Cursus Philosophicus Thomisticus, Secunda Pars Artis Logicae

Porphyry, in the chapter on Property, set out FOUR ACCEPTIONS OF PROPERTY, and by this very division seems to have defined each one. For property is divided in four ways. First, property is said of what belongs to the species alone, but not to every individual of it, as being grammatical or being a physician in a human being. Second, it is said of what, conversely, belongs to every individual but not to the species alone, as being two-footed belongs to a human being. Third, it is said of what belongs to the species alone and to every individual, but not always, as a human being’s growing gray in old age. Fourth, it is said of what is most proper, which belongs to the species alone, to every individual, and always, as a human being’s being capable of laughter. This is most proper because it is fully convertible with its subject.

Here Porphyry explained every account of property in some way by reference to a species, that is, to some nature of a thing, whether it be an infima species or a subaltern species, since property can in some way follow upon any such nature. He then derives the perfect account of property from its perfect agreement and adequation with the species or nature and with what is contained under the species. Something is said to be convertible when, whenever the subject exists, the property is found in it and nowhere outside it. For precisely because it is found in others, it is not perfectly proper to that thing, but is also common to others; it will be proper or accommodated to that thing alone only in a qualified way, as we see many accidents found outside their proper subject, such as heat, cold, whiteness, and so on. For an accident to accompany a subject perpetually and not exist outside it, it must have in that subject some root or principle by which it is connected to it and from which it flows. Accidents that belong also to subjects in which they have no root are called common, because they lack a principle by which they would belong to those subjects alone.

Thus it happens that when an accident has a principle and root in some nature and is communicated from it to another—for example, light, which has its root in the sun, from which it flows, but is communicated to the air; or heat, which has its root in fire but is communicated to water or another body—that accident has the character of a property with respect to the subject from which it flows, not with respect to the subject to which it is communicated. Further, an accident communicated outside its proper subject is not in other subjects in the same way as in its proper subject: in the others it is there as though by participation and imperfectly, whereas in its proper subject it is there fully and perfectly, being joined to its own proper principle. Hence, under the perfection and in the manner in which it is in its proper subject, it is never communicated outside that subject.

This is why some authors say that a proper accident cannot grow or increase, even intrinsically, in the very subject of which it is the proper passion, because there it has the highest perfection naturally suited to it. It can increase only in an alien subject, just as light cannot grow in the sun nor heat in fire. This is discussed more fully in the Physics¹, and theologians treat it when discussing the fullness of Christ’s grace, 3. p. q. 7. art. 11.

THEREFORE TWO THINGS REMAIN FOR US TO EXPLAIN: First, what is divided by this division of property, and what the division itself into four modes is. Second, how the definition of property in the fourth mode is to be explained.

Regarding the first, I ANSWER AND SAY, FIRST: What is divided in this division is not the fourth predicable, property, but property taken commonly, whose account consists in a relation of agreement with one, with the exclusion of partnership or communication with another.

For what is proper is so peculiar that it is not another’s nor common to it. Accordingly, in this division we proceed as we do in dividing difference into common, proper, and most proper.

THE REASON for the conclusion is that the account of the fourth predicable consists in being predicated “in quale,” accidentally and necessarily. It is distinguished from the other predicables by these features: by “in quale” from genus and species; by “accidentally” from difference, which is a “quale” essentially; and by “necessarily” from common accident, which is the fifth predicable. But these conditions do not belong to what is divided in this division; they belong only to one of the dividing members, namely property in the fourth mode. Therefore the fourth predicable is not what is divided here, since it is a dividing member; consequently, what is divided is property taken commonly. This is because the division is proposed so that, among the many things that can take the name “property,” we may investigate that which is a proper passion and to which the fourth predicability is assigned. The fourth predicable itself, then, should not be taken as what is divided; rather, among the dividing members we must seek out and distinguish it from the others, which may seem to have the account of property but do not attain the account of a proper passion.

I SAY, SECOND: Property taken commonly is divided by an analogous division into these four modes of property.

