  Some Naiyāyikas, especially Bhāsarvajña and Raghunātha, reject the ‘cross-connection’ impediment, pointing out the problems encountered trying to apply it to non-biological natural kinds (e.g. redness and greenness overlap, as do pothood and goldhood). Raghunātha suggests that consistent application of this principle would eliminate virtually all universals from the ontology. Udayana’s criterion of a property to be ‘natural’ is thus not a necessary one, and neither is it sufficient: none of his impediments shows why the pair ‘blue-green’ is more natural than Goodman’s pair ‘grue-bleen’ (where x is grue iff x is green and examined before time t, and is blue otherwise, and vice versa for bleen.)