size of the extension of a composite thing and the sizes of the extensions of the things of which this composite thing consists.