If we cannot find a way to interpret the utterances and other behaviour of a creature as revealing a set of beliefs largely consistent and true by our own standards, we have no reason to count that creature as rational, as having beliefs, or as saying anything.
Donald Davidson (b. 1917), U.S. professor of philosophy; has taught at Berkeley (Chicago,) Rockefeller, Princeton, and Stanford. Dialectica, 27 (1973). Truth and Interpretation, "Radical Interpretation," p. 137, Clarendon Press (1984).