Commentaria in Summam contra Gentiles, Liber II

I. Because to the aforesaid arguments, by which it was proved that the soul is the form of the body, someone might reply, according to Plato's opinion, that in us there are not one and the same nutritive, sensitive, and intellective soul; and therefore, although the sensitive soul is the form of the body, it does not follow that the intellective is the form of the body: Saint Thomas shows this position of Plato to be impossible, namely, that the sensitive, nutritive, and intellective souls are three souls in us ¹.

I. And he argues first as follows ². Given this supposition, it would follow that these predications are per accidens: "Man is an animal," and "Animal is a living thing." But this is false: because man, insofar as he is man, is an animal; and animal, insofar as it is animal, is living. Therefore etc. The consequence is proved. Because those things attributed to something according to diverse forms are predicated of one another only per accidens: just as white is said to be musical per accidens, because whiteness and music both befall Socrates. Now we are called men according to the intellective soul; animals according to the sensitive soul; and living things according to the nutritive soul. Therefore etc.

2. If the consequence is denied, because, although souls are diverse, they nevertheless have an order to one another, and thus there can be per se predication: it is argued against this. For then predication will not be according to that mode of speaking per se which is taken according to form, but according to that which is taken according to matter and subject. But this is impossible. Therefore, etc. — The consequence is proved. Because the order of the nutritive to the sensitive, and of the sensitive to the intellective, is like the order of potency to act. — The falsity is also proved. Because in that mode of speaking per se, what is formal is predicated per se of the subject, and the subject is placed in the definition of the predicate. Neither of these is found when I say, Man is an animal; rather it is the contrary.

3. It must be noted, according to the doctrine of St. Thomas in I Posterior Analytics ³, that the first mode of per se is taken in relation to form and essence: namely, because the predicate is said of the essence of the subject, and therefore it is placed in its definition. The second mode, however, is taken in relation to subject and matter: namely, insofar as the predicate is not of the essence of the subject of the proposition, but that of which it is predicated is its matter and subject. This mode of per se is constituted from the fact that the form of the subject is a prerequisite to the form of the predicate; and the form of the predicate naturally follows upon the form of the subject, just as risibility naturally follows upon humanity. And therefore in this mode the subject is placed in the definition of the predicate. Hence St. Thomas rightly says that if, on account of the order of forms, there is per se predication when it is said, Man is an animal, or, An animal is living; there it will not be per se predication of the first mode, which is taken according to form and essence, but of the second mode, which is taken according to matter and subject: namely, because the predicate then is not of the essence of the subject, which is its total form; but there is only a per se order there on account of the natural order of the form of the subject and the form of the predicate, from which the second mode of per se is constituted.

II. But a doubt arises concerning this argument. For it seems that St. Thomas holds that, according to this second mode of per se, the formal must be predicated per se of its subject; hence man would have to be predicated per se of animal, because he is formal with respect to animal, since the intellective principle, by which man is man, is related to the sensitive principle, from which animal is taken, as the formal is related to the material. Against this, however, it seems otherwise, because every defining element is related to what is defined as the formal to the material: for the Philosopher places, and St. Thomas with him, in Physics II ⁴ and Metaphysics V ⁵, the definitions in the genus of formal cause. And thus it does not seem that, on account of the order of forms, man must be predicated of animal as the formal; but rather the reverse, since animal is formal with respect to man. Hence it does not seem that the proposition "Man is an animal" is excluded from the second mode of per se on the ground that the predicate is not related to the subject as the formal to the material.

III. For the solution of this difficulty, it must be considered that one must speak differently of these terms "man" and "animal" if several souls are posited in man, and differently if only one soul is posited. For if several souls are posited, then there will be one form from which man is called man, and another from which he is called animal. And since the sensitive soul, from which "animal" is taken, is compared to the intellective soul, from which "man" is taken, as potency to act, and as the imperfect to the perfect—for it is prior in generation (for the animal is generated before the man)—therefore animal is compared to man as the material to the formal, not as the formal to the material. And what I say of animal with respect to man must be said likewise of every superior term, if the superior and inferior are taken from different forms of the thing: for the form from which the superior is taken is always compared to the form from which the inferior is taken as the imperfect to the perfect, and as potency to act.

