Summa contra Gentiles3.82 Chapter LXXXII. That the inferior bodies are ruled by God by means of the heavenly bodies

| Just as in intellectual substances some are of higher and some of lower degree, so too arethere in corporeal substances. Now intellectual substances are governed by higher sub- stances, so that the disposition of divine providence may reach down proportionately to the lowest things, as we have already said. Therefore in like manner bodies of lower degree are ruled by those of a higher.

- Again. The higher a body is as regards its place, the more formal it is: hence it is reasonably the place of a lower body, because form contains even as place does; thus water is more formal than earth, air than water, fire than air. Now the heavenly bodies have a higher place than all others. Therefore they are more formal and consequently more active than all other bodies. Therefore they act on lower bodies: and consequently the latter are ruled by them.

_ Besides. That which in its nature is perfect without contrariety, is of more universal power than that which in its nature is not perfected without contrariety: because con- trariety arises from differences which determine and contract the genus: wherefore in the conception of the intellect, forasmuch as it is universal, the species of contraries are not contrary to one another, since they coexist in the intellect.

Now the heavenly bodies are perfect in their respective natures without any contrariety: for they are neither light nor heavy, neither hot nor cold: whereas the inferior bodies are not perfect in their respective natures without any contrariety. This is proved by their movements: for there is no contrary to the circular movement of the heavenly bodies, so that there can be nothing violent in them: whereas there are movements contrary to that of the lower bodies; for instance, downward movement is contrary to upward movement. Therefore heavenly bodies havea more universal power than the inferior bodies. Now universal powers move particular powers, as we have proved.! Therefore the heavenly bodies move and govern lower bodies.

Moreover. We have shown? that all other things are ruled by intellectual substances. Now the heavenly bodies resemble the intellectual substances, more than other bodies do, forasmuch as they are incorruptible. Moreover they are nearer to them, inasmuch as they are moved by them immediately, as we have shown above.? Therefore the lower bodies are ruled by them.

Further. The first principle of movement must be something immovable. Consequently things that approach nearest to immobility, must be the movers of others. Now heavenly bodies approach nearer to the immobility of a first principle than do the inferior bodies: because they have but one species of movement, namely local: whereas other bodies have all manner of movements. Therefore the heavenly bodies move and rule the lower bodies.

Again. In each genus the first ts the cause of that which comes after. Now the heavenly movement is the first of all movements. First, because local movement precedes all others—Both in point of time, because it alone can be everlasting, as is proved in 8 Phys. vii—And naturally: because without it there could be no other: since a thing cannot be increased without a previous alteration, whereby that which was dissimilar is transformed and assimilated:

'place, since in order that there be alteration, the cause of alteration must become nearer to the subject altered than it ‘was before:—And in perfection: because local movement does not cause a thing to vary in respect of something inherent, but only in respect of something extrinsic; and for this reason belongs to a thing already perfect—Secondly, because even among local movements, circular movement holds the first place—Both in point of time: because it alone can be everlasting, as proved in 8 Phys. viii—And naturally: because it excels in simplicity and unity, since it is not divided ‘into beginning, middle and end, but is all middle, as it were.—And in perfection, because it returns to its principle—Thirdly, because alone the heavenly movement is always regular and uniformy since in the movements of heavy and light bodies the’ speed increases towards the end if the movement be natural, and decreases if the movement be violent—tTherefore the movement of the heaven must be the cause of all other movements.

Further. As that which is simply immovable is in comparison with movement simply, so is that which is immovable in respect of a particular kind of movement, in comparison with that particular movement. Now that which is simply immovable is the principle of all movement, as we have proved.' Therefore that which is immovable in respect of alteration, is the principle of all alteration. Now of all things corporeal the heavenly bodies alone are inalterable: this is proved by their disposition which is always the same. Therefore the heavenly body is the cause of alteration in all things alterable. Butin this lower world alteration is the principle of allmovement: because alterationleads to increase and generation: and the generator is a pey se mover in the local movement of heavy and lightbodies. Consequently the heaven must be the cause of all movement in these lower bodies.

Therefore it is evident that the lower bodies are governed by Gog by means of the heavenly bodies.