Commentaria in Summam contra Gentiles, Liber III

Because certain words of Augustine seem to be against the aforesaid determination, therefore St. Thomas, in order to show that Augustine does not think against this truth, examines his words and shows that they in no way conflict with his own opinion¹.

These are Augustine's words, in IX de Trin.: The mind, just as it gathers the knowledge of corporeal things through the senses of the body, so it gathers the knowledge of incorporeal things through itself. Therefore it also knows itself through itself, because it is incorporeal. From these words Augustine seems to want the mind to understand itself through itself; and, in understanding itself, to understand separate substances; and consequently that in this life we can know separate substances. This is contrary to what was said above.

I. To this authority of Augustine St. Thomas says two things². The first is that it is not his mind that our soul can understand of itself through itself what it is: that is, that it itself is the principle by which it understands itself as to what it is, in the way in which the intelligible species of man is the principle by which one arrives at the knowledge of the quiddity and essence of man. And he shows both that this is impossible and that it is contrary to the mind of Augustine and Aristotle³.

He argues, however, first⁴. If this were so, the soul would always understand of itself what it is. This is clearly false. Therefore. — The consequence is proved. Because, since a cognitive potency is actually cognizing through the fact that the cognized object is in it⁵, if it is in it in potency, it cognizes in potency; if in act, it cognizes in act; if in an intermediate way, it cognizes in habit. But the soul itself is always present to itself in act, and never in potency or in habit only.

II. It seems, however, that this argument does not conclude. Indeed St. Thomas solves it in Qu. Verit., q. x, a. 8, ad 11, saying that, just as it is not necessary that that be always actually understood whose knowledge is had habitually through intentions existing in the intellect, so it is not necessary that the mind always be actually understood, whose knowledge is in us habitually through the fact that its very essence is present to our intellect. From these things it is clear that that conditional, and the assumption taken for its proof, namely that the soul is never present to itself in habit only, is false.

III. For the evidence of this, it must be considered that, since two things are required in order that something be understood, namely that it be understood in act and that it become one with the one understanding, the more the thing understood in act is one with the one understanding, the more it has to be understood by such an intellect. Therefore, if it is one with it not totally in act, but partly in potency and partly in act, it is understood, as St. Thomas says, not in perfect act, but partly in act and partly in potency, which is to be understood habitually. But if it is one with it perfectly in act, it is understood perfectly and according to actual consideration.

But the intelligible is one with the one understanding in one way when the same thing understands itself through itself immediately, and in another way when it understands something other than itself. For when some thing understood in act understands itself through itself, so that its mere presence is to itself the reason why it is known by itself, the one understanding and the thing understood are entirely one: because the essence of the one understanding and that by which it understands are entirely the same thing. But when the one understanding understands something other than itself, the one understanding and the thing understood, or that by which it understands, are not entirely one and the same, but are one through a certain union: inasmuch as the thing understood is united to the one understanding either through its own substance or through an intelligible species. But one and the same thing numerically cannot be more and less, or more perfectly and less perfectly, the same to itself, but it is always really the same to itself in a perfect way. But one and the same thing can well be united to another more perfectly and less perfectly. Therefore, if perfect identity is the reason why something knows itself quidditatively, it is necessary that it always know itself quidditatively: since such a thing understood is never the same as the one understanding in an imperfect way, but is always the same to it in a perfect way. But if the perfect union of the thing understood with the one understanding is the cause of something being actually understood, it is not necessary that it always be understood in act: because its perfect union with the one understanding is not always present, but sometimes imperfect.

From these things it is clear that St. Thomas's argument is efficacious. For since the soul is always present to itself by identity, and never in potency or in habit only, which is to be in some way one and in some way not one: if presence and identity to itself is to the one understanding the reason why it understands itself quidditatively, it follows that it always understands itself, because of the perfect union and presence to itself which is always present to it. Hence the response to St. Thomas's argument is null. Nor is the case similar between that which is known through its intention existing in the intellect and the soul knowing itself through itself, as has been shown. Because such an intelligible is not always united to the intellect in a perfect way, as the soul is to itself, but sometimes in an imperfect way. For that reason it is sometimes known in act, sometimes however in habit only. — But what St. Thomas intends in that response ⁶ will be said in the second conclusion ⁷.

IV. Second ⁸. This being granted, all men would know of the soul what it is, since all have a soul. This is false. Therefore etc.

