Aquinas: On Being and Essence - Chapter 6

Chapter Six

ESSENCE AS FOUND IN ACCIDENTS

[1] Now that we have explained how essence is present in all substances, it remains for us to see how essence exists in accidents. Because essence is what the definition signifies, as has been said,†1 accidents must have an essence in the same way that they have a definition. Now their definition is incomplete, because they cannot be defined without including a subject in their definition.†2 This is because they do not have being in themselves, independent of a subject; as substantial being results from form and matter when they come together, so accidental being results from an accident and a subject when the former comes to the latter. For the same reason neither a substantial form nor matter has a complete essence, because the definition of a substantial form must include the subject of the form. It is defined, therefore, by adding something outside its genus, just like the definition of an accidental form. That is also why the body is included in the definition of the soul when it is defined by the natural philosopher, who considers the soul only as the form of a physical body.

[2] There is a considerable difference, however, between substantial and accidental forms. As a substantial form does not have being in itself, independent of that to which it is united, so neither does the matter to which it is joined. From their union results that being in which the reality subsists in itself, and from them is produced something essentially one. An essence, therefore, results from their union. It follows that although a form, considered in itself, does not have the complete nature of an essence, nevertheless it is part of a complete essence. But that to which an accident is added is a complete being in itself, subsisting in its own being; and this being is by nature prior to the supervening accident. That is why the supervening accident, by its union with the subject to which it comes, does not cause that being in which the reality subsists, and through which the reality is a being in itself. Rather, it causes a secondary being, without which we can conceive the subsistent reality to exist, as what is primary can be understood without what is secondary. So the accident and its subject do not produce something essentially, but accidentally, one. This explains why their union does not result in an essence, like the conjunction of form and matter. It also explains why an accident neither has the nature of a complete essence nor is part of a complete essence. As it is a being in a qualified sense, so it has an essence in a qualified sense.†3

[3] Furthermore, that which is said to be most fully and truly in a genus is the cause of everything posterior in the genus. For example, fire, which is the ultimate in heat, is the cause of heat in hot things, as the Metaphysics says.†4 That is why substance, which holds the first place in the genus of being, having essence most truly and fully, must be the cause of accidents, which share the nature of being secondarily and in a qualified sense.

[4] This happens in different ways. The parts of substance being matter and form, some accidents result principally from form and others from matter.†5 There is a form whose being does not depend on matter (for example, the intellectual soul),†6 whereas matter has being only through form. That is why among accidents that result from form there are some that have nothing in common with matter, as for example understanding, which does not take place through a bodily organ, as the Philosopher proves.†7 On the contrary, other accidents deriving from form do have something in common with matter, as for example sensation and the like. But no accident results from matter without having something in common with form.

[5] Among accidents that derive from matter we find the following difference. Some accidents result from matter because of its relation to a special form. Examples are male and female among animals--a difference that is reducible to matter, as the Metaphysics says.†8 That is why, once the form of animal has been removed, these accidents no longer remain except in an equivocal sense. Other accidents result from matter in its relation to a general form. In this case, when the special form is taken away, these accidents still remain in the matter. An example is the blackness of an Ethiopian's skin, which comes from the mixture of the elements and not from the nature of the soul, with the result that it remains in him after death.

[6] Because everything is individuated by matter and located in a genus or species through its form, accidents that derive from matter are accidents of the individual and they differentiate individuals within the same species. On the contrary, accidents that result from the form are properties belonging to the genus or species, and consequently they are found in everything sharing the nature of the genus or species. For example, the ability to laugh results from man's form, for laughter occurs because of some perception on the part of the human soul.

[7] Another point to notice is that accidents are sometimes caused in perfect actuality by the essential principles, like heat in fire, which is always actually hot. But sometimes accidents are caused only as aptitudes, and they are completed by an external agent, like transparency in the air, which is complemented by an external luminous body.†9 In cases like these the aptitude is an inseparable accident, whereas the completion that comes from a source external to the essence of the thing, or that does not enter into its constitution, will be separable from it, like movement and other accidents of this kind.

[8] Still another fact worthy of notice is that genus, species, and difference are derived differently in accidents and in substances. In substances, from substantial form and matter there is constituted something essentially one, the consequence of their union being one nature that is properly in the category of substance. That is why, in the case of substances, concrete names that signify the composite are properly said to be in a category, either as a species or as a genus, as for example 'man' or 'animal'. Form or matter, on the contrary, is not in a category in this way but only by reduction, as principles are said to be in a category.†10 From an accident and its subject, however, there is not produced something essentially one. Hence the result of their union is not one nature to which the notion of genus or species can be attributed. That is why terms designating accidents concretely, like 'something white' or 'something musical', cannot be placed in a category except by reduction. They are in a category only when expressed abstractly, like 'whiteness' or 'music'.

