Whether the intelligible species are derived by the soul from certain separate forms?

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.

Objection 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.

Objection 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).

Reply to Objection 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.

Reply to Objection 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 (I:79:4; and not by a separate intelligence, as proximate cause, although perchance as remote cause.


Whether the intellectual soul knows material things in the eternal types?

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.

Objection 2. Further, it is written (Romans 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.

Objection 3. Further, the eternal types are nothing else but ideas, for Augustine says (QQ. 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 should subsist of 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 (QQ. 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, one 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 (Psalm 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 (QQ. 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.


Whether intellectual knowledge is derived from sensible things?

Objection 1. It would seem that intellectual knowledge is not derived from sensible things. For Augustine says (QQ. 83, qu. 9) that "we cannot expect to learn the fulness of truth from the senses of the body." This he proves in two ways.

First, because "whatever the bodily senses reach, is continually being changed; and what is never the same cannot be perceived."

Secondly, because, "whatever we perceive by the body, even when not present to the senses, may be present to the imagination, as when we are asleep or angry: yet we cannot discern by the senses, whether what we perceive be the sensible object or the deceptive image thereof. Now nothing can be perceived which cannot be distinguished from its counterfeit." And so he concludes that we cannot expect to learn the truth from the senses. But intellectual knowledge apprehends the truth. Therefore intellectual knowledge cannot be conveyed by the senses.

Objection 2. Further, Augustine says (Gen. ad lit. xii, 16): "We must not think that the body can make any impression on the spirit, as though the spirit were to supply the place of matter in regard to the body's action; for that which acts is in every way more excellent than that which it acts on." Whence he concludes that "the body does not cause its image in the spirit, but the spirit causes it in itself." Therefore intellectual knowledge is not derived from sensible things.

Objection 3. Further, an effect does not surpass the power of its cause. But intellectual knowledge extends beyond sensible things: for we understand some things which cannot be perceived by the senses. Therefore intellectual knowledge is not derived from sensible things.

On the contrary, The Philosopher says (Metaph. i, 1; Poster. ii, 15) that the principle of knowledge is in the senses.

I answer that, On this point the philosophers held three opinions. For Democritus held that "all knowledge is caused by images issuing from the bodies we think of and entering into our souls," as Augustine says in his letter to Dioscorus (cxviii, 4). And Aristotle says (De Somn. et Vigil.) that Democritus held that knowledge is cause by a "discharge of images." And the reason for this opinion was that both Democritus and the other early philosophers did not distinguish between intellect and sense, as Aristotle relates (De Anima iii, 3). Consequently, since the sense is affected by the sensible, they thought that all our knowledge is affected by this mere impression brought about by sensible things. Which impression Democritus held to be caused by a discharge of images.

Plato, on the other hand, held that the intellect is distinct from the senses: and that it is an immaterial power not making use of a corporeal organ for its action. And since the incorporeal cannot be affected by the corporeal, he held that intellectual knowledge is not brought about by sensible things affecting the intellect, but by separate intelligible forms being participated by the intellect, as we have said above (Articles 4 and 5). Moreover he held that sense is a power operating of itself. Consequently neither is sense, since it is a spiritual power, affected by the sensible: but the sensible organs are affected by the sensible, the result being that the soul is in a way roused to form within itself the species of the sensible. Augustine seems to touch on this opinion (Gen. ad lit. xii, 24) where he says that the "body feels not, but the soul through the body, which it makes use of as a kind of messenger, for reproducing within itself what is announced from without." Thus according to Plato, neither does intellectual knowledge proceed from sensible knowledge, nor sensible knowledge exclusively from sensible things; but these rouse the sensible soul to the sentient act, while the senses rouse the intellect to the act of understanding.

Aristotle chose a middle course. For with Plato he agreed that intellect and sense are different. But he held that the sense has not its proper operation without the cooperation of the body; so that to feel is not an act of the soul alone, but of the "composite." And he held the same in regard to all the operations of the sensitive part. Since, therefore, it is not unreasonable that the sensible objects which are outside the soul should produce some effect in the "composite," Aristotle agreed with Democritus in this, that the operations of the sensitive part are caused by the impression of the sensible on the sense: not by a discharge, as Democritus said, but by some kind of operation. For Democritus maintained that every operation is by way of a discharge of atoms, as we gather from De Gener. i, 8. But Aristotle held that the intellect has an operation which is independent of the body's cooperation. Now nothing corporeal can make an impression on the incorporeal. And therefore in order to cause the intellectual operation according to Aristotle, the impression caused by the sensible does not suffice, but something more noble is required, for "the agent is more noble than the patient," as he says (De Gener. i, 5). Not, indeed, in the sense that the intellectual operation is effected in us by the mere impression of some superior beings, as Plato held; but that the higher and more noble agent which he calls the active intellect, of which we have spoken above (I:79:4) causes the phantasms received from the senses to be actually intelligible, by a process of abstraction.

According to this opinion, then, on the part of the phantasms, intellectual knowledge is caused by the senses. But since the phantasms cannot of themselves affect the passive intellect, and require to be made actually intelligible by the active intellect, it cannot be said that sensible knowledge is the total and perfect cause of intellectual knowledge, but rather that it is in a way the material cause.

Reply to Objection 1. Those words of Augustine mean that we must not expect the entire truth from the senses. For the light of the active intellect is needed, through which we achieve the unchangeable truth of changeable things, and discern things themselves from their likeness.

Reply to Objection 2. In this passage Augustine speaks not of intellectual but of imaginary knowledge. And since, according to the opinion of Plato, the imagination has an operation which belongs to the soul only, Augustine, in order to show that corporeal images are impressed on the imagination, not by bodies but by the soul, uses the same argument as Aristotle does in proving that the active intellect must be separate, namely, because "the agent is more noble than the patient." And without doubt, according to the above opinion, in the imagination there must needs be not only a passive but also an active power. But if we hold, according to the opinion of Aristotle, that the action of the imagination, is an action of the "composite," there is no difficulty; because the sensible body is more noble than the organ of the animal, in so far as it is compared to it as a being in act to a being in potentiality; even as the object actually colored is compared to the pupil which is potentially colored. It may, however, be said, although the first impression of the imagination is through the agency of the sensible, since "fancy is movement produced in accordance with sensation" (De Anima iii, 3), that nevertheless there is in man an operation which by synthesis and analysis forms images of various things, even of things not perceived by the senses. And Augustine's words may be taken in this sense.

Reply to Objection 3. Sensitive knowledge is not the entire cause of intellectual knowledge. And therefore it is not strange that intellectual knowledge should extend further than sensitive knowledge.


Whether the intellect can actually understand through the intelligible species of which it is possessed, without turning to the phantasms?

Objection 1. It would seem that the intellect can actually understand through the intelligible species of which it is possessed, without turning to the phantasms. For the intellect is made actual by the intelligible species by which it is informed. But if the intellect is in act, it understands. Therefore the intelligible species suffices for the intellect to understand actually, without turning to the phantasms.

Objection 2. Further, the imagination is more dependent on the senses than the intellect on the imagination. But the imagination can actually imagine in the absence of the sensible. Therefore much more can the intellect understand without turning to the phantasms.

Objection 3. There are no phantasms of incorporeal things: for the imagination does not transcend time and space. If, therefore, our intellect cannot understand anything actually without turning to the phantasms, it follows that it cannot understand anything incorporeal. Which is clearly false: for we understand truth, and God, and the angels.

On the contrary, The Philosopher says (De Anima iii, 7) that "the soul understands nothing without a phantasm."

I answer that, In the present state of life in which the soul is united to a passible body, it is impossible for our intellect to understand anything actually, except by turning to the phantasms.

