  The principle is, admittedly, as strong one. Wittgenstein (Tractatus 5.5302) points out that it entails the logical impossibility of a universe containing two identical spheres; Wiggins notes that it implies the logical impossibility of even a single sphere (or any other symmetrical object), since it entails the identity of the two hemispheres (and so on until one reaches a geometrical point). More to the point, as the Vaiśeṣikas implicitly realised, it implies the logical impossibility of more than one atom of a given substance (having a certain velocity, spin, etc.). Rather than reject the principle, however, they instead introduced new intrinsic properties, the basic differentia, thereby avoiding the unpalatable consequence.