Thomas Aquinas

“ Although one angel sees the intelligible species of another, by the fact that the species are proportioned to the rank of these substances according to greater or lesser universality, yet it does not follow that one knows how far another makes use of them by actual consideration. ”

“ There is another knowledge of the angels, which renders them happy; it is the knowledge whereby they see the Word, and things in the Word. By such vision they know mysteries of grace, but not all mysteries: nor do they all know them equally ”

“ Further, material things are not actually intelligible, but are knowable by apprehension of sense and of imagination, which does not exist in angels. Therefore angels do not know material things.
On the contrary, Whatever the lower power can do, the higher can do likewise. But man's intellect, which in the order of nature is inferior to the angel's, can know material things. Therefore much more can the mind of an angel. ”

“ Consequently all that is in the will, and all things that depend only on the will, are known to God alone. Now it is evident that it depends entirely on the will for anyone actually to consider anything; because a man who has a habit of knowledge, or any intelligible species, uses them at will. ”

“ Further, the ideas of our intellect resemble the angel more than do the images in our imagination; because the former are actually understood, while the latter are understood only potentially. But the images in our imagination can be known by an angel as corporeal things are known: because the imagination is a corporeal faculty. Therefore it seems that an angel can know the thoughts of the intellect.
On the contrary, What is proper to God does not belong to the angels. ”

“ The manner in which an angel knows singular things can be considered from this, that, as things proceed from God in order that they may subsist in their own natures, so likewise they proceed in order that they may exist in the angelic mind. Now it is clear that there comes forth from God not only whatever belongs to their universal nature, but likewise all that goes to make up their principles of individuation ”

“ Therefore, it must be said differently, that, as man by his various powers of knowledge knows all classes of things, apprehending universals and immaterial things by his intellect, and things singular and corporeal by the senses, so an angel knows both by his one mental power. ”

“ But the material things cannot enter by their essence into man's soul, nor into the angel's mind. Therefore they cannot be known by intellectual vision, but only by imaginary vision, whereby the images of bodies are apprehended, and by sensible vision, which regards bodies in themselves. Now there is neither imaginary nor sensible vision in the angels, but only intellectual. Therefore the angels cannot know material things. ”

“ The first is his natural knowledge, according to which he knows things both by his essence, and by innate species. By such knowledge the angels cannot know mysteries of grace. For these mysteries depend upon the pure will of God: and if an angel cannot learn the thoughts of another angel, which depend upon the will of such angel, much less can he ascertain what depends entirely upon God's will. The Apostle reasons in this fashion (1 Cor. 2:11) : "No one knoweth the things of a man [*Vulg.: 'What man knoweth the things of a man, but . . . ?'] , but the spirit of a man that is in him." ”

“ For thought is sometimes discovered not merely by outward act, but also by change of countenance; and doctors can tell some passions of the soul by the mere pulse. Much more then can angels, or even demons, the more deeply they penetrate those occult bodily modifications. ”

“ Yet the angels do not necessarily know the movement of the sensitive appetite and the imaginative apprehension of man in so far as these are moved by the will and reason; because, even the lower part of the soul has some share of reason, as obeying its ruler, as is said in Ethics iii, 12. ”

“ Hence Augustine says (De divin. daemon.) that demons "sometimes with the greatest faculty learn man's dispositions, not only when expressed by speech, but even when conceived in thought, when the soul expresses them by certain signs in the body" ”

“ For the order of things runs in this way, that the higher a thing is, so much the more is its power united and far-reaching: thus in man himself it is manifest that the common sense which is higher than the proper sense, although it is but one faculty, knows everything apprehended by the five outward senses, and some other things which no outer sense knows ”

“ This manner of knowing future events exists in the angels, and by so much the more than it does in us, as they understand the causes of things both more universally and more perfectly; thus doctors who penetrate more deeply into the causes of an ailment can pronounce a surer verdict on the future issue thereof. ”

“ And although God revealed in general to the prophets what He was one day to do regarding the salvation of the human race, still the apostles knew some particulars of the same, which the prophets did not know. ”

“ I answer that, The established order of things is for the higher beings to be more perfect than the lower; and for whatever is contained deficiently, partially, and in manifold manner in the lower beings, to be contained in the higher eminently, and in a certain degree of fulness and simplicity. Therefore, in God, as in the highest source of things, all things pre-exist supersubstantially in respect of His simple Being itself, as Dionysius says (Div. Nom. 1) . But among other creatures the angels are nearest to God, and resemble Him most ”