I answer that, We must of necessity say that the world is governed by one. For since the end of the government of the world is that which is essentially good, which is the greatest good; the government of the world must be the best kind of government. Now the best government is the government by one. The reason of this is that government is nothing but the directing of the things governed to the end; which consists in some good. But unity belongs to the idea of goodness, as Boethius proves (De Consol. iii, 11) from this, that, as all things desire good, so do they desire unity; without which they would cease to exist. For a thing so far exists as it is one. Whence we observe that things resist division, as far as they can; and the dissolution of a thing arises from defect therein. Therefore the intention of a ruler over a multitude is unity, or peace. Now the proper cause of unity is one. For it is clear that several cannot be the cause of unity or concord, except so far as they are united. Furthermore, what is one in itself is a more apt and a better cause of unity than several things united. Therefore a multitude is better governed by one than by several. From this it follows that the government of the world, being the best form of government, must be by one. This is expressed by the Philosopher (Metaph. xii, Did. xi, 10): "Things refuse to be ill governed; and multiplicity of authorities is a bad thing, therefore there should be one ruler."
Reply Obj. 1: Movement is "the act of a thing moved, caused by the mover." Wherefore dissimilarity of movements is caused by diversity of things moved, which diversity is essential to the perfection of the universe (Q. 47, AA. 1,2; Q. 48, A. 2), and not by a diversity of governors.
Reply Obj. 2: Although contraries do not agree with each other in their proximate ends, nevertheless they agree in the ultimate end, so far as they are included in the one order of the universe.
Reply Obj. 3: If we consider individual goods, then two are better than one. But if we consider the essential good, then no addition is possible. _______________________
FOURTH ARTICLE [I, Q. 103, Art. 4]
Whether the Effect of Government Is One or Many?
Objection 1: It would seem that there is but one effect of the government of the world and not many. For the effect of government is that which is caused in the things governed. This is one, namely, the good which consists in order; as may be seen in the example of an army. Therefore the government of the world has but one effect.
Obj. 2: Further, from one there naturally proceeds but one. But the world is governed by one as we have proved (A. 3). Therefore also the effect of this government is but one.
Obj. 3: Further, if the effect of government is not one by reason of the unity of the Governor, it must be many by reason of the many things governed. But these are too numerous to be counted. Therefore we cannot assign any definite number to the effects of government.
On the contrary, Dionysius says (Div. Nom. xii): "God contains all and fills all by His providence and perfect goodness." But government belongs to providence. Therefore there are certain definite effects of the Divine government.