But if one and the same soul is posited as really existing, from which the nature of the genus and of the species is taken, then something else must be said about these terms. For they can be taken in two ways: in one way, with respect to the very nature signified; in another way, with respect to that from which the account of such a nature is taken. With respect to the very nature signified, they can likewise be considered in two ways, according to the teaching of St. Thomas in the Treatise on Being and Essence ⁶: in one way, according as the nature of animal is considered with a precision setting aside another perfection; in another way, according as it is considered without such a precision, but as implicitly including the specific perfections. - If, therefore, the nature of animal is considered as implicitly containing the specific perfections, then animal is compared to man as genus, and as formal cause: for thus it signifies the essence of man, which is his form. - But if it is considered with a precision setting aside another perfection, then it is not the genus of man, but his part: for man is composed of the sensitive and the intellective. It is not, however, a formal part but a material part: because the intellective is more actual and more perfect than the sensitive. - Similarly, if they are considered with respect to that from which the account of each is taken, then again animal has not the character of a formal but of a material principle, in comparison with man: because the sensitive, from which the account of animal is taken, is material with respect to the intellective, from which the account of man is taken.

It must be noted, however, that not everything having the character of a form of another is compared to it as formal to material, but only when it is compared to it as one part to another part. For we say that the intellectual soul is the form of man, inasmuch as it gives him specific esse and completes man's essence; yet man is not compared to the intellectual soul as matter to form, but as whole to formal part.

Thus, then, it must be said that animal, and every superior term insofar as it implicitly contains the specific perfections, is compared to its inferior as a form, inasmuch as it signifies the nature and essence of the inferior, which is completed through the form. And for this reason those parts of a definition which are predicated of the thing defined directly are placed by the Philosopher and St. Thomas under the genus of formal cause. — But insofar as it excludes other perfections, and with respect to that from which the meaning of the name is taken, it is not compared to the inferior as a form, but as its material part with respect to another part.

IV. Whence, to the doubt ⁷ it is said that what is stated here by Saint Thomas does not contradict what is said elsewhere by him and by the Philosopher. For here he speaks of animal as considered with respect to that from which the ratio of animal is taken. Thus, since in the second mode of per se, of which he treats, the form from which the predicate is taken must be compared to the form from which the subject is taken as act to potency and as the formal to the material; therefore, if animal were predicated of man in the second mode of per se, it would be necessary that that from which animal is taken be compared to that from which man is taken as the formal to the material. And since this is false, therefore there is not there a second mode of per se predication. This, however, does not prevent animal, insofar as the nature signified implicitly contains the perfections of the species, from being compared to man—not indeed as form to matter, but as the form of the whole to that which is constituted by such a form.

V. But in response to this argument of St. Thomas, Scotus, in the Fourth book, d. XI, q. III ⁸, says two things. The first is that, on the face of it, nothing seems to be gathered from this argument except that the predicate taken from a posterior form is not predicated per se of that which is taken from a prior form. And thus nothing is established except that this is not per se: Animal is man. Which is granted. — The second is that if it were also said to be concluded by this argument that neither conversely is the proposition per se when saying Man is animal, then what is precisely taken from a posterior form and what is precisely taken from a prior form are so related that one is not predicated per se of the other. But if one is taken from a posterior form yet not precisely, and the other from a prior form, there can be between them a per se predication. And therefore neither is genus predicated of difference per se, nor difference of genus: because one is taken from a prior form and the other precisely from a posterior form. But genus is indeed predicated of species per se: because, although species imports the ultimate difference as principal in its account, it does not nevertheless import it precisely, but along with this the account of genus, as belonging to its concept per se.