First of all because the intellect, being a power that does not make use of a corporeal organ, would in no way be hindered in its act through the lesion of a corporeal organ, if for its act there were not required the act of some power that does make use of a corporeal organ. Now sense, imagination and the other powers belonging to the sensitive part, make use of a corporeal organ. Wherefore it is clear that for the intellect to understand actually, not only when it acquires fresh knowledge, but also when it applies knowledge already acquired, there is need for the act of the imagination and of the other powers. For when the act of the imagination is hindered by a lesion of the corporeal organ, for instance in a case of frenzy; or when the act of the memory is hindered, as in the case of lethargy, we see that a man is hindered from actually understanding things of which he had a previous knowledge.

Secondly, anyone can experience this of himself, that when he tries to understand something, he forms certain phantasms to serve him by way of examples, in which as it were he examines what he is desirous of understanding. For this reason it is that when we wish to help someone to understand something, we lay examples before him, from which he forms phantasms for the purpose of understanding.

Now the reason of this is that the power of knowledge is proportioned to the thing known. Wherefore the proper object of the angelic intellect, which is entirely separate from a body, is an intelligible substance separate from a body. Whereas the proper object of the human intellect, which is united to a body, is a quiddity or nature existing in corporeal matter; and through such natures of visible things it rises to a certain knowledge of things invisible. Now it belongs to such a nature to exist in an individual, and this cannot be apart from corporeal matter: for instance, it belongs to the nature of a stone to be in an individual stone, and to the nature of a horse to be in an individual horse, and so forth. Wherefore the nature of a stone or any material thing cannot be known completely and truly, except in as much as it is known as existing in the individual. Now we apprehend the individual through the senses and the imagination. And, therefore, for the intellect to understand actually its proper object, it must of necessity turn to the phantasms in order to perceive the universal nature existing in the individual. But if the proper object of our intellect were a separate form; or if, as the Platonists say, the natures of sensible things subsisted apart from the individual; there would be no need for the intellect to turn to the phantasms whenever it understands.

Reply to Objection 1. The species preserved in the passive intellect exist there habitually when it does not understand them actually, as we have said above (I:79:6). Wherefore for us to understand actually, the fact that the species are preserved does not suffice; we need further to make use of them in a manner befitting the things of which they are the species, which things are natures existing in individuals.

Reply to Objection 2. Even the phantasm is the likeness of an individual thing; wherefore the imagination does not need any further likeness of the individual, whereas the intellect does.

Reply to Objection 3. Incorporeal things, of which there are no phantasms, are known to us by comparison with sensible bodies of which there are phantasms. Thus we understand truth by considering a thing of which we possess the truth; and God, as Dionysius says (Div. Nom. i), we know as cause, by way of excess and by way of remotion. Other incorporeal substances we know, in the present state of life, only by way of remotion or by some comparison to corporeal things. And, therefore, when we understand something about these things, we need to turn to phantasms of bodies, although there are no phantasms of the things themselves.


Whether the judgment of the intellect is hindered through suspension of the sensitive powers?

Objection 1. It would seem that the judgment of the intellect is not hindered by suspension of the sensitive powers. For the superior does not depend on the inferior. But the judgment of the intellect is higher than the senses. Therefore the judgment of the intellect is not hindered through suspension of the senses.

Objection 2. Further, to syllogize is an act of the intellect. But during sleep the senses are suspended, as is said in De Somn. et Vigil. i and yet it sometimes happens to us to syllogize while asleep. Therefore the judgment of the intellect is not hindered through suspension of the senses.

On the contrary, What a man does while asleep, against the moral law, is not imputed to him as a sin; as Augustine says (Gen. ad lit. xii, 15). But this would not be the case if man, while asleep, had free use of his reason and intellect. Therefore the judgment of the intellect is hindered by suspension of the senses.

I answer that, As we have said above (Article 7), our intellect's proper and proportionate object is the nature of a sensible thing. Now a perfect judgment concerning anything cannot be formed, unless all that pertains to that thing's nature be known; especially if that be ignored which is the term and end of judgment. Now the Philosopher says (De Coel. iii), that "as the end of a practical science is action, so the end of natural science is that which is perceived principally through the senses"; for the smith does not seek knowledge of a knife except for the purpose of action, in order that he may produce a certain individual knife; and in like manner the natural philosopher does not seek to know the nature of a stone and of a horse, save for the purpose of knowing the essential properties of those things which he perceives with his senses. Now it is clear that a smith cannot judge perfectly of a knife unless he knows the action of the knife: and in like manner the natural philosopher cannot judge perfectly of natural things, unless he knows sensible things. But in the present state of life whatever we understand, we know by comparison to natural sensible things. Consequently it is not possible for our intellect to form a perfect judgment, while the senses are suspended, through which sensible things are known to us.

Reply to Objection 1. Although the intellect is superior to the senses, nevertheless in a manner it receives from the senses, and its first and principal objects are founded in sensible things. And therefore suspension of the senses necessarily involves a hindrance to the judgment of the intellect.

Reply to Objection 2. The senses are suspended in the sleeper through certain evaporations and the escape of certain exhalations, as we read in De Somn. et Vigil. iii. And, therefore, according to the amount of such evaporation, the senses are more or less suspended. For when the amount is considerable, not only are the senses suspended, but also the imagination, so that there are no phantasms; thus does it happen, especially when a man falls asleep after eating and drinking copiously. If, however, the evaporation be somewhat less, phantasms appear, but distorted and without sequence; thus it happens in a case of fever. And if the evaporation be still more attenuated, the phantasms will have a certain sequence: thus especially does it happen towards the end of sleep in sober men and those who are gifted with a strong imagination. If the evaporation be very slight, not only does the imagination retain its freedom, but also the common sense is partly freed; so that sometimes while asleep a man may judge that what he sees is a dream, discerning, as it were, between things, and their images. Nevertheless, the common sense remains partly suspended; and therefore, although it discriminates some images from the reality, yet is it always deceived in some particular. Therefore, while man is asleep, according as sense and imagination are free, so is the judgment of his intellect unfettered, though not entirely. Consequently, if a man syllogizes while asleep, when he wakes up he invariably recognizes a flaw in some respect.

The Summa Theologiæ of St. Thomas AquinasSecond and Revised Edition, 1920Literally translated by Fathers of the English Dominican ProvinceOnline Edition Copyright © 2017 by Kevin Knight Nihil Obstat. F. Innocentius Apap, O.P., S.T.M., Censor. Theol.Imprimatur. Edus. Canonicus Surmont, Vicarius Generalis. Westmonasterii.APPROBATIO ORDINISNihil Obstat. F. Raphael Moss, O.P., S.T.L. and F. Leo Moore, O.P., S.T.L.Imprimatur. F. Beda Jarrett, O.P., S.T.L., A.M., Prior Provincialis AngliæMARIÆ IMMACULATÆ - SEDI SAPIENTIÆ

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Whether our intellect understands corporeal and material things by abstraction from phantasms?

Objection 1. It would seem that our intellect does not understand corporeal and material things by abstraction from the phantasms. For the intellect is false if it understands an object otherwise than as it really is. Now the forms of material things do not exist as abstracted from the particular things represented by the phantasms. Therefore, if we understand material things by abstraction of the species from the phantasm, there will be error in the intellect.

Objection 2. Further, material things are those natural things which include matter in their definition. But nothing can be understood apart from that which enters into its definition. Therefore material things cannot be understood apart from matter. Now matter is the principle of individualization. Therefore material things cannot be understood by abstraction of the universal from the particular, which is the process whereby the intelligible species is abstracted from the phantasm.

Objection 3. Further, the Philosopher says (De Anima iii, 7) that the phantasm is to the intellectual soul what color is to the sight. But seeing is not caused by abstraction of species from color, but by color impressing itself on the sight. Therefore neither does the act of understanding take place by abstraction of something from the phantasm, but by the phantasm impressing itself on the intellect.

