Article 8 — Whether the mind knows itself through its essence or through some species

Eighth, it is asked whether the mind knows itself through its essence or through some species? (Parallel texts: above, q. 8, a. 6; ST I.14.2, ad 3; I.87.1; SCG II.75; III.46; Disputed Questions on the Soul, a. 16, ad 8; Commentary on Aristotle's On the Soul, bk. 2, lect. 6; bk. 3, lect. 9.)

Obj. 1: It seems that it knows itself through some species, for as the Philosopher says: (Aristotle, On the Soul 3.7, 431a16.) our intellect understands nothing without a phantasm. But it cannot receive a phantasm of the very essence of the soul. Therefore, our mind must understand itself through some other species abstracted from phantasms.

Obj. 2: Those things which are seen through their essence are most certainly apprehended without error. But many err about the human mind, for some (Democritus and Leucippus, as Aristotle refers in On the Soul 1.2, 403b31.) say it is air, others (Diogenes, according to Aristotle, On the Soul, 1.2, 405a21, see also Augustine, On the Trinity, bk. 10, ch. 7 (PL 42:978).) fire, and hold many other foolish opinions about it. Therefore, the mind does not see itself through its essence.

Obj. 3: It was said that through its essence the mind sees that it exists, but can err in the investigation of its nature.

On the contrary, to know something through its essence is to know what it is, for the essence of a thing is the same as its quiddity. Therefore, if the soul saw itself through its essence, everyone would unerringly know the essence of his soul, which is obviously false.

Obj. 4: Our soul is a form joined to matter. But every form of this kind is known through abstraction of the species from matter and from material conditions. Therefore, the soul is known through an abstracted species.

Obj. 5: Understanding is not an act of the soul alone, but of the composite, as is said in On the Soul. (Aristotle, On the Soul 1.4, 408b11.) But every such act is common to soul and body. Therefore, there must always be something from the body in understanding. But this would not be if the mind saw itself through its essence without any species abstracted from the bodily senses. Therefore, the mind does not see itself through its essence.

Obj. 6: The Philosopher says (Aristotle, On the Soul 3.4, 430a2.) that the intellect understands itself just as it understands other things. But it does not understand other things through its essence, but through species. Therefore, it does not understand itself through its essence.

Obj. 7: Powers are known through their acts, and acts through their objects. (Aristotle, On the Soul 2.4, 415a18.) But the essence of the soul can be known only when its powers are known, for what a thing can do manifests the nature of the thing. Therefore, it has to know its essence through its acts and through the species of its objects.

Obj. 8: As sense is related to what is sensible, so understanding is related to what is intelligible. But there has to be some distance between sense and the sensible. For this reason, the eye cannot see itself. Therefore, there also has to be some distance in intellectual vision, with the result that mind can never understand itself through its essence.

Obj. 9: According to the Philosopher, (Aristotle, Posterior Analytics 1.3, 72b25.) in a demonstration we should not proceed in a circle, because it would follow that a thing would become known through itself. Thus, it would follow that it would exist before itself and be better known than itself, which is impossible. But, if the mind sees itself through its essence, that which is known and that through which it is known will be the same. Therefore, the same untenable conclusion would follow, for something would exist before itself and be better known than itself.

Obj. 10: Dionysius (Pseudo-Dionysius, On the Divine Names, ch. 7, para. 2 (PG 3:868B); ch. 6.) says that the soul knows the truth of existing things in a sort of circle. However, a circular movement is from the same thing to the same thing. Therefore, it seems that the soul goes out from itself in its understanding, and through things outside returns to knowledge of itself. Thus, it does not understand itself through its essence.

Obj. 11: While the cause remains, the effect remains. Therefore, if the mind saw itself through its essence because its essence is present to it, it would always see it, for it is always present to it. Therefore, since it is impossible to understand many things at once, the mind would never understand anything else.

Obj. 12: Things that follow have more composition than those which come earlier. But understanding follows existing. Therefore, there is more composition in the understanding of the soul than in its existence. But, in the soul, "that which exists" is not the same as "that by which it exists." Therefore, that in the soul by which it understands will not be the same as that which is understood. Thus, the mind does not see itself through its essence.

