Isagoge Philosophica

Many things indeed are called universals among philosophers with some addition; as universal causes, universal signs, universal utterances, and those which in other modes so have unity that they nevertheless pertain to many. But the universal simply, and absolutely, and in no way singular, is defined to be that alone which, since it is some one thing, is apt by its nature to be in many; as animal in individual animals, and man in individual men. It is described also from a certain property: something one by nature apt to be predicated of many, or to be truly said. For since a thing is, or is not, a statement is called true or false. Thus animal is predicated of Alexander and Bucephalus, because it is perceived to be in them; and man similarly of Socrates, Plato, and Alcibiades, because it has its being in them.

It is not, however, necessary that what is universal be some one thing in reality in those of which it is predicated, as a road is said of that which is both ascending and descending at the same time in reality for those setting out from here and there; but in name and reason or concept. For as many things as there are in reality in which the universal exists, so many must that thing be in reality; in which manner we say animal in Alexander and Bucephalus to be two certain things, and man in Socrates, Plato, and Alcibiades three; yet not only the name, but also the reason of animal in Alexander and Bucephalus is one and the same; and in the same manner the name and reason of man in Socrates, Plato, and Alcibiades.

Nor indeed did philosophers say that whatever is universal is actually in many, but apt to be in many; because even if it is actually in only one singular, or even in none; if nevertheless it has the aptitude to be in many, whether simultaneously, as Orator or Prophet; or successively, as Monarch or Supreme Pontiff; it must by all means be reckoned universal.

Moreover the universal is said to be apt, not by external power, but by its own nature; because if something in the nature of things were such that by alien power it could not exist in many, to which, however, the nature of the thing considered would nothing repugn in being found in many; this part of its own nature and condition would be sufficient for it to be called universal. Although these two, which certain pagan philosophers, and certain others of ours in the World, and separate substances, thought to be true simultaneously, we judge to fight against each other.

Moreover it is not enough that some thing can be in many in any way, to be called universal by reason of their relation, as by real composition or inhesion; the latter definition shows this. For the soul is in man and horse as a real form in composite things; and whiteness in the swan and marble, as a real accident in inhesion in subjects: yet neither is this universal by comparison of the swan and marble; nor that with respect to man and horse, since they cannot be truly said of them: which same thing is easily observed in very many other things. But it is necessary that it be able to be in them by true identity, and such that those many affirm that thing to be in them.

Although neither is this enough, unless it is as it were their form: it will be, however, if it gives some being to them, either pertaining to their essence, or adjoined, or applied as it were to them as subjects. For which reason neither is body called universal by comparison of white and black; nor white or black with respect to sweet and soft, with which in butter white is conjoined, and black in cassia.

Finally, by the name of many, must be understood not any many, but such that in them that one thing is multiplied, and can be called many by its own name, as man in Socrates and Plato many men; and animal in man and horse many animals. For if something common is so in many, and is said of many, that nevertheless it is not multiplied in them, nor can many be called in them by its own name, that will no longer be said to be universal, but singular; in which manner the Best and Greatest God behaves in the comparison of divine persons.

Since, therefore, whatever is universal, by some mode of reason one and the same can be in many; from the multiplicity of the modes of being, so to speak, in many of one and the same reason, it must be gathered how many are the genera of universals.

But the same one reason can be said (if indeed it be understood fully) in four ways. For either it is one and the same in a certain way, namely by sole attribution to some one thing, or proportion of many among themselves, simply however many and diverse, as the reasons of the healthy and the sick: for some things are called healthy or sick because they are affected by health or sickness; others because they produce or preserve these; others because they indicate: and just as the body behaves with respect to such external affections, so in a certain way the soul with respect to internal ones, and its own. Or it is indeed the same simply in those to which it agrees, whether equally participated by them, but not one simply, that is, in itself, such are the reasons of house, ship, world, army, and other things of this kind; because although they agree with them in the same way; none of them is one in itself, or declares some one nature: but many things coagmented and disposed in a certain way or order, from which no one nature results. Or on the contrary it has the nature of the thing, that it is one simply and in itself, but not the same simply in those of which it is said; such is the reason of the colored by comparison of the white and the coal. For although it declares a truly one nature, yet it agrees with the white by essential relation, with the coal however by accidental. Or finally it is both one simply and the same simply, or (as it is wont to be said) wholly one and the same; because it is both one in itself, and is participated in the same way by those of which it is said; such are the reasons of man and animal.