There is no great disagreement among authors on this conclusion; they commonly follow it, especially the Thomists.

We call property taken commonly what is property considered, as it were, physically or metaphysically, insofar as it is opposed to what is common—not property as the fourth predicable, as we have said. Here we deal only with the nature of property, not with the intention. Thus, just as we rightly say that what is taken absolutely as common is that which has the conditions required for the account of the common, so property taken commonly is that which has the conditions required for something to be proper. And just as the common signifies a relation of communication or agreement with many, so the proper signifies a relation of agreement with one, with the exclusion of communication to what is foreign.

Thus these two conditions are generally required for the account of property. To the extent that both conditions are observed without qualification, the account of property is found without qualification; if they are found only in a qualified way, the thing is not property without qualification. The four modes stand as follows: only in the fourth mode are both conditions found without qualification, not in the others. The first condition is that it belong to one without separating from it in respect of that agreement; the second, that it not belong to another, something foreign. For the first condition to hold, it must belong wherever that thing is found and always—that is, firmly and inseparably. Something belongs firmly to a thing when it has a root and principle in it. If it has no root there, it belongs transiently and separably by the force of the connection, even if, by accident, it can persist in existence through some extrinsic conserver—not in respect of its belonging. The second condition requires that it belong to that thing alone, since it must not belong to another outside it.

Therefore, when any of these conditions is lacking, property is not found without qualification or fully, because it lacks the very account of property and the conditions essentially required for it. They are lacking in the first three modes of property. The first mode belongs to the species alone, but not to every individual or always; hence it is separable and so is not property. In the second mode it belongs to every individual, but not to the species alone, and so is common to others. In the third mode it belongs to every individual and to the species alone, but not always; hence it is not permanent but separable. This is not to possess and have it as a property—not merely because it does not at some time exist in the subject, but because it does not always belong to it.

But if you ask why things that are proper in these modes are called properties, when they are not truly properties—

The answer is that they are properties in a qualified sense. First, because they at least share some conditions of property, such as belonging either to the species alone or to every individual. Second, although they are not properties absolutely, they are properties comparatively: for example, although being two-footed is not absolutely proper to a human being, it is proper to a human being comparatively with quadrupeds.

Hence it is clear at last that the division is adequate, since of the three conditions required for property—belonging to every individual, to the species alone, and always—either all are present or one is missing. If all are present, it is property without qualification and belongs to the fourth mode. If one is missing, either the first is missing, namely that it belong to every individual, and it is property in the first mode; or the second, namely that it belong to the species alone, and it is property in the second mode; or the third is missing, and it is property in the third mode. If all are missing, it is property in no way.

Regarding the second point: From what has been said, the definition of property without qualification is clear. It is given in two ways: by Porphyry, property in the fourth mode is “what belongs to every individual, to the species alone, and always”; and by Aristotle, Topics 1, ch. 5,² property is “what does not indicate the being of the thing, but inheres in the species alone and is predicated convertibly.” Here what is explained is rather the underlying subject matter of the fourth predicable—that is, the proper passion itself—than the account of the fourth predicable itself. In Porphyry’s definition, if “belongs” means the same as “is predicated” or “can be predicated,” and “every” is taken distributively for the inferiors, the definition will be intentional and will concern the logical predicable. It can then be put in this form: “Property is what is predicated of many in quale, accidentally and necessarily.” We shall explain this definition in the following article. But if “belongs” means the same as “inheres,” “is fitting,” or “is due,” then “belongs” is taken in the first intention for that which grounds universal predication in the manner of the fourth predicable. The definition will take this form: “Property is what necessarily follows upon some nature and belongs to it accidentally but convertibly.” In this way we also include the Philosopher’s definition, insofar as it states accidental and convertible agreement.