Third. It follows that what the soul is will be naturally known. Therefore no one would err about what the soul is. This is false, as is evident from the various opinions about the nature of the soul. Therefore etc. — The first consequence is proved. Because the knowledge which takes place through something naturally implanted in us is natural, as is evident about the first principles, which are known through the light of the agent intellect. — The second is also proved. Because in those things which are naturally known no one can err, as is also evident about the first principles.

Concerning this proposition, The knowledge which takes place through something naturally implanted in us is natural, it must be noted that knowledge can be called natural in two ways. In one way, as it is distinguished against knowledge had supernaturally, or against knowledge received from a higher light than the light of the agent intellect. And in this way every knowledge acquired by us by the power of a natural principle in any manner whatsoever, whether, I say, immediately or mediately, is called natural. It is not taken in this way here. — In another way, as it is distinguished against knowledge acquired through study and exercise: and in this way that knowledge is called natural which is caused at once and without any inquiry in the intellect. And it is taken in this way here. For such knowledge is caused in us through some natural principle immediately, that is, with no intervening knowledge: just as the knowledge of the first principles is caused immediately by the light of the agent intellect, not indeed actual, but habitual, because, as was shown above ⁹ concerning the mind of St. Thomas, the agent intellect is not itself the habit of the first principles, but is its cause, by illuminating the phantasms, which are received from the senses.

Fourth. If that is so, it will be per se known what the soul is. Therefore it will be first known, and the principle of knowing other things. This is false, since in science what the soul is is not supposed as known, but is proposed as to be inquired into. Therefore etc. — The first consequence is evident. Because it will be known through the soul itself. — The second is proved. Because in any order that which is per se is prior to that which is through another, and is its principle.

2. Fifth ¹⁰. It is also shown that this is the mind of Augustine, by his own authority in X de Trin., where he wants that the soul indeed knows itself as present, but not as distinct from others, which would be to know what it itself is. For what a thing is is known when it is known as it is distinct from others.

From this it is also evident that in the words cited at the beginning of the chapter Augustine did not want the soul to know of itself what it is through itself.

Sixth, it is argued by the authority of Aristotle. The possible intellect understands itself as it understands other things, as is said in III de Anima, text. 16 ¹¹. Therefore not through itself.

For the evidence of the antecedent, St. Thomas notes that one must speak differently of our intellect and differently of separate substances. For our intellect, considered in itself, is only in potency to intelligible being; but nothing is known according as it is in potency, but according as it is in act; therefore it understands itself not through itself, but through the intelligible species by which it is made in act in the genus of intelligibles and actually understanding. But separate substances, because they are something in act in the genus of intelligibles, understand of themselves what they are through their own substances.

How the intellective soul, for here the intellective soul, the possible intellect, and the mind are taken for the same, because the soul itself is considered as having the power of understanding, is pure potency in the genus of intelligibles and is constituted in act through the intelligible species, was shown in the second book ¹².

V. Only one doubt occurs which was not touched in that place. For many times, according to the mind of Aristotle, III de Anima ¹³, it has been said that the intellective soul, by the power of the agent intellect, makes material things actually intelligible, which before were intelligible in potency. For this seems false. For it cannot make actually intelligible except what is actually intelligible: just as it cannot make actually hot what is not actually hot. Therefore the intellective soul is in the genus of intelligibles not as pure potency, but as existing in act.

2. It is answered that in the order of the object something can be said to be actually intelligible in two ways: in one way, because it is actually intelligible from its own nature, or from the nature of its species it has that it can first move or terminate the intellect; in another way, because it is not actually intelligible from the nature of its species, but it comes to it accidentally from another. What makes something actually intelligible in the first way must be so as to be understood in act according to itself: as God, who produces the intelligences, is according to himself maximally intelligible. But in this way the agent intellect does not make things actually intelligible: for it does not produce material things subsisting by themselves outside individual matter. — But what makes something actually intelligible in the second way need not be actually understood according to itself, but it suffices that it be something of the genus of intelligibles and of intellective substances, born to acquire its perfection from another. But in this way the intellective soul through the agent intellect makes things actually intelligible: inasmuch as it makes the things which are in themselves material immaterial, not indeed in themselves and outside the intellect, but in the possible intellect, from which immateriality they have that they be actually intelligible. Therefore the intellective soul, as productive of such intelligibles, is indeed actually intelligible as that by which something is actually intelligible, but not as that which is born from itself to be understood. Hence St. Thomas in Qq. Verit., q. x, a. 8, in the response to the tenth, among those solved in the second place, says that the light of the agent intellect is understood by us through itself inasmuch as it is the reason of the intelligible species, making them actually intelligible: just as corporeal light is seen inasmuch as it is the reason of the visibility of visible things. And in the First Part, q. lxxxvii ¹⁴, he says that the light of the agent intellect is the act of the intelligibles themselves.

