MP_C30.qxd 11/23/06 2:36 AM Page 227 30 Thomas Aquinas On Being and Essence Prologue Because a small error in the beginning grows enormous at the end, as the Philosopher remarks in Book 1 of On the Heavens and the World,1 and being and essence are the first things to be conceived by our understanding, as Avicenna declares in Book 1 of his Metaphysics,2in order to avoid falling into error about them, and to reveal their difficulties, we should see what are signified by the names of being and essence, how these are found in various things, and how they are related to the logical intentions3 of genus, species, and difference. And since we need to arrive at the cognition of simple components from the cognition of what they compose, and from those that are posterior to those that are prior, so that the discussion may suitably progress from the easier subjects, we should proceed from the signification of the name of being to the signification of the name of essence.4 1 Aristotle, De Caelo, lb. 1, c. 5, A271; Commentaryof St. Thomas, lc. 9. 2 Avicenna, Metaphysica, lb. 1, c. 6. 3 The “logical intentions” are second-order concepts (secundae intentiones) whereby we conceive of first-order concepts [primae intentiones], which in turn are concepts whereby we conceive of things that are not concepts. For example, by means of the first-order concepts of humans and of dogs we con- ceive of human beings and of dogs, which are not concepts. But by means of the second-order con- cept of species we conceive of the first-order, specific concepts of humans, dogs, donkeys, etc., and by means of the second-order concept of genus we conceive of the generic concepts of animals, plants, elements, etc. 4 This passage is a neat expression of Aquinas’s general Aristotelian epistemological stance. We should start with the things with which we are more familiar, namely, the things given in our everyday experi- ence, which are, nevertheless, metaphysically posterior to their simple components. But through the careful conceptual analysis of these things we may arrive at the understanding of their simple meta- physical constituents, which will then enable us to see how these constituents can be found even in things beyond our everyday experience. MP_C30.qxd 11/23/06 2:36 AM Page 228 228 S C Chapter 1. The Meanings of the Names of Being and Essence5 SI Y H P We should know that, as the Philosopher says in Book 5 of the Metaphysics, something is A T said to be a being [ens per se]6in two different senses: in one sense, [only] those things [are E M called beings] that are sorted into the ten categories; in the other sense [calling something a L, U being] signifies the truth of a proposition. And the difference between the two is that in the O S second sense everything can be said to be a being of which a [true] affirmative proposition E H can be formed, even if it posits nothing in reality; it is in this way that privations and nega- T F tions are said to be beings, for we say that an affirmation is the opposite of negation, and O Y that there is blindness in an eye. But in the first sense only that can be said to be a being PH which posits something in reality.7 Therefore, blindness and the like are not beings in the O S first sense. So, the name “essence” [essentia] is not derived from “being” [ens] in the second O L sense (for some things are said to be beings in this sense although they do not have an essence, HI P as is clear in the case of privations), but from “being” as it is used in the first sense. This is E, why the Commentator remarks in the same passage: “‘Being’ in the first sense signifies the R U T substance of the thing.”8 A N And since, as has been said, beings in this sense are sorted into the ten categories; F O “essence” has to signify something that is common to all natures on account of which Y various beings fall under the diverse genera and species, as for example humanity is the essence H OP of man, and so on for the rest. And because that by which a thing is constituted in its proper S O genus or species is what we signify by the definition indicating what [quid] this thing is, philo- L HI sophers changed the name of essence into the name “quiddity” [quidditas], and this is what P the Philosopher in Book 7 of the Metaphysics often calls “what something was to be” [quod 5 The division of the text into seven chapters follows the Boyer edition, used for this translation (“Opusculum De ente et essentia, introductione et notis auctum,” ed. C. Boyer, Textus et Documenta, Series Philosophica, 5: Pontificia Universitas Gregoriana (Rome, 1933)). The chapter titles are added by the translator. 