Thomas Aquinas

“ Angels need an assumed body, not for themselves, but on our account; that by conversing familiarly with men they may give evidence of that intellectual companionship which men expect to have with them in the life to come. Moreover that angels assumed bodies under the Old Law was a figurative indication that the Word of God would take a human body ”

“ Now whenever we find something imperfect in any genus we must presuppose something perfect in that genus. Therefore in the intellectual nature there are some perfectly intellectual substances, which do not need to acquire knowledge from sensible things. Consequently not all intellectual substances are united to bodies; but some are quite separated from bodies, and these we call angels. ”

“ Further, speech is the function of a living subject, for it is produced by the voice, while the voice itself is a sound conveyed from the mouth. But it is evident from many passages of Sacred Scripture that angels spoke in assumed bodies. Therefore in their assumed bodies they exercise functions of life. ”

“ Therefore they cannot exercise functions of life through assumed bodies.
I answer that, Some functions of living subjects have something in common with other operations; just as speech, which is the function of a living creature, agrees with other sounds of inanimate things, in so far as it is sound; and walking agrees with other movements, in so far as it is movement. Consequently vital functions can be performed in assumed bodies by the angels, as to that which is common in such operations ”

“ For the bodies are assumed merely for this purpose, that the spiritual properties and works of the angels may be manifested by the properties of man and of his works. This could not so fittingly be done if they were to assume true men; because the properties of such men would lead us to men, and not to angels. ”

“ Movement coming from a united mover is a proper function of life; but the bodies assumed by the angels are not thus moved, since the angels are not their forms. Yet the angels are moved accidentally, when such bodies are moved, since they are in them as movers are in the moved; and they are here in such a way as not to be elsewhere which cannot be said of God. Accordingly, although God is not moved when the things are moved in which He exists, since He is everywhere; yet the angels are moved accidentally according to the movement of the bodies assumed. ”

“ Sensation is entirely a vital function. Consequently it can in no way be said that the angels perceive through the organs of their assumed bodies. Yet such bodies are not fashioned in vain; for they are not fashioned for the purpose of sensation through them, but to this end, that by such bodily organs the spiritual powers of the angels may be made manifest ”

“ And this is what we mean by an angel assuming a body.
Reply to Objection 3: Although air as long as it is in a state of rarefaction has neither shape nor color, yet when condensed it can both be shaped and colored as appears in the clouds. ”