[9] Because accidents are not composed of matter and form, we cannot take their genus from matter and their difference from form, as we do in composite substances. Rather, we must take their primary genus from their mode of being, because the term 'a being' is predicated in diverse ways, by priority and posteriority, of the ten genera of the categories.†11 For example, quantity is called a being because it is the measure of substance, quality because it is the disposition of substance, and so on with the other accidents, as the Philosopher says.†12 Their differences, however, are derived from the diversity of the principles that cause them. And because properties result from the specific principles of the subject, this subject takes the place of the difference in their definition when they are defined in the abstract, which is the way they are properly in a category. For instance, we say that snubness is a curvature of the nose. But the converse would be true if we defined them in the concrete. In this case the subject would be placed in their definition as the genus, because these accidents would then be defined like composite substances, in which the concept of the genus is derived from matter. An example is calling a snub nose a curved nose. The same is true when one accident is the principle of another, as action, passion, and quantity are principles of relation. (That is why the Philosopher divides relation with reference to these in the Metaphysics).†13 But because the specific principles of accidents are not always evident, we sometimes take the differences of accidents from their effects, as when we say that colors are differentiated as 'dilating' and 'expanding'--differences that are caused by the abundance and scarcity of light, which produce the different species of color.†14

[10] It is clear, then, how essence exists in substances and in accidents, and in composite and simple substances. It is also evident how the universal concepts of logic are related to all these, with the exception of the first cause, which is absolutely simple. Because of its simplicity, neither the notion of genus nor of species, nor consequently the notion of definition, applies to it. In this being may our treatise find its end and fulfillment.

Amen

Aquinas: On Being and Essence - Chapter 5

Chapter Five

ESSENCE AS FOUND IN DIFFERENT BEINGS

[1] From what has been said we can see how essence is found in different things. There are in fact three ways in which substances have essence. There is a reality, God, whose essence is his very being.†1 This explains why we find some philosophers who claim that God does not have a quiddity or essence, because his essence is not other than his being.†2 From this it follows that he is not in a genus, for everything in a genus must have a quiddity in addition to its being. The reason for this is that the quiddity or nature of a genus or species does not differ, as regards the notion of the nature, in the individuals in the genus or species, whereas being is diverse in these different individuals.†3

[2] If we say that God is pure being, we need not fall into the mistake of those who held that God is that universal being by which everything formally exists.†4 The being that is God is such that no addition can be made to it. Because of its purity, therefore, it is being distinct from all other being. That is why the commentary on the Book of Causes says that the first cause, which is pure being, is individuated through its pure goodness.†5 But even though the notion of universal being does not include any addition, it implies no prescinding from an addition. If it did, we could not conceive anything existing in which there would be an addition to being.†6

[3] Furthermore, although God is pure being, it is not necessary that he lack other perfections or excellences. On the contrary, he possesses all the perfections of every kind of thing, so that he is called absolutely perfect, as the Philosopher and Commentator say.†7 In fact, he possesses these perfections in a more excellent way than other things, because in him they are one, whereas in other things they are diversified. This is because all these perfections belong to him in virtue of his simple being.†8 In the same way if someone could produce the operations of all the qualities through one quality alone, in that one quality he would possess every quality.†9 Similarly, God possesses all perfections is his being itself.

[4] Essence is found in a second way in created intellectual substances. Their being is other than their essence, though their essence is without matter. Hence their being is not separate but received, and therefore it is limited and restricted to the capacity of the recipient nature. But their nature or quiddity is separate and not received in matter. That is why the Book of Causes says that the intelligences are unlimited from below and limited from above.†10 They are, in fact, limited as to their being, which they receive from a higher reality, but they are not limited from below, because their forms are not limited to the capacity of a matter that receives them.

[5] That is why among these substances we do not find a multitude of individuals in the same species, as has been said,†11 except in the case of the human soul because of the body to which it is united. And even though the individuation of the soul depends on the body as for the occasion of its beginning, because it acquires its individuated being only in the body of which it is the actuality, it is not necessary that the individuation cease when the body is removed. Because the soul has a separate being, once the soul has acquired its individuated being by having been made the form of a particular body, that being always remains individuated. That is why Avicenna says that the individuation and multiplication of souls depends on the body as regards its beginning but not as regards its end.†12

[6] Furthermore, because the quiddity of these substances is not identical with their being, they can be classified in a category. For this reason they have a genus, species, and difference, though their specific differences are hidden from us.†13 Even in the case of sensible things we do not know their essential differences;†14 we indicate them through the accidental differences that flow from the essential differences, as we refer to a cause through its effect. In this way 'biped' is given as the difference of man. We are ignorant, however, of the proper accidents of immaterial substances; so we can designate their differences neither through themselves nor through accidental differences.