6 Aristotle, Metaphysics, Bk. 5, c. 7, 1017a22–3; Commentary of St. Thomas, lc. 7.In the passage to which Aquinas refers, Aristotle contrasts “coincidental being” (ens per accidens) with “non-coincidental being” [ens per se]. A coincidental being is something identified on the basis of merely coincidental fea- tures, on account of which it would belong to two different categories; for example, a tall musician, described as such, is a merely coincidental being, described in terms of a quantity (height) and a qual- ity (a capacity to play music). So, the person conceived and described in this way is a merely coinci- dental being, an ens per accidens. On the other hand, the same person considered merely as a human being, as such, is not described in coincidental terms, so, the person considered in this way is an ens per se. Obviously, the distinction itself is not a real distinction between two different sorts of things, but a mere distinction of reason between different ways of conceiving of the same thing. 7 This, initially puzzling, distinction between the two main senses of the term “being” is what is often referred to as the distinction between “real being” (ens reale) and “being of reason” (ens rationis) (some- times also referred to as “being as true” (ens ut verum)). The distinction will at once be less puzzling, if it is read in its proper context, i.e., the “inherence theory of predication” and the corresponding theory of signification, assumed here by Aquinas, without any preliminary explanation. For detailed analyses of this distinction along these lines, see G. Klima, “The Semantic Principles Underlying Saint Thomas Aquinas’s Metaphysics of Being,” Medieval Philosophy and Theology, 5 (1996), pp. 87–141; “Aquinas’ Theory of the Copula and the Analogy of Being,” Logical Analysis and History of Philosophy, 5 (2002), pp. 159–76; “The Changing Role of Entia Rationis in Medieval Philosophy: A Comparative Study with a Reconstruction,” Synthese96 (1993), pp. 25–59. 8 Averroës, In Metaph., lb. 5, com. 14. MP_C30.qxd 11/23/06 2:36 AM Page 229 229 E quid erat esse], that is to say, that on account of which something is what it is. It is also called C N “form,” because “form” signifies the perfection and determinate character [certitudo]of every E S thing, as Avicenna says in Book 2 of his Metaphysics.9 It is also called “nature,” taking ES “nature” in the first of the four senses assigned to it by Boethius in his On Two Natures,10 ND A namely, in the sense in which a nature is said to be that which can in any way be appre- G hended by the intellect. For a thing is intelligible only on account of its essence and N EI definition; and it is also in this sense that the Philosopher in Book 5 of the Metaphysicssays B N that every substance is a nature. But the name “nature” taken in this way seems to signify O the essence of a thing insofar as it is related to the thing’s proper operation, since nothing S A N is deprived of its proper operation. The name “quiddity,” on the other hand, is derived from UI the fact that it is signified by the definition; but it is called “essence” [essentia], because it is Q A that through which and in which a thing has its being [esse]. Chapter 2. The Essence of Material Substances But because a substance is said to be a being primarily and without qualification, whereas an accident is a being only secondarily and, as it were, with qualification, only a substance has an essence in a strict and true sense, while an accident has it only somehow, with qualification. Some substances are simple, others are composite, and both sorts have their essence, but the simple ones in a more genuine and excellent way, just as they have a more excellent way of being. For they are the cause of the composite ones; at least this is true of the first, simple substance, which is God. However, since the essences of these substances are quite hidden from us, we should begin with the essences of composite substances, so that our discussion may more suitably proceed from the easier subjects. In composite substances, therefore, form and matter are known [components],11 as are soul and body in man. But it cannot be said that one of these alone should be called the essence of the thing. That matter alone is not the essence of the thing is clear, because the thing is knowable through its essence, and it is on account of its essence that it falls under its proper species and genus; but its matter is not the principle of cognition of the thing, and it is not on account of its matter that a thing is determined to be in its proper genus or species, but that on account of which it actually exists. However, the form of a thing alone cannot be said to be its essence either, even if some people want to make this claim.12 For on the basis of what has been said so far it is clear that the essence of a thing is what its definition signifies. But the definition of things of nature contains not only form, but matter as well; otherwise natural definitions would not differ from mathematical 9 Avicenna, Metaph., 1, 6; 2, 2. 10 De persona et duabus naturis, c. 1. Migne Patrologia Latina (ML), 64, 1341. 