There are those who demand 'proof' that God exists before they will believe in Him, and those who claim to have 'proof' that He doesn't exist.
I just found this little mathematical trick which shows that 'proof' is not necessarily infallible - I'm not a mathematician, but it all makes sense to me.
Theorem : 2 + 2 = 3
Suppose: a + b = c
This can also be written as: 4a - 3a + 4b - 3b = 4c - 3c
After reorganising: 4a + 4b - 4c = 3a + 3b - 3c
Take the constants out of the brackets: 4 * (a+b-c) = 3 * (a+b-c)
Remove the same term left and right: 4 = 3
Therefore, if 2 + 2 = 4, then 2 + 2 = 3
The point is that once you have a hypothesis, it's very easy to 'prove' it one way or another. But God doesn't ask us to believe because we have proof - He asks us to believe because we have faith.