Full Idea
We understand under what circumstances to say of any given statement that it is true, just as clearly as we understand the statement itself.
Gist of Idea
If we understand a statement, we know the circumstances of its truth
Source
Willard Quine (Mr Strawson on Logical Theory [1953], II)
Book Reference
Quine,Willard: 'Ways of Paradox and other essays' [Harvard 1976], p.142
A Reaction
This probably shouldn't be taken as a theory of meaning (in which Quine doesn't really believe) but as a plausible statement of correlated facts. Hypothetical assertions might be a problem case. 'If only I could be in two places at once'?