Physics tells us what is objectively there. It has no place for the colours of things. So colours are not objectively there. Hence, if there is such a thing at all, colour is mind-dependent. This argument forms the background to disputes over whether common sense makes a mistake about colours. It is assumed that..

we explore the view that defines rigidity of general terms as sameness of designation across possible worlds. On this view, a general term is rigid just in case it designates the same universal (species, substance or property) in every possible world. This view has been proposed most notably by Bernard Linsky, Nathan Salmon and more recently by Joseph LaPorte, and it has been criticised by several philosophers, including Stephen Schwartz and Scott Soames.

A highly condensed account of the author's present view of some philosophical problems unresolved in The Structure of Scientific Revolutions. The concept of incommensurability, now considerably developed, remains at center stage, but the evolutionary metaphor, introduced in the final pages of the book, now also plays a principal role.