John Locke also formed one of the few coherent philosophical structures for the concept of faith that I've ever seen. He tried to justify it as an acceptable chain of evidence. His example was the proposition "The angels rebelled." How can we determine the truth of this proposition? We can have no direct evidence, so if it is to be believed, it must be accepted on the basis of faith. But what does faith amount to? He argued that we can have reason to believe the people who translated the Bible, and that we implicitly trust that they had good reason to believe the document they received was an acurate recording, and so on up the line, until the final person, who has to be trusted to know he is receiving the word of God. I don't entirely buy it, but it is an interesting argument nonetheless.