Broadly considered, radical interpretation is interpretation of a speaker from scratch—without relying on bilinguals or dictionaries. The term was introduced by American philosopher Donald Davidson (1973) and is meant to suggest important similarity to W. V. O. Quine's radical translation, which is translation of a speaker's language from scratchDavidson, Donald. Radical Interpretation. Originally published in Dialectica, 27 (1973), 314-28. Reprinted in Inquiries into Truth and Interpretation (2n. ed. 125-39). New York: Clarendon Press..

Even more so than radical translation did for Quine, radical interpretation plays an important role in Davidson's work, but the exact nature of this role is up for debate. Some see Davidson as using radical interpretation directly in his arguments against conceptual relativism and the possibility of massive error—-of most of our beliefs being falseLepore, Ernest and Kirk Ludwig. Donald Davidson: Meaning, Truth, Language and Reality. Oxford. 2005.. But Davidson seems to explicitly reject this reading in "Radical Interpretation Interpreted"Davidson, Donald. Radical Interpretation Interpreted. Philosophical Perspectives, 8 (1994), 121-128..

There is also a more narrow and technical version of radical interpretation used by Davidson(see first RII ref): given the speaker's attitudes of holding particular sentences true in particular circumstances--the speaker's hold-true attitudes--, the radical interpreter is to infer a theory of meaning--a truth theory meeting a modified version of Alfred Tarski's Convention T--for the speaker's idiolect. Ernest Lepore and Kirk Ludwig characterize this as inference from sentences of the form:

Ceteris paribus, S holds true s at t if and only if p.

to corresponding T-sentences of the form

s is true (S, t) if and only if q

where s is a sentence is the idiolect of the speaker S, t is a time, and p and q are filled in with sentences in the metalanguage(see first LL ref).

References

---