Objection 4. Further, the Philosopher says (De Anima iii, 5) there are two things in the intellectual soul—the passive intellect and the active intellect. But it does not belong to the passive intellect to abstract the intelligible species from the phantasm, but to receive them when abstracted. Neither does it seem to be the function of the active intellect, which is related to the phantasm, as light is to color; since light does not abstract anything from color, but rather streams on to it. Therefore in no way do we understand by abstraction from phantasms.

Objection 5. Further, the Philosopher (De Anima iii, 7) says that "the intellect understands the species in the phantasm"; and not, therefore, by abstraction.

On the contrary, The Philosopher says (De Anima iii, 4) that "things are intelligible in proportion as they are separate from matter." Therefore material things must needs be understood according as they are abstracted from matter and from material images, namely, phantasms.

I answer that, As stated above (I:84:7), the object of knowledge is proportionate to the power of knowledge. Now there are three grades of the cognitive powers. For one cognitive power, namely, the sense, is the act of a corporeal organ. And therefore the object of every sensitive power is a form as existing in corporeal matter. And since such matter is the principle of individuality, therefore every power of the sensitive part can only have knowledge of the individual. There is another grade of cognitive power which is neither the act of a corporeal organ, nor in any way connected with corporeal matter; such is the angelic intellect, the object of whose cognitive power is therefore a form existing apart from matter: for though angels know material things, yet they do not know them save in something immaterial, namely, either in themselves or in God. But the human intellect holds a middle place: for it is not the act of an organ; yet it is a power of the soul which is the form the body, as is clear from what we have said above (I:76:1). And therefore it is proper to it to know a form existing individually in corporeal matter, but not as existing in this individual matter. But to know what is in individual matter, not as existing in such matter, is to abstract the form from individual matter which is represented by the phantasms. Therefore we must needs say that our intellect understands material things by abstracting from the phantasms; and through material things thus considered we acquire some knowledge of immaterial things, just as, on the contrary, angels know material things through the immaterial.

But Plato, considering only the immateriality of the human intellect, and not its being in a way united to the body, held that the objects of the intellect are separate ideas; and that we understand not by abstraction, but by participating things abstract, as stated above (I:84:1.

Reply to Objection 1. Abstraction may occur in two ways:

First, by way of composition and division; thus we may understand that one thing does not exist in some other, or that it is separate therefrom.

Secondly, by way of simple and absolute consideration; thus we understand one thing without considering the other. Thus for the intellect to abstract one from another things which are not really abstract from one another, does, in the first mode of abstraction, imply falsehood. But, in the second mode of abstraction, for the intellect to abstract things which are not really abstract from one another, does not involve falsehood, as clearly appears in the case of the senses. For if we understood or said that color is not in a colored body, or that it is separate from it, there would be error in this opinion or assertion. But if we consider color and its properties, without reference to the apple which is colored; or if we express in word what we thus understand, there is no error in such an opinion or assertion, because an apple is not essential to color, and therefore color can be understood independently of the apple. Likewise, the things which belong to the species of a material thing, such as a stone, or a man, or a horse, can be thought of apart from the individualizing principles which do not belong to the notion of the species. This is what we mean by abstracting the universal from the particular, or the intelligible species from the phantasm; that is, by considering the nature of the species apart from its individual qualities represented by the phantasms. If, therefore, the intellect is said to be false when it understands a thing otherwise than as it is, that is so, if the word "otherwise" refers to the thing understood; for the intellect is false when it understands a thing otherwise than as it is; and so the intellect would be false if it abstracted the species of a stone from its matter in such a way as to regard the species as not existing in matter, as Plato held. But it is not so, if the word "otherwise" be taken as referring to the one who understands. For it is quite true that the mode of understanding, in one who understands, is not the same as the mode of a thing in existing: since the thing understood is immaterially in the one who understands, according to the mode of the intellect, and not materially, according to the mode of a material thing.

Reply to Objection 2. Some have thought that the species of a natural thing is a form only, and that matter is not part of the species. If that were so, matter would not enter into the definition of natural things. Therefore it must be said otherwise, that matter is twofold, common, and "signate" or individual; common, such as flesh and bone; and individual, as this flesh and these bones. The intellect therefore abstracts the species of a natural thing from the individual sensible matter, but not from the common sensible matter; for example, it abstracts the species of man from "this flesh and these bones," which do not belong to the species as such, but to the individual (Metaph. vii, Did. vi, 10), and need not be considered in the species: whereas the species of man cannot be abstracted by the intellect form "flesh and bones."

Mathematical species, however, can be abstracted by the intellect from sensible matter, not only from individual, but also from common matter; not from common intelligible matter, but only from individual matter. For sensible matter is corporeal matter as subject to sensible qualities, such as being cold or hot, hard or soft, and the like: while intelligible matter is substance as subject to quantity. Now it is manifest that quantity is in substance before other sensible qualities are. Hence quantities, such as number, dimension, and figures, which are the terminations of quantity, can be considered apart from sensible qualities; and this is to abstract them from sensible matter; but they cannot be considered without understanding the substance which is subject to the quantity; for that would be to abstract them from common intelligible matter. Yet they can be considered apart from this or that substance; for that is to abstract them from individual intelligible matter. But some things can be abstracted even from common intelligible matter, such as "being," "unity," "power," "act," and the like; all these can exist without matter, as is plain regarding immaterial things. Because Plato failed to consider the twofold kind of abstraction, as above explained (Reply to Objection 1), he held that all those things which we have stated to be abstracted by the intellect, are abstract in reality.

Reply to Objection 3. Colors, as being in individual corporeal matter, have the same mode of existence as the power of sight: therefore they can impress their own image on the eye. But phantasms, since they are images of individuals, and exist in corporeal organs, have not the same mode of existence as the human intellect, and therefore have not the power of themselves to make an impression on the passive intellect. This is done by the power of the active intellect which by turning towards the phantasm produces in the passive intellect a certain likeness which represents, as to its specific conditions only, the thing reflected in the phantasm. It is thus that the intelligible species is said to be abstracted from the phantasm; not that the identical form which previously was in the phantasm is subsequently in the passive intellect, as a body transferred from one place to another.

Reply to Objection 4. Not only does the active intellect throw light on the phantasm: it does more; by its own power it abstracts the intelligible species from the phantasm. It throws light on the phantasm, because, just as the sensitive part acquires a greater power by its conjunction with the intellectual part, so by the power of the active intellect the phantasms are made more fit for the abstraction therefrom of intelligible intentions. Furthermore, the active intellect abstracts the intelligible species from the phantasm, forasmuch as by the power of the active intellect we are able to disregard the conditions of individuality, and to take into our consideration the specific nature, the image of which informs the passive intellect.

Reply to Objection 5. Our intellect both abstracts the intelligible species from the phantasms, inasmuch as it considers the natures of things in universal, and, nevertheless, understands these natures in the phantasms since it cannot understand even the things of which it abstracts the species, without turning to the phantasms, as we have said above (I:84:7).


Whether the intelligible species abstracted from the phantasm is related to our intellect as that which is understood?

Objection 1. It would seem that the intelligible species abstracted from the phantasm is related to our intellect as that which is understood. For the understood in act is in the one who understands: since the understood in act is the intellect itself in act. But nothing of what is understood is in the intellect actually understanding, save the abstracted intelligible species. Therefore this species is what is actually understood.

Objection 2. Further, what is actually understood must be in something; else it would be nothing. But it is not in something outside the soul: for, since what is outside the soul is material, nothing therein can be actually understood. Therefore what is actually understood is in the intellect. Consequently it can be nothing else than the aforesaid intelligible species.

Objection 3. Further, the Philosopher says (1 Peri Herm. i) that "words are signs of the passions in the soul." But words signify the things understood, for we express by word what we understand. Therefore these passions of the soul—viz. the intelligible species, are what is actually understood.

On the contrary, The intelligible species is to the intellect what the sensible image is to the sense. But the sensible image is not what is perceived, but rather that by which sense perceives. Therefore the intelligible species is not what is actually understood, but that by which the intellect understands.

