Is there a non-occult faith that believes God and Satan are the same entity?

I've always felt God and Satan are the good and dark sides of the same entity. It's the only thing that makes sense to me, and if it is true, you know the organized religions, especially Christianity, wouldn't want their followers to know, so they would deny it. Since I've been getting into sorcery, I've been reading about old sorcerers who worship both, pray to both and do both white and black magic. I know Christians would blow a fuse at the very idea, but are there any organized religions, past or current, that believe Satan is the Left Hand of God?