2. But that neither of these removes the force of the argument can easily be seen from the very form of the argument. First, it is clear that it is not to the purpose of the argument. For the argument of St. Thomas does not lead to the conclusion that this is not per se, "Animal is man," but rather that this is not per se, "Man is animal," or this one, "Animal is living." And he argues as follows: if the propositions "Man is animal" and "Animal is living" are per se on account of the order of the forms of subject and predicate, they cannot be per se in the first mode, but only in the second, in which is found a natural sequela and an order of forms. But neither can they be per se in the second mode. For in that mode the predicate, with respect to that from which it is taken, is formal relative to the subject, and the subject is placed in the definition of the predicate. But neither holds when it is said, "Man is animal," or "Animal is living." For man is not predicated of animal, which would have to be the case if the order of forms were being attended to, where the predicate ought to be formal; rather, animal is predicated of man, which is material relative to man. Nor is man placed in the definition of animal, but conversely. Therefore not by reason of the order of forms are the aforesaid propositions said to be per se. — Thus it is clear that Scotus's first point proceeds from a bad understanding of St. Thomas's argument.

The second is also of no weight. For in the second mode, per se is predicated that which is formal, in respect of that from which the predicate itself, as such, is said to be formally such. And thus it is necessary that the act and form from which the predicate is formally said to be such be posterior to the form from which the subject is formally said to be such: as in this per se proposition, "The surface-colored is colored," color, from which something is formally said to be colored, is a form posterior to surface, from which a body is said to be surface-colored; and in this one, "Fire is hot," heat, from which "hot" is taken, is posterior to the form from which "fire" is taken. And thus it is necessary that the form of the subject and of the predicate be related as what precedes and what follows, as is clear from the First Part, q. 76, a. 3, if there the proposition is per se on account of the order of forms. Therefore, to import the posterior form precisely or not precisely makes no difference to the matter at hand: since in the mode of per se predication that is on account of the order of forms, the predicate must always express a form posterior and more actual than the form from which the subject is said to be formally such, even though the subject, together with that form, includes another prior form. And since this is not so in the proposition "Man is an animal"—for the sentient, from which "animal" is taken, is not more formal and more actual, but more material and more potential, than the intellective, from which man is formally taken—it follows necessarily that in that proposition there is not the mode of per se predication that occurs on account of the order of forms. — And thus no part of Scotus's reply overthrows the argument of Saint Thomas.

VI. Secondly ⁹. It would follow that man will not be one being, but many. For a thing is said to be one being by reason of one form. For just as each thing has its esse from its form, so too does it have its unity, since "one" follows upon "being."

If it is said that the order of forms suffices for the unity of man: this does not hold. For to be one by way of order is not to be one simply, since the unity of order is the least of unities.

VII. To this argument Scotus, in the place cited above ¹⁰, replies in two ways. First, he denies that one esse requires only a single form. For just as being is divided into the simple and the composite, so too is esse. And therefore, just as the whole of being includes those partial entities from many forms, so the esse of the whole composite, which is one, includes many partial esses of many parts or forms. And thus it is not necessary that the one esse of a composite be from only one form.

Second, he responds: If force is made, he says, in the word, I concede that the formal esse of the whole composite is principally through one form, which is the last, arriving to all the preceding ones. And in this way the whole composite is divided into two essential parts: namely, into its proper act, which is the last form, and which is that which is; and into the proper potency of that act, which includes prime matter together with all the preceding forms.

2. But the first of these responses proceeds from a poor understanding of St. Thomas's reasoning. For it is said first that, when St. Thomas says that one esse proceeds from one form, he is not speaking principally of the esse of actual existence, as Scotus seems to understand it, but of the esse that expresses the essence of a thing, although secondarily he speaks of the esse of actual existence: for one essence is from one form.

It is said second, that one essence, however composite it may be, can be only from one form. For each substantial form arriving at matter constitutes one essential esse: since one follows upon being, the form that constitutes a being also makes one being. Therefore, where several forms are posited, several essences must be constituted from them, each of which is one in itself. And thus it is clear that one essence is from one form alone.

