Article 7 — Whether the angel and the soul are of different species

Seventh, it is asked whether the angel and the soul are of different species. (Parallel texts: ST I.75.7; SCG II.94–95; In II Sent., d. 3, q. 1, a. 6; d. 17, q. 2, a. 2, ad 5; On the Power of God, q. 3, a. 10, ad 10.)

Obj. 1: It seems that they are not. For things which possess the same proper and natural operation have the same species because the nature of a thing is known by its operations. (Cf. Aristotle, On the Soul 1.1, 403a10–15; SCG II.94; ST I.75.7, s.c.) Now the same proper and natural operation of understanding belongs to the soul and to the angel. Consequently, the soul and the angel are of the same species.

Obj. 2: (Objections 2–8 are similar to obj. 2 in Aquinas’s In II Sent., d. 3, q. 1, a. 6; cf. ST I.58.3.) But it might be said that the soul’s act of understanding is discursive whereas the angel’s is not. (Cf. Aquinas, On Truth, q. 8, a. 15.) Thus, the operation of the soul and that of the angel are not the same in species.

On the contrary, operations which are diverse in species are not operations of the same power. But by one and the same power, that is, the potential intellect, we understand certain things without discourse, namely, first principles, (Cf. Aristotle, Posterior Analytics 2.19, 100b3–5.) and understand certain other things discursively, namely, conclusions. Hence, understanding discursively and understanding without discourse are not different in species.

Obj. 3: Further, to understand discursively, and to do so without discourse, are seen to differ as being-in-motion differs from being-at-rest, for discourse is a certain movement of the intellect from one thing to another. (Aquinas, On Truth, q. 8, a. 15, resp.; ST I.58.3, ad 1.) But to be in motion and to be at rest do not differ in species, (Aristotle, Physics 3.5, 205a4–6.) because a motion belongs to that genus wherein the termination of the motion is found, as the Commentator says in On the Physics 3. (Averroes, Commentary on Aristotle’s Physics, bk. 3, text. 4.) Hence, the Philosopher also says, in the same work, that there are as many species of motion as there are species of being, (Aristotle, Physics 3.1, 201a8–9.) that is, terminations of motion. Consequently, to understand discursively, and to do so without discourse, do not differ in species from each other.

Obj. 4: Further, as the angel understands things in the Word, so also do the souls of the blessed. But the knowledge contained in the Word is not discursive. Hence, Augustine says in On the Trinity that there will be no discursive knowledge in heaven. (Augustine, On the Trinity, bk. 15, ch. 16, para. 26 (CCSL 50A:500–501; PL 42:1079); cf. ST I.57.5; I.58.5–7.) Therefore, the soul does not differ from an angel because the former understands discursively, the latter without discourse.

Obj. 5: Further, all angels are not the same in species as many maintain. (Cf. Augustine, To Orosius, bk. 1, ch. 11, para. 14 (CCSL 49:177–78; PL 42:678); Enchiridion on Faith, Hope, and Charity, bk. 1, ch. 58, n. 15 (CCSL 46:80–81; PL 40:259–60); John Damascene (d. ca. 749 AD), On the Orthodox Faith, bk. 2, ch. 3 [ch. 17] (PG 94:866–74); Aquinas, In II Sent., d. 3, q. 1, a. 4, resp.; SCG II.93; ST I.50.4; I.75.7; On Being and Essence, ch. 4.) But every angel understands without discourse. Therefore, to understand discursively, and to do so without discourse, do not cause diversity of species in the case of intellectual substances.

Obj. 6: But it might be said, too, that some angels understand more perfectly than others. (Cf. ST I.55.3.)

On the contrary, more and less do not diversify species. But to understand more perfectly and to do so less perfectly, differ only in terms of more and less. Therefore, angels do not differ in species because some understand more perfectly, others less perfectly.

Obj. 7: Further, all human souls are of the same species. However, all do not understand equally well. Therefore, intellectual substances do not differ in species from one another due to the act of the understanding of one being more perfect than that of another.

Obj. 8: Further, the human soul is said to understand discursively in view of the fact that it understands a cause through its effect, and vice versa. But this also occurs in angels, for it is said in the Book of Causes that an intelligence is cognizant of the being that is above it because it is caused by that being. (The Book of Causes, proposition 7 [8].) It also knows the being beneath it because it is the cause of this being. Hence, an angel does not differ in species from a soul, because the latter understands discursively and the former without discourse.