Obj. 13: The same thing under the same aspect cannot be form and that which is informed. But, since the understanding is a power of the soul, it is a kind of form of its essence. Therefore, the essence of the soul cannot be the form of the understanding. Therefore, the mind does not see itself through its essence.

Obj. 14: The soul is a subsistent substance. However, intelligible forms are not of themselves subsistent. Otherwise, knowledge, which is made up of these intelligible forms, would not be classified as an accident. Therefore, the essence of the soul cannot have the character of intelligible form by which the mind sees itself.

Obj. 15: Since acts and movements are distinguished in their terms, intelligible things which belong to the same species are understood according to their species in the same way. But the soul of Peter belongs to the same species as that of Paul. Therefore, the soul of Peter understands itself just as it understands Paul’s soul. But it does not understand Paul’s soul through its essence, for it is not present to it. Therefore, it does not understand itself through its essence.

Obj. 16: Form is simpler than that which is informed through the form. But the mind is not simpler than itself. Therefore, it is not informed by itself. Consequently, since it is informed by that through which it knows, it will not know itself through itself.

On the contrary (1), Augustine says: (Augustine, On the Trinity, bk. 9, ch. 3 (PL 42:963).) mind knows itself through itself because it is incorporeal. For, if it does not know itself, it does not love itself.

Furthermore (2), the gloss on the second Epistle to the Corinthians 12:2 reads: (Peter Lombard, Commentary on 2 Corinthians, at 2 Cor 12:2 (PL 192:81C); from Augustine, On the Literal Interpretation of Genesis, bk. 12, ch. 24 (PL 34:474).) by that sight which is called intellectual, those things are known which are not bodies and do not have any forms like bodies, as mind itself and every disposition of the soul. The same gloss adds: (Peter Lombard, Commentary on 2 Corinthians, at 2 Cor 12:2 (PL 192:80D); from Augustine, On the Literal Interpretation of Genesis, bk. 12, ch. 6 (PL 34:458).) intellectual sight contains those things which have no likenesses not identical with themselves. Therefore, the mind does not know itself through something not identical with it.

Furthermore (3), in On the Soul we read: (Aristotle, On the Soul 3.4, 430a3.) in things separated from matter, that which understands and that by which it is understood are the same. But the mind is an immaterial thing. Therefore, it is understood through its essence.

Furthermore (4), everything which, as intelligible, is present to the understanding is understood by the understanding. But the essence of the soul is present to understanding in an intelligible manner, for it is present to it through its truth. Truth, however, is the reason for understanding, as goodness is the reason for loving. Therefore, the mind understands itself through its essence.

Furthermore (5), the species through which something is understood is simpler than that which we understand through it. But the soul does not have any species simpler than itself to be abstracted from it. Therefore, the soul does not understand itself through a species, but through its essence.

Furthermore (6), all knowledge takes place through an assimilation of the knower to the thing known. (Aquinas commonly attributes this to Aristotle: cf. In I Sent., d. 34, q. 3, a. 1, obj. 4; d. 35, a. 1, obj. 4; Aristotle, On the Soul 1.2, 404b15‒26; 1.5, 409b25‒32; Ethics 6.1, 1139a10; Isaac Israeli ben Solomon, Liber de definitionibus; Aquinas, Commentary on the De Trinitate of Boethius, q. 5, a. 3; Algazel, Metaphysics, part 1, tract. 3, sent. 2; Aristotle, Metaphysics 12.7, 1072b20.) But there is nothing else more like the soul than its essence. Therefore, it understands itself through nothing else but its essence.

Furthermore (7), that which is a cause by which other things are made knowable is not known through anything other than itself. But the soul is a cause which makes other physical things knowable, for they are intelligible inasmuch as we make them intelligible, as the Commentator says. (Averroes, Metaphysics, bk. 2, comm. 1.) Therefore, the soul is understood only through itself.

Furthermore (8), according to the Philosopher, (Aristotle, On the Soul 1.1, 402a1.) knowledge about the soul is most certain. But that which is more certain is not known through that which is less certain. Therefore, we do not have knowledge of the soul through something other than itself.

