Full Idea
True ideas are those that we can assimilate, validate, corroborate and verify. False ideas are those that we cannot.
Gist of Idea
True ideas are those we can assimilate, validate, corroborate and verify (and false otherwise)
Source
William James (Pragmatism - eight lectures [1907], Lec 6)
Book Reference
James,William: 'Pragmatism - eight lectures' [Dover 1995], p.77
A Reaction
The immediate question is why you should label something as 'false' simply on the grounds that you can't corroborate it. Proving the falsity is a stronger position than the ignorance James seems happy with. 'Assimilate' implies coherence.