Full Idea
You do not improve the truth value of a false proposition by calling attention to a coherent system of propositions of which it is one.
Gist of Idea
A false proposition isn't truer because it is part of a coherent system
Source
Richard Cartwright (Intro to 'Philosophical Essays' [1987], xi)
Book Reference
Cartwright,Richard: 'Philosophical Essays' [MIT 1987], p.-16
A Reaction
We need to disentangle the truth-value from the justification here. If it is false, then we can safely assume that is false, but we are struggling to decide whether it is false, and we want all the evidence we can get. Falsehood tends towards incoherence.