Furthermore (9), every species through which our soul understands is abstracted from sensible things. But there is no sensible thing from which the soul can abstract its own quiddity. Therefore, the soul does not know itself through any likeness.

Furthermore (10), as physical light makes all things actually visible, so the soul through its light makes all material things actually intelligible, as is clear from On the Soul. (Aristotle, On the Soul 3.5, 430a15.) But physical light is seen through itself and not through any likeness of itself. Therefore, the soul, too, is understood through its essence and not through any likeness.

Furthermore (11), as the Philosopher says, (Aristotle, On the Soul 3.5, 430a22.) the agent intellect does not at one time understand and at another not understand, but always understands. But it is only itself which it understands at all times. This would not be possible if it understood itself through a species abstracted from the senses, for thus it would not understand itself before the abstraction. Therefore, our mind understands itself through its essence.

I answer that when we ask if something is known through its essence, we can understand the question in two ways. In the first, “through its essence” is taken to refer to the thing known, so that we understand that a thing is known through its essence when its essence is known, and that it is not known through its essence when not its essence but only certain of its accidents are known. In the second way, it is taken to refer to that by which something is known, so that we thus understand that something is known through its essence because the essence itself is that by which it is known. It is in this sense that we ask here if the soul understands itself through its essence.

For a clear understanding of this question we should observe that each person can have a twofold knowledge of the soul, as Augustine says. (Augustine, On the Trinity, bk. 9, cc. 4, 6 (PL 42:965).) One of these is the knowledge by which the soul of each man knows itself only with reference to that which is proper to it. The other is that by which the soul is known with reference to that which is common to all souls. This latter, which concerns all souls without distinction, is that by which the nature of the soul is known. However, the knowledge which each has of his soul, in so far as it is proper to himself, is the knowledge of the soul as it exists in this individual. Thus, it is through this knowledge that one knows whether the soul exists, as when someone perceives that he has a soul. Through the other type of knowledge, however, one knows what the soul is and what its proper accidents are.

With reference to the first type of cognition we must make a distinction, because one can know something habitually or actually. Concerning the actual cognition by which one actually considers that he has a soul, I say that the soul is known through its acts. For one perceives that he has a soul, that he lives, and that he exists, because he perceives that he senses, understands, and carries on other vital activities of this sort. For this reason, the Philosopher says: (Aristotle, Ethics 9.9, 1170a31.) we sense that we sense, and we understand that we understand, and because we sense this, we understand that we exist. But one perceives that he understands only from the fact that he understands something. For to understand something is prior to understanding that one understands. Therefore, through that which it understands or senses the soul arrives at actual perception of the fact that it exists. Concerning habitual knowledge I say this, that the soul sees itself through its essence, that is, the soul has the power to enter upon actual cognition of itself from the very fact that its essence is present to it. This is like the case of one who, because he has the habit of some knowledge, can by reason of the presence of the habit perceive those things which fall under that habit. But no habit is required for the soul’s perception of its existence and its advertence to the activity within it. The essence alone of the soul, which is present to the mind, is enough for this, for the acts in which it is actually perceived proceed from it.

But, if we speak of the knowledge of the soul when the human mind is limited to specific or generic knowledge, we must make another distinction. For the concurrence of two elements, apprehension and judgment about the thing apprehended, is necessary for knowledge. Therefore, the knowledge by which the nature of the soul is known can be considered with reference to apprehension and with reference to judgment. If, then, we consider this knowledge with reference to apprehension, I say that we know the nature of the soul through species which we abstract from the senses. For our soul holds the last place among intellectual things, just as first matter does among sensible things, as the Commentator shows. (Averroes, On the Soul, bk. 3, comm. 5 and 17.) For, as first matter is in potency to all sensible forms, so our potential intellect is in potency to all intelligible forms. Thus, it is, in fact, pure potency in the order of intelligible things, as matter is in the order of sensible reality. Therefore, as matter is sensible only through some added form, so the potential intellect is intelligible only through a species which is brought into it. Hence, our mind cannot so understand itself that it immediately apprehends itself. Rather, it comes to a knowledge of itself through apprehension of other things, just as the nature of first matter is known from its receptivity for forms of a certain kind. This becomes apparent when we look at the manner in which philosophers have investigated the nature of the soul. For, from the fact that the human soul knows the universal natures of things, they have perceived that the species by which we understand is immaterial. Otherwise, it would be individuated and so would not lead to knowledge of the universal. From the immateriality of the species by which we understand, philosophers have understood that the intellect is a thing independent of matter. And from this they have proceeded to a knowledge of the other properties of the intellective soul. Thus, the Philosopher says: (Aristotle, On the Soul 3.4, 430a2.) the intellect is intelligible just as the other intelligible things are. The Commentator also affirms this in his explanation: (Averroes, On the Soul, bk. 3, comm. 15.) intellect is understood through an intention in it, just as other intelligible things. This intention is nothing but the intelligible species. But this intention is in the intellect as actually intelligible. In other things, however, it is not actually but only potentially intelligible.

