The notion of faith for most people who call themselves faith-based has nothing to do with any logical or spiritual definition of faith--in fact, it's usually the opposite.

Faith quite simply is a mode of perception. In the same way that the five senses allow sentient beings to perceive sensory data from the physical world, faith allows the individual to perceive data from the non-physical (metaphysical) realm.

Now it's entirely possible that there is no reality other than the physical world. But that doesn't change the essence of the concept of faith. If there is a a world other than the physical world, then faith is the means by which we perceive it. If there is no world other than the physical world, then nothing will allow you to perceive what doesn't exist, but in any case, the five senses / scientific observation certainly won't, because they don't deal with metaphysics, so you may as well relegate faith to the empty set of "modes that explain the non-physical world."

Now when your average "oh by jingo" Christian claims to espouse faith, they actually mean something more akin to "superstition" (i.e. the denial of sensory perception as a way to understand the world.) An assertion like "If you do X you will go to heaven" is simple superstition, as is "If you do Z, you will go to hell." It's like saying "I have faith that I'll win the lottery with the ticket I just bought." If you think that there is a benevolent divine force at work in the world, it should be because you have perceived that particular benevolent force at work in the world, not because some "holy" book tells you that this such a force exists.

Most religions that I'm familiar with (except maybe Buddhism, which some Buddhists would argue is not a religion) believe that there is some way to apprehend the non-physical world. But fundamentalist Christians, in my view, don't have a bat's chance of going beyone the physical world because they don't even understand the physical world with their heads buried deeply in the sand of irrationality, let alone anything beyond that world.