[7] We must observe that the genus and difference are not derived in the same way in these substances and in sensible substances.†15 In sensible substances the genus is obtained from the material side of the thing, whereas the difference is obtained from its formal side. That is why Avicenna says †16 that in substances composed of matter and form, the form is the simple difference of that which is constituted by it; not that the form itself is the difference but that it is the principle of the difference, as he says in his Metaphysics.†17 A difference of this kind is called a simple difference because it is derived from a part of the quiddity of the thing, namely its form. But since immaterial substances are simple quiddities, we cannot take their difference from a part of the quiddity, but from the whole quiddity. As Avicenna says, only those species have a simple difference whose essences are composed of matter and form.†18

[8] The genus of immaterial substances is also obtained from the whole essence, though in a different way. Separate substances are like one another in being immaterial, but they differ in their degree of perfection, depending on their distance from potentiality and their closeness to pure act. Their genus, then, is derived from what follows upon their immateriality, as for example intellectuality, or something of this sort. Their difference, which in fact is unknown to us, is derived from what follows upon their degree of perfection.

[9] These differences need not be accidental because they are determined by degrees of perfection, which do not diversity the species. True, the degree of perfection in receiving the same form does not produce different species, as for example the more white and the less white in participating whiteness of the same nature. But different degrees of perfection in the forms themselves or in the participated natures do produce different species. Nature, for example, advances by degrees from the plant to the animal world using as intermediaries types of things that are between animals and plants, as the Philosopher says.†19 Of course intellectual substances do not always have to be divided by two real differences; as the Philosopher shows, this cannot happen in all cases.†20

[10] In a third way essence is found in substances composed of matter and form. In these, too, being is received and limited, because they have being from another. Their nature or quiddity, moreover, is received in designated matter. Thus they are limited both from above and from below. A multitude of individuals in the same species is also possible in their case because of the division of designated matter. As for the relation of the essence of these substances to logical notions, that has been explained above.†21

Aquinas: On Being and Essence - Chapter 4

Chapter Four

ESSENCE AS FOUND IN SEPARATE SUBSTANCES

[1] It remains for us to see how essence exists in the separate substances: in souls, intelligences,†1 and the first cause. Although everyone admits the simplicity of the first cause, some would like to introduce a composition of form and matter in intelligences and souls,†2 an opinion that seems to have begun with Avicebron, the author of The Source of Life.†3 But this is opposed to what philosophers generally say; they call these substances separated from matter and prove that they are completely immaterial.†4 This is best demonstrated from their power of understanding.†5 We see that forms are actually intelligible only when they are separated from matter and its conditions; and they are made actually intelligible only through the power of an intelligent substance, by receiving them into itself and acting upon them.†6 That is why every intellectual substance must be completely free from matter, neither having matter as a part of itself nor being a form impressed on matter, as is the case with material forms.

[2] The position is untenable that not all matter prevents intelligibility but only corporeal matter. If this resulted only from corporeal matter, matter would have this opaqueness to understanding from its corporeal form, since matter is called corporeal only because it exists under a corporeal form. This is impossible, because this corporeal form, like other forms, is actually intelligible insofar as it is abstracted from matter. In a soul or intelligence, therefore, there is no composition of matter and form, understanding matter in them as it is in corporeal substances. But there is in them a composition of form and being.†7 That is why the commentary on the Book of Causes says that an intelligence is that which has form and being;†8 and by form is here understood the quiddity itself or simple nature.

[3] It is easy to see how this is so. Whenever things are so related to each other that one is the cause of the other's being, the one that is the cause can have being without the other, but not vice versa. Now matter and form are so related that form gives being to matter. Matter, then, cannot exist without some form, but there can be a form without matter: form as such does not depend on matter. If we find some forms that can exist only in matter, this happens to them because they are far removed from the first principle, which is the primary and pure act. It follows that those forms closest to the first principle are forms subsisting in themselves without matter. In fact, not every kind of form needs matter, as has been said; and the intelligences are forms of this kind. There is no necessity, then, that the essences or quiddities of these substances be anything else than form.

[4] The essence of a composite substance accordingly differs from that of a simple substance because the essence of a composite substance is not only form but embraces both form and matter, whereas the essence of a simple substance is form alone. Two other differences follow from this. The first is that we can signify the essence of a composite substance as a whole or as a part. This happens because of the designation of matter, as has been said.†9 As a result we do not attribute the essence of a composite in every way to the composite; we cannot say, for example, that man is his quiddity. But the essence of a simple reality, which is its form, can only be signified as a whole, because nothing is there beside the form as its recipient. That is why the essence of a simple substance, no matter how we conceive it, can be attributed to the substance. As Avicenna says, "The quiddity of a simple substance is the simple entity itself," because there is nothing else that receives it.†10

[5] The second difference is that the essences of composite things, by being received in designated matter, are multiplied according as it is divided. From this it happens that there are things the same in species and different in number. But since the essence of a simple entity is not received in matter, it cannot be multiplied in this way. That is why in these substances we cannot find many individuals in the same species; there are as many species among them as there are individuals, as Avicenna expressly says.†11