Obj. 9: Further, things perfected by the same perfections evidently belong to the same species, for a particular actuality perfects a particular potency. But the angel and the soul are perfected by the same perfections, namely, grace, glory, and charity. (Cf. Aquinas, In II Sent., d. 3, q. 1, a. 4, obj. 2.) Therefore, they are of the same species.

Obj. 10: Further, things having the same end are seen to be of the same species, for a thing is directed to its end by its form, which is the principle of its species. But the end of the angel and that of the soul is the same, namely, eternal beatitude, as is clear from the statement that the children of the resurrection shall be as the angels in heaven (Matt 22:30). Gregory also says that souls are elevated to the ranks of the angels. (Gregory the Great (ca. 540–604 AD), Homilies on the Gospels, bk. 2, homily 34, para. 11 (PL 76:1252–53).) Therefore, the angel and the soul are of the same species. (Cf. ST I.75.7, obj. 1.)

Obj. 11: Further, if the angel and the soul differ in species, the angel must be superior to the soul in the order of nature and so will be midway between the soul and God. But there is nothing midway between our soul and God, as Augustine says. (Augustine, The Profit of Believing, ch. 15, para. 33 (CSEL 25:40; PL 42:82); On the Trinity, bk. 15, ch. 1, para. 1 (CCSL 50A:460; PL 42:1057).) Consequently, the angel and the soul do not differ in species.

Obj. 12: Further, impressions of the same image in different individuals are not thereby made diverse in species, for the image of Hercules in gold and that in silver are the same in species. (Cf. Aristotle, Metaphysics 7.11, 1036a31–b2.) Now the image of God is present in the soul and in the angel as well. Therefore, the angel and the soul do not differ in species.

Obj. 13: Further, things having the same definition belong to the same species. But the definition of the angel is the same as that of the soul, for Damascene says that an angel is an incorporeal substance always moved by free choice, ministering to God by grace, not by nature, and remaining unchanged. (John Damascene, On the Orthodox Faith, bk. 2, ch. 3 [ch. 17] (PG 94:866); see below: q. 14, obj. 3.) Now this is proper to every human soul. Consequently, the soul and the angel are of the same species.

Obj. 14: Further, things agreeing in an ultimate difference are of the same species, because an ultimate difference determines the species. But the angel and the soul share a common ultimate difference, namely, the possession of intellectual being. This must be an ultimate difference because there is nothing nobler than this in the nature of the soul or in that of the angel, for an ultimate difference is always most complete. Therefore, the angel and the soul do not differ in species. (Cf. Aquinas, In II Sent., d. 3, q. 1, a. 6, obj. 1; ST I.75.7, obj. 2.)

Obj. 15: Further, things not found in a species cannot differ in species. Now the soul is not found in a species, rather is it part of a species. (Above: q. 1, ad 1 and ad 3.) Hence, it cannot differ in species from an angel.

Obj. 16: Further, the definition coincides expressly with the species. (Cf. Aristotle, Topics 1.8, 103b15; 7.3, 153a15–16; Posterior Analytics 2.3, 90b30; SCG I.25; ST I.3.5, resp.) Consequently, things not definable apparently do not exist in a species. But the angel and the soul are not definable, because they are not composed of matter and form, as has been shown above. (Above: qq. 2, 6; cf. Aquinas, On Being and Essence, ch. 5.) For in every definition there is something like matter and something like form, as is evident from what the Philosopher says in Metaphysics 8, where he himself points out that, if the species of things were devoid of matter, as Plato held, they would not be definable. (Aristotle, Metaphysics 8.3, 1043b23–32; 8.6, 1045a34–b4; 7.6, 1031b4–6; 7.15, 1039b30–1040b4; cf. Aquinas, Commentary on Aristotle’s Metaphysics, bk. 8, lect. 3, n. 1707; On Being and Essence, ch. 2; ST I.75.4; SCG IV.81; On the Power of God, q. 9, a. 1, obj. 7.) Therefore, the angel and the soul cannot properly be said to differ in species.