But, if we consider the knowledge which we have of the nature of the soul in the judgment by which we decide that it exists in such a way, as we had apprehended from the deduction mentioned above, we have knowledge of the soul inasmuch as we contemplate inviolable truth. This is the truth from which we define to the best of our power not the kind of mind each man has, but the kind of mind it ought to be according to eternal norms, as Augustine says. (Augustine, On the Trinity, bk. 9, ch. 6 (PL 42:966).) We see this inviolable truth in its likeness which is impressed on our mind to the extent that we naturally know some things as self-evident. We examine all other things with reference to these, judging of them according to these.

Thus it is clear that our mind knows itself in some way through its essence, as Augustine says, (Augustine, On the Trinity, bk. 9, ch. 3 (PL 42:963); Pseudo-Augustine (Alcher of Clairvaux), On the Spirit and the Soul, ch. 1.) and in some way through an intention or species, as the Philosopher (Aristotle, On the Soul 3.4, 430a2.) and the Commentator (Averroes, On the Soul, bk. 3, comm. 15.) say; and, moreover, in some way in the contemplation of inviolable truth, as Augustine says. (Augustine, On the Trinity, bk. 9, ch. 6 (PL 42:966).) In this way, then, one must answer both sets of reasons.

Reply Obj. 1: Our understanding can actually understand nothing before it abstracts from phantasms. Nor can it have habitual knowledge of things other than itself, which are not within it, before the abstraction just mentioned, because species of other intelligible things are not innate in it. However, its essence is innate in it, so that it does not have to obtain it from phantasms, just as it is not the essence of matter which is received from the natural agent, but only its form, which is related to physical matter as intelligible form is related to sensible matter, as the Commentator says. (Averroes, On the Soul, bk. 3, comm. 18–19.) Therefore, before the mind abstracts from phantasms, it has habitual knowledge of itself, by which it can perceive that it exists.

Reply Obj. 2: No one has ever made the mistake of not perceiving that he was alive, (Cf. Augustine, On the Trinity, bk. 10, ch. 10 (PL 42:981).) a fact which belongs to the knowledge by which one knows in its singularity what goes on in his soul. It is according to this knowledge that the soul is said to be habitually known through its essence. Many, however, do fall into error regarding knowledge of the specific nature of the soul, and on this point the conclusion of the objection is true.

Reply Obj. 3: From this the answer to the third difficulty is clear.

Reply Obj. 4: Although the soul is joined to matter as its form, it is not so dominated by matter that it becomes material, and thus not actually intelligible, but only potentially intelligible by abstraction from matter.

Reply Obj. 5: The objection holds for actual knowledge, according to which the soul perceives its existence only by perceiving its act and object, as has been said.

Reply Obj. 6: The citation from the Philosopher should be taken as referring to the intellect’s understanding of what it is and not to the habitual knowledge which it has of the fact that it exists.

Reply Obj. 7: The seventh difficulty must be answered in like manner.

Reply Obj. 8: Sensitive activity is brought to completion through the action of the sensible thing on the sense. This is action which is connected with position and therefore needs a definite distance. Intellectual activity is not limited to any position. Therefore, in this way they are not alike.