[6] Substances of this kind, though pure forms without matter, are not absolutely simple; they are not pure act but have a mixture of potentiality. The following consideration makes this evident. Everything that does not belong to the concept of an essence or quiddity comes to it from outside and enters into composition with the essence, because no essence can be understood without its parts. Now, every essence or quiddity can be understood without knowing anything about its being. I can know, for instance, what a man or a phoenix is and still be ignorant whether it has being in reality.†12 From this it is clear that being is other than essence or quiddity, unless perhaps there is a reality whose quiddity is its being. This reality, moreover, must be unique and primary;†13 because something can be multiplied only [1] by adding a difference (as a generic nature is multiplied in species), [2] by the reception of a form in different parts of matter (as a specific nature is multiplied in different individuals), [3] by the distinction between what is separate and what is received in something (for example, if there were a separated heat,†14 by the fact of its separation it would be distinct from heat that is not separated). Now, granted that there is a reality that is pure being, so that being itself is subsistent, this being would not receive the addition of a difference, because then it would not be being alone but being with the addition of a form. Much less would it receive the addition of matter, because then it would not be subsistent, but material, being. It follows that there can be only one reality that is identical with its being. In everything else, then, its being must be other than its quiddity, nature, or form. That is why the being of the intelligences must be in addition to their form; as has been said,†15 an intelligence is form and being.

[7] Whatever belongs to a thing is either caused by the principles of its nature (as the capacity for laughter in man) or comes to it from an extrinsic principle (as light in the air from the influence of the sun). Now being itself cannot be caused by the form or quiddity of a thing (by 'caused' I mean by an efficient cause), because that thing would then be its own cause and it would bring itself into being, which is impossible.†16 It follows that everything whose being is distinct from its nature must have being from another. And because everything that exists through another is reduced to that which exists through itself as to its first cause, there must be a reality that is the cause of being for all other things, because it is pure being.†17 If this were not so, we would go on to infinity in causes, for everything that is not pure being has a cause of its being, as has been said. It is evident, then, that an intelligence is form and being, and that it holds its being from the first being, which is being in all its purity; and this is the first cause, or God.

[8] Everything that receives something from another is potential with regard to what it receives, and what is received in it is its actuality. The quiddity or form, therefore, which is the intelligence, must be potential with regard to the being it receives from God, and this being is received as an actuality. Thus potency and act are found in the intelligences, but not form and matter, except in an equivocal sense.†18 So, too, 'to suffer', 'to receive', 'to be a subject', and all similar expressions which seem to be attributed to things because of matter, are understood in an equivocal sense of intellectual and corporeal substances, as the Commentator remarks.†19

[9] Because, as we have said,†20 the quiddity of an intelligence is the intelligence itself, its quiddity or essence is identical with that which it is, while its being, which is received from God, is that by which it subsists in reality.†21 That is why some say that a substance of this kind is composed of 'that by which it is' (quo est) and 'that which is' (quod est),†22 or, according to Boethius, of 'that which is' (quod est) and 'being' (esse).†23

[10] Since there is both potency and act in the intelligences, it will not be difficult to find a multitude of them, which would be impossible if they had no potentiality. That is why the Commentator says †24 that if the nature of the possible intellect were unknown, we could not find a multitude of separate substances. These substances, moreover, are distinct from one another according to their degree of potency and act, a superior intelligence, being closer to the primary being, having more act and less potency, and so with the others. This gradation ends with the human soul, which holds the lowest place among intellectual substances. As a result, its possible intellect bears the same relation to intelligible forms that primary matter, which holds the lowest position in sensible being, bears to sensible forms, as the Commentator says.†25 That is why the Philosopher compares the possible intellect to a blank tablet on which nothing is written.†26 Having more potentiality than other intellectual substances, the human soul is so close to matter that a material reality is induced to share its own being, so that from soul and body there results one being in the one composite, though this being, as belonging to the soul, does not depend on the body.†27 After this form, which is the soul, there are found other forms which have more potentiality and are even closer to matter, to such a point that they do not have being without matter. Among these forms, too, we find an order and a gradation, ending in the primary forms of the elements, which are closest to matter. For this reason they operate only as required by the active and passive qualities and other factors that dispose matter to receive form.

Aquinas: On Being and Essence - Chapter 3

Chapter Three

THE RELATION OF ESSENCE TO GENUS, SPECIES, AND DIFFERENCE

[1] Having seen what the term 'an essence' means in composite substances, we must examine how it is related to the notion †1 of genus, species, and difference. That to which the notion of genus, species, or difference belongs is attributed to an individual, determinate thing. It is therefore impossible that the notion of universal (that is to say, of genus or species) should belong to an essence when it is expressed as a part, for example by the term 'humanity' or 'animality'. That is why Avicenna says †2 that 'rationality' is not a difference, but the principle of a difference; and for the same reason 'humanity' is not a species nor 'animality' a genus. Nor can we say that the notions of genus and species belong to an essence as a reality existing outside individual things, as the Platonists held,†3 because then the genus and species would not be attributed to the individual: we cannot say that Socrates is something separated from himself. This separated entity, moreover, would be of no help in knowing the individual. We conclude, therefore, that the notion of genus or species applies to an essence when it is expressed as a whole, for example by the term 'man' or 'animal', containing implicitly and indistinctly everything in the individual.