11 Matter and form are the obviously given metaphysical components of any material substance, as it is clear from the hylomorphic analysis of physical change, provided by Aquinas in his On the Principles of Nature. 12 In particular, Averroës and his followers made this claim against Avicenna. Aquinas sides with Avicenna on the issue. Cf. Aquinas, In Metaphysica, lb. 7, lc. 9, n. 1467; In Quattuor Libros Sententiarum Petri Lombardi(SN) 4, d. 44, q. 1, a. 1b, resp. 2. MP_C30.qxd 11/23/06 2:36 AM Page 230 230 S C definitions.13 And it cannot be said that matter is included in the definition of a natural SI Y substance as something added to its essence, or as something existing outside of its essence, H P for this sort of definition is proper to accidents, which do not have perfect essence, and there- A ET fore they have to receive in their definition their subject, which is outside their essence.14 M L, It is clear, therefore, that essence comprises both matter and form. U Nevertheless, it cannot be said that “essence” signifies a relation between matter and form, O S or something superadded to these, because that would necessarily be an accident or extrinsic E H to the thing, and the thing would not be known on account of it, none of which can apply T F to an essence. For by the form, which is the actuality of matter, matter is made into an actual O Y being and this[particular] thing [hoc aliquid]. Therefore, whatever supervenes does not give H P actual being to matter absolutely speaking, but it makes it actual in some respect, just as O S accidents do, as whiteness makes something actually white. So, when a form of this sort is O HIL acquired, the thing is not said to be generated absolutely speaking, but only in some respect. P What remains, therefore, is that the name “essence” in composite substances signifies what E, R is composed of matter and form. And Boethius agrees with this position in his Commentary U T on the Categories, when he says that ousia signifies something composite; for ousia signifies A N the same for the Greeks as “essence” does for us, as he says in his On Two Natures. Avicenna F O also says that the quiddity of composite substances is the composition of matter and form Y H itself.15 And even Averroës declares in his Commentary on Book 7 of the Metaphysics: “the P O nature that the species of generable and corruptible things have is a certain intermediary, S O that is, composed of matter and form.”16 L HI And reason agrees with this as well, for the act of being [esse] of a composite substance is P neither of the form alone, nor of matter alone, but of the composite itself; and the essence is that on account of which the thing is said to be. Therefore, the essence, on account of which the thing is denominated a “being,” cannot be the form alone or the matter alone, but has to be both, although it is the form that causes this act of being in its own way. We can see also in cases of other things composed of several principles that the thing is not denom- inated on account of only one of those principles that constitute it, but on account of what comprises both, as is clear in the case of flavors: for sweetness is caused by the action of warmth spreading wetness, and although in this way warmth causes sweetness, still, a body is not denominated sweet on account of its warmth, but on account of its flavor, which com- prises both warmth and wetness.17 13 For example, the geometrical definition of a sphere would not differ from the natural definition of a pearl. But even if all pearls are essentially spherical (more or less), they also essentially consist of layers of crystallized calcium carbonate held together by conchiolin, which is why not all spherical bod- ies are pearls. 14 This point is discussed in more detail in c. 7 below, considering the definition of “pugness,” which is necessarily a curvature of a nose, but in and of itself is the curvature only, having to have a nose as its subject. Cf. also n. 67 below. 15 Avicenna, Metaph., 5, 5. 16 Averroës, In Metaph., 7, 7, com. 27. 17 The example, based on the somewhat obscure Aristotelian doctrine of how the composite qualit- ies of mixed bodies can be derived from the interaction of the simple active and passive qualities of the four elements, is not very illuminating to us. But the point is clear, and can, in fact, be illustrated by another, more familiar example: punch flavor is caused by mixing various fruit juices (and maybe some rum). Still, a punch-flavored cake or scoop of ice cream is not denominated by any of the com- ponents, but by the composite flavor resulting from the mixture. MP_C30.qxd 11/23/06 2:36 AM Page 231 231 E However, since the principle of individuation is matter, from this it may appear to C N follow that the essence, which comprises both matter and form, is only particular and not E S S universal, from which it would further follow that universals would not have definitions, if E D an essence is something that the definition signifies. N A And for this reason we should know