Summa contra Gentiles2.91 Chapter XCI. That there are some intellectual substances which are not united to bodies

It may be shown from the foregoing that there are some intellectual substances which are in no way united to bodies.

For it has been proved above that when the body perishes the substance of the intellect remains inasmuch as it is everlasting. And if the substance of the intellect which remains be one in all, as some assert, it follows of necessity that it is, in its being, separate from the body. And thus our point is proved, namely that some intellectual substance subsists apart from a body. If, however, many intellectual souls survive the destruction of bodies, it will be competent to some intellectual substances to subsist apart from a body: especially since it has been proved that souls do not pass from one body to another. Now this separation from bodies is accidentally competent to souls, since they are naturally forms of bodies. But that which is accidental must be \j preceded hy that which is per se. Therefore there are some intellectual substances, naturally prior to souls, to which it is per se competent to subsist apart from a body.

Moreover. Whatever belongs to the generic nature must belong to the specific nature: whereas certain things belong to the specific nature which are not in the generic nature. Thus rational belongs to the essence of man, but not to the essence of animal. Now that which belongs to the specific nature and not to the generic nature, does not of necessity belong to every species of the genus: for there are many species of irrational animals. And it belongs to the intellectual substance, by reason of its genus, to be per se subsistent, since it has a per se operation, as we have shown above. Now it belongs to the nature of a per se subsistent thing, not to be united to another. Therefore it does not belong to the nature of an intellectual substance to be united to another, although it does belong to the nature of some intellectual substance, namely the soul. Therefore there are some intellectual substances that are not united to a body.

Again. The higher nature in its lowest degree touches the lower nature in its highest degree. Now the intellectual nature is higher than the corporeal: and it touches it in respect of one of its parts, namely the intellective soul. Therefore it follows that, just as the body that is perfected by the intellective soul is the highest in the genus of bodies, so the intellective soul that is united to a body is the lowest in the genus of intellectual substances. Therefore there are some intellectual substances not united to bodies which, in the order of nature, are higher than the soul.

Again. If, in a genus, there be something imperfect, we find that there is something above it which, in the order of nature, is perfect in that genus.' Now forms that are in matter are imperfect acts: since they have not complete being. Wherefore there are some forms that are complete acts, subsistent in themselves, and having a complete species. But every form that subsists in itself without matter is an intellectual substance: since immunity from matter gives intellectual being, as was shown above. Therefore there are some intellectual substances that are not united to bodies: for every body is material.

Moreover. Substance can be without quantity, although there cannot be quantity apart from substance: because substance precedes the other genera in time, idea, and knowledge. But no corporeal substance is without quantity. Therefore there can be some things in the genus of substance that are altogether without a body. Now all possible natures are found in the order of things: otherwise the universe would be imperfect. Moreover in everlasting things there is no difference between actual and possible being. Therefore there are some substances subsistent apart from a body, below the first substance which is God, Who is in no genus, as we proved above; and above the soul which is united to a body.

Further. If we find a thing composed of two, and one of these which is the less perfect be found to exist by itself, the one which is more perfect and less dependent on the other is also to be found by itself. Now a certain substance is found to be composed of an intellectual substance and a body, as shown above. And a body is found existing by itself, as evidenced in all inordinate bodies. Much more therefore are some intellectual substances found existing without being united to bodies.

Again. The substance of a thing should be proportionate to its operation: because operation is the act and the good of the operator's substance. Now understanding is the proper operation of an intellectual substance. Wherefore an intellectual substance should be such as is competent to exercise the aforesaid operation. But since understanding is an operation that is not exercised by means of a corporeal organ, it needs not the body except in so far as intelligible objects are taken from sensibles. Yet this is an imperfect way of understanding: since the perfect way of understanding is to understand things that are intelligible by their nature.: whereas that only those things be understood which are not intelligible in themselves, but are rendered intelligible by the intellect, is an imperfect way of understanding. Therefore, if before every imperfect thing there must needs be something perfect in the same genus,' it follows that above human souls which understand by receiving from phantasms, there are some intellectual substances which understand things that are intelligible in themselves, without receiving knowledge from sensibles, and for this reason are by their nature altogether separate from bodies. -—Further. Aristotle argues (11 Metaph.y as follows. A movement that is continuous, regular, and so far as it is concerned, unfailing, must needs be from a mover which is not moved, neither per se nor accidentally, as we have proved above.' Also, several movements must proceed from several movers. Now the movement of the heaven is continuous, regular, and so far as it is concerned, unfailing: and besides the first movement, there are many such movements in the heaven, as is proved by the observations of astronomers. Hence there must be several movers who are not moved, neither per se nor accidentally. But no body moves unless itself be moved, as we proved above.' Moreover an incorporeal mover that is united to a body, is moved accidentally according as the body is moved, as instanced by the soul. Therefore there must be several movers, that are neither bodies nor united to bodies. Now the heavenly movements proceed from an intellect, as was shown above. Therefore there are several intellectual substances that are not united to bodies. This agrees with the opinion of Dionysius who says (Div. Nom. iv.) in speaking of the angels, that they are understood to be immaterial and incorporeal.

Hereby is refuted the error of the Sadducees who said that there is no spirit: as also the assertion of the philosophers of old who said that every substance is corporeal: * and the opinion of Origen who said that with the exception of the Divine Trinity, no substance can subsist apart from a body: and of all those others who hold that all the angels both good and bad, have bodies naturally united to them.