I answer that, Some have asserted that our intellectual faculties know only the impression made on them; as, for example, that sense is cognizant only of the impression made on its own organ. According to this theory, the intellect understands only its own impression, namely, the intelligible species which it has received, so that this species is what is understood.

This is, however, manifestly false for two reasons.

First, because the things we understand are the objects of science; therefore if what we understand is merely the intelligible species in the soul, it would follow that every science would not be concerned with objects outside the soul, but only with the intelligible species within the soul; thus, according to the teaching of the Platonists all science is about ideas, which they held to be actually understood [I:84:1].

Secondly, it is untrue, because it would lead to the opinion of the ancients who maintained that "whatever seems, is true" [Aristotle, Metaph. iii. 5], and that consequently contradictories are true simultaneously. For if the faculty knows its own impression only, it can judge of that only. Now a thing seems according to the impression made on the cognitive faculty. Consequently the cognitive faculty will always judge of its own impression as such; and so every judgment will be true: for instance, if taste perceived only its own impression, when anyone with a healthy taste perceives that honey is sweet, he would judge truly; and if anyone with a corrupt taste perceives that honey is bitter, this would be equally true; for each would judge according to the impression on his taste. Thus every opinion would be equally true; in fact, every sort of apprehension.

Therefore it must be said that the intelligible species is related to the intellect as that by which it understands: which is proved thus. There is a twofold action (Metaph. ix, Did. viii, 8), one which remains in the agent; for instance, to see and to understand; and another which passes into an external object; for instance, to heat and to cut; and each of these actions proceeds in virtue of some form. And as the form from which proceeds an act tending to something external is the likeness of the object of the action, as heat in the heater is a likeness of the thing heated; so the form from which proceeds an action remaining in the agent is the likeness of the object. Hence that by which the sight sees is the likeness of the visible thing; and the likeness of the thing understood, that is, the intelligible species, is the form by which the intellect understands. But since the intellect reflects upon itself, by such reflection it understands both its own act of intelligence, and the species by which it understands. Thus the intelligible species is that which is understood secondarily; but that which is primarily understood is the object, of which the species is the likeness. This also appears from the opinion of the ancient philosophers, who said that "like is known by like." For they said that the soul knows the earth outside itself, by the earth within itself; and so of the rest. If, therefore, we take the species of the earth instead of the earth, according to Aristotle (De Anima iii, 8), who says "that a stone is not in the soul, but only the likeness of the stone"; it follows that the soul knows external things by means of its intelligible species.

Reply to Objection 1. The thing understood is in the intellect by its own likeness; and it is in this sense that we say that the thing actually understood is the intellect in act, because the likeness of the thing understood is the form of the intellect, as the likeness of a sensible thing is the form of the sense in act. Hence it does not follow that the intelligible species abstracted is what is actually understood; but rather that it is the likeness thereof.

Reply to Objection 2. In these words "the thing actually understood" there is a double implication—the thing which is understood, and the fact that it is understood. In like manner the words "abstract universal" imply two things, the nature of a thing and its abstraction or universality. Therefore the nature itself to which it occurs to be understood, abstracted or considered as universal is only in individuals; but that it is understood, abstracted or considered as universal is in the intellect. We see something similar to this is in the senses. For the sight sees the color of the apple apart from its smell. If therefore it be asked where is the color which is seen apart from the smell, it is quite clear that the color which is seen is only in the apple: but that it be perceived apart from the smell, this is owing to the sight, forasmuch as the faculty of sight receives the likeness of color and not of smell. In like manner humanity understood is only in this or that man; but that humanity be apprehended without conditions of individuality, that is, that it be abstracted and consequently considered as universal, occurs to humanity inasmuch as it is brought under the consideration of the intellect, in which there is a likeness of the specific nature, but not of the principles of individuality.

Reply to Objection 3. There are two operations in the sensitive part. One, in regard of impression only, and thus the operation of the senses takes place by the senses being impressed by the sensible. The other is formation, inasmuch as the imagination forms for itself an image of an absent thing, or even of something never seen. Both of these operations are found in the intellect. For in the first place there is the passion of the passive intellect as informed by the intelligible species; and then the passive intellect thus informed forms a definition, or a division, or a composition, expressed by a word. Wherefore the concept conveyed by a word is its definition; and a proposition conveys the intellect's division or composition. Words do not therefore signify the intelligible species themselves; but that which the intellect forms for itself for the purpose of judging of external things.


Whether the more universal is first in our intellectual cognition?

Objection 1. It would seem that the more universal is not first in our intellectual cognition. For what is first and more known in its own nature, is secondarily and less known in relation to ourselves. But universals come first as regards their nature, because "that is first which does not involve the existence of its correlative" (Categor. ix). Therefore the universals are secondarily known as regards our intellect.

Objection 2. Further, the composition precedes the simple in relation to us. But universals are the more simple. Therefore they are known secondarily by us.

Objection 3. Further, the Philosopher says (Phys. i, 1), that the object defined comes in our knowledge before the parts of its definition. But the more universal is part of the definition of the less universal, as "animal" is part of the definition of "man." Therefore the universals are secondarily known by us.

Objection 4. Further, we know causes and principles by their effects. But universals are principles. Therefore universals are secondarily known by us.

On the contrary, "We must proceed from the universal to the singular and individual" (Phys. i, 1)

I answer that, In our knowledge there are two things to be considered.

First, that intellectual knowledge in some degree arises from sensible knowledge: and, because sense has singular and individual things for its object, and intellect has the universal for its object, it follows that our knowledge of the former comes before our knowledge of the latter.

Secondly, we must consider that our intellect proceeds from a state of potentiality to a state of actuality; and every power thus proceeding from potentiality to actuality comes first to an incomplete act, which is the medium between potentiality and actuality, before accomplishing the perfect act. The perfect act of the intellect is complete knowledge, when the object is distinctly and determinately known; whereas the incomplete act is imperfect knowledge, when the object is known indistinctly, and as it were confusedly. A thing thus imperfectly known, is known partly in act and partly in potentiality, and hence the Philosopher says (Phys. i, 1), that "what is manifest and certain is known to us at first confusedly; afterwards we know it by distinguishing its principles and elements." Now it is evident that to know an object that comprises many things, without proper knowledge of each thing contained in it, is to know that thing confusedly. In this way we can have knowledge not only of the universal whole, which contains parts potentially, but also of the integral whole; for each whole can be known confusedly, without its parts being known. But to know distinctly what is contained in the universal whole is to know the less common, as to "animal" indistinctly is to know it as "animal"; whereas to know "animal" distinctly is know it as "rational" or "irrational animal," that is, to know a man or a lion: therefore our intellect knows "animal" before it knows man; and the same reason holds in comparing any more universal idea with the less universal.

Moreover, as sense, like the intellect, proceeds from potentiality to act, the same order of knowledge appears in the senses. For by sense we judge of the more common before the less common, in reference both to place and time; in reference to place, when a thing is seen afar off it is seen to be a body before it is seen to be an animal; and to be an animal before it is seen to be a man, and to be a man before it seen to be Socrates or Plato; and the same is true as regards time, for a child can distinguish man from not man before he distinguishes this man from that, and therefore "children at first call men fathers, and later on distinguish each one from the others" (Phys. i, 1). The reason of this is clear: because he who knows a thing indistinctly is in a state of potentiality as regards its principle of distinction; as he who knows "genus" is in a state of potentiality as regards "difference." Thus it is evident that indistinct knowledge is midway between potentiality and act.

We must therefore conclude that knowledge of the singular and individual is prior, as regards us, to the knowledge of the universal; as sensible knowledge is prior to intellectual knowledge. But in both sense and intellect the knowledge of the more common precedes the knowledge of the less common.

Reply to Objection 1. The universal can be considered in two ways.