But if you ask what it means to follow upon and flow from an essence, or to have that essence as its root, and what kind of causality this flowing is—

The answer is that this belongs to metaphysics. Briefly, however, we say that flowing is not properly efficient causality, that is, causality that acts through an action, but has the mode of efficiency. For substance by itself, without accidents, does not properly effect anything; therefore the accidents by which it effects and operates are said to flow from substance—not because they are produced by substance, for they are produced by an agent together with the substance itself, though dependently on the substance, whose proper passions they are and from which they derive participation, as secondary and less principal forms depend on the radical and primary form. What is such by participation depends on what is such principally and radically. This dependence is called flowing because it is participated in from that thing as from a principle; thus it has an account that is quasi-active or reductively active, not formally active, insofar as it is a kind of participation and connection with a nature. On this see St. Thomas, 1. p. q. 77. art. 6. ad 3 and art. 7. ad 1, and opusc. 48, chapter “On Property,” at the end.³ One may also see Cajetan, chapter 7 of De Ente et Essentia, q. 16, § Accedit, where he discusses how a proper passion is caused by its subject in the genera of material, efficient, and final causality. We explain this more fully in the Physics, q. 12.⁴ and in the book On the Soul, q. 2.⁵

THE ARGUMENTS ARE ANSWERED.

Against the division given, it is argued to prove that what is divided in it is not property taken in the first intention and physically, but property taken in the second intention. For property as it is found in a thing is individual and singular. Therefore, property is either proper insofar as it is singular, or proper in itself. If it is proper insofar as singular, it is not property in the fourth mode, since it does not flow from an essential principle but from an individual one. If it is proper in itself, it does not belong to every singular subject as a property, but as something common, because it belongs to many individuals. Therefore property is never found in a thing, but only with respect to the second intention.

But if property is taken in the singular—for example, this capacity for laughter in relation to this individual, say Peter—such a property is individual. We are not discussing it here, but rather what is proper to a nature and can be the fourth predicable.

It is further confirmed that property thus divided is said of many, namely, that it belongs to every individual, and so on. Therefore it is not property as it exists physically in a thing, but as it exists in the intellect. Thus it is property taken logically.

THE ANSWER IS that property as it is found in a thing is indeed singular, since nothing but singulars are found in things; yet it is not proper by reason of the subject’s singularity, but by reason of its nature. Thus it inheres in each singular as a property, not of the singular itself, but of the nature found in it. Likewise, the predicates that constitute a nature are found in things as singularized, but they are not quidditative and essential by reason of singularity; they are so by reason of the nature that they essentially constitute in the thing as a nature, and individually as this nature. A passion that flows from a nature in a thing stands in the same way.

To the confirmation, the answer is that property said of many is found in a thing with respect to the underlying reality on which this predicability of many rests, but not with respect to the mode of predicability. Likewise, genus and species, in the second intention, are not in a thing; but with respect to the underlying nature they are in the thing, although in another mode. So property is found in a thing with respect to the relation of property and to the thing itself, which is the proper passion. Fundamentally, this has to belong to every individual and be predicated of many; the formal intention of predicability, however, belongs through the intellect. In this division we consider the very account of property in itself, not the intention.

Second, it is argued: What is divided in this division must be some accident. Therefore, it either abstracts from the fourth and fifth predicables, or determines the fourth, or determines the fifth. If the first, what is divided in this division is not property, but something abstracting from proper and common accident. If the second, then we wrongly denied that what is divided in this division is the fourth predicable. If the third, how can one of the dividing members be the fourth predicable—namely, property in the fourth mode—which is opposed to the fifth predicable?

It is confirmed that property in the second mode is a common accident: it belongs to every individual, but not to the species alone, and therefore in no way pertains to the account of property but is opposed to it. For the intention of any property, whether in the first or second mode, should not be the intention of the fifth predicable.

THE ANSWER IS that what is divided in this division is not an accident insofar as it abstracts from proper and common accident, because this division does not formally consider division under the account of the fourth or fifth predicable, although things are predicated in those modes. Rather, what is divided is an accident insofar as it can introduce and ground the conditions of property and a relation of agreement with something under the formal character of property. The account of difference, which is divided into common, proper, and most proper, is likewise not difference under the concept of a predicable, but under the concept of that which makes things differ. And because that formal character of property and the conditions required for it are not found equally in every property, this division is made analogically, according to the different modes of possessing property.

