Even if you are a self-proclaimed "skeptic", and only believe in things you can prove, you still have faith. You assume you won't get in a car accident on the way home, you assume the sun will rise in the morning even though it is hid from you at night, you assume the logic you used to prove something is infallible despite the fact that we don't know everything about our world yet. You have faith that your science is perfect, the world will continue on as you believe it will, and that you will live another day. You can't "prove" any of the things we assume and because of that everyone has faith in something. The difference is that Christians have faith in a God that created the world, created us, and created knowledge.
"Now faith is being sure of what we hope for and certain of what we do not see."
- Hebrews 11:1
[concept from Jay Beckley, pastor of Stone Creek Bible Church]