Summa contra Gentiles3.91 Chapter XCI. How human affairs may be referred to higher causes

From what has been proved we are able to gather how human affairs are to be referred to higher causes, and do not happen by chance.

For acts of choice and will are under the immediate governance of God. Human knowledge pertaining to the intellect is directed by God through angelic intermediaries. While things pertaining to the body, whether internal or external, and adapted to man’s use, are governed by God by means of the angels and heavenly bodies. There is one general reason for this. Because every thing that is multiform, changeable and defectible must be referred to a principle that is uniform, unchangeable and indefectible. And every thing connected with us is multiform, changeable and defectible.

For it is clear that our choice is made in many different ways: since different people choose different things in different circumstances. Again our choice is changeable: both through the instability of the mind which is not firmly fixed on the last end; and because things themselves change in the midst of which we live. That man’s choice is defectible is proved by his sins. On the other hand the divine will is uniform, since by willing one he wills all things, and is unchangeable and indefectible, as we proved in the First Book. Therefore all movements of will and choice must be traced to the divine will: and not to any other cause, because God alone is the cause of our willing and choosing.

In like manner our intelligence is manifold, since from many sensible objects we gather into one, as it were, the intelligible truth. It is also changeable since by discoursing it passes from one thing to another, from the known to the unknown. Again it is defectible, through admixture of imagination and sense, as the errors of men testify.'—-On the other hand the cognition of the angels is uniform, because they receive the knowledge of truth from the one fount of verity, namely God. It is also unchangeable, because they see the truth about things, not by discoursing from effects to cause or vice versa, but by simple intuition. It is also indefectible, since they see intuitively the very natures or quiddities of things in themselves, about which the intellect cannot err, as neither can the senses about their proper sensible objects: whereas we gather the nature of a thing from its accidents and effects. Therefore our intellectual knowledge must be ruled by the knowledge of the angels.

Again, as to human bodies and the external things of which men make use, it is evident that they are blended together and contrary to one another in many ways: also that they are not always moved in the same way, because their movements cannot be continual: and that they are defectible by alteration and corruption.—Whereas heavenly bodies are uniform, being simple and devoid of all contrariety. Also, their movements are uniform, continual and unchangeable. Nor can there be corruption or alteration in them. Consequently our bodies and whatever else serves for our use must be ruled by the movements of the heavenly bodies.