Reply Obj. 9: There are two ways in which we can say a thing is known by means of something else. In the first, from knowledge of another thing one arrives at knowledge of the thing in question. In this way conclusions are said to be known from principles. A thing cannot be known by means of itself in this way. In the second way, a thing is said to be known by means of something else in the sense that it is known in that something. In this case, an act of cognition distinct from that in which the thing is known is not required in order that the medium in which the thing is known might itself be known. So, there is nothing to prevent something from being known by means of itself in this way, as God knows himself by means of himself. Thus, in some way the soul, too, knows itself through its essence.

Reply Obj. 10: We do find a circle in the knowledge of the soul, in so far as it seeks the truth of existing things by reasoning. Hence, Dionysius says this in order to show how the knowledge of the soul falls short of the knowledge of an angel. The circularity is observed in this, that reason reaches conclusions from principles by way of discovery, and by way of judgment examines the conclusions which have been found, analyzing them back to the principles. Therefore, this difficulty is not to the point.

Reply Obj. 11: Just as it is not necessary always actually to understand that of which we have habitual knowledge through species existing in the understanding, so, too, it is not necessary always actually to understand the mind, knowledge of which is habitually in us because its essence is present to our understanding.

Reply Obj. 12: “That by which a thing is understood” and “that which is understood” are not related to each other as “that by which a thing is” and “that which is.” For existence is the act of a being, but understanding is not the act of that which is understood but of that which understands. Hence, “that by which a thing is understood” is related to that which understands as “that which is to that by which it is.” And, therefore, just as in the soul “that which is,” is different from “that by which it is,” so that by which it understands, that is to say, the intellective power, which is the source of the act of understanding, is different from its essence. However, it does not necessarily follow from this that the species by which a thing is understood must be different from that which is understood.

Reply Obj. 13: The intellective power is a form of the soul with reference to its act of existing, for it has existence in the soul as a property in a subject. But there is nothing to prevent the opposite of this from being true with reference to the act of understanding.

Reply Obj. 14: The knowledge by which the soul knows itself is not classified as an accident in so far as it is the source of habitual knowledge, but only as an act of cognition which is an accident. Thus, Augustine also says (Augustine, On the Trinity, bk. 9, ch. 4 (PL 42:964).) that knowledge is in the mind substantially in so far as the mind knows itself.

Reply Obj. 15: The objection holds for the knowledge of the soul by which it is known according to the nature of the species in which all souls share.

Reply Obj. 16: When the mind understands itself, the mind is not itself the form of the mind, because nothing is its own form. But it does follow the manner of form, inasmuch as the action by which it knows itself terminates at itself. Hence, it is not necessary for it to be simpler than itself, unless, perhaps, according to the manner of understanding, in so far as that which is understood is taken as simpler than the intellect itself which understands, and is thus considered as a perfection of the intellect.

Reply Sed Contra 1: We must understand these words of Augustine to mean that the mind knows itself through itself, since from itself the mind has the power to enter upon the act by which it actually knows itself, by perceiving that it exists. Similarly, from the species habitually retained in the mind, there results in the mind the power actually to consider the thing. But the mind can perceive what its own nature is only from the consideration of its object, as has been said.

Reply Sed Contra 2: The words of the gloss (Peter Lombard, Commentary on 2 Corinthians, at 2 Cor 12:2 (PL 192:80); from Augustine, On the Literal Interpretation of Genesis, bk. 12, ch. 24 (PL 34:474).) which read: intellectual sight contains those things, are to be referred to the object of knowledge rather than to that by which it is understood. This is clear from a consideration of what is said about other kinds of sight. For the same gloss reads: through bodily sight bodies are seen; through spiritual sight (that is, sight of imagination) likenesses of bodies are seen; through intellectual sight those things which are neither bodies nor likenesses of bodies are seen. (Peter Lombard, Commentary on 2 Corinthians, at 2 Cor 12:2 (PL 192:80); from Augustine, On the Literal Interpretation of Genesis, bk. 12, ch. 24 (PL 34:474).) If this were referred to that by which we understand, there would be no difference between bodily sight and spiritual sight (that of imagination), because even bodily sight takes place through the likeness of a body. For the stone is not in the eye, but a likeness of the stone. (Aristotle, On the Soul 3.8, 431b29.) But between the kinds of sight mentioned there is this difference, that bodily sight terminates at the body itself, whereas the sight of imagination terminates at the image of the body, as at its object. So, also, when it is said that intellectual sight embraces things which have no likenesses not identical with themselves, this does not mean that spiritual sight does not take place through species which are not the same as the things understood, but that intellectual sight does not terminate at the likeness of a thing but at the very essence of the thing. For, as by bodily sight one sees a body itself without seeing a likeness of the body, although he sees through a likeness of the body, so in intellectual sight one sees the very essence of a thing without seeing the similitude of the thing, although sometimes he sees that essence through some likeness, as is clear from experience. For, when we understand the soul, we do not construct a likeness of the soul and look at it, as happens in imagination. Rather, we study the essence of the soul itself. Nevertheless, this does not deny that this sight takes place through a species.

