Full Idea
A private attitude is not intelligible except as an adjustment to the public norms provided by language. It follows that a creature must be a member of speech community if it is to have the concept of belief.
Gist of Idea
Concepts are only possible in a language community
Source
Donald Davidson (Thought and Talk [1975], p.170)
Book Reference
Davidson,Donald: 'Inquiries into Truth and Interpretation (2nd ed)' [OUP 2001], p.170
A Reaction
This obviously draws on Wittgenstein's private language argument, and strikes me as blatantly wrong, because I take higher animals to have concepts without language. Pure vision gives rise to concepts. I don't even think they are necessarily conscious.