First, the universal nature may be considered together with the intention of universality. And since the intention of universality—viz. the relation of one and the same to many—is due to intellectual abstraction, the universal thus considered is a secondary consideration. Hence it is said (De Anima i, 1) that the "universal animal is either nothing or something secondary." But according to Plato, who held that universals are subsistent, the universal considered thus would be prior to the particular, for the latter, according to him, are mere participations of the subsistent universals which he called ideas.

Secondly, the universal can be considered in the nature itself—for instance, animality or humanity as existing in the individual. And thus we must distinguish two orders of nature: one, by way of generation and time; and thus the imperfect and the potential come first. In this way the more common comes first in the order of nature; as appears clearly in the generation of man and animal; for "the animal is generated before man," as the Philosopher says (De Gener. Animal ii, 3). The other order is the order of perfection or of the intention of nature: for instance, act considered absolutely is naturally prior to potentiality, and the perfect to the imperfect: thus the less common comes naturally before the more common; as man comes before animal. For the intention of nature does not stop at the generation of animal but goes on to the generation of man.

Reply to Objection 2. The more common universal may be compared to the less common, as the whole, and as the part. As the whole, considering that in the more universal is potentially contained not only the less universal, but also other things, as in "animal" is contained not only "man" but also "horse." As part, considering that the less common contains in its idea not only the more common, but also more; as "man" contains not only "animal" but also "rational." Therefore "animal" in itself comes into our knowledge before "man"; but "man" comes before "animal" considered as part of the same idea.

Reply to Objection 3. A part can be known in two ways.

First, absolutely considered in itself; and thus nothing prevents the parts being known before the whole, as stones are known before a house is known.

Secondly as belonging to a certain whole; and thus we must needs know the whole before its parts. For we know a house vaguely before we know its different parts. So likewise principles of definition are known before the thing defined is known; otherwise the thing defined would not be known at all. But as parts of the definition they are known after. For we know man vaguely as man before we know how to distinguish all that belongs to human nature.

Reply to Objection 4. The universal, as understood with the intention of universality, is, indeed, in a way, a principle of knowledge, in so far as the intention of universality results from the mode of understanding by way of abstraction. But what is a principle of knowledge is not of necessity a principle of existence, as Plato thought: since at times we know a cause through its effect, and substance through accidents. Wherefore the universal thus considered, according to the opinion of Aristotle, is neither a principle of existence, nor a substance, as he makes clear (Metaph. vii, Did. vi, 13). But if we consider the generic or specific nature itself as existing in the singular, thus in a way it is in the nature of a formal principle in regard to the singulars: for the singular is the result of matter, while the idea of species is from the form. But the generic nature is compared to the specific nature rather after the fashion of a material principle, because the generic nature is taken from that which is material in a thing, while the idea of species is taken from that which is formal: thus the notion of animal is taken from the sensitive part, whereas the notion of man is taken from the intellectual part. Thus it is that the ultimate intention of nature is to the species and not to the individual, or the genus: because the form is the end of generation, while matter is for the sake of the form. Neither is it necessary that, as regards us, knowledge of any cause or principle should be secondary: since at times through sensible causes we become acquainted with unknown effects, and sometimes conversely.


Whether we can understand many things at the same time?

Objection 1. It would seem that we can understand many things at the same time. For intellect is above time, whereas the succession of before and after belongs to time. Therefore the intellect does not understand different things in succession, but at the same time.

Objection 2. Further, there is nothing to prevent different forms not opposed to each other from actually being in the same subject, as, for instance, color and smell are in the apple. But intelligible species are not opposed to each other. Therefore there is nothing to prevent the same intellect being in act as regards different intelligible species, and thus it can understand many things at the same time.

Objection 3. Further, the intellect understands a whole at the same time, such as a man or a house. But a whole contains many parts. Therefore the intellect understands many things at the same time.

Objection 4. Further, we cannot know the difference between two things unless we know both at the same time (De Anima iii, 2), and the same is to be said of any other comparison. But our intellect knows the difference and comparison between one thing and another. Therefore it knows many things at the same time.

On the contrary, It is said (Topic. ii, 10) that "understanding is of one thing only, knowledge is of many."

I answer that, The intellect can, indeed, understand many things as one, but not as many: that is to say by "one" but not by "many" intelligible species. For the mode of every action follows the form which is the principle of that action. Therefore whatever things the intellect can understand under one species, it can understand at the same time: hence it is that God sees all things at the same time, because He sees all in one, that is, in His Essence. But whatever things the intellect understands under different species, it does not understand at the same time. The reason of this is that it is impossible for one and the same subject to be perfected at the same time by many forms of one genus and diverse species, just as it is impossible for one and the same body at the same time to have different colors or different shapes. Now all intelligible species belong to one genus, because they are the perfections of one intellectual faculty: although the things which the species represent belong to different genera. Therefore it is impossible for one and the same intellect to be perfected at the same time by different intelligible species so as actually to understand different things.

Reply to Objection 1. The intellect is above that time, which is the measure of the movement of corporeal things. But the multitude itself of intelligible species causes a certain vicissitude of intelligible operations, according as one operation succeeds another. And this vicissitude is called time by Augustine, who says (Gen. ad lit. viii, 20,22), that "God moves the spiritual creature through time."

Reply to Objection 2. Not only is it impossible for opposite forms to exist at the same time in the same subject, but neither can any forms belonging to the same genus, although they be not opposed to one another, as is clear from the examples of colors and shapes.

Reply to Objection 3. Parts can be understood in two ways.

First, in a confused way, as existing in the whole, and thus they are known through the one form of the whole, and so are known together. In another way they are known distinctly: thus each is known by its species; and so they are not understood at the same time.

Reply to Objection 4. If the intellect sees the difference or comparison between one thing and another, it knows both in relation to their difference or comparison; just, as we have said above (Reply to Objection 3), as it knows the parts in the whole.


Whether our intellect understands by composition and division?

Objection 1. It would seem that our intellect does not understand by composition and division. For composition and division are only of many; whereas the intellect cannot understand many things at the same time. Therefore it cannot understand by composition and division.

Objection 2. Further, every composition and division implies past, present, or future time. But the intellect abstracts from time, as also from other individual conditions. Therefore the intellect does not understand by composition and division.

Objection 3. Further, the intellect understands things by a process of assimilation to them. But composition and division are not in things, for nothing is in things but what is signified by the predicate and the subject, and which is one and the same, provided that the composition be true, for "man" is truly what "animal" is. Therefore the intellect does not act by composition and division.

On the contrary, Words signify the conceptions of the intellect, as the Philosopher says (Peri Herm. i). But in words we find composition and division, as appears in affirmative and negative propositions. Therefore the intellect acts by composition and division.

I answer that, The human intellect must of necessity understand by composition and division. For since the intellect passes from potentiality to act, it has a likeness to things which are generated, which do not attain to perfection all at once but acquire it by degrees: so likewise the human intellect does not acquire perfect knowledge by the first act of apprehension; but it first apprehends something about its object, such as its quiddity, and this is its first and proper object; and then it understands the properties, accidents, and the various relations of the essence. Thus it necessarily compares one thing with another by composition or division; and from one composition and division it proceeds to another, which is the process of reasoning.

But the angelic and the Divine intellect, like all incorruptible things, have their perfection at once from the beginning. Hence the angelic and the Divine intellect have the entire knowledge of a thing at once and perfectly; and hence also in knowing the quiddity of a thing they know at once whatever we can know by composition, division, and reasoning. Therefore the human intellect knows by composition, division and reasoning. But the Divine intellect and the angelic intellect know, indeed, composition, division, and reasoning, not by the process itself, but by understanding the simple essence.

Reply to Objection 1. Composition and division of the intellect are made by differentiating and comparing. Hence the intellect knows many things by composition and division, as by knowing the difference and comparison of things.