[2] Understood in this sense, a nature or essence can be considered in two ways.†4 First, absolutely, according to its proper meaning. In this sense nothing is true of it except what belong to it as such; whatever else may be attributed to it, the attribution is false. For example, to man as man belong 'rational', 'animal', and everything else included in his definition; but 'white' or 'black', or any similar attribute not included in the notion of humanity, does not belong to man as man. If someone should ask, then, whether a nature understood in this way can be called one or many, we should reply that it is neither, because both are outside the concept of humanity, and it can happen to be both. If plurality belonged to its concept, it could never be one, though it is one when present in Socrates. So, too, if oneness belonged to its concept, the nature of Socrates and of Plato would be identical, and it could not be multiplied in many individuals.

[3] In a second way a nature or essence can be considered according to the being it has in this or that individual. In this way something is attributed to it accidentally, because of the subject in which it exists, as we say that man is white because Socrates is white, though this does not belong to man insofar as he is man.

[4] This nature has a twofold being: one in individual things and the other in the soul, and accidents follow upon the nature because of both beings. In individuals, moreover, the nature has a multiple being corresponding to the diversity of individuals; but none of these beings belongs to the nature from the first point of view, that is to say, when it is considered absolutely. It is false to say that the essence of man as such has being in this individual: if it belonged to man as man to be in this individual it would never exist outside the individual. On the other hand, if it belonged to man as man not to exist in this individual, human nature would never exist in it. It is true to say, however, that it does not belong to man as man to exist in this or that individual, or in the soul. So it is clear that the nature of man, considered absolutely, abstracts from every being, but in such a way that is prescinds from no one of them; and it is the nature considered in this way that we attribute to all individuals.

[5] Nevertheless, it cannot be said that a nature thus considered has the character of a universal,†5 because unity and community are included in the definition of a universal, neither of which belongs to human nature considered absolutely. If community were included in the concept of man, community would be found in everything in which humanity is found. This is false, because there is nothing common in Socrates; everything in him is individuated.†6 Neither can it be said that human nature happens to have the character of a genus or species through the being it has in individuals, because human nature is not found in individual men as a unity, as though it were one essence belonging to all of them, which is required for the notion of a universal.

[6] It remains, then, that human nature happens to have the character of a species only through the being it has in the intellect. Human nature has being in the intellect abstracted from all individuating factors, and thus it has a uniform character with regard to all individual men outside the soul, being equally the likeness of all and leading to a knowledge of all insofar as they are men. Because it has this relation to all individual men, the intellect discovers the notion of species and attributes it to the nature. This is why the Commentator says that it is the intellect that causes universality in things.†7 Avicenna makes the same point.†8

[7] Although this nature apprehended by the intellect has the character of a universal from its relation to things outside the soul, because it is one likeness of them all, nevertheless as it has being in this or that intellect it is a particular apprehended likeness. The Commentator was clearly in error then; he wanted to conclude that the intellect is one in all men from the universality of the apprehended form.†9 In fact, the universality of this form is not due to the being it has in the intellect but to its relation to things as their likeness. In the same way, if there were a material statue representing many men, the image or likeness of the statue would have its own individual being as it existed in this determinate matter, but it would have the nature of something common as the general representation of many men.

[8] Because it is human nature absolutely considered that is predicated of Socrates, this nature does not have the character of a species when considered absolutely; this is one of the accidents that accompany it because of the being it has in the intellect. That is why the term 'species' is not predicated of Socrates, as though we were to say 'Socrates is a species'. This would necessarily happen, however, if the notion of species belonged to man in his individual being in Socrates, or according to his absolute consideration, namely insofar as he is man; for we predicate of Socrates everything that belongs to man as man. Nevertheless, it is essential to a genus to be predicated: this is included in its definition. Predication is something achieved by the intellect in its act of combining and dividing, having for its foundation in reality the unity of those things, one of which is attributed to the other.†10 That is why the notion of predicability can be included in the meaning of the notion of genus, a notion that is also produced by an act of the intellect. But that to which the intellect attributes the notion of predicability, combining it with something else, is not the concept itself of genus, but rather that to which the intellect attributes the concept of genus, as for example what is signified by the term 'animal'.

[9] From this we can see how essence or nature is related to the notion of species. The notion of species is not one of those items that belong to the nature when it is considered absolutely, nor is it one of the accidents that follow upon the nature because of the being it has outside the soul, like whiteness or blackness. Rather, the notion of species is one of the accidents that follow upon the nature because of the being it has in the intellect; and it is in this way, too, that the notions of genus and difference belong to it.

Aquinas: On Being and Essence - Chapter 2

Chapter Two

ESSENCE AS FOUND IN COMPOSITE SUBSTANCES

[1] Form and matter are found in composite substances, as for example soul and body in man. But it cannot be said that either one of these alone is called the essence. That the matter alone of a thing is not its essence is evident, for through its essence a thing is knowable and fixed in its species and genus. But matter is not a principle of knowledge, and a thing is not placed in a genus or species through it but through that by which a thing is actual.†1 Neither can the form alone of a composite substance be called its essence, though some want to assert this.†2 It is evident from what has been said that the essence is what is signified through the definition of a thing.†3 Now the definition of natural substances includes not only form but also matter; otherwise there would be no difference between definitions in physics and in mathematics.†4 Nor can it be said that the definition of a natural substance includes matter as something added to its essence, or as something outside its essence. This is the kind of definition proper to accidents; not having a perfect essence, their definition must include their subject, which is outside their genus. It is evident, therefore, that essence embraces both matter and form.