that matter considered in just any way is not the G principle of individuation, but only designated matter is. And by designated matter I mean N EI matter considered under determinate dimensions. This matter is not included in the B N definition of man as such, but it would be included in Socrates’ definition, if Socrates had a O definition. The definition of man, on the other hand, includes non-designated matter; for the S A N definition of man does not include this bone or this flesh, but bones and flesh absolutely, UI which are the non-designated matter of man.18 Q A Chapter 3. The Composition of Material Substances In this way it is clear that the essence of man and the essence of Socrates differ only as des- ignated and non-designated, and this is why the Commentator declares in his Commentary on Book 7 of the Metaphysics: “Socrates is nothing other than animality and rationality, which are his quiddity.”19It is also in the same way that the essence of the genus and the essence of the species differ as designated and non-designated, although the manner of designation is different in the two cases. For the designation of the individual with respect to the species takes place through matter determined by dimensions, whereas the designation of the species regarding the genus occurs through a constitutive difference, which is taken from the form of the thing. But the determination or designation of the species with respect to the genus is not through anything in the essence of the species that would in no way be in the essence of the genus; rather, whatever is in the species is also in the genus indeterminately. For if an animal were not the same as the whole that is a man, but only a part of it, then animal would not be predicated of man, for no integral part is predicated of its whole. We can see how this happens if we consider how body, insofar as it is taken to be a part of an animal, differs from body,insofar as it is taken to be a genus; for it cannot be a genus in the sense in which it is an integral part. The name “body,” therefore, can be taken in several senses. For a body, insofar as it is in the genus of substance, is said to be a body because it has a nature on account of which three dimensions can be designated in it; while 18 It is important to note here that the difference between designated and non-designated matter is, again, not a difference between two different kinds of entities, but rather a difference between two different ways of considering the same kind of entity; that is to say, the distinction between designated and non-designated matter is not a real distinction, but a distinction of reason. All matter in reality is designated matter, i.e., concrete chunks of matter existing under the determinate dimensions of the individual bodies they constitute. But just as the individuals can be considered in a universal manner, disregarding their individuating features, so their matter can be considered generally, not as this or that particular chunk of matter. And it is obvious that it is only matter considered in this way that can be signified by the definition of the species (the definition that signifies the specific essence of each individual), for it is clear that the definition of man, for example, cannot signify the flesh and bones of Socrates as thisparticular matter belonging to Socrates, for otherwise all men (i.e., all individuals having the essence signified by this definition) ought to have Socrates’ flesh and bones, which is clearly absurd. Cf. n. 26 below. 19 Averroës, In Metaph., 7, c. 5, com. 20. MP_C30.qxd 11/23/06 2:36 AM Page 232 232 S C the three designated dimensions themselves are the body which is in the genus of quantity. SI Y But it happens that something that has some perfection also reaches a further perfection, as H P is obvious in the case of man, who has a sensitive nature and beyond that also an intellec- A ET tive one. Likewise, to the perfection of a thing’s having a form on account of which three M L, dimensions can be designated in it, a further perfection can be added, such as life, or some- U thing like that. The name “body,” therefore, can signify something which has a form from O S which there follows the designatability of three dimensions exclusively, namely, in such way E H that from that form no further perfection would follow, but if something is added, then it T F is beyond the signification of “body” in this sense. And in this sense the body will be O Y an integral and material part of an animal, for in this way the soul will be beyond the signification H P of the name “body,” and it will be superadded to the body itself, so that the animal will be O S constituted from these two, namely, from the soul and the body, as its parts. O HIL But the name “body” can also be taken to signify some thing that has a form on account P of which three dimensions can be designated in it, whatever that form may be, whether it