Full Idea
The truth of P-and-Q is (roughly) a function of the truth of P and the truth of Q; but the consistency of P&Q isn't a function of the consistency of P and the consistency of Q.
Gist of Idea
P-and-Q gets its truth from the truth of P and truth of Q, but consistency isn't like that
Source
Jerry A. Fodor (LOT 2 [2008], Ch.4.5 n33)
Book Reference
Fodor,Jerry A.: 'LOT 2: the Language of Thought Revisited' [OUP 2008], p.121
A Reaction
This is a nice deep issue. Fodor is interested in artificial intelligence at this point, but I am interested in the notion of coherence, as found in good justifications. Even consistency isn't elementary logic, never mind coherence.