[2] Neither can it be said that essence signifies the relation between matter and form, or something added to them, because this would necessarily be accidental or not belonging to the thing, nor could the thing be known through it, both of which are characteristics of essence. For through form, which actualizes matter, matter becomes an actual being and this particular thing. Anything that comes after that does not give matter its basic actual being, but rather a certain kind of actual being, as accidents do, whiteness for example making something actually white. When a form of this kind is acquired, we say that something comes into being not purely and simply but in a certain respect.

[3] It remains, then, that in the case of composite substances the term 'an essence' signifies the composite of matter and form. Boethius agrees with this in his commentary on the Categories, where he says that {ousia} signifies the composite;†5 for {ousia} in Greek means the same as our essentia, as Boethius himself observes.†6 Furthermore, Avicenna remarks that the quiddity of composite substances is the composition itself of form and matter.†7 The Commentator, too, says, "The nature that species have in things subject to generation is something intermediate, a composite of matter and form."†8 This is reasonable, too, for the being that a composite substance has is not the being of the form alone nor of the matter alone but of the composite, and it is essence according to which a thing is said to be.†9 So the essence, according to which a thing is called a being, cannot be either the form alone or the matter alone, but both, though form alone is in its own way the cause of this being. We observe in the case of other things composed of several principles that they do not take their name from one of these principles alone, but from both together. This is clear in tastes. Sweetness is caused by the action of the hot dissolving the moist; and although in this way heat is the cause of sweetness, a body is not called sweet from its heat but from its taste, which includes the hot and the moist.†10

[4] Because matter is the principle of individuation, it might seem to follow that an essence, which embraces in itself both matter and form, is only particular and not universal. If this were true, it would follow that universals could not be defined, granted that essence is what is signified by the definition. What we must realize is that the matter which is the principle of individuation is not just any matter, but only designated matter.†11 By designated matter I mean that which is considered under determined dimensions.†12 This kind of matter is not part of the definition of man as man, but it would enter into the definition of Socrates if Socrates could be defined. The definition of man, on the contrary, does include undesignated matter. In this definition we do not put this particular bone and this particular flesh, but bone and flesh absolutely, which are the undesignated matter of man.

[5] It is clear, therefore, that the difference between the essence of Socrates and the essence of man lies solely in what is designated and not designated. This is why the Commentator says, "Socrates is nothing else than animality and rationality, which are his quiddity."†13 The essence of the genus and the essence of the species also differ as designated and undesignated, though the mode of designation is different in the two cases. The individual is designated with respect to its species through matter determined by dimensions, whereas the species is designated with respect to the genus through the constitutive difference, which is derived from the form of the thing. This determination or designation which is in a species with regard to its genus is not caused by something existing in the essence of the species and in no way in the essence of the genus; rather, whatever is in the species is also in the genus but in an undetermined way. If indeed 'animal' were not wholly what 'man' is, but only a part of him, 'animal' could not be predicated of 'man', since no integral part may be predicated of its whole.

[6] We can see how this comes about if we examine the difference between body when it means a part of animal and body when it means a genus; for it cannot be a genus in the same way that it is an integral part. In short, the term 'body' can have several meanings.†14 In the genus of substance we give the name 'body' to that which has a nature such that three dimensions can be counted in it; but these three determined dimensions themselves are a body in the genus of quantity. It does happen that something having one perfection may also possess a further perfection, as is evident in man, who has a sensitive nature and, besides this, an intellectual nature. So, too, over and above the perfection of having a form such that three dimensions can be designated in it, another perfection can be added, such as life, or something of the kind. The term 'body', therefore, can signify that which has such a form as allows the determination of three dimensions in it, prescinding †15 from everything else, so that from that form no further perfection may follow. If anything else is added, it will be outside the meaning of body thus understood. In this way body will be an integral and material part of a living being, because the soul will be outside what is signified by the term 'body' and will be joined to this body in such a way that a living being is made up of these two, body and soul, as of two parts.

[7] The term 'body' can also be taken to mean a thing having a form such that three dimensions can be counted in it, no matter what that form may be, whether some further perfection can be derived from it or not. In this sense of the term, body is the genus of animal, because animal does not include anything that is not implicitly contained in body. The soul is not a form different from that which gives to the thing three determined dimensions. That is why, when we said that a body is that which has such a form as allows the determination of three dimensions in it, we understood this to mean any form whatsoever: animality, stoneness, or any other form. In this way the form of animal is implicitly contained in the form of body, inasmuch as body is its genus. And such also is the relation of animal to man. If 'animal' designated only a certain reality endowed with a perfection such that it could sense and be moved through an internal principle, prescinding from any other perfection, then any further perfection would be related to animal as a part and not as implicitly contained in the notion of animal, and then animal would not be a genus. But it is a genus when it signifies a thing whose form can be the source of sensation and movement, no matter what that form may be, whether it be only a sensitive soul or a soul that is both sensitive and rational.