Reply Sed Contra 3: What the Philosopher says should be understood of an intellect which is altogether separated from matter, as the intellects of angels. And this is the way in which the Commentator explains the passage. (Averroes, On the Soul, bk. 3, comm. 15.) However, it should not be applied to the human intellect; otherwise, it would follow that speculative science would be the same as the thing known. But this is impossible, as the Commentator also concludes.

Reply Sed Contra 4: The soul is present to itself as intelligible, in the sense that it can be understood, but not in the sense that it is understood through itself, but from its object, as has been said. (Above: a.9, ad 1.)

Reply Sed Contra 5: The soul is not known through a species abstracted from it, but through the species of its object, which becomes its form in so far as it actually understands. Hence, the reason does not follow.

Reply Sed Contra 6: Although our soul is most like itself, it cannot be the principle of knowing itself in the manner of an intelligible species, just as first matter cannot. The reason for this is that our understanding occupies a position in the order of intelligible things similar to that of first matter in the order of sensible things, as the Commentator says. (Averroes, On the Soul, bk. 3, comm. 5, 17, and 19.)

Reply Sed Contra 7: The soul is the cause why other things are knowable not in so far as it is a means of knowing, but in so far as physical things are made intelligible through the activity of the soul.

Reply Sed Contra 8: Knowledge about the soul is most certain in this, that each one experiences within himself that he has a soul and that acts of the soul are within him. But it is very difficult to know what the soul is. Hence, the Philosopher adds: (Aristotle, On the Soul 1.1, 402a10.) it is extremely difficult to get any assurance about it.

Reply Sed Contra 9: The soul is not known through a species abstracted from sensible beings, as though that species were understood to be a likeness of the soul. Rather, from a study of the nature of the species abstracted from sensible things we discover the nature of the soul in which such a species is received, just as matter is known from form.

Reply Sed Contra 10: Physical light is seen through itself only in so far as it is the reason for the visibility of visible things and a kind of form making them actually visible. Now, we see the light which exists in the sun only through its likeness which exists in our sight. For as the specific nature of stone is not in the eye, but its likeness, so the form of light which is in the sun cannot be the same form that is in the eye. Similarly, we understand the light of the agent intellect, in so far as it is the reason for the intelligible species, making them actually intelligible.

Reply Sed Contra 11: What the Philosopher says can be explained in two ways, according to the two opinions about the agent intellect. For some (Avicenna, On the Soul, bk. 5, ch. 5; Alexander Aphrodisias; cf. SCG II.76; Averroes, On the Soul, bk. 3, comm. 36.) have held that the agent intellect is a separated substance, one of a number of intelligences. According to this it always actually understands, as the other intelligences do. Others, (E.g. Albert the Great, Summa de homine, q. 55, a. 3; Bonaventure, In II Sent., d. 24, part 1, a. 2, q. 4.) hold that the agent intellect is a power of the soul. According to this it is said that the agent intellect is not a power which "sometimes understands and sometimes does not," because the cause of understanding at some times and not at others does not come from it, but from the potential intellect. For, in every act by which man understands, the action of the agent intellect and that of the potential intellect concur. Moreover, the agent intellect does not receive anything from outside. Only the potential intellect does so. Hence, with reference to the requirements for our thought, there is nothing on the part of the agent intellect to keep us from always understanding, but there is on the part of the potential intellect, for it is brought to completion only through intelligible species abstracted from the senses.