3. But if it is objected that then the material thing, made intelligible, will be more perfect in the genus of intelligibles than the intellective soul, because it will both be of the genus of intelligibles and in that genus will hold itself as act, or as a being in act: — it is said that it is not unfitting that the material thing, as abstracted, be in a certain respect in a more perfect way in the genus of intelligibles than the soul according to a certain participation received from another, not however through its own essence. Simply, however, the intellective soul has more perfect being in that genus. Because it itself, although it holds the lowest place among intellectual substances, is nevertheless per se in that genus as a substance subsisting by itself and intellective, and also as actually intelligible in the way that by which another is actually intelligible. But the material nature is not in that genus as a substance subsisting by itself, nor as an intellective nature, but through the accidental being which it has in the intellect, according to which it is made immaterial by the power of the agent intellect.

VI. The second thing, as St. Thomas says ¹⁵, is that the intention of blessed Augustine is that the mind knows itself through itself inasmuch as it knows of itself that it is, that is, inasmuch as it knows that it exists: and so, by knowing itself, it knows of the separate substances that they exist, not however what they are. For unless the soul knew from itself this very thing that it is intellectual, we would in no way know, whether through demonstration or through faith, that some intellectual substances exist. A sign of this is that the science about the intellect of the soul must be used as a principle for all the things which we know about separate substances.

St. Thomas proves, however, that the soul knows that it exists through itself, in this way. The soul, from the fact that it perceives itself to act, perceives that it exists. But it acts through itself. Therefore it also knows that it exists through itself.

2. But because someone could object: Although the soul does not know of itself through itself what it is, but only that it is, nevertheless through the speculative sciences it can arrive at this, that it knows of itself what it is. Therefore, although through the knowledge by which the soul knows that it exists we do not arrive at the knowledge of the separate substances except that they exist, nevertheless through the speculative sciences we will be able to arrive at that knowledge: — St. Thomas answers that the reason is not the same. Because our understanding, by which we come to knowing what the soul is, is very remote from the understanding of a separate substance, that is, from that very understanding which is act.

He adds, however, that nevertheless, by knowing what the soul is, one can arrive at knowing some remote genus of separate substances.

Lastly he infers from what has been said this corollary ¹⁶, that the case is similar regarding those things which are in our soul, namely the habits and potencies, as it is regarding the soul. Because inasmuch as we perceive their acts, we know that they exist: but what they are we find out from the quality of their acts.

VII. Concerning the argument by which it is proved that the soul knows that it exists through itself, there is doubt. For from that major the opposite of the intended conclusion seems to follow, arguing in this way. The soul, from the fact that it perceives itself to act, perceives that it exists. But its acting is not the soul itself. Therefore it knows that it exists through another, not through itself. Hence in the First Part ¹⁷ St. Thomas concludes that Socrates or Plato knows that he has a soul not through the soul itself, but through its acts.

2. It is answered, from the doctrine of St. Thomas, Verit., q. x, a. 8 and 9, that the soul can be known to exist in two ways: namely actually, and habitually. If we speak of actual knowledge, in this way no one knows that he has a soul through the soul itself, but through its acts: for example, through sensing, understanding, being moved, and the like. And St. Thomas speaks of this knowledge in the First Part. — But if we speak of habitual knowledge, in this way someone knows that he has a soul through the soul itself, from the fact namely that it is present to him.

Therefore St. Thomas's argument concludes, not of actual knowledge, but of habitual knowledge. For from the fact that the soul actually knows that it exists because it knows itself to act, since it itself is through itself the principle of that action, by which, once known, the soul is known to exist; it follows that the very presence of the soul is the reason why it is able to go out into the act of the cognition of itself, which is for it to know that it exists through itself habitually.

When the argument to the opposite is deduced from that major, it is said that through it it is indeed concluded that the soul knows itself actually not through itself, but through another, namely through its acts: not however that it is not known habitually through itself. Indeed from that same major, with the minor subsumed which St. Thomas subsumes, namely that it acts through itself, it follows that it is known habitually through itself.

