Because the idea of that which a perfect being exists then so it must. God means such a perfect being. Therefore more than one God cannot logically exist in any fashion nor the concept of no God at all. More than one God would mean perfection over perfection; however, what is what is perfect cannot counter that of it and have more than is perfect. And the belief that a thought is such (i.e. the concept of God ever being created) means that without it the word itself, “God”, should not or could not have existed at all. However it does, which leads us to believe that a being can and does exist.