Reply to Objection 2. Although the intellect abstracts from the phantasms, it does not understand actually without turning to the phantasms, as we have said (Article 1; I:84:7). And forasmuch as it turns to the phantasms, composition and division of the intellect involve time.

Reply to Objection 3. The likeness of a thing is received into the intellect according to the mode of the intellect, not according to the mode of the thing. Wherefore something on the part of the thing corresponds to the composition and division of the intellect; but it does not exist in the same way in the intellect and in the thing. For the proper object of the human intellect is the quiddity of a material thing, which comes under the action of the senses and the imagination. Now in a material thing there is a twofold composition.

First, there is the composition of form with matter; and to this corresponds that composition of the intellect whereby the universal whole is predicated of its part: for the genus is derived from common matter, while the difference that completes the species is derived from the form, and the particular from individual matter. The second comparison is of accident with subject: and to this real composition corresponds that composition of the intellect, whereby accident is predicated of subject, as when we say "the man is white." Nevertheless composition of the intellect differs from composition of things; for in the latter the things are diverse, whereas composition of the intellect is a sign of the identity of the components. For the above composition of the intellect does not imply that "man" and "whiteness" are identical, but the assertion, "the man is white," means that "the man is something having whiteness": and the subject, which is a man, is identified with a subject having whiteness. It is the same with the composition of form and matter: for animal signifies that which has a sensitive nature; rational, that which has an intellectual nature; man, that which has both; and Socrates that which has all these things together with individual matter; and according to this kind of identity our intellect predicates the composition of one thing with another.


Whether the intellect can be false?

Objection 1. It would seem that the intellect can be false; for the Philosopher says (Metaph. vi, Did. v, 4) that "truth and falsehood are in the mind." But the mind and intellect are the same, as is shown above (I:79:1). Therefore falsehood may be in the mind.

Objection 2. Further, opinion and reasoning belong to the intellect. But falsehood exists in both. Therefore falsehood can be in the intellect.

Objection 3. Further, sin is in the intellectual faculty. But sin involves falsehood: for "those err that work evil" (Proverbs 14:22). Therefore falsehood can be in the intellect.

On the contrary, Augustine says (QQ. 83, qu. 32), that "everyone who is deceived, does not rightly understand that wherein he is deceived." And the Philosopher says (De Anima iii, 10), that "the intellect is always true."

I answer that, The Philosopher (De Anima iii, 6) compares intellect with sense on this point. For sense is not deceived in its proper object, as sight in regard to color; has accidentally through some hindrance occurring to the sensile organ—for example, the taste of a fever-stricken person judges a sweet thing to be bitter, through his tongue being vitiated by ill humors. Sense, however, may be deceived as regards common sensible objects, as size or figure; when, for example, it judges the sun to be only a foot in diameter, whereas in reality it exceeds the earth in size. Much more is sense deceived concerning accidental sensible objects, as when it judges that vinegar is honey by reason of the color being the same. The reason of this is evident; for every faculty, as such, is per se directed to its proper object; and things of this kind are always the same. Hence, as long as the faculty exists, its judgment concerning its own proper object does not fail. Now the proper object of the intellect is the "quiddity" of a material thing; and hence, properly speaking, the intellect is not at fault concerning this quiddity; whereas it may go astray as regards the surroundings of the thing in its essence or quiddity, in referring one thing to another, as regards composition or division, or also in the process of reasoning. Therefore, also in regard to those propositions, which are understood, the intellect cannot err, as in the case of first principles from which arises infallible truth in the certitude of scientific conclusions.

The intellect, however, may be accidentally deceived in the quiddity of composite things, not by the defect of its organ, for the intellect is a faculty that is independent of an organ; but on the part of the composition affecting the definition, when, for instance, the definition of a thing is false in relation to something else, as the definition of a circle applied to a triangle; or when a definition is false in itself as involving the composition of things incompatible; as, for instance, to describe anything as "a rational winged animal." Hence as regards simple objects not subject to composite definitions we cannot be deceived unless, indeed, we understand nothing whatever about them, as is said Metaph. ix, Did. viii, 10.

Reply to Objection 1. The Philosopher says that falsehood is in the intellect in regard to composition and division. The same answer applies to the Second Objection concerning opinion and reasoning, and to the Third Objection, concerning the error of the sinner, who errs in the practical judgment of the appetible object. But in the absolute consideration of the quiddity of a thing, and of those things which are known thereby, the intellect is never deceived. In this sense are to be understood the authorities quoted in proof of the opposite conclusion.


Whether one person can understand one and the same thing better than another can?

Objection 1. It would seem that one person cannot understand one and the same thing better than another can. For Augustine says (QQ. 83, qu. 32), "Whoever understands a thing otherwise than as it is, does not understand it at all. Hence it is clear that there is a perfect understanding, than which none other is more perfect: and therefore there are not infinite degrees of understanding a thing: nor can one person understand a thing better than another can."

Objection 2. Further, the intellect is true in its act of understanding. But truth, being a certain equality between thought and thing, is not subject to more or less; for a thing cannot be said to be more or less equal. Therefore a thing cannot be more or less understood.

Objection 3. Further, the intellect is the most formal of all that is in man. But different forms cause different species. Therefore if one man understands better than another, it would seem that they do not belong to the same species.

On the contrary, Experience shows that some understand more profoundly than do others; as one who carries a conclusion to its first principles and ultimate causes understands it better than the one who reduces it only to its proximate causes.

I answer that, A thing being understood more by one than by another may be taken in two senses.

First, so that the word "more" be taken as determining the act of understanding as regards the thing understood; and thus, one cannot understand the same thing more than another, because to understand it otherwise than as it is, either better or worse, would entail being deceived, and such a one would not understand it, as Augustine argues (QQ. 83, qu. 32). In another sense the word "more" can be taken as determining the act of understanding on the part of him who understands; and so one may understand the same thing better than someone else, through having a greater power of understanding: just as a man may see a thing better with his bodily sight, whose power is greater, and whose sight is more perfect. The same applies to the intellect in two ways.

First, as regards the intellect itself, which is more perfect. For it is plain that the better the disposition of a body, the better the soul allotted to it; which clearly appears in things of different species: and the reason thereof is that act and form are received into matter according to matter's capacity: thus because some men have bodies of better disposition, their souls have a greater power of understanding, wherefore it is said (De Anima ii, 9), that "it is to be observed that those who have soft flesh are of apt mind."

Secondly, this occurs in regard to the lower powers of which the intellect has need in its operation: for those in whom the imaginative, cogitative, and memorative powers are of better disposition, are better disposed to understand.

The reply to the First Objection is clear from the above; likewise the reply to the

Second, for the truth of the intellect consists in the intellect understanding a thing as it is.

Reply to Objection 3. The difference of form which is due only to the different disposition of matter, causes not a specific but only a numerical difference: for different individuals have different forms, diversified according to the difference of matter.


Whether the intellect understands the indivisible before the divisible?

Objection 1. It would seem that the intellect understands the indivisible before the divisible. For the Philosopher says (Phys. i, 1) that "we understand and know from the knowledge of principles and elements." But principles are indivisible, and elements are of divisible things. Therefore the indivisible is known to us before the divisible.

Objection 2. Further, the definition of a thing contains what is known previously, for a definition "proceeds from the first and more known," as is said Topic. vi, 4. But the indivisible is part of the definition of the divisible; as a point comes into the definition of a line; for as Euclid says, "a line is length without breadth, the extremities of which are points"; also unity comes into the definition of number, for "number is multitude measured by one," as is said Metaph. x, Did. ix, 6. Therefore our intellect understands the indivisible before the divisible.

Objection 3. Further, "Like is known by like." But the indivisible is more like to the intellect than is the divisible; because "the intellect is simple" (De Anima iii, 4). Therefore our intellect first knows the indivisible.

On the contrary, It is said (De Anima iii, 6) that "the indivisible is expressed as a privation." But privation is known secondarily. Therefore likewise is the indivisible.