And those things indeed which are of the first mode of one and the same reason, although they are often called universals by Aristotle, and sometimes excluded from equivocals; as when he says, being and one are most universal; and being indeed is said in many ways, but not equivocally: we, however, do not treat them more fully here; partly because they are not properly called universals, but by opinion of some, and imitation of properly so-called universals; partly because they are more truly numbered in equivocals than in univocals, and are comprehended under the name of equivocals at the very beginning of the book of Categories by Aristotle, that they may be excluded from the treatise of Predicaments. Wherefore it is enough if Dialecticians understand here that many things also of this kind of universals fall under the science, and are apt that demonstrations be made of them and from them: which Aristotle often teaches. Those things, however, which are of the second mode of one and the same reason, because they are not of some one true nature, nor per se (if the thing indeed is expended more diligently) have a place in the predicaments; are not properly to be treated here: yet nevertheless, because their reasons are communicated in the same way to those of which they are said, they must be held as it were proper universals; and to them must be attributed a certain dissimulation, which here will be said of genera, species, and other universal forms; especially since in so great ignorance of universals, these are often brought forth by philosophers as example, and treated as true genera and species. Those things, however, which are of the third mode of one and the same reason, although inasmuch as they are not participated in the same way, nor are said univocally, have no place in this treatment, just as neither in the predicaments; simply however, because they are of one true and sincere nature, they regard both disputations, because they can be conferred with those by which they are communicated equally, as the colored with the white and black. But those which are of the fourth, extreme mode, are one and the same reason, are reckoned truly and properly universal in every respect, those alone absolutely and simply are understood in the definition of the universal; so those alone are henceforth to be distributed by us into various forms, and to be treated commonly and divisively, insofar as it will be permitted.

These same things, however, are rightly divided into the five common species, from the diverse mode of being in their particulars, in this manner it will be understood. For either they pertain to their essence, or not at all: if they pertain, either they are predicated of them in the question what it is, or in the question what kind it is: if in the question what it is, either they contain their whole common quiddity, or a part: if a part, they are genera; if the whole, species. But if they pertain to their essence, yet not in the question what it is, but in the question what kind it is, they are said of them, they are differences. Finally if they do not pertain to their essence, and yet necessarily agree, they are properties; if contingently, accidents. So there is no reason why more or fewer species of true and properly so-called universals should be posited.

Nor is any specific distinction of them taken from this, that some are predicated of things different in number alone, as man; others of things different or diverse in genus, as white or relative; because although this distinction is enough for judging some to be more universal, others less universal; it is not enough for discerning the natures of universality, as it were, or communality, since it is not taken from the diverse mode of being in particulars, but from the greater or lesser multitude of particulars. All these things will become more open from the proper explanation of each species.

To each universal there correspond, on the other side, many particulars, just as many parts correspond to each whole, whether essential or integral. For the universal, which in Greek is τὸ καθ’ ὅλου, as it were means what can be predicated of a whole multitude; and the particular, called τὸ καθ’ ἕκαστον, means what is numbered through individual things, or one by one. They are related in turn as a common whole and a part subjected to it. A particular is one thing that can be subjected to some universal, as Socrates to man, and man to animal or to one who is awake. For just as something need not actually inhere or be predicated in order to be universal and predicable, but need only be capable of inhering and being predicated, so something need not actually be subject or actually receive predication in order to be particular and, so to speak, subjectible; it need only be capable of being a subject and of being subjected in predication. Thus, even if “awake” is not a universal predicate in relation to man, nor man a particular subject in relation to “awake,” if no one is actually awake; “awake” always remains universal and predicable in relation to man, and man particular and subjectible in relation to it.

Just as among universals some are less universal, such as man and whiteness; some more universal, such as animal and color; and some most universal, such as substance and quality, so among particulars some are less particular, such as those two just mentioned, animal and color; some more particular, such as man and whiteness; and others most particular, such as this man and this whiteness. These are called singulars and individuals.

A singular, or individual, is something which, being one, cannot by its nature exist in many or be predicated of many. All this is to be understood in the same way as in the definitions of the universal. Something is also called an individual when it is, or can be, predicated of one alone. In this explanation, the difference that distinguishes it from the universal combines an affirmative claim that it is predicated of one with a denial that it is predicated of anything else. Although predicating something wholly identical of itself is unartful and in a way tautological—and Aristotle does not deign to include it under the name of predication when he says that there is no predication of primary substances—it must nevertheless be included here under the verb “to predicate,” so that the definition agrees with Aristotle’s account of all individuals. For since he holds that primary substances, which are the principal individuals, cannot be predicated of anything by natural and direct predication, and altogether rejects indirect predication, as contrary to nature and accidental, it follows that the one thing of which each of them is said to be predicated according to this definition is that very primary substance which is predicated.

