Here are some thoughts on the nature and validity of faith by Wolfhart Pannenberg.
I found these in Systematic Theology, Volume 3. (There is no Kindle edition for that yet — sorry to say.)
Faith is a form of the way we relate to truth, and is comparable in this regard to knowledge. In Hebrew the terms for “truth” (’emet) and “faith” (he’emin) are linguistically related, deriving from the same root. Truth in the sense of ’emet is what is constant and therefore trustworthy, so that we can build on it. He’emin denotes the confidence that establishes itself on the basis of that which is constant, so that those who have it achieve steadfastness and constancy. But only God and his Word and works are fully stable and trustworthy (Ps. 111:7-8; 119:90-91; 146:6; etc.). Hence, those who would be firmly established themselves must be established in God.