To the confirmation, the answer is that property in the second mode pertains to the fifth predicable because it is simply a common accident. Yet under the account of agreement, property, and property considered physically, it takes on the character of property—not without qualification, but with respect to one condition, namely, that it belongs to every individual; and not absolutely, but relatively and comparatively. For example, being two-footed absolutely belongs also to things other than a human being, but with respect to quadrupeds it is proper to a human being. In this way it pertains reductively to property in the fourth mode as to its principal analogate. Nor is it unreasonable for something to pertain simply to one predicable, and in a qualified and reductive way to another, just as “rational” with respect to Peter and Paul is a difference, but with respect to this rational being and that one it takes on the mode of a species.

Finally, it is argued against the definition of property in the fourth mode. The particle “always” does not belong to all proper passions; therefore it is wrongly included.

The antecedent is proved as follows. First, God can separate a proper passion from its subject, as quantity from a body in the Eucharist, or preserve the subject without it, as the sun without light. Indeed, a proper passion can naturally be impeded, as downward motion in a stone, cold in water, and the sensitive powers in an animal, although they flow from the soul. Finally, existence belongs contingently to every creature and cannot be a proper passion; otherwise the same thing would produce itself if existence flowed from itself. Yet existence belongs per se to form, as roundness does to a circle, as St. Thomas says in Contra Gentiles 2, ch. 55. Therefore, if a form is subsistent, it is incorruptible precisely because existence belongs to it per se. Therefore a proper passion does not consist in flowing from and belonging per se to its subject.

THE ANSWER IS: The antecedent is denied. As for the proof, concerning the separation of a proper passion from its subject, it is not the business of logic to dispute this. We admit that real passions can be separated from their subject, although modal passions—which consist in a mere mode or include some privation or negation required on the subject’s part—cannot exist separately, because they are not really distinct from the subject. Since only real passions can be separated, we say that in the definition of property, “belongs always” does not mean that it exists or is present in the subject; rather, “belongs” means that it is due to, connected with, and demanded by the subject, although it may not always actually exist in it. Thus St. Thomas is to be understood when he says in Quaestiones disputatae de spiritualibus creaturis, art. ult., ad 7,⁶ that it is unintelligible for a subject to exist without its proper passion—that is, for the proper passion not to belong or be connected to it. We assign this agreement on the ground that the subject cannot, of itself, fail to require and demand that proper passion, so that the proper passion could be denied of the subject or fail to belong to it, although it can be separated from the subject by the intellect’s first operation. But common accident, which is distinguished from property, can also be denied of a subject by the second operation without destroying it, as St. Thomas rightly notes in opusc. 48, chapter “On Accident”⁷ and in 1. dist. 26, in the exposition of the text.⁸

As for the other part of the argument about proper passions that are impeded, the answer is that although all proper passions flow from their subject and are connected to it, they do not all do so in the same way. Some flow absolutely, with no dependence other than on the subject from which they flow, such as the capacity for laughter and intellect from a human being, transparency from the heavens, and light from the sun. Others flow on the supposition of some connatural state: a stone is fitted to be at rest not absolutely but at the center, and to move not absolutely but outside the center; grace in the consummated state has the light of glory, and in the state of the wayfarer faith and hope; water has its greatest cold in its connatural state; an animal has sensitive powers on the supposition of an organ’s proper temperament; and, finally, a heavy body is fitted to move through an unimpeded, free medium. We say, then, that these passions can be impeded by something extrinsic, because they do not flow from the subject absolutely, but on the supposition of some state or extrinsic condition. The first kind, which flow absolutely from the subject, cannot naturally be impeded once the subject is posited. Some properties also belong to a subject not determinately but vaguely, such as some shape to quantity, or some color to a mixture—if indeed these are properties.

