God personally told this one to Moses...right from his own lips...

"Thou shall put no other gods before me" he was so insistant on this that he made it a commandment.

So god himself knows there are other gods. So he must have seen them or heard them to think this, after all he's god, he knows everything.

OH MY GOD...god's as delusional as his followers...even HE has imaginary friends.