Biblical faith is not a "leap in the dark"; it is not a "blind" entity; it is not a contentless sense of well-being; it is not an ambiguous feeling of conviction; it does not begin with content derived from human sources; and it is not the result of wanting something so badly that it just "has" to happen.
So, what is it? In a nutshell, faith is a fundamental acceptance of something God has actually said.
Fundamental means several things. First, it means that the acceptance actually affects the emotional stability of the person who "believes" because fundamental acceptance gets down to the level of understanding that exists beneath feelings. Second, it means that the acceptance involves the myriad issues of truth, the most critical being that the acceptance actually sets up the anticipations regarding what is, or is about to become. And third, it means that the mind/heart complex has been rearranged to include what has been "believed" into the resident world-view of the "believer".
Acceptance also means several things. First, it means that the mind has exalted the content of what is "believed" over contrary claims and evidences. When contrary opinions exist, and no conclusion has been drawn as to their relative accuracy, faith does not exist. Faith is a commitment to specific content that unseats other content. Second, it means that the emotions are now being dominated by the content. It is foolishness to say that "I believe" something if there is no corresponding reality in the realm of my emotions. In fact, emotions were created by God as an aid to helping us determine what we really do believe because we are so adept at deluding ourselves at the mental level. Third, it means that the volition is now being directed by the reality that has been accepted. It is also foolish to say "I believe" when the will is still making choices that are contrary to the content "believed".
The phrase "something God has actually said" is, perhaps the most important part of this definition. We are continually exhorted to "believe", as if that was all there was to it. Often, sports teams are told "You gotta believe!" as a motivation to give their best efforts. But the question must arise: Believe what? When it comes to biblical faith, the answer is always "whatever it is that God has said". It is never "whatever it is that you want so very badly". It is never "whatever the human who claims to be speaking for God says". It is never "the machinations of a confused mind that hears all manner of voices from within making reality claims as a basis for the choice that is looming on the horizon". The object of biblical faith is always the biblical God, and the biblical God only expects to be believed when He has said something. If God has not spoken, there is nothing to believe; and if He has spoken, what He has said supercedes all other claims that purport to define reality.
In our generation, our adversary has smoked up the battlefield of faith so badly that the words "I believe" seldom carry truth these days. When we do not know something for sure, we say "Well, I believe that...". No, we simply think it may be possible that.... That is a common distortion of the word "believe". Then we say "I believe..." while biting our fingernails and fretting through the night. Another lie. We also say "I believe" when what we really mean is that "I want this very badly so I am comforting myself with the possibility that it could happen...". Another delusion. Biblical faith has the words of God as its content, and it accepts those words as the functional definition of reality.