Summa Th. I EN Qu.84 a.1
Objection: 1. It would seem that the soul does not know bodies through the intellect. For Augustine says (Soliloq. ii, 4) that "bodies cannot be understood by the intellect; nor indeed anything corporeal unless it can be perceived by the senses." He says also (Gn ad lit. xii, 24) that intellectual vision is of those things that are in the soul by their essence. But such are not bodies. Therefore the soul cannot know bodies through the intellect.
2. Further, as sense is to the intelligible, so is the intellect to the sensible. But the soul can by no means, through the senses, understand spiritual things, which are intelligible. Therefore by no means can it, through the intellect, know bodies, which are sensible.
3. Further, the intellect is concerned with things that are necessary and unchangeable. But all bodies are mobile and changeable. Therefore the soul cannot know bodies through the intellect.
On the contrary Science is in the intellect. If, therefore, the intellect does not know bodies, it follows that there is no science of bodies; and thus perishes natural science, which treats of mobile bodies.
I answer that It should be said in order to elucidate this question, that the early philosophers, who inquired into the natures of things, thought there was nothing in the world save bodies. And because they observed that all bodies are mobile, and considered them to be ever in a state of flux, they were of opinion that we can have no certain knowledge of the true nature of things. For what is in a continual state of flux, cannot be grasped with any degree of certitude, for it passes away ere the mind can form a judgment thereon: according to the saying of Heraclitus, that "it is not possible twice to touch a drop of water in a passing torrent," as the Philosopher relates (Metaph. iv, Did. iii, 5).
After these came Plato, who, wishing to save the certitude of our knowledge of truth through the intellect, maintained that, besides these things corporeal, there is another genus of beings, separate from matter and movement, which beings he called "species" or "ideas," by participation of which each one of these singular and sensible things is said to be either a man, or a horse, or the like. Wherefore he said that sciences and definitions, and whatever appertains to the act of the intellect, are not referred to these sensible bodies, but to those beings immaterial and separate: so that according to this the soul does not understand these corporeal things, but the separate species thereof.
Now this may be shown to be false for two reasons. First, because, since those species are immaterial and immovable, knowledge of movement and matter would be excluded from science (which knowledge is proper to natural science), and likewise all demonstration through moving and material causes. Secondly, because it seems ridiculous, when we seek for knowledge of things which are to us manifest, to introduce other beings, which cannot be the substance of those others, since they differ from them essentially: so that granted that we have a knowledge of those separate substances, we cannot for that reason claim to form a judgment concerning these sensible things.
Now it seems that Plato strayed from the truth because, having observed that all knowledge takes place through some kind of similitude, he thought that the form of the thing known must of necessity be in the knower in the same manner as in the thing known. Then he observed that the form of the thing understood is in the intellect under conditions of universality, immateriality, and immobility: which is apparent from the very operation of the intellect, whose act of understanding has a universal extension, and is subject to a certain amount of necessity: for the mode of action corresponds to the mode of the agent's form. Wherefore he concluded that the things which we understand must have in themselves an existence under the same conditions of immateriality and immobility.
But there is no necessity for this. For even in sensible things it is to be observed that the form is otherwise in one sensible than in another: for instance, whiteness may be of great intensity in one, and of a less intensity in another: in one we find whiteness with sweetness, in another without sweetness. In the same way the sensible form is conditioned differently in the thing which is external to the soul, and in the senses which receive the forms of sensible things without receiving matter, such as the color of gold without receiving gold. So also the intellect, according to its own mode, receives under conditions of immateriality and immobility, the species of material and mobile bodies: for the received is in the receiver according to the mode of the receiver. We must conclude, therefore, that through the intellect the soul knows bodies by a knowledge which is immaterial, universal, and necessary.
Reply to Objection: 1. These words of Augustine are to be understood as referring to the medium of intellectual knowledge, and not to its object. For the intellect knows bodies by understanding them, not indeed through bodies, nor through material and corporeal species; but through immaterial and intelligible species, which can be in the soul by their own essence.