I answer that, The object of our intellect in its present state is the quiddity of a material thing, which it abstracts from the phantasms, as above stated (I:84:7. And since that which is known first and of itself by our cognitive power is its proper object, we must consider its relationship to that quiddity in order to discover in what order the indivisible is known. Now the indivisible is threefold, as is said De Anima iii, 6.

First, the continuous is indivisible, since actually it is undivided, although potentially divisible: and this indivisible is known to us before its division, which is a division into parts: because confused knowledge is prior to distinct knowledge, as we have said above (Article 3).

Secondly, the indivisible is so called in relation to species, as man's reason is something indivisible. This way, also, the indivisible is understood before its division into logical parts, as we have said above (De Anima iii, 6); and again before the intellect disposes and divides by affirmation and negation. The reason of this is that both these kinds of indivisible are understood by the intellect of itself, as being its proper object. The third kind of indivisible is what is altogether indivisible, as a point and unity, which cannot be divided either actually or potentially. And this indivisible is known secondarily, through the privation of divisibility. Wherefore a point is defined by way of privation "as that which has no parts"; and in like manner the notion of "one" is that is "indivisible," as stated in Metaph. x, Did. ix, 1. And the reason of this is that this indivisible has a certain opposition to a corporeal being, the quiddity of which is the primary and proper object of the intellect.

But if our intellect understood by participation of certain separate indivisible (forms), as the Platonists maintained, it would follow that a like indivisible is understood primarily; for according to the Platonists what is first is first participated by things.

Reply to Objection 1. In the acquisition of knowledge, principles and elements are not always (known) first: for sometimes from sensible effects we arrive at the knowledge of principles and intelligible causes. But in perfect knowledge, the knowledge of effects always depends on the knowledge of principles and elements: for as the Philosopher says in the same passage: "Then do we consider that we know, when we can resolve principles into their causes."

Reply to Objection 2. A point is not included in the definition of a line in general: for it is manifest that in a line of indefinite length, and in a circular line, there is no point, save potentially. Euclid defines a finite straight line: and therefore he mentions a point in the definition, as the limit in the definition of that which is limited. Unity is the measure of number: wherefore it is included in the definition of a measured number. But it is not included in the definition of the divisible, but rather conversely.

Reply to Objection 3. The likeness through which we understand is the species of the known in the knower; therefore a thing is known first, not on account of its natural likeness to the cognitive power, but on account of the power's aptitude for the object: otherwise sight would perceive hearing rather than color.

The Summa Theologiæ of St. Thomas AquinasSecond and Revised Edition, 1920Literally translated by Fathers of the English Dominican ProvinceOnline Edition Copyright © 2017 by Kevin Knight Nihil Obstat. F. Innocentius Apap, O.P., S.T.M., Censor. Theol.Imprimatur. Edus. Canonicus Surmont, Vicarius Generalis. Westmonasterii.APPROBATIO ORDINISNihil Obstat. F. Raphael Moss, O.P., S.T.L. and F. Leo Moore, O.P., S.T.L.Imprimatur. F. Beda Jarrett, O.P., S.T.L., A.M., Prior Provincialis AngliæMARIÆ IMMACULATÆ - SEDI SAPIENTIÆ

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Whether our intellect knows singulars?

Objection 1. It would seem that our intellect knows singulars. For whoever knows composition, knows the terms of composition. But our intellect knows this composition; "Socrates is a man": for it belongs to the intellect to form a proposition. Therefore our intellect knows this singular, Socrates.

Objection 2. Further, the practical intellect directs to action. But action has relation to singular things. Therefore the intellect knows the singular.

Objection 3. Further, our intellect understands itself. But in itself it is a singular, otherwise it would have no action of its own; for actions belong to singulars. Therefore our intellect knows singulars.

Objection 4. Further, a superior power can do whatever is done by an inferior power. But sense knows the singular. Much more, therefore, can the intellect know it.

On the contrary, The Philosopher says (Phys. i, 5), that "the universal is known by reason; and the singular is known by sense."

I answer that, Our intellect cannot know the singular in material things directly and primarily. The reason of this is that the principle of singularity in material things is individual matter, whereas our intellect, as have said above (I:85:1), understands by abstracting the intelligible species from such matter. Now what is abstracted from individual matter is the universal. Hence our intellect knows directly the universal only. But indirectly, and as it were by a kind of reflection, it can know the singular, because, as we have said above (I:85:7), even after abstracting the intelligible species, the intellect, in order to understand, needs to turn to the phantasms in which it understands the species, as is said De Anima iii, 7. Therefore it understands the universal directly through the intelligible species, and indirectly the singular represented by the phantasm. And thus it forms the proposition "Socrates is a man." Wherefore the reply to the first objection is clear.

Reply to Objection 2. The choice of a particular thing to be done is as the conclusion of a syllogism formed by the practical intellect, as is said Ethic. vii, 3. But a singular proposition cannot be directly concluded from a universal proposition, except through the medium of a singular proposition. Therefore the universal principle of the practical intellect does not move save through the medium of the particular apprehension of the sensitive part, as is said De Anima iii, 11.

Reply to Objection 3. Intelligibility is incompatible with the singular not as such, but as material, for nothing can be understood otherwise than immaterially. Therefore if there be an immaterial singular such as the intellect, there is no reason why it should not be intelligible.

Reply to Objection 4. The higher power can do what the lower power can, but in a more eminent way. Wherefore what the sense knows materially and concretely, which is to know the singular directly, the intellect knows immaterially and in the abstract, which is to know the universal.


Whether our intellect can know the infinite?

Objection 1. It would seem that our intellect can know the infinite. For God excels all infinite things. But our intellect can know God, as we have said above (I:12:1). Much more, therefore, can our intellect know all other infinite things.

Objection 2. Further, our intellect can naturally know "genera" and "species." But there is an infinity of species in some genera, as in number, proportion, and figure. Therefore our intellect can know the infinite.

Objection 3. Further, if one body can coexist with another in the same place, there is nothing to prevent an infinite number of bodies being in one place. But one intelligible species can exist with another in the same intellect, for many things can be habitually known at the same time. Therefore our intellect can have an habitual knowledge of an infinite number of things.

Objection 4. Further, as the intellect is not a corporeal faculty, as we have said (I:76:1, it appears to be an infinite power. But an infinite power has a capacity for an infinite object. Therefore our intellect can know the infinite.

On the contrary, It is said (Phys. i, 4) that "the infinite, considered as such, is unknown."

I answer that, Since a faculty and its object are proportional to each other, the intellect must be related to the infinite, as is its object, which is the quiddity of a material thing. Now in material things the infinite does not exist actually, but only potentially, in the sense of one succeeding another, as is said Phys. iii, 6. Therefore infinity is potentially in our mind through its considering successively one thing after another: because never does our intellect understand so many things, that it cannot understand more. On the other hand, our intellect cannot understand the infinite either actually or habitually. Not actually, for our intellect cannot know actually at the same time, except what it knows through one species. But the infinite is not represented by one species, for if it were it would be something whole and complete. Consequently it cannot be understood except by a successive consideration of one part after another, as is clear from its definition (Phys. iii, 6): for the infinite is that "from which, however much we may take, there always remains something to be taken." Thus the infinite could not be known actually, unless all its parts were counted: which is impossible.

For the same reason we cannot have habitual knowledge of the infinite: because in us habitual knowledge results from actual consideration: since by understanding we acquire knowledge, as is said Ethic. ii, 1. Wherefore it would not be possible for us to have a habit of an infinity of things distinctly known, unless we had already considered the entire infinity thereof, counting them according to the succession of our knowledge: which is impossible. And therefore neither actually nor habitually can our intellect know the infinite, but only potentially as explained above.