E, R may give rise to some further perfection or not. And in this sense body will be a genus of U T animal, because animalcontains nothing that is not contained implicitly in body. For the soul A N is not another form than that on account of which in that thing three dimensions can be F O designated;20 and so when it was said that a body is something that has a form on account Y H of which three dimensions can be designated in it, this form was understood to be anyform, P O regardless of whether it is animality or lapideity [rock-ness] or anything else of this sort. S O And in this way the form of animal is implicitly contained in the form of body, insofar as L HI bodyis its genus. P There is a similar relationship between manand animal. For if “animal” only named a thing that has the perfection of sensing and moving on account of an intrinsic principle with the exclusionof any further perfection, then any further supervening perfection would be related to animal as to a part, and not as implicitly contained in the notion of animal. And in this way animalwould not be a genus. But it isa genus insofar as it signifies a certain thing whose form can give rise to sensation and motion, no matter what sort of form it is, whether it is a sensitive soul only or a soul that is sensitive and rational as well. In this way, therefore, the genus indeterminately signifies the whole that is in the species, for it does not signify only matter. Likewise, the difference signifies the whole and not only form; and even the definition signifies the whole, as does the species, but in different ways. For the genus signifies the whole as a certain denomination determining what is material in the thing without determining its proper form; and the genus is taken from matter, although it is not matter. Hence it is clear that something is said to be a body because it has the perfection that three dimensions can be designated in it, which is a perfection that is related as something material to the further perfections. The difference, on the other hand, is a certain determination taken from a deter- minate form without having some determinate matter in its primary notion, as is clear in the case of animate, namely, something that has a soul [anima], for this does not determine 20 This is an important expression of Aquinas’s famous, and in his time very controversial, thesis of the unity of substantial forms. For a detailed discussion of this passage, see G. Klima, “Man = Body + Soul: Aquinas’s Arithmetic of Human Nature,” in B. Davies (ed.), Thomas Aquinas: Contemporary Philosophical Perspectives, Oxford: Oxford University Press, pp. 257–73. For more discussion of the the- sis and its history, see D. A. Callus, “Forms, Unicity and Plurality of,” in New Catholic Encyclopedia, New York: McGraw-Hill; 1967–79. MP_C30.qxd 11/23/06 2:36 AM Page 233 233 E what sort of thing it is, whether a body or something else. This is why Avicenna says21that C N the genus is not understood in the difference as a part of its essence, just as their subject is E S S not part of the understanding of attributes [passiones]; and so the genus is not predicated of E D the difference per se, as the Philosopher remarks in Book 3 of the Metaphysics and Book 4 N of the Topics,22except, perhaps, in the way the subject is predicated of the attribute. But the A G definition and the species comprise both, namely, the determinate matter designated by N EI the name of the genus and the determinate form designated by the name of the difference. B N And from this it is clear why the genus, difference, and species are analogous to matter, O form, and the composite in nature, although they are not identical with them. For the genus S A N is not matter, but is taken from matter as signifying the whole, and the difference is not form, UI but is taken from the form as signifying the whole. Therefore, we say that man is a rational Q A animal, but not that man is composed ofanimal and rational, as we say that man is composed of body and soul. For man is said to be composed of soul and body, as a third thing con- stituted by two things, neither of which is identical with it. For a man is neither soul nor body. But if manis somehow said to consist of animaland rational, then it will not be a third thing constituted by two other things, but rather a third concept constituted by two other concepts. For the concept of animaldoes not determine the specific form expressing the nature of the thing, because it is material with respect to the ultimate perfection; and the concept of the difference rational consists in the determination of the specific form; and the concept of the definition or species is constituted by these two concepts. Therefore, just as a thing constituted by others cannot be said to be any of those that constitute it, so a concept cannot be said to be any of the concepts that constitute it; for we do not say that the definition is the genus