  This is a rough sketch, omitting many technicalities, of how the Vaiśeṣika philosophers tried to build their system of categories on logical principles (for an example of such technicalities, see TSD 3(c). The Manual of Reason points out that a substance cannot be defined as the substratum of qualities, because of the Vaiśeṣika doctrine that substances do not possess any qualities at the moment when they are created.)