“Now faith is the assurance of things hoped for, the conviction of things not seen.  For by it the people of old received their commendation.  By faith we understand that the universe was created by the word of God, so that what is seen was not made out of things that are visible.” (Hebrews 11:1-3 (ESV)
“Faith is the assurance of things hoped for, the conviction of things not seen.” Often when I ask what faith is I get this verse in response. It is kind of odd. I say that because it is only one aspect of what faith is, but these days the verse is sort of abused by many. What happens is we read Kierkegaards “leap of Faith” into the word faith wherever it is written into scripture. We read faith, but we hear blind faith.” Then we turn faith into a work, our leap into the unknown, holding a position despite any evidence to the contrary, or despite evidence for it! People actually get a little scared that if they hear a solid argument for faith, they might lose faith.
Now, faith is a gift of God, and it is the assurance f things hoped for, and also the conviction of things not seen. There are things I believe in, that I have never seen, such as the 6 day creation of the world. Faith in that conviction has led me to question the epistemological arguments for and against the faith, and also for and against evolution. Now I used the term “epistemological” for a reason. This is the name for that philosophical discipline that deals with “knowledge.” The question is “How do you know, what you know?’ However the root of the word is Pistis, Greek both for knowledge, and faith. There wasn’t really a difference in Greek. You believed what you knew, you could believe facts, have faith in them.
So it is with the Christian faith. I have reason for believing what I do. No, I can’t prove something like the Trinity from anything other than the Biblical literature. But an historical argument for the validity of the resurrection, does give me reason to believe Jesus Christ and his word’s concerning the Trinity. And having reason to believe, based in historical fact, does not negate that I have faith. Doubting Thomas had much reason for believing after he touched the wounds of Christ, yet he believed. I don’t get to touch the wounds, so perhaps I don't see as he did. That is not really the point. Faith isn’t despite knowledge and reason, but is supported by knowledge and reason. And it still saves, because it wasn’t your work to begin with.