3. Nor does it avail to say that in one composite there are several partial essences, constituted by particular forms, but that there is one total composite essence, which results from several forms and partial essences.

First, because from two substances in act a per se unity cannot be made, as is said in Metaphysics VII, text 49 ¹¹. And it is clear that the Philosopher speaks there of partial substances: for, as is evident from the words of the Commentator there, it would follow that one esse arises from two substances in act, if the universal were part of the substance of the demonstrated individual besides the substance proper to it. Against this the Philosopher argues, because from two substances in act one cannot be made: where it is clear that he speaks of partial substances.

Second, because: — suppose that in man, besides the intellectual soul, there is a form of corporeity constituting the essence of the body, or a sensitive soul constituting the essence of the animal: it is asked whether the intellectual soul, coming to that essence, constitutes the essence of the body or of the animal, or whether it constitutes only the intellective or the rational. The first cannot be. First because one and the same partial essence in number cannot be made by several substantial forms, since different forms constitute different essences. Second because what is does not come into being anew; yet before the advent of the intellectual soul there was already the essence of the body or of the animal. — Nor can the second be said. Because then body or animal would not be the genus of man but his part: for man would consist of animal and rational as of two parts distinct from each other. And consequently they could not be predicated of him essentially and in an unqualified sense: for a part is not predicated essentially of its whole.

4. The second response against every philosophy is this: he says that the proper power from which, together with the ultimate act, there is made one thing per se, is something composed of matter and preceding forms.

First, because the Philosopher, in the place cited above ¹², assigning the reason why from two substances more than one is not made one in act, says: because act separates. Where the Commentator says: And the cause of this is that act makes what is added to be divided and two; and therefore it is impossible that one be made from two in act. Therefore the proper matter from which, together with act, one is constituted simply speaking, cannot be something existing in act of itself.

Second. By the same reasoning it could be said that from a subject and an accident there comes to be one thing simply in act, for instance, from the diaphanous and light. For the diaphanous, although it is something in act, is nevertheless in its own proper potency with respect to light.

Third. It is supposed that those several forms are not introduced into matter simultaneously, but that the form of corporeity is introduced first, from which body is taken, which is the genus; for no agent introduces several forms into the same matter at once. Then thus. Concerning that prior form, it is asked whether the form of body gives some specific esse, or not? The latter cannot be said: because even according to Scotus himself, in II Sent., d. xii, q. ii¹³, whatever determines a genus to itself as forms do determines to itself some species in that genus; and thus nothing can be in the genus of body without being in some species of it. — If the first, then against. Either that species is animate or inanimate. Not the latter: because then, after the arrival of the intellectual soul, it would be true to say that man is an inanimate body, if body is admitted to be predicated of man, since it is his genus. But this is known to be false: since man is an animate body. — If that species is animate or living, it will be either sentient or insentient. If insentient, then it would at some time be true to say, Man is insentient. If sentient or animal, it will be either rational or irrational: for, as has been said, a genus is not found without species. If irrational, therefore man will be an irrational animal. If rational, therefore from the same form something is a living body, an animal, and rational or man. And consequently it will not be necessary to posit in man another form distinct from the form of corporeity.

VIII. Third main argument¹⁴. The intellective and sensitive soul would arrive accidentally. Therefore neither "man" nor "animal" would signify one thing simply, nor would any genus or species¹⁵ in the category of substance, but only per accidens. — The first consequence is proved. What arrives at something after its complete esse arrives at it accidentally. But on that supposition, the said souls would arrive after complete esse: since the vegetative soul, after which the sensitive and intellective would arrive, is a substantial form; and a substantial form makes a complete being in the genus of substance, inasmuch as it makes a being in act and this something. Therefore, etc.

2. To this argument, following Scotus's principles, as above¹⁶, it can be answered that, if by complete esse is understood every substantial esse, it does not follow that every form arriving at a thing after complete esse must be accidental: for one substantial form can come to another form and yet give substantial esse. — But if by complete esse is understood the ultimate substantial esse of a thing, then it is false that every substantial form gives complete esse. For only the last substantial form gives complete esse; the preceding forms, however, give partial substantial esses and are included in the proper potentiality of the composite which is constituted by the ultimate form.

