Thomas Aquinas

“ Therefore, when it is said that all things, even the angels, would lapse into nothing, unless preserved by God, it is not to be gathered therefrom that there is any principle of corruption in the angels; but that the nature of the angels is dependent upon God as its cause. For a thing is said to be corruptible not merely because God can reduce it to non-existence, by withdrawing His act of preservation; but also because it has some principle of corruption within itself, or some contrariety, or at least the potentiality of matter. ”

“ I answer that, It must necessarily be maintained that the angels are incorruptible of their own nature. The reason for this is, that nothing is corrupted except by its form being separated from the matter. Hence, since an angel is a subsisting form, as is clear from what was said above (A [2] ) , it is impossible for its substance to be corruptible. For what belongs to anything considered in itself can never be separated from it; but what belongs to a thing, considered in relation to something else, can be separated, when that something else is taken away, in view of which it belonged to it. ”

“ A token of this incorruptibility can be gathered from its intellectual operation; for since everything acts according as it is actual, the operation of a thing indicates its mode of being. Now the species and nature of the operation is understood from the object. But an intelligible object, being above time, is everlasting. Hence every intellectual substance is incorruptible of its own nature. ”

“ Art. 1 - Whether an angel is altogether incorporeal? Objection 1: It would seem that an angel is not entirely incorporeal. For what is incorporeal only as regards ourselves, and not in relation to God, is not absolutely incorporeal. ”

“ And if the angels had matter, not even then could there be several angels of one species. For it would be necessary for matter to be the principle of distinction of one from the other, not, indeed, according to the division of quantity, since they are incorporeal, but according to the diversity of their powers; and such diversity of matter causes diversity not merely of species, but of genus.
Reply to Objection 1: "Difference" is nobler than "genus," as the determined is more noble than the undetermined, and the proper than the common, but not as one nature is nobler than another ”

“ Whereas in immaterial things there is no separate determinator and thing determined; each thing by its own self holds a determinate grade in being; and therefore in them "genus" and "difference" are not derived from different things, but from one and the same. Nevertheless, this differs in our mode of conception; for, inasmuch as our intellect considers it as indeterminate, it derives the idea of their "genus" ”

“ The first is that of form and matter, whereby the nature is constituted. Such a composite nature is not its own existence but existence is its act. Hence the nature itself is related to its own existence as potentiality to act. Therefore if there be no matter, and supposing that the form itself subsists without matter, there nevertheless still remains the relation of the form to its very existence, as of potentiality to act. And such a kind of composition is understood to be in the angels ”

“ Further, form is properly limited and perfected by matter. So the form which is not in matter is an infinite form. But the form of an angel is not infinite, for every creature is finite. Therefore the form of an angel is in matter. ”

“ More and less change the species, not according as they are caused by the intensity or remissness of one form, but according as they are caused by forms of diverse degrees; for instance, if we say that fire is more perfect than air: and in this way the angels are diversified according to more or less.
Reply to Objection 3: The good of the species preponderates over the good of the individual. Hence it is much better for the species to be multiplied in the angels than for individuals to be multiplied in the one species. ”

“ But things distinguished by the intellect are not necessarily distinguished in reality; because the intellect does not apprehend things according to their mode, but according to its own mode. Hence material things which are below our intellect exist in our intellect in a simpler mode than they exist in themselves. Angelic substances, on the other hand, are above our intellect; and hence our intellect cannot attain to apprehend them, as they are in themselves, but by its own mode, according as it apprehends composite things ”

“ Now the medium compared to one extreme appears to be the other extreme, as what is tepid compared to heat seems to be cold; and thus it is said that angels, compared to God, are material and corporeal, not, however, as if anything corporeal existed in them.
Reply to Objection 2: Movement is there taken in the sense in which it is applied to intelligence and will. Therefore an angel is called an ever mobile substance, because he is ever actually intelligent, and not as if he were sometimes actually and sometimes potentially, as we are. ”

“ The reason whereof is this, because, since it is the perfection of the universe that God chiefly intends in the creation of things, the more perfect some things are, in so much greater an excess are they created by God. ”

“ Therefore irrational animals differ in species according to the various determined degrees of sensitive nature; and in like manner all the angels differ in species according to the diverse degrees of intellectual nature. ”

“ Therefore angels are corporeal.
On the contrary, It is said (Ps. 103:4) : "Who makes His angels spirits."
I answer that, There must be some incorporeal creatures. For what is principally intended by God in creatures is good, and this consists in assimilation to God Himself. And the perfect assimilation of an effect to a cause is accomplished when the effect imitates the cause according to that whereby the cause produces the effect; as heat makes heat. Now, God produces the creature by His intellect and will (Q [14] , A [8] ; Q [19] , A [4] ) . ”

“ Further, the proper effect of the separate substances seems to be the movements of the heavenly bodies. But the movements of the heavenly bodies fall within some small determined number, which we can apprehend. Therefore the angels are not in greater number than the movements of the heavenly bodies. ”