Obj. 17: Further, every species is comprised of a genus and a specific difference. (Cf. Aristotle, Metaphysics 7.10, 1034b20.) Now genus and difference have their foundation in different things. For instance, the genus of man, which is “animal,” has its foundation in his sensory nature, and his difference, which is “rational,” is rooted in his intellective nature. However, in the angel and the soul there are no diversities on which genus and difference can be based, because their essence is constituted of form alone. Furthermore, their act of existing can be neither a genus nor a difference, for the Philosopher proves in Metaphysics 3 that the act of existing is neither a genus nor a species. (Aristotle, Metaphysics 3.3, 998b20–27.) Consequently, the angel and the soul have neither a genus nor a specific difference and so cannot differ in species. (Cf. SCG II.95.)

Obj. 18: Further, things differing in species differ through contrary differences. (Cf. Aristotle, Metaphysics 7.12, 1037b20.) But there is no contrariety in immaterial substances, for contrariety is the principle of corruption. (Cf. Aristotle, Physics 1.7, 191a3–7; 1.5, 188a26–b8; 3.5, 205a6; 8.2, 252b10; Aquinas, Commentary on Aristotle’s Physics, bk. 1, lect. 13, n. 116; Commentary on Aristotle’s On the Soul, bk. 2, lect. 14.) Hence, the angel and the soul do not differ in species.

Obj. 19: Further, the angel and the soul are seen to differ above all because the angel is not united to a body, whereas the soul is. But this cannot make the soul differ in species from the angel, since the body is related to the soul as matter, and matter does not give species to form, but rather the reverse. Therefore, the angel and the soul do not differ in species in any way whatever. (Cf. Aquinas, In II Sent., d. 3, q. 1, a. 6, obj. 3; ST I.75.7, obj. 3.)

On the contrary, things differing in number, but not in species, differ only because of matter. But the angel and the soul do not have matter, as is clear from the preceding question. (Above: q. 1.) Therefore, if the angel and the soul do not differ in species, neither do they differ in number, which is evidently false. Therefore, it follows that they differ in species.

I answer that some say that the human soul and the angel are of the same species, and this seems to have been maintained first by Origen. (Origen, On First Principles, bk. 3, ch. 5, para. 4; bk. 2, ch. 8, para. 2.) Wishing to avoid the errors of the ancient heretics, who attributed the diversity of things to different principles by introducing a duality of good and evil, Origen held that the diversity of all things had proceeded from free choice. (Origen, On First Principles, bk. 2, ch. 9, para. 6.) For he said that God made all rational creatures equally perfect in the beginning: certain of these adhering to God acquired greater perfection in proportion to the measure of their adherence; others, falling away from God through an act of free choice, descended to positions of lesser importance in proportion to the extent of their fall. Accordingly, some were incorporated into the heavenly bodies, others were perverted to the point of demonic maliciousness, though all were equally perfect in the beginning. (Cf. SCG II.44; On Separated Substances, ch. 12; Disputed Questions on Evil, q. 5, a. 4, resp.) So far as Origen’s position is concerned, it can be seen that he regarded the good of singular creatures and neglected to consider the good of the whole. (Origen, On First Principles, bk. 1, cc. 7–8.) Now a wise artificer arranging parts takes into consideration not only the good of the individual parts, but the good of the whole even more. For this reason, a builder does not make all parts of a house equally valuable but gives them greater or lesser importance inasmuch as this is required for the good disposition of the house. Likewise, in an animal’s body, not all parts have the transparency of the eye, because the animal would then be imperfect, but in an animal’s parts there is diversity in order so that the animal may be perfect. In the same way, God, in his wisdom, did not make all things in the universe of equal worth, because if he had, the universe, lacking many grades of being, would be imperfect. Consequently, to inquire why God, by his activity, made one creature better than another, is the same as asking why an artificer introduced a diversity of parts into his work. (Cf. ST I.47.2; I.65.2; I.90.4; SCG II.44–45, 83, 95; On the Power of God, q. 3, a. 16, resp.; On Evil, q. 3, a. 4.)