3. For the evidence of this response, however, two things must be considered. The first is that the acts and operations of the soul can be known in two ways: in one way, as to their being; in another way, as to their condition and nature. In the first way, they are the medium through which the soul comes into the actual cognition of itself that it is: for from the fact that someone knows himself to perform the operations of the soul, he knows that he has a soul. Therefore St. Thomas said that from the fact that he perceives himself to act he knows that he exists: to give to understand that not just any knowledge of the acts leads into the knowledge of the being of the soul, but that knowledge by which someone knows that the acts of the soul are in him. — In the second way, however, they are the principle of the knowledge of the soul as to what it is. Hence St. Thomas said that Aristotle demonstrates the nature of the possible intellect from understanding itself, namely that it is unmixed and incorruptible.

The second is that for something to know through its own essence that it exists by actual cognition is to make the presence of its essence to the intellect be actually known that it itself is, with nothing else required: just as we say that a separate substance always knows itself in act through itself, because the mere presence of its substance to its intellect makes it actually understand itself. But to know that one exists by habitual cognition through one's essence is for the mere presence of the essence to make it able to proceed into the act of the cognition of its existence. Because, therefore, the mere presence of the soul in someone does not make someone actually know that he has a soul, otherwise everyone would always actually know that he has a soul, because the soul is always present to him; but it is required that acts proceed from the soul itself, in which the existence of the soul itself is known, just as, when some action is known to be in someone, the principles of such an action are known to be in him: therefore St. Thomas well says ¹⁸ that the soul does not know by actual cognition through its own essence that it exists, but habitually it knows itself through its own essence; because no habit is required for it to perceive itself and what is done in itself, but for this the essence of the soul itself suffices, which is present to the mind, just as from it proceed the acts in which its being is known. Hence St. Thomas in his argument, from the fact that the soul acts by itself, that is, by the power of its nature, concludes that it understands of itself through itself that it is, namely habitually, inasmuch as through its presence someone is able to know of it that it exists, by eliciting the acts in which it is known.

VIII. But many doubts arise concerning this declaration. The first is. The soul cannot go out into any act of cognition unless it is actualized by an intelligible species, since it is pure potency in the genus of intelligibles, as was said above ¹⁹. Therefore through its own essence it can neither understand another than itself, nor understand itself to understand, nor that it exists: but it needs some habit, or some species, in order to perceive that it exists. Therefore not through its mere presence can someone know that he has a soul. Therefore it does not know that it exists habitually through its own essence.

The second is, because above ²⁰ St. Thomas said that the soul is always present to itself not according to potency or in habit only, but in act. Therefore it does not know that it exists habitually through itself: for something is known only habitually through that which is habitually in the intellect.

The third is. Just as the soul is known to exist through the acts of the soul, so through them one arrives at the knowledge of what it is, although in one way and another. Therefore if, because it produces through itself the acts in which it itself is known to exist, it is said to know itself habitually that it exists, by the same reason it will be said also to know itself habitually as to what it is.

IX. For the solution of the first doubt, it must be considered that, since an operation demonstrates that every principle of its own exists—because an operation cannot exist unless all its principles are posited—in whatever way things are principles of an operation, especially proximate ones, they are known through the operation. And if such an operation is a cognition, the mere presence of each principle is the ground (ratio) whereby that principle can be known to exist: since every principle of cognition per se concurs in its own order toward the operation. For just as heat is the ground why a hot thing can heat, so any principle of cognition is the ground why the knower can elicit cognition. And because it is natural that a principle of cognition is known to exist from cognition, just as from any operation the principle of operation can be known, therefore the presence of a principle of cognition in the knower is the ground whereby the knower can know that that principle exists. Whence both the intellective nature, which per se is a principle of intellection in the manner of an intellective principle (including the intellect under the name of intellective nature), is for itself the ground that it knows that it understands, and thus knows that it exists. And similarly the intelligible species, which concurs toward intellection in the manner of a form actuating the intellect, by its presence alone in the intellect is the ground that it is known to exist by him who knows that some intelligible species concurs to the act of intellection, inasmuch as per se in its own order it is a cause of intellection, and through intellection is known to exist. The same holds concerning every habit of the intellect. And thus it is clear that per se both the essence of the soul and the intelligible species and habit is that through which someone is capable of knowing that he has a soul, or that he has an intelligible species or habit.

From these things it is clear that this consequence is not valid: The intellective soul cannot go out into an act of intellection unless it is actuated by an intelligible species; therefore through its own essence it cannot understand that it understands nor that it exists, as a ground standing on the part of the knower, and a medium by which it habitually understands itself; for the intelligible species does not bring it about that the soul has an intellective potency, since that potency follows the proper nature of the soul. But it rightly follows: Therefore it cannot understand itself through itself as through the total and complete productive principle of intellection. Just as it does not follow: The intelligible species cannot go out into the act of intellection except simultaneously with the intellective potency, and unless there is present the intention applying the species to the act; therefore it is not through itself the ground whereby it can be known to exist, as a principle of intellection; but it rightly follows: Therefore it is not the total principle of such actual intellection.

