William James 
The Meaning of Truth 

THE pivotal part of my book named Pragmatism is its account of the relation called ‘truth’ which may obtain between an idea (opinion, belief, statement, or what not) and its object. ‘Truth, ‘ I there say, ‘is a property of certain of our ideas. It means their agreement, as falsity means their disagreement, with reality. Pragmatists and intellectualists both accept this definition as a matter of course.
‘Where our ideas [do] not copy definitely their object, what does agreement with that object mean? … Pragmatism asks its usual question. ‘Grant an idea or belief to be true, ‘ it says, ‘what concrete difference will its being true make in any one’s actual life? What experiences [may] be different from those which would obtain if the belief were false? How will the truth be realized? What, in short, is the truth’s cash-value in experiential terms?’ The moment pragmatism asks this question, it sees the answer: TRUE IDEAS ARE THOSE THAT WE CAN ASSIMILATE, VALIDATE, CORROBORATE, AND VERIFY. FALSE IDEAS ARE THOSE THAT WE CANNOT. That is the practical difference it makes to us to have true ideas; that therefore is the meaning of truth, for it is all that truth is known as.