Hence, with this view of Origen shown as false, some adopt a similar position, (Above: obj. 5; ST I.90.4; cf. Augustine, On the Literal Interpretation of Genesis, bk. 7, ch. 24 (CSEL 28.1:222–23; PL 34:368).) claiming that all intellectual substances are of the same species for the reasons mentioned in the objections. However, this position is seen to be impossible. For if the angel and the soul are not composed of matter and form, but are forms alone, as was explained in the preceding question, (Above: qq. 1, 6.) every difference whereby angels are distinguished from one another, or from the soul as well, must be a formal one; (Cf. Aquinas, In II Sent., d. 32, q. 2, a. 3, resp.; On the Power of God, q. 3, a. 10.) unless perhaps it might be maintained that angels, like souls, were also united to bodies in order that there might be a material difference in them resulting from this relationship with bodies, as we explained above is true of souls. (Above: q. 6, ad 13; Aquinas, On Spiritual Creatures, aa. 2–3, 5.) But this view is not commonly held, and even if it were, it would not lend any weight to this position, because it is evident that the bodies (Namely, the bodies which angels would have.) would differ in species from human bodies to which souls are united. Moreover, there must be different specific perfections for bodies that are diverse in species. Therefore, with this position that angels are forms of bodies shown as false, since they are not composed of matter and form, it follows that angels differ from one another, or from the soul, only by reason of a formal difference. (Cf. Aquinas, In II Sent., d. 3, q. 1, a. 4, resp.; On Being and Essence, ch. 4.) But a formal difference diversifies species, for the form gives a thing its mode of existing. (Aristotle, Physics 2.3, 194b25–26.) Hence, it follows that angels not only differ in species from the soul, but also from each other.

However, even if someone claims that angels and souls are composed of matter and form, this position (Namely, that souls and angels are of the same species.) cannot be upheld. For if there were one matter common to angels and souls alike, just as there is one matter for inferior bodies, (Aristotle, On Generation and Corruption 1.1, 314b26–27.) diversified only by form, the division of that one common matter would have to be the principle whereby angels are made distinct from one another, and from the soul. Now since it is of the very account of matter in itself to be void of all form, the division of matter could not be understood to exist before it received a form, which is given a multiple existence as a result of the division of matter, unless matter itself were divided by quantitative dimensions. (Cf. Aquinas, In II Sent., d. 3, q. 1, a. 4, resp.; On Being and Essence, ch. 2.) Hence the Philosopher says in Physics 1 that substance remains indivisible when quantity is removed. (Aristotle, Physics 1.2, 185a32–b5; 185b16; 3.5, 204a8–12; cf. Aquinas, In II Sent., d. 3, q. 1, a. 4, resp.; d. 30, q. 2, a. 1, resp.; Commentary on Boethius’s De Trinitate, q. 4, a. 2, resp.; Commentary on Aristotle’s Physics, bk. 1, lect. 3, n. 23; On the Blend of the Elements.) However, things which are composed of matter determined by dimensions are themselves bodies, not merely things united to a body. According to this argument, therefore, the angel and the soul are bodies. Now no one of sound mind maintained this, particularly because it has been proved that understanding cannot be the act of a body. (Above: q. 1, resp.; q. 2, resp.) Certainly, if the matter of the angels and that of the soul is not one and common, just as it is maintained that there is not one common matter for heavenly and earthly bodies, but belongs to diverse orders, this can only be because it is ordered to different forms, and thus material diversity of this sort causes diversity of species. For this reason, it is clearly impossible for the angels and the soul to be of the same species.