2. As Augustine says (De Civ. Dei xxii, 29), it is not correct to say that as the sense knows only bodies so the intellect knows only spiritual things; for it follows that God and the angels would not know corporeal things. The reason of this diversity is that the lower power does not extend to those things that belong to the higher power; whereas the higher power operates in a more excellent manner those things which belong to the lower power.
3. Every movement presupposes something immovable: for when a change of quality occurs, the substance remains unmoved; and when there is a change of substantial form, matter remains unmoved. Moreover the various conditions of mutable things are themselves immovable; for instance, though Socrates be not always sitting, yet it is an immovable truth that whenever he does sit he remains in one place. For this reason there is nothing to hinder our having an immovable science of movable things.
Objection: 1. It would seem that the soul understands corporeal things through its essence. For Augustine says (De Trin. x, 5) that the soul "collects and lays hold of the images of bodies which are formed in the soul and of the soul: for in forming them it gives them something of its own substance." But the soul understands bodies by images of bodies. Therefore the soul knows bodies through its essence, which it employs for the formation of such images, and from which it forms them.
2. Further, the Philosopher says (De Anima iii, 8) that "the soul, after a fashion, is everything." Since, therefore, like is known by like, it seems that the soul knows corporeal things through itself.
3. Further, the soul is superior to corporeal creatures. Now lower things are in higher things in a more eminent way than in themselves, as Dionysius says (Coel. Hier. xii). Therefore all corporeal creatures exist in a more excellent way in the soul than in themselves. Therefore the soul can know corporeal creatures through its essence.
On the contrary Augustine says (De Trin. ix, 3) that "the mind gathers knowledge of corporeal things through the bodily senses." But the soul itself cannot be known through the bodily senses. Therefore it does not know corporeal things through itself.
I answer that The ancient philosophers held that the soul knows bodies through its essence. For it was universally admitted that "like is known by like." But they thought that the form of the thing known is in the knower in the same mode as in the thing known. The Platonists however were of a contrary opinion. For Plato, having observed that the intellectual soul has an immaterial nature, and an immaterial mode of knowledge, held that the forms of things known subsist immaterially. While the earlier natural philosophers, observing that things known are corporeal and material, held that things known must exist materially even in the soul that knows them. And therefore, in order to ascribe to the soul a knowledge of all things, they held that it has the same nature in common with all. And because the nature of a result is determined by its principles, they ascribed to the soul the nature of a principle; so that those who thought fire to be the principle of all, held that the soul had the nature of fire; and in like manner as to air and water. Lastly, Empedocles, who held the existence of our four material elements and two principles of movement, said that the soul was composed of these. Consequently, since they held that things exist in the soul materially, they maintained that all the soul's knowledge is material, thus failing to discern intellect from sense.
But this opinion will not hold. First, because in the material principle of which they spoke, the various results do not exist save in potentiality. But a thing is not known according as it is in potentiality, but only according as it is in act, as is shown Metaph. ix (Did. viii, 9): wherefore neither is a power known except through its act. It is therefore insufficient to ascribe to the soul the nature of the principles in order to explain the fact that it knows all, unless we further admit in the soul natures and forms of each individual result, for instance, of bone, flesh, and the like; thus does Aristotle argue against Empedocles (De Anima i, 5). Secondly, because if it were necessary for the thing known to exist materially in the knower, there would be no reason why things which have a material existence outside the soul should be devoid of knowledge; why, for instance, if by fire the soul knows fire, that fire also which is outside the soul should not have knowledge of fire.
We must conclude, therefore, that material things known must needs exist in the knower, not materially, but immaterially. The reason of this is, because the act of knowledge extends to things outside the knower: for we know things even that are external to us. Now by matter the form of a thing is determined to some one thing. Wherefore it is clear that knowledge is in inverse ratio of materiality. And consequently things that are not receptive of forms save materially, have no power of knowledge whatever---such as plants, as the Philosopher says (De Anima ii, 12). But the more immaterially a thing receives the form of the thing known, the more perfect is its knowledge. Therefore the intellect which abstracts the species not only from matter, but also from the individuating conditions of matter, has more perfect knowledge than the senses, which receive the form of the thing known, without matter indeed, but subject to material conditions. Moreover, among the senses, sight has the most perfect knowledge, because it is the least material, as we have remarked above (Question [78], Article [3]): while among intellects the more perfect is the more immaterial.