[8] The genus, then, signifies indeterminately everything in the species and not the matter alone. Similarly, the difference designates the whole and not the form alone, and the definition also signifies the whole, as does the species too, though in a different way. The genus signifies the whole as a name designating what is material in the thing without the determination of the specific form. Thus the genus is taken from matter, though it is not matter, as we can clearly see from the fact that we call a body that which has a perfection such that it is determined by three dimensions, a perfection that is related as material with respect to a further perfection. On the contrary, the difference is a term taken from a definite form in a precise way, without including a definite matter in its primary notion; as for example when we say 'animated' (in other words, what has a soul) we do not specify what the thing is, whether it is a body or something else. That is why Avicenna says that the genus is not conceived in the difference as a part of its essence, but only as something outside its essence, as the subject is contained in the notion of its properties.†16 That is also why, according to the Philosopher,†17 a genus is not predicated of a difference properly speaking, except perhaps as a subject is predicated of its property. As for the definition or species, it embraces both, namely the determinate matter signified by the name of the genus, and the determinate form signified by the name of the difference.

[9] From this it is clear why genus, species, and difference are related proportionately to matter, form, and composite in nature, though they are not identical with them. A genus is not matter, but it is taken from matter as designating the whole; and a difference is not form, but it is taken from form as designating the whole. That is why we say that man is a rational animal, and not that he is composed of animal and rational, as we say that he is composed of soul and body. We say that man is a being composed of soul and body as from two things there is constituted a third entity which is neither one of them: man indeed is neither soul nor body. If in a sense we may say that man is composed of animal and rational, it will not be as a third reality is made up of two other realities, but as a third concept is formed from two other concepts. The concept 'animal' signifies the nature of a being without the determination of its special form, containing only what is material in it with respect to its ultimate perfection. The concept of the difference 'rational', on the other hand, contains the determination of the special form. From these two concepts is formed the concept of the species or definition. This is why, just as a reality composed of several things cannot be the subject of attribution of its constituent elements, neither can a concept be the subject of attribution of the concepts from which it is formed: we do not say that the definition is the genus or difference.

[10] Although the genus signifies the whole essence of the species, it is not necessary that different species of the same genus have one essence. The unity of the genus comes from its indetermination or indifference, but not in such a way that what is signified by the genus is a nature numerically the same in different species, to which would be added something else (the difference) determining it as a form determines a matter that is numerically one. Rather, the genus denotes a form (though not precisely any one in particular) which the difference expresses in a definite way, and which is the same as that which the genus denotes indeterminately. That is why the Commentator asserts †18 that primary matter is said to be one because of the elimination of all forms, whereas a genus is said to be one because of the community of the designated form. It is clear, therefore, that when the indetermination which caused the unity of the genus is removed by the addition of the difference, there remain species different in essence.

[11] As we have said,†19 the nature of the species is indeterminate with regard to the individual, as the nature of the genus with regard to the species. It follows that, just as the genus, when attributed to the species, implies indistinctly in its signification everything that is in the species in a determinate way, so the species, when attributed to the individual, must signify everything essentially in the individual, though in an indistinct way. For example, the term 'man' signifies the essence of the species, and therefore 'man' is predicated of Socrates. But if the nature of the species is signified with precision from designated matter, which is the principle of individuation, then it will have the role of a part. This is the way it is signified by the term 'humanity', for humanity signifies that by which man is man. Now designated matter does not make man to be man, and thus it is not in any way included among the factors that make man to be man. Since, therefore, the concept of humanity includes only that which makes man to be man, its meaning clearly excludes or prescinds from designated matter; and because the part is not predicated of the whole, humanity is predicated neither of man nor of Socrates. Avicenna concludes †20 from this that the quiddity of a composite is not the composite itself whose quiddity it is, though the quiddity itself is a composite. For example, although humanity is a composite, it is not man; in fact, it must be received in something else, namely designated matter.

[12] As was said above,†21 the species is determined relative to the genus through form, while the individual is determined relative to the species through matter. That is why it is necessary that the term signifying that from which the nature of the genus is derived, prescinding from the determinate form completing the species, signify the material part of the whole, as for example the body is the material part of man. On the contrary, the term signifying that from which the nature of the species is derived, prescinding from designated matter, signifies the formal part. For this reason 'humanity' is a term signifying a certain form, called the form of the whole.†22 Not indeed that it is something as it were added to the essential parts, form and matter, as the form of a house is added to its integral parts; but it is the form which is the whole, embracing both form and matter, but prescinding from those factors which enable matter to be designated.
[13] It is clear, then, that the essence of man is signified by the two terms 'man' and 'humanity', but in different ways, as we have said.†23 The term 'man' expresses it as a whole, because it does not prescind from the designation of matter but contains it implicitly and indistinctly, as we said the genus contains the difference.†24 That is why the term 'man' can be predicated of individuals. But the term 'humanity' signifies the essence of man as a part, because its meaning includes only what belongs to man as man, prescinding from all designation of matter. As a result it cannot be predicated of individual men. Because of this the term 'essence' is sometimes attributed to a thing and sometimes denied of it: we can say 'Socrates is an essence' and also 'the essence of Socrates is not Socrates'.