Regarding what is added about existence, the answer is that existence has no necessary connection with any creature, but belongs contingently; otherwise it would belong always and from eternity by the connection of eternal truth, whereas it depends on a free efficient cause, namely God. Existence is said to belong per se to a form, not by logical per se-ness, which is founded on a relation of intrinsic connection, but by physical per se-ness, which is founded on the thing as produced and insofar as it is under the physical influence of the agent. Existence is said to follow upon form as splendor follows upon light, because existence takes its determination and specification from the form of which it is the existence; as determined and specified, it is therefore of that form. For the existence of a human being, insofar as it is specifically human and not angelic, follows upon the human form, since existence is not determinate and specified of itself, but only by reason of that of which it is the existence. In a form dependent on matter, the existence is dissolved when the form is separated from matter, because the form is lost. But if the form does not depend on matter, existence can be taken from it only by suspending the action of the agent on which that form alone depends; this is to cease through annihilation.

THERE ARE TWO THINGS in this fourth predicable, insofar as it is a universal, that require explanation. The first is whether the account of the fourth predicable belongs only to a property in the fourth mode, or also to other things. The second is with respect to which inferiors this universality of the fourth predicable belongs to it.

With regard to the first, not a few DOCTORS think that the intention of the fourth predicable belongs not only to a property in the fourth mode, but also to a property in the second mode, or even to all properties. The entire basis seems to reduce to this: these properties, at least what is a property in the second mode, are predicated in “what kind” accidentally and in a way distinct from the fifth predicable, which says only that something can be present and absent; and they belong necessarily, because what is a property in the second mode, such as a human being’s being two-footed, belongs to it necessarily, although not to it alone. Therefore it pertains to the fourth predicable.

This is confirmed because there is no accident that does not flow from some substance, although it can also belong to other subjects from which it does not flow. Hence St. Thomas in chapter 7 of On Being and Essence¹ teaches without qualification that all accidents flow from substance. This is clear because every accident is a certain participation in substance. Therefore, under the aspect in which it flows from substance, it ought to pertain to the fourth predicable, although insofar as it is communicated to others from which it does not flow, it falls short of the perfect account of a property.

NEVERTHELESS, the opposite must be held. And I say: Only a property in the fourth mode, or what is reduced to it, is the substratum of the intention of the fourth predicable.

This is the more common opinion among Thomists; on this one may consult Soto, Masius, Araujo, and others, together with the Carmelite Course, disputation 8, question 1.

THE REASON is taken from what the Philosopher establishes in Posterior Analytics I, chapter 4² and lecture 10 in St. Thomas’s commentary³: when he assigns the four modes of per se and explains the second, namely, when the subject is placed in the definition of the predicate, he says that this is the difference between a proper and a common accident: when the subject is placed in the definition of some predicate, it is a proper accident. But if some predicate is not placed in the definition of the subject, nor the subject in the definition of the predicate, such things are common accidents and are predicated accidentally. Now, when something is not signified as proper in the fourth mode, which belongs to all, to it alone, and always, the subject is not placed in the definition of that accident; for example, man is not placed in the definition of two-footed, nor swan in the definition of white. Therefore it is not a property, as distinguished from the fifth predicable. That the subject is not placed in the definition of such a predicate is clear because the predicate is found outside that subject: although it belongs to all of the subject, it does not belong to it alone.

You will say: On this reasoning it would be proved that being capable of laughter is not a property in the fourth mode with respect to Peter and other individuals, because Peter too is not placed in the definition of being capable of laughter, just as man is not placed in the definition of two-footed.

It is answered that Peter is placed in the definition of being capable of laughter not by reason of his singularity, but by reason of the specific nature that is in Peter. For everything that pertains to Peter’s specific nature is placed in the definition of being capable of laughter, but not what pertains to Peter’s singularity; whereas the whole nature of man is not placed in the definition of two-footed. This is why generic properties are more often properties in the second mode with respect to species than specific properties are.