It is therefore clear from the foregoing, that if there be an intellect which knows all things by its essence, then its essence must needs have all things in itself immaterially; thus the early philosophers held that the essence of the soul, that it may know all things, must be actually composed of the principles of all material things. Now this is proper to God, that His Essence comprise all things immaterially as effects pre-exist virtually in their cause. God alone, therefore, understands all things through His Essence: but neither the human soul nor the angels can do so.
Reply to Objection: 1. Augustine in that passage is speaking of an imaginary vision, which takes place through the image of bodies. To the formation of such images the soul gives part of its substance, just as a subject is given in order to be informed by some form. In this way the soul makes such images from itself; not that the soul or some part of the soul be turned into this or that image; but just as we say that a body is made into something colored because of its being informed with color. That this is the sense, is clear from what follows. For he says that the soul "keeps something"---namely, not informed with such image---"which is able freely to judge of the species of these images": and that this is the "mind" or "intellect." And he says that the part which is informed with these images---namely, the imagination---is "common to us and beasts."
2. Aristotle did not hold that the soul is actually composed of all things, as did the earlier philosophers; he said that the soul is all things, "after a fashion," forasmuch as it is in potentiality to all---through the senses, to all things sensible---through the intellect, to all things intelligible.
3. Every creature has a finite and determinate essence. Wherefore although the essence of the higher creature has a certain likeness to the lower creature, forasmuch as they have something in common generically, yet it has not a complete likeness thereof, because it is determined to a certain species other than the species of the lower creature. But the Divine Essence is a perfect likeness of all, whatsoever may be found to exist in things created, being the universal principle of all.
Objection: 1. It would seem that the soul understands all things through innate species. For Gregory says, in a homily for the Ascension (xxix in ), that "man has understanding in common with the angels." But angels understand all things through innate species: wherefore in the book De Causis it is said that "every intelligence is full of forms." Therefore the soul also has innate species of things, by means of which it understands corporeal things.
2. Further, the intellectual soul is more excellent than corporeal primary matter. But primary matter was created by God under the forms to which it has potentiality. Therefore much more is the intellectual soul created by God under intelligible species. And so the soul understands corporeal things through innate species.
3. Further, no one can answer the truth except concerning what he knows. But even a person untaught and devoid of acquired knowledge, answers the truth to every question if put to him in orderly fashion, as we find related in the Meno (xv seqq.) of Plato, concerning a certain individual. Therefore we have some knowledge of things even before we acquire knowledge; which would not be the case unless we had innate species. Therefore the soul understands corporeal things through innate species.
On the contrary The Philosopher, speaking of the intellect, says (De Anima iii, 4) that it is like "a tablet on which nothing is written."
I answer that Since form is the principle of action, a thing must be related to the form which is the principle of an action, as it is to that action: for instance, if upward motion is from lightness, then that which only potentially moves upwards must needs be only potentially light, but that which actually moves upwards must needs be actually light. Now we observe that man sometimes is only a potential knower, both as to sense and as to intellect. And he is reduced from such potentiality to act---through the action of sensible objects on his senses, to the act of sensation---by instruction or discovery, to the act of understanding. Wherefore we must say that the cognitive soul is in potentiality both to the images which are the principles of sensing, and to those which are the principles of understanding. For this reason Aristotle (De Anima iii, 4) held that the intellect by which the soul understands has no innate species, but is at first in potentiality to all such species.