X. To the second ²¹ it is said that the soul's being present to itself can be understood in two ways: in one way absolutely, as to its nature absolutely considered; in another way, precisely as a ground of knowing in the intellect. In the first way St. Thomas understood it in the first argument of this chapter. For the soul is not at one time imperfectly the same as itself and at another time perfectly, so that it could be said to be present to itself at one time according to habit, and at another time according to act; but it is always perfectly so, as was declared there ²². And therefore St. Thomas deduced that the soul would always understand in actu what it is from itself, if from this alone the soul knows what it is of itself because it is present to itself absolutely through identity: since it is always present to itself in a perfect manner. But in this response, taken from the Qq. de Veritate, St. Thomas understands the soul to be present to itself in the second way. For it is not unfitting that the soul be present to the intellect as a ground of some cognition habitually: inasmuch as the very presence of the soul in the intellect is the ground that it is capable of knowing itself as to its esse, but is not the ground that it actually understands itself. Whence also it is not necessary, if the soul is in this way always present to itself, that it always understand itself in actu; but it suffices that it is always capable of understanding itself, just as it is also always, as long as it exists, capable of acting in the manner of an intellective virtue.

XI. To the third ²³ it is said that there is not the same rationale concerning the cognition of the soul as to that it is (quia est), and as to what it is (quid est). Because for habitual cognition that it is, it suffices that it is productive of the act through which it is known to exist, and is present to the intellect; but this belongs to it through itself. For cognition of what it is, however, it is required that it be something understood in actu: because nothing is a medium, as a species, or in the manner of an intelligible species, by which something is known as to what it is, even habitually, unless it is something understood in actu; for on account of this it is posited that through material things themselves it cannot be known what they are unless by the power of the agent intellect they become intelligible in actu through a species caused in the possible intellect. But the intellective soul is not understood in actu through itself, as it is conjoined to the body, but through species abstracted from phantasms. Therefore through itself it does not know concerning itself, even habitually, what it is, but only potentially: although it is productive of the act through which the nature of the soul, by a certain investigation and deduction, is known.

XII. Concerning that which is said ²⁴, since we could not even receive through faith this knowledge that there are certain intellectual substances, unless our soul knew from itself what is intellectual ²⁵, it should be noted that this is not said as if through that cognition whereby the soul, by knowing that it exists, knows that it is intelligible, the cognition of faith is caused through some natural argumentation, by which we know that some separate and intellectual substances exist: for the cognition of infused faith, as such, does not depend necessarily upon any natural argumentation. But it must be understood thus: that just as in other things that are of faith, it is necessary to know beforehand what is signified by the names, otherwise the intellect would not adhere to them even through faith, because it would understand nothing of the meaning of the propositions; so that cognition whereby we know, whether through demonstration or through faith, that there are some separate intellectual substances, must be preceded by the cognition whereby, from the soul itself known through its acts, we know with certainty that something intellectual exists; because through that cognition we know what it is for intellectual substances to exist.

XIII. Concerning the corollary ²⁶, it should be noted, from the doctrine of St. Thomas in the cited passage of De Veritate ²⁷, that although we know habits, and other things that are in our soul, as to that they are, inasmuch as from them we perceive the acts themselves, but find what they are from the quality of the acts, as is the case concerning the soul; nevertheless, those two cognitions are ordered differently concerning habits than concerning the soul. For the cognition concerning habits that they are presupposes the cognition what they are; but the cognition that it is concerning the soul does not presuppose the cognition what it is concerning it, since many know that they have a soul who do not know what the soul is. The reason for this is that it cannot be known through acts that some principle is in us unless it is known beforehand that it is the principle of such an act: just as I cannot know from some act that justice is in me, unless I know that justice is the principle of that act. But a habit is through its essence the principle of such an act, namely in such a way that its essence consists in this, that it is the principle of such an act: just as the what it is of justice consists in this, that it is that through which one renders to each what is his own. Therefore it cannot be known through an act that some habit is in us unless it is known beforehand what that habit is. But while the soul is known to be the principle of some act, its essence is not thereby known: because its what it is does not consist in this, that it is the principle of such an act; since it is not through its essence the principle of the act, namely immediately, but through a potency. Therefore it is not necessary to know beforehand concerning it what it is, while it is known to be in us: but it suffices to know that in it there is a potency productive of such an act.