Then, as St. Thomas very well notes in opusculum 48, chapter On Property⁴, common accidents have a relation to their subject only as to a material and receptive cause, since a material cause as such does not posit a necessary connection with an accidental form. A property, however, regards its subject not only as a receptive cause, but as a principle from which it flows, because it has a cause of connection with it. St. Thomas also observes this in the cited place in Posterior Analytics I. Therefore, for something to be a property as fourth predicable, as distinguished from the fifth, its subject must not only be capable of receiving it, but must also be the root of that accident and have a necessary connection with it. But if it does not belong to that subject alone, it does not have a necessary connection with it, since it is common to others and cannot have diverse essences as its essential and radical principle, inasmuch as those essences are diverse. Therefore, to be a fourth predicable, it must belong to all, to it alone, and always. Hence St. Thomas says in Sentences I, d. 8, q. 1, art. 1, ad 1⁵, that “when something is said to belong properly on the part of the subject, what is extraneous to the subject’s nature must be excluded by the property, as when being capable of laughter is said to be proper to man, because it belongs to nothing extraneous to human nature.” What belongs to all but not to it alone, then, belongs to what is extraneous to the subject’s nature, and so does not belong properly.

TO THE GROUNDS OF THE OPPOSING OPINION it is answered that other properties, including those that are properties in the second mode, are not predicated necessarily by a necessity that is, as it were, formal and intrinsic to a connection, but by a necessity that is, as it were, material, or a necessity of the individual matter, as is inferred from St. Thomas, opusculum 48, chapter On Property⁶, as we shall say of an inseparable accident in the following question. But what is predicated necessarily by a necessity that is, as it were, formal, from the principles of the nature and not only from individual principles and the necessity of matter, is a property as fourth predicable. The fifth predicable, however, is said to be what can be present and absent because it has no intrinsic connection or root in the principles of the nature, although, as regards existence, it cannot be separated because of some extrinsic cause.

In a human being, being two-footed, if it is a property in the fourth mode with respect to some subordinate degree, will be a fourth predicable with respect to that degree; and it will be in the second mode of property only in a qualified sense, insofar as it is not said convertibly with respect to man.

To the confirmation it is answered that all accidents are caused by substance, as St. Thomas says there, but some are caused by formal principles, and these are proper attributes, because they have a connection of formal necessity; others are caused by material principles, and are common accidents or accidents of individuals, as St. Thomas says there. Those caused by formal principles, if communicated to another subject, will be common accidents with respect to the subject to which they are communicated, as heat with respect to water or wood, but properties with respect to that from which they are caused.

As for the second point, namely, with respect to which subjects the account of the fourth predicable belongs: whether with respect to the species with which the property is convertible, or with respect to the inferiors of which it is said.

THE REASON FOR DOUBT is that a property in the fourth mode belongs to individuals neither necessarily nor convertibly; therefore with respect to them it is not predicable as a property. The antecedent is clear: a property does not belong to an individual alone, but to others too; therefore it does not have a necessary connection with the individual insofar as it is this individual. Nor is it convertible with the individual, because there is no mutual consequence between individuals and the property: although “He is Peter, therefore he is capable of laughter” follows, “He is capable of laughter, therefore he is Peter” does not. Therefore it is not related convertibly to individuals.

This is confirmed because the properties of a genus with respect to its inferiors do not function as properties in the fourth mode, but in the second; therefore they are not called fourth predicables with respect to inferiors, but with respect to the nature with which they are convertible. The antecedent is proved as follows: two-footed is a proper attribute of animal, distinguished from quadrupeds—which is an unnamed genus with respect to all two-footed animals—yet with respect to man it is a property in the second mode. Indeed, all common accidents, such as whiteness, blackness, and the like, are properties in the fourth mode with respect to some subject, yet are said of singular bodies as common accidents; therefore the fourth predicable is not said to be such with respect to inferiors. Finally, an argument like that made above about difference can be made, because this predication, “Man is capable of laughter,” is of the fourth predicable, since it does not pertain to another mode of predicating, and is universal because it is predicated convertibly of a universal, namely man; therefore it is a universal of the fourth predicable with respect to the species.