Aquinas: On Being and Essence - Prologue. Chapter I

ON BEING AND ESSENCE

Latin: De Ente et Essentia


PROLOGUE

A slight initial error eventually grows to vast proportions, according to the Philosopher.†1 Now the first conceptions of the intellect are (as Avicenna says)†2'a being' and 'an essence'. If, then, we are to avoid mistakes through ignorance of these, we must begin exploring their difficulty by stating what is meant by saying 'a being' and 'an essence', how they are found in different things, and how they are related to the logical notions †3 of genus, species, and difference.

Chapter One

THE GENERAL MEANING OF THE TERMS 'A BEING' AND 'AN ESSENCE'

[1] We ought to get our knowledge of simple things from composite things and arrive at what is prior by way of what is posterior, so that the learning process will begin, appropriately, with what is easier. For this reason we must begin with the meaning of 'a being' and proceed to the meaning of 'an essence'.†1

[2] We must realize (with the Philosopher)†2 that the term 'a being' in itself has two meanings. Taken one way it is divided by the ten categories; taken in the other way it signifies the truth of propositions. The difference between the two is that in the second sense anything can be called a being if an affirmative proposition can be formed about it, even though it is nothing positive in reality. In this way privations and negations are called beings, for we say that affirmation is opposed to negation, and that blindness is in the eye. But in the first way nothing can be called a being unless it is something positive in reality. In the first sense, then, blindness and the like are not beings.†3

[3] The term 'an essence' is not derived from this second meaning of 'a being', for in this sense some things are called beings that do not have an essence, as is clear in the case of privations. Rather, 'an essence' is derived from 'a being' in the first meaning of the term. As the Commentator says,†4 a being in the first sense of the term is that which signifies the essence of a thing. And because, as we have said,†5'a being' in this sense is divided by the ten categories, essence must mean something common to all the natures through which different beings are placed in different genera and species, as for example humanity is the essence of man, and so with regard to other things.

[4] Because the definition telling what a thing is signifies that by which a thing is located in its genus or species, philosophers have substituted the term 'quiddity' for the term 'essence'. The Philosopher frequently calls this 'what something was to be';†6 that is to say, that which makes a thing to be what it is. It is also called 'form',†7 because form signifies the determination †8 of each thing, as Avicenna says.†9 Another term used for this is 'nature', using 'nature' in the first of the four senses enumerated by Boethius.†10 In this sense anything is called a nature which the intellect can grasp in any way; for a thing is intelligible only through its definition and essence. That is why the Philosopher, too, says that every substance is a nature.†11 The term 'nature'†12 in this sense seems to mean the essence of a thing as directed to its specific operation, for no reality lacks its specific operation. The term 'quiddity' is derived from what is signified by the definition, while 'essence'†13 is used because through it, and in it, that which is has being.†14

[5] Because we use the term 'a being' absolutely and primarily of substances,†15 and secondarily and with qualification of accidents, it follows that essence is in substances truly and properly, but in accidents in a restricted way and in a qualified sense.

[6] Furthermore, some substances are simple and some composite,†16 and essence is in both; but it is present in simple substances more truly and perfectly because they also have being more perfectly. Simple substances are also the cause of those that are composite; at least this is true of the primary and simple substance, which is God. But because the essences of these substances are to a greater degree hidden from us, we must start with the essences of composite substances, so that the learning process will begin, appropriately, with what is easier.

Reproduced from:

ST. THOMAS AQUINAS


ON BEING AND ESSENCE


Translated with an Introduction and Notes

by

ARMAND MAURER, C.S.B.


SECOND REVISED EDITION


THE PONTIFICAL INSTITUTE OF MEDIAEVAL STUDIES


On Being and Essence Bibliographic Data p 4
LIBRARY OF CONGRESS CATALOGING DATA (Revised)
Thomas Aquinas, Saint, 1225?-1274.
On being and essence. Tr., with an introd. and notes, by Armand Maurer. 2d. rev. ed. Toronto, Pontifical Institute of Mediaeval Studies, 1968.
(Mediaeval sources in translation; I ISSN 0316-0874)
79 p.
Bibliography: p. [73]-76.
Index: p. [77]-79.
ISBN 0-88844-250-5
B765.T53D431968189':4

First edition 1949
Second edition 1968
Reprinted 1991
(c) 1949, 1968, 1991 by

Pontifical Institute of Mediaeval Studies
59 Queen's Park Crescent East
Toronto, Ontario, Canada MSS 2C4
Reprinted by Universa, Wetteren, Belgium