Full Idea
Properly construed, the principle of charity is a holistic constraint applying, not to individual beliefs, but rather to systems of belief: we must interpret a speaker so that most of the beliefs in his system are, by our lights, true.
Gist of Idea
The principle of charity is holistic, saying we must hold most of someone's system of beliefs to be true
Source
Alexander Miller (Philosophy of Language [1998], 8.7)
Book Reference
Miller,Alexander: 'Philosophy of Language' [UCL Press 1998], p.271
A Reaction
This is a lot more plausible than applying the principle to individual sentences, particularly if you are in the company of habitual ironists or constitutional liars.