But since that which has a form actually, is sometimes unable to act according to that form on account of some hindrance, as a light thing may be hindered from moving upwards; for this reason did Plato hold that naturally man's intellect is filled with all intelligible species, but that, by being united to the body, it is hindered from the realization of its act. But this seems to be unreasonable. First, because, if the soul has a natural knowledge of all things, it seems impossible for the soul so far to forget the existence of such knowledge as not to know itself to be possessed thereof: for no man forgets what he knows naturally; that, for instance, the whole is larger than the part, and such like. And especially unreasonable does this seem if we suppose that it is natural to the soul to be united to the body, as we have established above (Question [76], Article [1]): for it is unreasonable that the natural operation of a thing be totally hindered by that which belongs to it naturally. Secondly, the falseness of this opinion is clearly proved from the fact that if a sense be wanting, the knowledge of what is apprehended through that sense is wanting also: for instance, a man who is born blind can have no knowledge of colors. This would not be the case if the soul had innate images of all intelligible things. We must therefore conclude that the soul does not know corporeal things through innate species.
Reply to Objection: 1. Man indeed has intelligence in common with the angels, but not in the same degree of perfection: just as the lower grades of bodies, which merely exist, according to Gregory (Homily on Ascension, xxix In ), have not the same degree of perfection as the higher bodies. For the matter of the lower bodies is not totally completed by its form, but is in potentiality to forms which it has not: whereas the matter of heavenly bodies is totally completed by its form, so that it is not in potentiality to any other form, as we have said above (Question [66], Article [2]). In the same way the angelic intellect is perfected by intelligible species, in accordance with its nature; whereas the human intellect is in potentiality to such species.
2. Primary matter has substantial being through its form, consequently it had need to be created under some form: else it would not be in act. But when once it exists under one form it is in potentiality to others. On the other hand, the intellect does not receive substantial being through the intelligible species; and therefore there is no comparison.
3. If questions be put in an orderly fashion they proceed from universal self-evident principles to what is particular. Now by such a process knowledge is produced in the mind of the learner. Wherefore when he answers the truth to a subsequent question, this is not because he had knowledge previously, but because he thus learns for the first time. For it matters not whether the teacher proceed from universal principles to conclusions by questioning or by asserting; for in either case the mind of the listener is assured of what follows by that which preceded.
Objection: 1. It would seem that the intelligible species are derived by the soul from some separate forms. For whatever is such by participation is caused by what is such essentially; for instance, that which is on fire is reduced to fire as the cause thereof. But the intellectual soul forasmuch as it is actually understanding, participates the thing understood: for, in a way, the intellect in act is the thing understood in act. Therefore what in itself and in its essence is understood in act, is the cause that the intellectual soul actually understands. Now that which in its essence is actually understood is a form existing without matter. Therefore the intelligible species, by which the soul understands, are caused by some separate forms.
2. Further, the intelligible is to the intellect, as the sensible is to the sense. But the sensible species which are in the senses, and by which we sense, are caused by the sensible object which exists actually outside the soul. Therefore the intelligible species, by which our intellect understands, are caused by some things actually intelligible, existing outside the soul. But these can be nothing else than forms separate from matter. Therefore the intelligible forms of our intellect are derived from some separate substances.
3. Further, whatever is in potentiality is reduced to act by something actual. If, therefore, our intellect, previously in potentiality, afterwards actually understands, this must needs be caused by some intellect which is always in act. But this is a separate intellect. Therefore the intelligible species, by which we actually understand, are caused by some separate substances.
On the contrary If this were true we should not need the senses in order to understand. And this is proved to be false especially from the fact that if a man be wanting in a sense, he cannot have any knowledge of the sensibles corresponding to that sense.
