Reply Obj. 1: It is part of the best agent to produce an effect which is best in its entirety; but this does not mean that He makes every part of the whole the best absolutely, but in proportion to the whole; in the case of an animal, for instance, its goodness would be taken away if every part of it had the dignity of an eye. Thus, therefore, God also made the universe to be best as a whole, according to the mode of a creature; whereas He did not make each single creature best, but one better than another. And therefore we find it said of each creature, "God saw the light that it was good" (Gen. 1:4); and in like manner of each one of the rest. But of all together it is said, "God saw all the things that He had made, and they were very good" (Gen. 1:31).
Reply Obj. 2: The first effect of unity is equality; and then comes multiplicity; and therefore from the Father, to Whom, according to Augustine (De Doctr. Christ. i, 5), is appropriated unity, the Son proceeds to Whom is appropriated equality, and then from Him the creature proceeds, to which belongs inequality; but nevertheless even creatures share in a certain equality—namely, of proportion.
Reply Obj. 3: This is the argument that persuaded Origen: but it holds only as regards the distribution of rewards, the inequality of which is due to unequal merits. But in the constitution of things there is no inequality of parts through any preceding inequality, either of merits or of the disposition of the matter; but inequality comes from the perfection of the whole. This appears also in works done by art; for the roof of a house differs from the foundation, not because it is made of other material; but in order that the house may be made perfect of different parts, the artificer seeks different material; indeed, he would make such material if he could. _______________________
THIRD ARTICLE [I, Q. 47, Art. 3]
Whether There Is Only One World?
Objection 1: It would seem that there is not only one world, but many. Because, as Augustine says (QQ. 83, qu. 46), it is unfitting to say that God has created things without a reason. But for the same reason He created one, He could create many, since His power is not limited to the creation of one world; but rather it is infinite, as was shown above (Q. 25, A. 2). Therefore God has produced many worlds.
Obj. 2: Further, nature does what is best and much more does God. But it is better for there to be many worlds than one, because many good things are better than a few. Therefore many worlds have been made by God.
Obj. 3: Further, everything which has a form in matter can be multiplied in number, the species remaining the same, because multiplication in number comes from matter. But the world has a form in matter. Thus as when I say "man" I mean the form, and when I say "this man," I mean the form in matter; so when we say "world," the form is signified, and when we say "this world," the form in the matter is signified. Therefore there is nothing to prevent the existence of many worlds.
On the contrary, It is said (John 1:10): "The world was made by Him," where the world is named as one, as if only one existed.
I answer that, The very order of things created by God shows the unity of the world. For this world is called one by the unity of order, whereby some things are ordered to others. But whatever things come from God, have relation of order to each other, and to God Himself, as shown above (Q. 11, A. 3; Q. 21, A. 1). Hence it must be that all things should belong to one world. Therefore those only can assert that many worlds exist who do not acknowledge any ordaining wisdom, but rather believe in chance, as Democritus, who said that this world, besides an infinite number of other worlds, was made from a casual concourse of atoms.