In the thirteen century, Aristotle became all the rage among European intellectuals. Aristotle had a systematic way of viewing universe as well as a compelling system of logic. But God played a very minor role in Aristotle’s system: Aristotle said there was an unmoved mover, the first cause (which medieval theologians took to be God) that had set the universe in motion. But God played no role in Aristotle beyond that. Aristotle argued that the rules that governed the universe  were there by necessity and he also argued that there was only one universe/world . This bothered medieval thinkers of the time because it seem to suggest that even if God wanted to create multiple universes/worlds, He could not. This all came to a head in 1277, when a massive condemnation of Aristotle was issued : article 34 stated that it was heresy to believe “that the first cause [i.e God] could not make several worlds.”  Thus the possibility of God creating multiple worlds/universes was needed to preserve God’s omnipotence, even though most thinkers assumed that God, in actuality, had probably only created one world/universe.
It’s interesting to see that atheist scientists have used multiple universes to get around the anthropic principle (that the universe is uniquely designed to support life, that if any of numerous factors were only slightly different there could be no life in the universe). People see the anthropic principle as proof of the existence of God, and atheist scientist argue that multiple universes could get around the issue because if there are billions (or whatever number) of universes then perhaps we are a lucky universe (one in a billion) in which, by random, all the right factors happened to come together.
Going from needing multiple universes to prove God’s majesty, to needing multiple universes to disprove it strikes me a rather ironic.
 This was the pre-Copernian view of the universe with the earth at the center, with a bunch of “planets” revolving around it, and then the starts beyond that. Pre-moderns often referred to this whole thing as the “world” as well as the universe. “Planets” meant wanderer because they were the heavenly objects that moved in an irregular pattern compared to the stars. It wasn’t until after Copernicus that intellectuals began to see that the plants would be “earths” or that the earth was a “planet.”
 Aristotle had insisted that there could be only one universe in opposition to pre-Socratics who had speculated about the possibility of multiple universes.
 Aristotle remained very influential despite this condemnation.
 Edward Grant, “Cosmology,” in Science in the Middle Ages, ed. David D. Lindberg (Chicago: University of Chicago Press, 1978), 280. Scholars even speculated that the other worlds/universes might have different laws, such as the possibility of there being a vacuum between planets (something Aristotle said was impossible). 280.
 Mormons seem to be pretty fine with multiple universes because between Moses 1 where God said he created worlds without number and the King Follett discourse where Joseph Smith suggested there were lots of gods, one would suspect that considerable space was needed for all these creative gods (like lots of universes).