Yes. The world is governed by one because the government of the world must be the best kind of government; but the best government is the government by one.
Mundus gubernatur ab uno quia necesse est quod mundi gubernatio sit optima; optima autem gubernatio est quae fit per unum.
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 formal aspect 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.
Cuius ratio est, quia gubernatio nihil aliud est quam directio gubernatorum ad finem, qui est aliquod bonum. Unitas autem pertinet ad rationem bonitatis, ut Boetius probat, in III de Consol., per hoc quod, sicut omnia desiderant bonum, ita desiderant unitatem, sine qua esse non possunt.
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.
Nam unumquodque intantum est, inquantum unum est, unde videmus quod res repugnant suae divisioni quantum possunt, et quod dissolutio uniuscuiusque rei provenit ex defectu illius rei. Et ideo id ad quod tendit intentio multitudinem gubernantis, est unitas sive pax. Unitatis autem causa per se est unum.
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.
Manifestum est enim quod plures multa unire et concordare non possunt, nisi ipsi aliquo modo uniantur. Illud autem quod est per se unum, potest convenientius et melius esse causa unitatis, quam multi uniti. Unde multitudo melius gubernatur per unum quam per plures. Relinquitur ergo quod gubernatio mundi, quae est optima, sit ab uno gubernante.
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."
Et hoc est quod philosophus dicit in XII Metaphys., "entia nolunt disponi male, nec bonum pluralitas principatuum, unus ergo princeps".