Full Idea
A creature cannot have a thought unless it is an interpreter of the speech of another.
Gist of Idea
A creature doesn't think unless it interprets another's speech
Source
Donald Davidson (Thought and Talk [1975], p.9)
Book Reference
'Mind and Language', ed/tr. Guttenplan,Samuel [OUP 1977], p.9
A Reaction
His use of the word 'creature' shows that he is perfectly aware of the issue of whether animals think, and he is, presumably, denying it. At first glance this sounds silly, but maybe animals don't really 'think', in our sense of the word.