faith - the substance of things hoped for, the evidence of things not seen.

you believe in the wind eventhough you can't see it physically. wind can be seen in a way though. you see the effects. things blowing around, etc.
i believe in God although i can't see him physically. i can see the effects. God has changed my life. he does miracles. he heals people.

people don't want to believe in God. they don't want to change the way they think. they don't want to change the way they live. stubbornness doesn't get you anywhere.