5 These things, then, being so, each deity will be contented with his own possessions, and will not be moved with any curiosity respecting the affairs of others; otherwise he would be unjust, and rapacious, and would cease to be what God is. Each creation, too, will glorify its own maker, and will be contented with him, not knowing any other; otherwise it would most justly be deemed an apostate by all the others, and would receive a richly-deserved punishment. For it must be either that there is one Being who contains all things, and formed in His own territory all those things which have been created, according to His own will; or, again, that there are numerous unlimited creators and gods, who begin from each other, and end in each other on every side; and it will then be necessary to allow that all the rest are contained from without by some one who is greater, and that they are each of them shut up within their own territory, and remain in it.
No one of them all, therefore, is God. For there will be [much] wanting to every one of them, possessing [as he will do] only a very small part when compared with all the rest. The name of the Omnipotent will thus be brought to an end, and such an opinion will of necessity fall to impiety.
Source: Adversus haereses (New Advent)