"Faith" is sometimes thought of as deliberately believing something impossible or untrue, just by an act of will. I've heard people brag about "having faith" in someone they actually know to be totally undependable, or walking into situations that have "disaster" written all over them.
This is not Biblical faith! One of the most powerful verses on the subject is Romans 1:17, where St Paul says speaks of the righteous living by faith. He is quoting the Old Testament prophet Habakkuk, who says it this way: "The righteous shall live by faithfulness". (Habakkuk 2:4) We are not called to blind stupidity, but to deliberate commitment. Faith is better defined as believing on the testimony of someone or something you know to be dependable. This is part of our calling to witness: being faithful people whose story is true.
In God's world, a true story can look impossible! Jesus' followers saw Him do things that were, by the standards of a skeptical world, impossible. We have records of God's having done the apparently impossible throughout His relationship with His people. When God set about moving a whole bunch of people into a promised land, who did He use? The ten guys who believed it couldn't be done, or Joshua, who had been faithful to God's leadership? How likely was it that a bratty little brother who got dropped in a well would become the prime minister of Egypt? Who did God use to build his earthly kingdom--the boy who was willing to face a giant, or his grandson who thought he could outdo his father and believed the wrong advice from the wrong people, and lost the larger part of the kingdom? Or the biggie of them all: using an unjust death to break the power of death--and a resurrection that we believe because there were credible witness that were faithful unto their own deaths.