But that this reply is no reply at all can easily be shown. For by complete esse Saint Thomas understands the essence of a thing, according to which something is what it is, and to which substantial esse follows. And the sense of the major proposition is: Whatever comes to a thing after its complete essence, and consequently also after that substantial esse by which it subsists in the order of nature, comes to it accidentally. Now it is evident that the proposition itself is true, from the proof which Saint Thomas adduces. For whatever is outside the essence of a thing is accidental to it. But everything coming after the complete essence is outside the essence of the thing: for it would not come after the essence if it were among those things that enter into the essence. — The major is proved. Because whatever is substantial enters into the essence of the thing: otherwise it would not be substantial to the thing; for the essence embraces all the substantial principles of the thing.

In the same sense, another proposition is also true, namely that every substantial form makes a complete being in the genus of substance. Saint Thomas gives the reason: because it makes a being in act and this something. For everything that exists of itself in nature and is this something, whether a singular thing pointed out, has a complete substantial essence: for to subsist as this something belongs only to things having a complete essence; for we do not say that Socrates exists in nature except after he has a complete essence. But every substantial form makes something existing of itself in act, and this something, according to its own condition. For the substantial form, by its union with matter, makes some composite constituted by it exist absolutely in nature: for by the fact that the form of a horse is united to matter, it is true absolutely and without any further addition to say that a horse is; and by the fact that the intellective soul informs matter, man is in nature. Therefore, etc.

And so it is evident that the given response does not undermine the argument of St. Thomas. For it is clear from what has been said that everything which comes to something as a form really informing it after its substantial esse arrives accidentally, since everything of this kind must be outside the essence of the thing, because only that which has an essence exists substantially in the first place.

It is also evident that every substantial form gives a complete and ultimate esse to a thing, according to the condition of that form itself. For the form of body makes corporeal essence and corporeal esse, which is the ultimate substantial esse of corporeal essence as such; and the form of animal makes the essence and esse of animal as such. For every other esse arriving after that is not of body or of animal precisely as such, but of man or horse, or of some other thing, by whose form such an esse is constituted.

3. This argument of St. Thomas is confirmed by the argument of the Commentator on Physics I, commentary 63. For when Avicenna posited that the form of corporeity informs matter before the arrival of the other forms, the Commentator argued against him, because then all subsequent forms would be accidents. If indeed his argument against Avicenna holds, we must say that this argument of St. Thomas is effective.

4. But a doubt arises concerning the last consequence which St. Thomas draws, as to that part in which he says that neither any genus nor species¹⁷ in the category of substance will signify one thing simply. For this does not seem to follow of a genus constituted by a single form, such as that genus which I call body, which is constituted by the form of corporeity alone. Since it does not posit several forms, it does not follow that it is one by accident: although this follows of man and animal, in which, according to Plato, several distinct souls are posited.

It can be answered that St. Thomas is not speaking universally of the genus of substance, but only of animated substance, which is the subject of this chapter, or even of corporeal substance. For it follows that no genus or species of living or corporeal substance would be one simply: because every such genus or species would have a form added to the form of corporeity or to the vegetative soul. For by the same reason that in man the intellective soul is posited as distinct from the sensitive and vegetative, by that same reason in all other living things there will be a form distinct from the form of the genus, which is the vegetative soul; and in every corporeal substance there will be a form distinct from the form of corporeity.

IX. Fourth. If, according to Plato's opinion, man is a soul using a body, this is understood either of the intellective soul alone, or of three souls or two. If the second, then man will not be one simply: for he will be three or two souls. If the first, namely such that the sensitive soul is the form of the body, and the intellective soul uses the ensouled body, it follows that man is not an animal, but uses an animal; and that he does not sense, but uses a sensing thing. These are absurdities. Therefore, etc.