However, the way they differ remains to be investigated. We must acquire our knowledge of intellectual substances by considering material substances. Now in material substances different grades of natural perfection constitute different species. (Cf. Romans 1:20; Aristotle, Metaphysics 2.1, 993b9–11.) Indeed, this becomes quite obvious if we reflect upon the genera of material substances. (Cf. Nemesius, On the Nature of Man, ch. 1; SCG III.97; ST I.47.2.) For it is evident that mixed bodies surpass the elements in the order of perfection; plants surpass minerals; animals surpass plants; and in singular genera a diversity of species is found in accordance with the order of natural perfection. For among the elements, earth is lowest, and fire most noble. (Cf. Aristotle, On Generation and Corruption 2.7, 334b17–30; 335a8–10; Aquinas, Commentary on Aristotle’s On the Soul, bk. 2, ch. 23.) Likewise, in the case of minerals, (That is, mixed bodies.) nature is found to ascend by degrees through diverse species up to the species of gold. In plants also, nature ascends progressively up to the species of perfect trees; and in animals up to the species of man. Moreover, certain animals are very near to plants, that is, the immobile ones which have touch only. Similarly, certain plants are more like inanimate bodies, as is clear from what the Philosopher says in the book On Plants 1. (Pseudo-Aristotle (Nicholas Damascene), On Plants 1.1, 815b35; Aquinas first attributed this to Aristotle, but after he read Alexander of Aphrodisias’s Commentary on Aristotle’s On Sense (ca. 1268), he began to attribute it to Theophrastus: cf. R. A. Gauthier’s Preface in the Leonine edition (vol. 45.2) of Aquinas’s Commentary on Aristotle’s On Sense and What Is Sensed, 97, 103*.)* For this reason, the Philosopher says in Metaphysics 8 that the species of natural things are like the species of numbers, wherein the addition or subtraction of a unit changes the species. (Aristotle, Metaphysics 8.3, 1043b33–1044a2.) Consequently, in immaterial substances also a different grade of natural perfection causes difference in species. (Cf. SCG II.95; ST I.47.2.)

But a grade of perfection is in some respect different in the case of immaterial substances from what it is in the case of material substances. For wherever diversity of grades exists, the grades must be considered through their order to some one principle. (Aristotle, Metaphysics 2.1, 993b24–27.) Therefore, in material substances diverse grades are observed to diversify species in relation to the first principle, matter. For this reason, first species (That is, those nearest to matter.) are most imperfect, whereas species farther removed from matter are more perfect, and related to the first by the addition of higher perfections. For instance, mixed bodies have a more perfect species than the elements have because they possess in themselves the perfections of the elements and higher perfections as well. Hence, the relation of plants to mineral bodies, and that of animals to plants, is similar.

In the case of immaterial substances, the order of diverse grades of species is certainly not considered in relationship to matter, which they do not have, but in relationship to the first agent, (Namely, God.) who must be most perfect. (Cf. The Book of Causes, proposition 18 [19].) Consequently, in the case of immaterial substances, the first species (That is, the one nearest to God.) is more perfect than the second, inasmuch as the former bears greater likeness to the first agent. The second species has less perfection than the first, and so on successively down to the last of them. Now the entire perfection of the first agent consists in this, that he has in one simple nature all his goodness and perfection. Therefore, the nearer an immaterial substance is to the first agent, the more does it have its perfection and goodness in one simple nature, and the less does it require inhering forms for its perfection. (Cf. SCG II.98; The Book of Causes, proposition 9 [10]; Pseudo-Dionysius, The Celestial Hierarchy, ch. 12, para. 2 (PG 3:298).) This continues progressively down to the human soul which occupies the lowest place among immaterial substances, just as prime matter holds the lowest place in the genus of sensible things. Hence, the soul does not have intelligible forms in its very nature, but is in potency to them, just as matter is to sensible forms. Therefore, in order to perform its proper operation, the soul must be actuated by intelligible forms by acquiring them from external realities through its sensory powers. And since the operation of a sense is performed through a bodily organ, it is proper to the soul, according to the very condition of its nature, to be united to the body, and to be part of the human species, not having a complete species in itself.

Reply Obj. 1: The act of understanding of the angel and that of the soul are not of the same species. For it is evident that if forms, which are principles of operation, differ in species, their operations must differ in species as well. For instance, the act of heating and that of cooling differ from each other because heat and cold differ. Now the intelligible species, through which the soul understands, are abstracted from phantasms, and thus are not of the same account as the intelligible species through which angels understand, because these are innate in the angels. Accordingly, it is said in the Book of Causes that every intelligence is filled with forms. (The Book of Causes, proposition 9 [10]; cf. On Truth, q. 8, a. 15, resp.; SCG II.98.) Therefore, the act of understanding of a man and that of an angel are not of the same species. In view of this difference it follows that the angel understands without any discourse, whereas the human soul understands discursively. It does this of necessity in order to know the powers of causes from their sensible effects, and to understand the essences of things, not perceived by the senses, from their sensible accidents.