I answer that Some have held that the intelligible species of our intellect are derived from certain separate forms or substances. And this in two ways. For Plato, as we have said (Article [1]), held that the forms of sensible things subsist by themselves without matter; for instance, the form of a man which he called "per se" man, and the form or idea of a horse which is called "per se" horse, and so forth. He said therefore that these forms are participated both by our soul and by corporeal matter; by our soul, to the effect of knowledge thereof, and by corporeal matter to the effect of existence: so that, just as corporeal matter by participating the idea of a stone, becomes an individuating stone, so our intellect, by participating the idea of a stone, is made to understand a stone. Now participation of an idea takes place by some image of the idea in the participator, just as a model is participated by a copy. So just as he held that the sensible forms, which are in corporeal matter, are derived from the ideas as certain images thereof: so he held that the intelligible species of our intellect are images of the ideas, derived therefrom. And for this reason, as we have said above (Article [1]), he referred sciences and definitions to those ideas.
But since it is contrary to the nature of sensible things that their forms should subsist without matter, as Aristotle proves in many ways (Metaph. vi), Avicenna (De Anima v) setting this opinion aside, held that the intelligible species of all sensible things, instead of subsisting in themselves without matter, pre-exist immaterially in the separate intellects: from the first of which, said he, such species are derived by a second, and so on to the last separate intellect which he called the "active intelligence," from which, according to him, intelligible species flow into our souls, and sensible species into corporeal matter. And so Avicenna agrees with Plato in this, that the intelligible species of our intellect are derived from certain separate forms; but these Plato held to subsist of themselves, while Avicenna placed them in the "active intelligence." They differ, too, in this respect, that Avicenna held that the intelligible species do not remain in our intellect after it has ceased actually to understand, and that it needs to turn (to the active intellect) in order to receive them anew. Consequently he does not hold that the soul has innate knowledge, as Plato, who held that the participated ideas remain immovably in the soul.
But in this opinion no sufficient reason can be assigned for the soul being united to the body. For it cannot be said that the intellectual soul is united to the body for the sake of the body: for neither is form for the sake of matter, nor is the mover for the sake of the moved, but rather the reverse. Especially does the body seem necessary to the intellectual soul, for the latter's proper operation which is to understand: since as to its being the soul does not depend on the body. But if the soul by its very nature had an inborn aptitude for receiving intelligible species through the influence of only certain separate principles, and were not to receive them from the senses, it would not need the body in order to understand: wherefore to no purpose would it be united to the body.
But if it be said that our soul needs the senses in order to understand, through being in some way awakened by them to the consideration of those things, the intelligible species of which it receives from the separate principles: even this seems an insufficient explanation. For this awakening does not seem necessary to the soul, except in as far as it is overcome by sluggishness, as the Platonists expressed it, and by forgetfulness, through its union with the body: and thus the senses would be of no use to the intellectual soul except for the purpose of removing the obstacle which the soul encounters through its union with the body. Consequently the reason of the union of the soul with the body still remains to be sought.
And if it be said with Avicenna, that the senses are necessary to the soul, because by them it is aroused to turn to the "active intelligence" from which it receives the species: neither is this a sufficient explanation. Because if it is natural for the soul to understand through species derived from the "active intelligence," it follows that at times the soul of an individual wanting in one of the senses can turn to the active intelligence, either from the inclination of its very nature, or through being roused by another sense, to the effect of receiving the intelligible species of which the corresponding sensible species are wanting. And thus a man born blind could have knowledge of colors; which is clearly untrue. We must therefore conclude that the intelligible species, by which our soul understands, are not derived from separate forms.
Reply to Objection: 1. The intelligible species which are participated by our intellect are reduced, as to their first cause, to a first principle which is by its essence intelligible---namely, God. But they proceed from that principle by means of the sensible forms and material things, from which we gather knowledge, as Dionysius says (Div. Nom. vii).
2. Material things, as to the being which they have outside the soul, may be actually sensible, but not actually intelligible. Wherefore there is no comparison between sense and intellect.
3. Our passive intellect is reduced from potentiality to act by some being in act, that is, by the active intellect, which is a power of the soul, as we have said (Question [79], Article [4]); and not by a separate intelligence, as proximate cause, although perchance as remote cause.
Objection: 1. It would seem that the intellectual soul does not know material things in the eternal types. For that in which anything is known must itself be known more and previously. But the intellectual soul of man, in the present state of life, does not know the eternal types: for it does not know God in Whom the eternal types exist, but is "united to God as to the unknown," as Dionysius says (Myst. Theolog. i). Therefore the soul does not know all in the eternal types.
