I argue that it follows from a very plausible principle concerning understanding that the truth of an ascription of understanding is context-relative. I use this to defend an account of lexical meaning according to which full understanding of a natural kind term or name requires knowing informative, uniquely identifying information about its referent. This point undermines Putnam-style 'elm-beech' arguments against the description theory of names and natural kind terms.

It is argued that david lewis' account of convention in "convention" required too much self-Consciousness of parties participating in a convention. In particular, It need not be known that there are equally good alternatives to the convention. This point affects other features of the definition, And suggests that the account is too much guided by the "rational assembly" picture of human conventions. (edited).