It has been shown above (B. I, Chap. XIII) that there is one first of beings, possessing the full perfection of all being, whom we call God. Out of the abundance of His perfection He bestows being on all things that exist; and thus He proves to be not only the first of beings, but also the first principle of all. He bestows being on other things, not out of any necessity of his nature, but by the free choice of His will, as has been shown (B. II, Chap. XXIII). Consequently He is master of the things that He has made: for we have dominion over the things that are subject to our will. This His dominion over the things that He has brought into being is a perfect dominion, since in producing them He needs the aid of no exterior agent, nor any subject matter to work upon, seeing that He is the universal efficient cause of all being. Of the things produced by the will of an agent every one is directed by that agent to some end: for some good and some end is the proper object of the will: hence the things that proceed from will must be directed to some end. Everything attains its last end by its own action, which is directed by Him who has given to things the principles whereby they act. It needs must be then that God, who is by nature perfect in Himself and by His power bestows being on all things that are, should be the ruler of all beings, Himself ruled by none: nor is there anything exempt from His government, as there is nothing that does not derive being from Him. He is then perfect in government, as He is perfect in being and causation.
The effect of this government appears variously in various natures according to the difference between them. Some creatures are brought into being by God to possess understanding, to bear his likeness and present His image. They not only are directed, but also direct themselves by proper actions of their own to their due end. If in the direction of themselves they remain subject to the divine guidance, they are admitted in course of that guidance to the attainment of their last end. Other beings, devoid of understanding, do not direct themselves to their own end, but are directed by another. Some of those are imperishable; and as they can suffer no defect in their natural being, so in their proper actions they never deflect one whit from the path that leads to the end prefixed to them, but are indefectibly subject to the rule of the prime ruler.* Other creatures are perishable, and liable to the failure of their natural being, which however is compensated by the gain of another: for the perishing of one is the engendering of another. In like manner in their proper actions they swerve from the natural order from which swerving however there accrues some compensatory good. Hence it appears that even apparent irregularities and departures from the order of the first rule escape not the power of the first ruler. These perishable bodies, created as they are by God, are perfectly subject to His power.
The Psalmist, filled with God's spirit, considering this truth , and wishing to point out to us the divine government of things, first describes to us the perfection of the first ruler, -- of His nature, when he says God; of His power, when he says, is a great Lord,* needing no co-operation to work the effect of His power; of His authority, when he says a great king above all gods, because, though there be many rulers, all are subject to His rule. Secondly he describes to us the manner of government, -- as well in respect of intelligent beings, which follow His rule and gain from Him their last end, which is Himself, and therefore he says, for the Lord will not reject his people, -- as also in respect of perishable beings, which, however they sometimes depart from their proper modes of action, still are never let go beyond the control of the prime ruler: hence it is said, in his hands are all the ends of the earth, -- likewise in respect of the heavenly bodies, which exceed all the height of the earth and of perishable bodies, and always observe the right order of divine rule: hence he says, and the heights of the mountains he beholdeth. Thirdly he assigns the reason of this universal control, which is, because things created by God needs must be ruled by Him: hence he says, For the sea is his, etc.
Since then in the first Book we have treated of the perfection of the divine nature, and in the second of the perfection of God's power, it remains for us in this third Book to treat of His perfect authority, or dignity, in as much as He is the last end and ruler of all things. This therefore will be our order of procedure, to treat first of God, as the final end of all things; secondly of His universal control, whereby He governs every creature; thirdly of the special control which He exercises in the government of creatures endowed with understanding.
2.101 : Whether to Separately Subsisting Intelligences all parts of their Natural Knowledge are simultaneously present
3.2 : That every Agent acts to some End