Full Idea
The principle of charity says that it is unavoidable that the pattern of sentences to which a speaker assents reflects the semantics of the logical constants.
Gist of Idea
The principle of charity says an interpreter must assume the logical constants
Source
Donald Davidson (Truth and Predication [2005], 3)
Book Reference
Davidson,Donald: 'Truth and Predication' [Belknap Harvard 2005], p.62
A Reaction
That is not all the principle says, of course. Davidson seems to assume classical logic here, with a bivalent semantics. I wonder if all speakers use 'false' in the normal way, as well as 'true'? Do all languages even contain 'true'?