Accordingly, from predication of one—which this latter definition joins to a denial of predication of anything else—four kinds of individuals can be derived in keeping with Aristotle’s account. First, things predicated in their own way in answer to “What is it?”, as Socrates of himself (for nothing is so one as the very thing itself). Second, things predicated in answer to “What sort of thing is it?” when something essential is being asked about, as Socrates’ individual difference of Socrates himself. Third, things predicated in answer to “What sort of thing is it?” when something accidental but necessary is being asked about, as “this true thing” of this gold. Fourth, things predicated contingently, as “this white thing” of this stone. All these are truly and properly singulars or individuals, also called designated, pointed out, and determinate.

There are also other individuals called partly “vague” and partly “by supposition.” Although in fact and by their nature both kinds can be said of many, they are sometimes used as true individuals. Vague individuals are universals themselves with a mark of particularity added, such as “some man” or “some animal.” Yet things that can be said of many things differing in species should rather be called vague particulars than vague individuals, since they are sometimes taken as universals—as when we say that some animal is a species. Properly speaking, then, vague individuals are formed not from genera but from the lowest species. Thus Aristotle, when he gives “a certain man” and “a certain horse” as examples of primary substances, takes “horse” not for the whole genus of horses (if horse is predicated of many things differing in species), but for a definite species of horse.

Those called individuals “by supposition” are actually said of one alone, because at that time there is nothing else of which they can be predicated, but by themselves are apt to be said of many. An example is “the son of Sophroniscus,” which was said of Socrates alone because Sophroniscus had no son other than Socrates. From this one can infer that an individual is not rightly defined as something whose several attributes are each said of many, but which, when joined together, will never belong to anything else—unless the definition is given only by supposition of an individual. For although many common attributes may at some time be joined together in a way that describes only one person, and may never in fact belong to anything else—for example, if someone described Paris as the eldest son of Priam, king of Troy, and Hecuba, or Aristotle as the son of Nicomachus and Phaestis and the tutor of Alexander the Great—it is nevertheless clear that, considered by the nature of the common attributes, they can be said of many. Priam could have had another eldest son by the same wife if he had first had a son at a different time; and Nicomachus could have had another son by Phaestis who was also Alexander’s tutor. However many common attributes are joined together, they never lose their common nature so as to confer on one another a singularity they do not possess in themselves. This is enough about the account and distinction of universals and particulars, and about singulars, most of which are known and evident to the senses themselves.

We know universals by abstraction, or by a certain separation from the singulars in which they exist—not a real separation, but one made by reason and consideration. Let the universals attributed to Plato be dismissed as worthless, like old wives’ tales: if they were really separated from singulars (as Aristotle either supposes or pretends that Plato supposed), they would contribute nothing either to the being of those singulars or to our knowledge of them.

This abstraction takes place when the intellect, with the senses as its ministers, gathers from singular things not the common natures themselves that exist in them, but certain species or natural likenesses by which those natures are represented without any individual difference. For each cognitive faculty in us abstracts and separates its object from the objects of other cognitive faculties by means of species received from the things themselves. For example, butter contains whiteness, sweetness, a distinctive odor, softness, and other accidents, as well as the singular substance of the butter itself. Sight abstracts and separates whiteness from sweetness and the other things present in the milk by means of the species of whiteness it receives through the eyes, although whiteness remains really joined to them. In the same way taste abstracts sweetness by means of its species, and so do the other senses, both external and internal. But because the senses are material and attached to bodily organs, they know only singulars and can abstract only certain material and sensible things from other material and sensible things. For this reason all the species they use in knowing are called sensible. The intellect, by contrast, is an immaterial power and is not attached to any bodily organ; by the nobility of its nature it can therefore perceive universals and abstract them from singulars by means of species of a higher nature, which are called intelligible.

This kind of abstraction occurs in the following way. The familiar external senses, as it were the first gatekeepers of our mind, receive and somehow draw in the species of sensible accidents belonging to things present to them. Through these species they gain intuitive, or present, awareness of those accidents. They then report to the common sense, which presides over them all and may be called partly internal and partly external, what accidents are before them. They do this by transmitting to it certain likenesses through which it can know all that each sense has perceived, compare these things with one another, and distinguish them. The common sense may be called partly internal and partly external because, although its seat and dwelling place are internal, it would make no difference to call its function external: like each of the five familiar external senses, it can know nothing privately within itself, but only when the things themselves are present.