or the difference. Although the genus signifies the entire essence of the species, still, the several species in the same genus do not have to have the same essence; for the unity of the genus stems from its indetermination or indifference. However, this does not happen in such a manner that what the genus signifies is some numerically one nature in the diverse species having some other thing supervening on it, namely, the difference determining it, as the form determines matter that is numerically one; rather, this happens because the genus signifies some form, but not determinately this or that form, which in turn is determinately expressed by the difference; however, this [determinately expressed form] is nothing else but what was indeterminately signified by the genus.23 And this is why the Commentator says in his Commentary on Book 12 of the Metaphysics that prime matter is said to be one on account of the removal of all forms, but the genus is one on account of the community of the form signified.24 So, it is clear that the addition of the difference, which removes the indeterm- ination that was the cause of the unity of the genus, yields essentially diverse species. And since, as has been said, the nature of the species is indeterminate with respect to the individual, just as the nature of the genus is with respect to the species, therefore, just as 21 Avicenna, Metaph., 5, 6. 22 Aristotle, Metaph., 3, 3, 998b24; St. Thomas’s Commentary, lc. 7; Topics, 4, 2, 122b20; 6, 6, 144a32. 23 So, “animal” indeterminately signifies the animality of Socrates and the animality of his dog. But Socrates’ animality is nothing else but his humanity, which is determinately signified by the difference “rational,” and his dog’s animality is nothing else but his “caninity” (dogginess), which is determinately signified by the proper specific difference of dogs (whatever that is). 24 Averroës, In Metaph., 12, com 14. MP_C30.qxd 11/23/06 2:36 AM Page 234 234 S C the genus, insofar as it is predicated of the species, contains25 in its signification everything SI Y that is determinately in the species, although indistinctly, so the species, insofar as it is H P predicated of the individual, has to signify everything that is essentially in the individual, although A ET indistinctly; and this is how the essence of the species is signified by the name “man”; M L, therefore, “man” is predicated of Socrates. However, if the nature of the species is signified U with the exclusion of designated matter, which is the principle of individuation, then it is O S related to the individual as its part, and this is how it is signified by the name “humanity”; E H for “humanity” signifies that on account of which a man is a man. But designated matter is T F not that on account of which a man is a man, and so it is not contained in any way among O Y the things from which a man has it that he is a man. Since, therefore, “humanity” includes in H P its understanding onlythose things from which a man has it that he is a man, it is clear that O S designated matter is excluded or cut off from its signification. And since a part is not predic- O HIL ated of the whole, this is why “humanity” is not predicated of a man or of Socrates.26This is P why Avicenna remarks that the quiddity of the composite [substance] is not the composite E, R [substance], although the quiddity itself is composite; just as humanity, even if it is composite, U T nevertheless, is not a man, but it has to be received in something, which is designated matter. A N But, as has been said, the designation of the species regarding the genus is by means F O of forms, whereas the designation of the individual regarding the species is by means of Y H P O S 25 We get this translation by amending the text with the addition of the obviously missing verb O L “continet.” HI P 26 That is to say, the propositions: “A man is a humanity” and “Socrates is a humanity” are false. This is an expression of Aquinas’ metaphysical claim that a material substance cannot be identical with its essence, but its essence is its part that is really distinct both from the whole and from the other part of the same individual, namely, its designated matter. Note that the real distinction between the specific essence and the designated matter of the same individual is not the same as the real distinction between the matter and substantial form of the same individual, although both distinctions are based on the materiality of the individual in question. These are two different ways of conceptually “carving up” the same individual. (This does not have to mean, however, that the parts thus distinguished are not really distinct: just because we can conceptually distinguish the left half and the right half, as well as the top half and the bottom half of a body, it does not mean that these parts are not really distinct regardless of whether we distinguish them or not.) The (prime) matter