Reply Obj. 2: The intellective soul understands both principles and conclusions through species abstracted from phantasms; and therefore, its understanding does not differ in species.

Reply Obj. 3: A motion is reduced to the genus and species of that particular order in which the motion is terminated, inasmuch as it is the same form that is in potency only before the motion begins, midway between act and potency during the motion itself, in complete act at the termination of the motion. (Cf. Aristotle, Physics 3.2, 201b30–35; Aquinas, Commentary on Aristotle’s Physics, bk. 3, lect. 3, n. 296.) However, an angel’s act of understanding, which takes place without any discourse, is not the same in species as that of the soul so far as the form is concerned. Consequently, it is not necessary that these two ways of understanding be one and the same in species.

Reply Obj. 4: A thing’s species is declared to be such in virtue of the operation that belongs to it by its own nature, and not in virtue of one that belongs to it because it participates in a higher nature. (Cf. Aristotle, Physics 1.8, 191b1–10; Aquinas, Commentary on Aristotle’s Physics, bk. 1, lect. 14, n. 123.) The species of iron, for instance, is not judged to be such because it is combustible, which belongs to it inasmuch as it is set on fire, for then the species of iron and that of wood, which also may be set on fire, would be considered to be the same. Moreover, I say that the act of understanding in the Word is an operation surpassing the nature of the soul and that of an angel, yet proper to each according as they participate in a superior nature, namely, the divine nature, through the light of glory. Consequently, it cannot be concluded that an angel and the soul are of the same species.

Reply Obj. 5: Intelligible species are not of the same nature in different angels; for the more superior an intellectual substance is, and the nearer to God—whom all understand through one thing, his essence—the more elevated are the intelligible forms within that substance, and thus more capable of knowing many things. (Cf. ST I.55.3.) Wherefore, it is said in the Book of Causes that superior intelligences understand through more universal forms. (The Book of Causes, proposition 9 [10].) Dionysius also says that superior angels have greater universal knowledge. (Pseudo-Dionysius, The Celestial Hierarchy, ch. 12, para. 2 (PG 3:291–94); cf. SCG II.98.) Therefore, the act of understanding of different angels is not of the same species, although each takes place without discourse because they understand through innate species and not through species received in some other way.

Reply Obj. 6: More and less are found in things in two ways. First, according as matter participates in different ways in the same form, as wood participates in whiteness. In this way more and less do not cause things to differ in species. Second, according as more and less are found in the different grades of perfection of forms. This causes difference in species. For colors differ in species by being related more or less closely to light. This is the way in which more and less are found in different angels.

Reply Obj. 7: Although all souls do not understand equally well, nevertheless all understand through species of the same nature, namely, those derived from phantasms. Hence, the fact that men do not understand equally well is a result of the difference in their sensory powers through which species are abstracted. This results in turn from the different disposition of their bodies. Consequently, it is evident, according to this, that more and less do not cause difference in species, since they are a consequence of material diversity.

Reply Obj. 8: To be cognizant of one thing through another occurs in two ways. First, when something known is understood through the knowledge of some other thing in such a way that there is a distinct knowledge of each, as a man knows conclusions from principles by considering both principles and conclusions separately. Second, when something known is understood through the species whereby it is understood, as when we see a stone through the species of the stone, which exists in the eye. Now it is in this way that angels know a cause through an effect and an effect through a cause, inasmuch as the essence itself of the angel bears some likeness to its cause, while the angel in turn causes its effect to be like itself.

Reply Obj. 9: The perfections of grace befit the soul and the angel by a participation in the divine nature. Hence, it is said, by which he has granted to us his precious and very great promises, that through these you may escape from the corruption that is in the world because of passion and become partakers of the divine nature (2 Pet 1:4). Therefore, because they have these perfections in common, it cannot be concluded that the angel and the soul are one in species.

Reply Obj. 10: Things having one and the same proximate and natural end are one and the same in species. (Aristotle, Nicomachean Ethics 1.1, 1094a3; Aquinas, Commentary on the Nicomachean Ethics, bk. 1, lect. 1; Commentary on Aristotle’s On the Heavens, bk. 2, lect. 4, n. 334.) However, eternal beatitude is an ultimate and supernatural end. Therefore, the conclusion stated in the objection does not follow. (Cf. Aquinas, In II Sent., d. 3, q. 1, a. 6, ad 5; ST I.75.7, ad 1; I.62.1–2; I-II.3.8; I-II.5.5.)