Fifth. If several souls were to be united so as to make something one, there would have to be something uniting them; for several souls in a man are not related as matter and form, but all are posited as certain acts and principles of actions. Now this cannot be a body, since the body is rather united by the soul. Therefore there will be something more formal than they are. And this will be more a soul than those several things which are united by it. And thus it will be argued in turn until one arrives at something that is one in itself.

Note that for this reason the unifier of those souls would have to be more a soul, because what unites is formally more perfect, more formal, and more powerful than the things united. But nothing among material forms is more formal than the soul, since the soul is the most perfect of all forms. And therefore several souls could not be united by something unless that something had more the character of a soul, as being more the act of an organic body.¹⁸ etc.

2. To this argument, perhaps, according to Scotus's principles in the place cited above¹⁹, it will be answered that there is no need to posit something uniting the said souls: for although they are not related as matter and form, they are nevertheless related as proper act and proper potency, or as the constitutive of a proper potency.

But against this response there are the arguments adduced above ²⁰ against Scotus's other responses, by which it was shown that a composite of matter and substantial form cannot be the proper potency of another substantial form.

Sixth. If that which subsists on the side of the soul in man is gathered together from several things, inasmuch as it includes several souls, it is necessary that each of these be related to each part of the body as whole to whole: whence Plato said that the rational soul is in the brain, the nutritive in the liver, and the concupiscible in the heart. But this is false. First, because the intellect cannot be attributed to any part of the body, since it is not the act of any body, as was shown above. — Second, because in one and the same part of the body there appear the operations of different parts: as is evident in the parts of animals which, when cut off, live, in which there is motion, sensation, and appetite; and in the cut-off parts of plants, which are nourished, grow, and germinate. — Therefore, and so on.

2. Concerning these proofs of the falsity of the consequent, a doubt arises: for they do not seem to prove what is intended. The first indeed proceeds from the intellective power; but we are speaking of the intellective soul. For although it is true that the intellective power is not the act of any body, it is nevertheless evident that the intellective soul itself is the act of a body.

The second, however, showed that several powers of the same soul—for example, the motive, sensitive, and appetitive powers, which are faculties of the sensitive soul—are found in the same part of the animal; and the nutritive, augmentative, and generative powers, which are faculties of the vegetative soul, are found in the same part of the plant. But what had to be proved was that the souls themselves, though diverse, are found in the same part of the body.

3. To the first of these it is said that that argument proceeds not only concerning the intellective power, but also concerning the soul itself. For the intellective soul, as such, is not the act of a body, but only insofar as it virtually contains the sensitive and vegetative: because it is not united to matter except on account of the sensitive powers, by which it has need for understanding. And therefore, if it were posited as distinct from the sensitive and vegetative in man, inasmuch as it has only what belongs to the intellective, it would be the act of no body. And for this reason no part of the body could be assigned to it as its matter.

To the second it can be replied that the argument proceeds on the supposition that, just as these souls are posited as distinct because of the diversity of their operations, so there must be distinct souls that are motive, sensitive, and appetitive, which are the principles of diverse operations; and by the same reasoning nutritive, augmentative, and generative. And therefore, if diverse parts of the body must be attributed to diverse souls, then the aforementioned souls could not be found in the same part of the body. Since this is false, it will also be false that several souls are to be found in man.

XII. Seventh, it is argued from a sign. The diverse operations of the soul impede one another: for while one is intense, another is relaxed. Therefore both the operations and the powers that are the principles of these operations must be reduced to one principle. Now this principle cannot be a body: first, because the body does not share in the act of understanding (that is, productively and instrumentally, though it shares in it objectively); second, because all these operations would then be found in all bodies. Therefore it will be the soul. Therefore there are not several souls in one man. — The first consequence is proved. Because diverse powers that are not rooted in the same principle do not impede one another in acting, unless perhaps their actions were contrary.

The conclusion is confirmed by what is said in the Book of Ecclesiastical Dogmas, where it is plainly stated that in man there are not several souls.

For the arguments against this conclusion, and their solutions, see Capreolus, in II Sent., d. xv, q. 1.