and substantial form of the same individual are distinguished on account of the analysis of substantial change: the prime matter of a thing is what takes on a new substantial form when the thing ceases to be, and a new thing comes to be from it, say, when hydrogen turns into helium in a nuclear fusion, or when a living being dies and turns into a corpse. Therefore, the form so distinguished excludes this matter from its notion. But the essence signified by the definition, as we could see above, does not exclude matter in general, but only thisdesignated matter in particular (see n. 18 above), and only when it is signified exclusively, by the abstract form of the name of the species, as by the name “humanity.” So, this essence, as signified by this term, is a formal component of the whole substance, received in, and individuated by, the designated matter of this substance. But this formal component is not exactly the same as the substantial form which is received in prime matter, for this formal component comprises both matter and form considered in general, excluding only what individuates them, namely, this designated matter, which is why this formal component, the essence, is also referred to as “the form of the whole” (forma totius), to distinguish it from “the form of the part” (forma partis), which is the form referred to in the other division, distinguishing substantial form and prime matter. So, an individual material substance, say, Socrates (disregarding his accidents) = substantial form (forma partis) + prime matter = essence (forma totius) + designated matter. Besides these two divisions of Socrates, there is a third one, not coinciding with either of these two, according to which Socrates = body + soul. MP_C30.qxd 11/23/06 2:36 AM Page 235 235 E matter; therefore, the name signifying that from which the nature of the genus is taken with C N the exclusion of the determinate form that perfects the species has to signify the material E S S part of the whole, as for example the body is the material part of man; while the name E D signifying that from which the nature of the species is taken, with the exclusionof designated N A matter, has to signify the formal part. So, humanity is signified as a sort of form, and is said G to be the form of the whole [forma totius], but not, as it were, as something added over and N EI above the essential parts, namely, form and matter, as the form of a house is added over B N and above its integral parts, but rather it is a form that is a whole, namely, comprising O both matter and form, however, with the exclusion of those things that are apt to design- S A ate matter.27 UIN In this way it is clear that the essence of man is signified both by the name “man” and by Q A the name “humanity,” but differently, as has been said. For the name “man” signifies it as a whole, namely, insofar as it does not exclude the designation of matter, but contains it implicitly and indistinctly, just as we said the genus contains the difference. And this is why the name “man” is predicated of the individuals. But the name “humanity” signifies it as a part, because it contains in its signification only what pertains to a man insofar as he is a man, and excludes all designation of matter; therefore it is not predicated of individual humans. And for this reason, the name “essence” is sometimes found to be predicated of a thing, for it is said that Socrates28is a certain essence; and sometimes it is negated, when we say that Socrates’ essence is not Socrates. Chapter 4. The Essence of Material Substance and the Logical Intentions Having seen what is signified by the name “essence” in material substances, we should see how it is related to the notions of genus, species, and difference. Now, since that to which the notion of genus, species, or difference applies is predicated of this designated individual,29 the notion of a universal, that is, of genus or species, cannot apply to essence insofar as it is signified as a part, for example, by the name “humanity” or “animality.” And this is why Avicenna says that rationality is not a difference, but the principle of a difference;30 and for the same reason, humanity is not a species, nor is animality a genus. Likewise, one cannot say that the notion of genus or species applies to essence insofar as it is something existing outside the singulars, as the Platonists believed; for in this way the genus and species would not be predicated of this individual; for it cannot be said that Socrates is something that is separate from him; and neither would that separate thing be of any use in the cognition of this singular. Therefore, it remains that the notion of genus or species applies to essence insofar as it is signified as a whole, for example, by the names “man” or “animal,” as it implicitly and indistinctly contains all that is in the individual. But a nature or essence so taken can be considered in two ways. In one way, according to its proper notion; and this is its absolute consideration. And in this way nothing is true 27 “Those things that are apt to designate matter” are the dimensions of the material substance, whereby it occupies its location in space, as distinct from other bodies. 