Reply Obj. 11: Augustine does not think there is nothing midway between our mind and God so far as the grades of dignity and of nature are concerned, because one nature is in fact nobler than another, but rather because our mind is immediately justified by God and beatified in him, just as if it might be said, for example, that a simple soldier is immediately under the king, not because there are no others superior to him under the king, but because no one has dominion over him except the king.

Reply Obj. 12: Neither the soul nor an angel is a perfect image of God, but the Son alone. Consequently, it is not necessary that the angel and the soul are of the same species. (Cf. ST I.93.3, resp.)

Reply Obj. 13: The aforesaid definition is not applicable to the soul in the same way as it is to an angel, for an angel is an incorporeal substance because it is not a body nor is it united to a body. This cannot be said of the soul.

Reply Obj. 14: To maintain that the soul and the angel belong to one species makes them, for this reason, equal in power. But this does not necessarily follow, for the ultimate difference should be nobler, not only with respect to nobility of nature, but also with respect to the way in which the nature is determined, because the ultimate difference is like an act in relation to all preceding differences. Consequently, the angel is nobler than the soul not because it is intellectual, but because it is intellectual in some particular way. This is evident in sensible things, otherwise all brute animals would be of the same species. (Cf. Aquinas, In II Sent., d. 3, q. 1, a. 6, ad 1; On the Power of God, q. 3, a. 10, ad 10; ST I.75.7, ad 2.)

Reply Obj. 15: The soul is a part of a species and is also a principle conferring species. (Cf. Aquinas, In II Sent., d. 3, q. 1, a. 6, resp.; SCG II.94.) The species of the soul is investigated in this way.

Reply Obj. 16: Although a species alone may be properly defined, yet it is not necessary that every species be definable. For the species of immaterial things are known neither by definition nor by demonstration, as something is known in the speculative sciences, but some of them are known by a simple intuition. Consequently, an angel cannot properly be defined, for we do not know what its essence is, but it can be known by certain negations or distinguishing characteristics. (Cf. Aquinas, On Being and Essence, ch. 5.) Again, the soul is defined inasmuch as it is the form of the body.

Reply Obj. 17: Genus and difference can be regarded in two ways. (Cf. ST I.66.2, ad 2; Commentary on Aristotle’s On the Soul, bk. 1, lect. 2; Commentary on Aristotle’s Metaphysics, bk. 7, lect. 17, n. 1649.) First, from a consideration of reality, so far as they are considered by metaphysics and by natural philosophy. Here it is manifest that genus and difference are based on different natures. Thus, nothing prevents us from saying that there is no genus and difference in spiritual substances, but that they are forms in their entirety, and simple species. (Cf. Aquinas, On Being and Essence, ch. 5.) Genus and difference can also be regarded from a logical consideration. (Cf. Aristotle, Physics 2.3, 193b22; 194a12; Aquinas, In I Sent., d. 19, q. 5, a. 2, ad 1; Commentary on Boethius’s De Trinitate, q. 6, a. 3, resp.; ST I.66.2, ad 2; I.88.2, ad 4; Commentary on Aristotle’s Metaphysics, bk. 10, lect. 10, n. 2139–42; Commentary on Aristotle’s On the Soul, bk. 1, lect. 2, n. 23.) In this case it is not necessary that genus and difference be founded on different natures, but on one and the same nature in which something proper and something common may be distinguished. In this way nothing prevents us from distinguishing genus and difference in spiritual substances. (Cf. ST I.88.2, ad 4.)

Reply Obj. 18: Speaking of genus and difference from the point of view of the real order, differences must be contraries. For matter, on which the nature of genus is based, is receptive of contrary forms. (Cf. Aquinas, Commentary on Aristotle’s Metaphysics, bk. 10, lect. 11.) However, from the point of view of logic, any opposition whatever in differences is sufficient, as is clear in the differences between numbers in which there is no contrariety. It is similar in the case of spiritual substances.

Reply Obj. 19: Although matter is not the basis of species, nevertheless the nature of a form is considered according to the relationship of matter to form.