FOURTH (THIRD) ARTICLE: WHETHER THERE IS ONLY ONE WORLD

State of the question. We are inquiring here about the fact, not the possibility, of the numerical unity of the world. It seems that there are many worlds: 1. because God could create many worlds; 2. because many worlds would be better than one, since many goods are better than a few; 3. as man is multiplied, the world ought also be multiplied. Democritus thought that many worlds resulted from the concourse of the atoms. The question asked here is not the same as that about the plurality of worlds in the sense of the stars being inhabited. The opinion that the stars or plants are inhabited is not contrary to the conclusion of this article, since the stars and planets and everything that moves in them constitute one universe.

Reply. St. Thomas' reply is that the world is unique.

1. This is proved from the language of the Scriptures: "The world was made by Him."[923]

2. It is proved also from the divine ordination to one and the same end. All the things that are from God have a relation to one another and to God Himself, that is, all things are coordinated and subordinated and thus constitute a complete whole, which is called the universe. The unity of the world, therefore, is a unity of order.

Reply to first objection. From the unity of order existing in things, Aristotle reached the conclusion that God the governor is one: "Beings are averse to being ill disposed, and a plurality of principles is not good. Therefore there is but one principle."[924] This text of Aristotle is adduced to prove that for him God is not only the ultimate end of the world, attracting all things to Himself, but also the governor, at least of the genera and species if not of individuals, as Averroes contended. From this argument it also follows that by His ordered power God cannot make many worlds without some relation to one another; they must at least be coordinated with regard to the same ultimate end, since it is the part of a wise being to put things in order.

Reply to second objection. No agent intends a material plurality as an end because a material multitude does not have a definite terminus and because it can always be increased; the material multitude must be ordered to something higher as matter is ordered to the form. From this it follows that there would be no reason for God to create two similar worlds only numerically distinct. We may ask why two worlds rather than three or four or more?

Reply to third objection. St. Thomas says: "It is not possible that there be another earth besides this one because every earth would be borne naturally to the same middle point," that is, to the center of the world. This is the opinion of the ancients proposed by Aristotle, but it was not proved.[925] Cajetan says that St. Thomas was speaking not of an absolute impossibility but of a physical impossibility under the present laws of the universe according to the Ptolemaic system.

Doubt. Whether God could create two unequal worlds? This does seem to be impossible because such worlds would be subordinated by reason of their inequality.