That, is where a leap of faith really comes in. You can't believe in god or gods without first having faith that they do exist without actual, concrete proof, or a reason why they do exist. They simply are there, and you just have to trust it if you're religious or reject it if you're not. Most people do attribute multiple gods to the idea of some kind fo birth from a larger, more ubiquious, but more apathetic god/being/entity. But where THAT god comes from is largely up in the air. In the Life of Pi, the author write that atheism is just as well a faith as well, because even that demands that the atheist takes a leap of faith into assuming that there is no god, even though there is some evidence that one might exist.