logic . if man could creat GOD man could creat life itself. and man could have created the universe because universe is not as big as GOD and if man can create GOD man can create any thing. wouldnt need to search for anything.
HE is real. more real than reality itself. and we will know for sure when we die. why not before that ? so that we know finally how much we did really believe.
it's a matter of trust, like we trust our friends?