"Theism" is the belief that there is one being who is all-powerful, all-knowing, all-loving, and who created all that exists. David Hume objected to the theistic paradigm. Hume especially responded to the design argument for God's existence, as that argument was formulated at the time. One of Hume's criticisms is that the design argument cannot lead us to the belief that only one God created the universe. He writes: "Nor can we attribute unity to the original cause of the universe on the basis of any analogy to human artifacts such as houses; as they are often built by a number of people working together. Perhaps, therefore, there is more than one God involved in the creation of the universe?" (Dialogues Concerning Natural Religion, 68-69)
Hume's "perhaps" is correct, but we need not follow it in order to be rational in our theistic belief. It is true that, in building a house, often more than one person is involved. But this is not necessarily so. Paley's "watch" example might serve us better here, since ordinarily a single watchmaker makes a watch. During Hume's time should we see a watch and ask "Who made it?" we expect that some individual person did. A single watchmaker is sufficient to explain the existence of a watch.
Analogously, if there is an all-powerful, all-knowing being, then such a being is sufficient to create a universe. No more gods need be posited. Using Ockham's Razor, it is not necessary to multiply causes unnecessarily. One Supreme Being will do. It is therefore rational to believe that such is the case. Just as, for example, while the pan of warm brownies on our kitchen table could have been made by ten people, nonetheless it is rational to believe they were made by only one person; in this case, my wife Linda.
If Hume's possible multiple gods were all omnipotent and omniscient, it is hard to see just what the difference would be between these many Supreme Beings and one Supreme Being, since they would all "be on the same page" when it comes to a knowledge of universe-making. If Hume's multiple gods were finite in power and knowledge, and furthermore if some of them were not loving, then we should expect the universe to look much different than it does today. For the issue is not simply the creation of our universe, but its design. One might, in such a case, expect to see far more diversity in our universe than uniformity.