I omit the arguments for proving that the inferiors of a property should not be the very properties individualized, for example, with respect to being capable of laughter, this and that instance of laughability, because in the similar case we already resolved this in the preceding question on Difference.

TO THE PROPOSED DIFFICULTY, THEN, I REPLY, in accordance with what was said in the preceding question on Difference, that a property assumes the account of a fourth predicable only with respect to the individuals of the species with which it is convertible. Accordingly, with respect to the metaphysical account of a proper attribute—that is, the account of necessary connection and convertibility with that of which it is a property—it has all this with respect to the species with which it is said convertibly, and is rather a fourth predicate than a fourth predicable. But with respect to the account of a fourth logical universal, it must necessarily regard the inferiors of the species with which it is convertible.

THE REASON IS that a property with respect to its singulars—for example, laughability with respect to this and that individual instance—is indeed superior and universal, but not in “what kind”; it is “in what,” like species and individuals. For a proper accident too has its own quiddity and nature, which it predicates of its inferiors. But with respect to the species or nature from which the property flows, taken in common, it is predicated in “what kind,” but not as something superior: it is equal and convertible. Hence it will be a concomitant universal, but not formally universal with respect to that species, since it is not something superior to it. Hence, although a property is predicated per se and of all, it is said per se with respect to the subject or nature from which it flows, and of all with respect to the things contained under such a nature, as St. Thomas aptly observed in Posterior Analytics I, lecture 9, § “He interposes,” etc.⁷

TO THE OPPOSING GROUNDS it is answered. To the first: The antecedent is denied. In response to the proof, it is said that a property has a necessary connection with individuals mediately and by reason of the nature from which it flows, not by reason of the individuation to which it is communicated. Likewise, it is mutually convertible with them by reason of their nature, not their individuation. The fact that it is common to many does not remove the account of a property with respect to the nature, because this commonality is not shared with extraneous things, but with individuals of the proper nature. Nor must the necessary connection be founded on something by reason of all the things that are in it or contained under it; it need only be founded by reason of the nature, root, and principle. Hence there need not be mutual consequence between a property of some nature and each individual; it suffices that there be mutual connection and consequence between the nature itself and the property.

To the confirmation it is answered that those which are truly properties of a genus belong to all its inferiors as properties in the fourth mode, no less than specific properties belong to the individuals of such a species—for example, the tactile faculty, which is a property of animal, and quantity with respect to body, provided that it follows upon the form of body and not only upon matter. For that quantity is a property of body is sufficiently indicated by St. Thomas in Quaestiones disputatae de spiritualibus creaturis, art. 3, ad 18.⁸ Others doubt this; see Cajetan, On Being and Essence, chapter 7, question 16, ad 1. This, however, does not pertain to the present matter.

As for what is said about being two-footed, it is not altogether clear that it is a property in the fourth mode; for St. Thomas lists it among essential differences in Metaphysics V, lecture 16, at the beginning⁹, yet lists it absolutely among accidental differences in On the Soul I, lecture 1, at the end¹⁰. It is said to be taken as an essential difference because we use accidental differences, which are better known to us, in place of essential ones.

In response to what is said about other accidents, it is answered that not all are proper attributes, because they do not all arise from the formal principles of a nature; some arise from material principles, as we said above on the authority of St. Thomas in chapter 7 of On Being and Essence¹¹. He says the same in Sentences I, d. 17, q. 1, art. 2, ad 2.¹² And some are not proper attributes of any nature, although from an extrinsic cause they may be inseparable in some subject, as blackness in a crow.

To the argument about predicating a property of a species it is answered that this is indeed a predication of a universal thing, but one that does not have universality with respect to the species, which is equal to it, not inferior to it; universality formally obtains only with respect to inferiors.

Finally, note that sometimes a proper attribute is not a determinate accident, but a disjunctive one, such as even or odd with respect to number, male and female with respect to animal. Then each of these is a determinate accident, whereas the disjunctive is what belongs per se. On this see St. Thomas, Posterior Analytics I, lecture 10, at the end¹³.