Believing (or theorizing) in the existence of every god, possibly because of ones opinion that all gods exist somewhere (whether in a spiritual plane, or within ones own mind) because of the belief in them.
This is probably not the only theory, however.
This belief system is widely used by practitioners of chaos magick, due to their practice of adopting a religious aspect and believing in one god (or spiritual being, fictional character, whatever the chaote chooses) for a particular spell, then changing aspect for a new spell.
"What religion are you?"
"I take no religious path, although I am a spiritually conglomotheist."
"Ah, I'm a christian."
"In that case, please take your retardation elsewhere."