I argue on linguistic grounds that when Mary comes to know what it's like to see a red thing, she comes to know a certain inexpressible truth about the character of her own experience. This affords a "no concept" reply to the knowledge argument. The reason the Knowledge Argument has proven so intractable may be that we believe that an inexpressible concept and an expressible concept cannot have the same referent.

[[This paper appears in my anthology _Philosophy of Mind: Classical and Contemporary Readings_ (Oxford University Press, 2002), pp. 608-633. It is a heavily revised version of a paper first written in 1994 and revised in 1995. Sections 1, 7, 8, and 10 are similar to the old version, but the other sections are quite different. Because the old version has been widely cited, I have made it available (in its 1995 version) at http://consc.net/papers/content95.html.