2. Further, it is written (Rm 1,20) that "the invisible things of God are clearly seen . . . by the things that are made." But among the invisible things of God are the eternal types. Therefore the eternal types are known through creatures and not the converse.
3. Further, the eternal types are nothing else but ideas, for Augustine says (Questions. 83, qu. 46) that "ideas are permanent types existing in the Divine mind." If therefore we say that the intellectual soul knows all things in the eternal types, we come back to the opinion of Plato who said that all knowledge is derived from them.
On the contrary Augustine says (Confess. xii, 25): "If we both see that what you say is true, and if we both see that what I say is true, where do we see this, I pray? Neither do I see it in you, nor do you see it in me: but we both see it in the unchangeable truth which is above our minds." Now the unchangeable truth is contained in the eternal types. Therefore the intellectual soul knows all true things in the eternal types.
I answer that As Augustine says (De Doctr. Christ. ii, 11): "If those who are called philosophers said by chance anything that was true and consistent with our faith, we must claim it from them as from unjust possessors. For some of the doctrines of the heathens are spurious imitations or superstitious inventions, which we must be careful to avoid when we renounce the society of the heathens." Consequently whenever Augustine, who was imbued with the doctrines of the Platonists, found in their teaching anything consistent with faith, he adopted it: and those thing which he found contrary to faith he amended. Now Plato held, as we have said above (Article [4]), that the forms of things subsist of themselves apart from matter; and these he called ideas, by participation of which he said that our intellect knows all things: so that just as corporeal matter by participating the idea of a stone becomes a stone, so our intellect, by participating the same idea, has knowledge of a stone. But since it seems contrary to faith that forms of things themselves, outside the things themselves and apart from matter, as the Platonists held, asserting that "per se" life or "per se" wisdom are creative substances, as Dionysius relates (Div. Nom. xi); therefore Augustine (Questions. 83, qu. 46), for the ideas defended by Plato, substituted the types of all creatures existing in the Divine mind, according to which types all things are made in themselves, and are known to the human soul.
When, therefore, the question is asked: Does the human soul know all things in the eternal types? we must reply that one thing is said to be known in another in two ways. First, as in an object itself known; as one may see in a mirror the images of things reflected therein. In this way the soul, in the present state of life, cannot see all things in the eternal types; but the blessed who see God, and all things in Him, thus know all things in the eternal types. Secondly, on thing is said to be known in another as in a principle of knowledge: thus we might say that we see in the sun what we see by the sun. And thus we must needs say that the human soul knows all things in the eternal types, since by participation of these types we know all things. For the intellectual light itself which is in us, is nothing else than a participated likeness of the uncreated light, in which are contained the eternal types. Whence it is written (Ps 4,6-7), "Many say: Who showeth us good things?" which question the Psalmist answers, "The light of Thy countenance, O Lord, is signed upon us," as though he were to say: By the seal of the Divine light in us, all things are made known to us.
But since besides the intellectual light which is in us, intelligible species, which are derived from things, are required in order for us to have knowledge of material things; therefore this same knowledge is not due merely to a participation of the eternal types, as the Platonists held, maintaining that the mere participation of ideas sufficed for knowledge. Wherefore Augustine says (De Trin. iv, 16): "Although the philosophers prove by convincing arguments that all things occur in time according to the eternal types, were they able to see in the eternal types, or to find out from them how many kinds of animals there are and the origin of each? Did they not seek for this information from the story of times and places?"
But that Augustine did not understand all things to be known in their "eternal types" or in the "unchangeable truth," as though the eternal types themselves were seen, is clear from what he says (Questions. 83, qu. 46)---viz. that "not each and every rational soul can be said to be worthy of that vision," namely, of the eternal types, "but only those that are holy and pure," such as the souls of the blessed.
From what has been said the objections are easily solved.
Summa Th. I EN Qu.84 a.1