28 Correcting the text’s “Socratis” to “Socrates.” 29 This is because according to the “canonical” definitions of Porphyry in his Isagoge(which was often referred to as Praedicabilia), all universals are “predicables,” i.e., items that can be predicated of several individuals. 30 Avicenna, Metaph., 5, 6. MP_C30.qxd 11/23/06 2:36 AM Page 236 236 S C of it except what pertains to it on account of what it is; therefore, if anything else is SI Y attributed to it, then the attribution is false. For example, to a man, on account of being a H P man, it pertains to be rational and animal and anything else that is in his definition; to be A ET white or black, however, and anything else that is not involved in the notion of humanity M L, does not pertain to a man on account of being a man. Therefore, if it is asked whether this U nature considered in this way can be said to be one or many, neither alternative should be O S accepted, because both are outside of the understanding of humanity, and either can pertain E H to it. For if plurality were included in its understanding, then it could never be one, although T F it is one insofar as it is in Socrates. Likewise, if unity were included in its notion and under- O Y standing, then Socrates and Plato would have [numerically] one and the same nature, and H P it could not be multiplied in several things.31In the other way nature is considered accord- O S ing to its existence in this or that thing. And in this way something can be predicated of it O HIL accidentally [per accidens], on account of the thing in which it is. For example, it is said that P a man is white, because Socrates is white, although this [i.e., being white] does not pertain E, R to a man on account of being a man. U T This nature has two sorts of existence [esse]: one in the singulars, another in the soul, and A N accidents follow upon this nature on account of each. And in the singulars it has several acts F O of existence [esse] according to the diversity of singulars. But the nature itself, according to Y H its proper, that is absolute, consideration, does not have to have any of these. For it is false P O to say that the nature of man as such should have existence in this singular, for then it could S O never exist outside this singular [i.e., in another singular]; likewise, if it pertained to [the nature L HI of] man as such not to exist in this singular, then it would never exist in this singular. But P it is true to say that to [the nature of] man as such it does not pertain that it should exist in this singular or in that one or in the soul. It is clear, therefore, that the nature of man absolutely considered abstracts from all existence, without, however, excluding any of them.32 And it is the nature considered in this way that is predicated of all the individuals [that have this nature].33 Nevertheless, one cannot say that the notion of universals applies to natures taken in this way; for the concept of universals includes unity and community,34but neither of these applies to human nature according to its absolute consideration. For if community were understood 31 This is why it is useful to think of this “common nature,” i.e., the essence of any thing con- sidered absolutely, as the common information content informing several individuals in its several instances, just as the common information content of a book is multiplied in its several copies, or the same genetic information is multiplied and reproduced in several generations of individual living things. 32 So the common nature as such is indifferent to any act of being and so to any mode of being, which is why it can exist in any appropriate singular subject in different ways, i.e., as the common information content of all these singulars, it can exist encoded in different media, whether in the soul or in the actual individuals, just as the same song, for example, can be encoded in magnetic or optical media, or as actual vibrations of the air, i.e., actual sounds. 33 Clearly, the predicate of the sentence “Socrates is a man” attributes to Socrates only what per- tains to the nature signified by it according to its absolute consideration. For knowing that this sen- tence is true, we know that Socrates is a rational animal, and that he is a sensitive living body, etc., namely, whatever is involved in being a man as such, but we certainly do not know whether he is black or white, short or tall, handsome or ugly, etc., anything that does not pertain to human nature according to its actual consideration. 34 For according to one formulaic definition, universale est unum commune multis, a universal is [some- thing] one common to many.