Reply to Objection 1. As we have said above (I:7:1), God is called infinite, because He is a form unlimited by matter; whereas in material things, the term 'infinite' is applied to that which is deprived of any formal term. And form being known in itself, whereas matter cannot be known without form, it follows that the material infinite is in itself unknowable. But the formal infinite, God, is of Himself known; but He is unknown to us by reason of our feeble intellect, which in its present state has a natural aptitude for material objects only. Therefore we cannot know God in our present life except through material effects. In the future life this defect of intellect will be removed by the state of glory, when we shall be able to see the Essence of God Himself, but without being able to comprehend Him.

Reply to Objection 2. The nature of our mind is to know species abstracted from phantasms; therefore it cannot know actually or habitually species of numbers or figures that are not in the imagination, except in a general way and in their universal principles; and this is to know them potentially and confusedly.

Reply to Objection 3. If two or more bodies were in the same place, there would be no need for them to occupy the place successively, in order for the things placed to be counted according to this succession of occupation. On the other hand, the intelligible species enter into our intellect successively; since many things cannot be actually understood at the same time: and therefore there must be a definite and not an infinite number of species in our intellect.

Reply to Objection 4. As our intellect is infinite in power, so does it know the infinite. For its power is indeed infinite inasmuch as it is not terminated by corporeal matter. Moreover it can know the universal, which is abstracted from individual matter, and which consequently is not limited to one individual, but, considered in itself, extends to an infinite number of individuals.


Whether our intellect can know contingent things?

Objection 1. It would seem that the intellect cannot know contingent things: because, as the Philosopher says (Ethic. vi, 6), the objects of understanding, wisdom and knowledge are not contingent, but necessary things.

Objection 2. Further, as stated in Phys. iv, 12, "what sometimes is and sometimes is not, is measured by time." Now the intellect abstracts from time, and from other material conditions. Therefore, as it is proper to a contingent thing sometime to be and sometime not to be, it seems that contingent things are not known by the intellect.

On the contrary, All knowledge is in the intellect. But some sciences are of the contingent things, as the moral sciences, the objects of which are human actions subject to free-will; and again, the natural sciences in as far as they relate to things generated and corruptible. Therefore the intellect knows contingent things.

I answer that, Contingent things can be considered in two ways; either as contingent, or as containing some element of necessity, since every contingent thing has in it something necessary: for example, that Socrates runs, is in itself contingent; but the relation of running to motion is necessary, for it is necessary that Socrates move if he runs. Now contingency arises from matter, for contingency is a potentiality to be or not to be, and potentiality belongs to matter; whereas necessity results from form, because whatever is consequent on form is of necessity in the subject. But matter is the individualizing principle: whereas the universal comes from the abstraction of the form from the particular matter. Moreover it was laid down above (Article 1) that the intellect of itself and directly has the universal for its object; while the object of sense is the singular, which in a certain way is the indirect object of the intellect, as we have said above (Article 1). Therefore the contingent, considered as such, is known directly by sense and indirectly by the intellect; while the universal and necessary principles of contingent things are known only by the intellect. Hence if we consider the objects of science in their universal principles, then all science is of necessary things. But if we consider the things themselves, thus some sciences are of necessary things, some of contingent things.

From which the replies to the objections are clear.


Whether our intellect can know the future?

Objection 1. It would seem that our intellect knows the future. For our intellect knows by means of intelligible species abstracted from the "here" and "now," and related indifferently to all time. But it can know the present. Therefore it can know the future.

Objection 2. Further, man, while his senses are in suspense, can know some future things, as in sleep, and in frenzy. But the intellect is freer and more vigorous when removed from sense. Therefore the intellect of its own nature can know the future.

Objection 3. The intellectual knowledge of man is superior to any knowledge of brutes. But some animals know the future; thus crows by their frequent cawing foretell rain. Therefore much more can the intellect know the future.

On the contrary, It is written (Ecclesiastes 8:6-7), "There is a great affliction for man, because he is ignorant of things past; and things to come he cannot know by any messenger."

I answer that, We must apply the same distinction to future things, as we applied above (Article 3) to contingent things. For future things considered as subject to time are singular, and the human intellect knows them by reflection only, as stated above (Article 1). But the principles of future things may be universal; and thus they may enter the domain of the intellect and become the objects of science.

Speaking, however, of the knowledge of the future in a general way, we must observe that the future may be known in two ways: either in itself, or in its cause. The future cannot be known in itself save by God alone; to Whom even that is present which in the course of events is future, forasmuch as from eternity His glance embraces the whole course of time, as we have said above when treating of God's knowledge (I:14:13). But forasmuch as it exists in its cause, the future can be known by us also. And if, indeed, the cause be such as to have a necessary connection with its future result, then the future is known with scientific certitude, just as the astronomer foresees the future eclipse. If, however, the cause be such as to produce a certain result more frequently than not, then can the future be known more or less conjecturally, according as its cause is more or less inclined to produce the effect.

Reply to Objection 1. This argument considers that knowledge which is drawn from universal causal principles; from these the future may be known, according to the order of the effects to the cause.

Reply to Objection 2. As Augustine says (Confess. xii, Gen. ad lit. xii. 13), the soul has a certain power of forecasting, so that by its very nature it can know the future; hence when withdrawn from corporeal sense, and, as it were, concentrated on itself, it shares in the knowledge of the future. Such an opinion would be reasonable if we were to admit that the soul receives knowledge by participating the ideas as the Platonists maintained, because in that case the soul by its nature would know the universal causes of all effects, and would only be impeded in its knowledge by the body, and hence when withdrawn from the corporeal senses it would know the future.

But since it is connatural to our intellect to know things, not thus, but by receiving its knowledge from the senses; it is not natural for the soul to know the future when withdrawn from the senses: rather does it know the future by the impression of superior spiritual and corporeal causes; of spiritual causes, when by Divine power the human intellect is enlightened through the ministry of angels, and the phantasms are directed to the knowledge of future events; or, by the influence of demons, when the imagination is moved regarding the future known to the demons, as explained above (I:57:3). The soul is naturally more inclined to receive these impressions of spiritual causes when it is withdrawn from the senses, as it is then nearer to the spiritual world, and freer from external distractions. The same may also come from superior corporeal causes. For it is clear that superior bodies influence inferior bodies. Hence, in consequence of the sensitive faculties being acts of corporeal organs, the influence of the heavenly bodies causes the imagination to be affected, and so, as the heavenly bodies cause many future events, the imagination receives certain images of some such events. These images are perceived more at night and while we sleep than in the daytime and while we are awake, because, as stated in De Somn. et Vigil. ii [De Divinat. per somn. ii.], "impressions made by day are evanescent. The night air is calmer, when silence reigns, hence bodily impressions are made in sleep, when slight internal movements are felt more than in wakefulness, and such movements produce in the imagination images from which the future may be foreseen."

Reply to Objection 3. Brute animals have no power above the imagination wherewith to regulate it, as man has his reason, and therefore their imagination follows entirely the influence of the heavenly bodies. Thus from such animals' movements some future things, such as rain and the like, may be known rather from human movements directed by reason. Hence the Philosopher says (De Somn. et Vig.), that "some who are most imprudent are most far-seeing; for their intelligence is not burdened with cares, but is as it were barren and bare of all anxiety moving at the caprice of whatever is brought to bear on it."

The Summa Theologiæ of St. Thomas AquinasSecond and Revised Edition, 1920Literally translated by Fathers of the English Dominican ProvinceOnline Edition Copyright © 2017 by Kevin Knight Nihil Obstat. F. Innocentius Apap, O.P., S.T.M., Censor. Theol.Imprimatur. Edus. Canonicus Surmont, Vicarius Generalis. Westmonasterii.APPROBATIO ORDINISNihil Obstat. F. Raphael Moss, O.P., S.T.L. and F. Leo Moore, O.P., S.T.L.Imprimatur. F. Beda Jarrett, O.P., S.T.L., A.M., Prior Provincialis AngliæMARIÆ IMMACULATÆ - SEDI SAPIENTIÆ

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