Next, the common sense, as it were by striking the imagination—which serves the intellect most closely and is wholly an internal sense—gives it occasion to draw from the species received from the external senses other species called phantasms. Among sensible, or material, species these are of so noble a nature that they can represent things absent, past, and future, as well as many things that the other senses have not perceived: a past injury from a blow, the future benefit of food, the poison in a harmful plant, and the usefulness of a wholesome one. Prompted and guided, as it were, by such phantasms, a dog flees a stick and a sheep a wolf, while the dog follows the hunter and the sheep the shepherd. Their power in human beings is so great, because imagination is joined to intellect, that some very learned men have held that phantasms can also represent the singular material substances themselves that lie hidden beneath sensible accidents. For the same reason, they hold, imagination can compose singular things from singular things and reason from one to another.

Finally, imagination, though a single power, takes on different names and accounts from the different functions it performs. By offering phantasms to the intellect, so to speak, it supplies the matter and objects for understanding. The phantasms themselves cannot act on the intellect, since they are material and the intellect is immaterial. But the intellect is twofold: one part can act on material things to produce immaterial effects; the other can be acted upon by immaterial things. The former is usually called the agent intellect, the latter the patient, receptive, or possible intellect. Raised by the light of the agent intellect, phantasms impress intelligible species upon the possible intellect, much as colors cannot of themselves, in darkness, send their species into the eyes; but when the light of the sun or a lamp arrives and raises them by its power, they can move the eyes and impress on them their likeness, so that the eyes can see them. The agent intellect is an inward, spiritual light which in a way makes things that are universal in potency universal in act, just as bodily light makes colors that are visible in potency visible in act, as Aristotle says.

By these intelligible species, which represent universal natures without any admixture of singularity, both intellects are said to abstract universal natures from singular things. The agent intellect produces these species; the patient intellect, as if looking straight at things through them, knows universals alone. Yet when it is in a way turned and directed downward, it also understands singulars through the same species together with phantasms. We must not deny that our intellect has true and determinate perception of singular things, especially since the higher cognitive faculties must be granted every kind of knowledge attributed to the lower faculties, though in a different and more noble mode.

From this it is clear that there are two kinds of abstraction, whether we consider the abstraction performed by the sensitive powers or that performed by the intellect. One is the separate representation of an object in a species; the other is its separate apprehension. We have spoken of abstraction by the sensitive powers by way of example and as a kind of guidance, and also to show the progress of the cognitive faculties up to the first abstraction of universal natures from singulars.

How the intellect alone abstracts more universal natures from less universal ones need not concern us here. The account is the same as for abstraction of universals from singulars: a nature is first said to exist universally in the mind when it is represented by any intelligible species or perceived by a concept corresponding to it, whether the species and concepts are more or less common, and whether the species are produced with the help of phantasms or by the intellect’s operation alone.

It is in this one sense that what philosophers commonly say—that universals are made by the operation of the intellect—can be true. For whatever comes to be acquires a new actual existence, and this is of two kinds. One is real existence, which universals as such cannot have, since whatever exists in reality must exist as a singular. The other is objective existence, which the sensitive faculties cannot give them. It follows that only through the intellect’s operation do universals as such come to be and, in their own way, arise—that is, have objective existence: habitually in the intelligible species by which they are represented, and actually in the concepts by which they are apprehended.

Finally, universals and particulars, like causes and effects, can be considered in three ways. Causes and effects are considered, first, as certain things—for example, the sun as sun and gold as gold; second, as causes or effects—for example, the sun as producing gold and gold as produced by the sun; and third, in their mutual relation, one as cause to effect and the other as effect to cause. The same applies to universals and particulars. In the first way they are considered as things, with no account taken of their universality or particularity, as animal insofar as it is animal and man insofar as he is man. In the second, they are considered as universals or particulars. For in animal, being animal is one thing, and being common to man and beast is another: being animal belongs to every animal, whereas being common to man and beast belongs only to animal taken precisely, that is, without consideration of any contracting difference. Likewise, in man, being man—which belongs to human beings alone—is one thing; being a species subjected to animal—which is shared with other animals—is another. In the third way they are considered insofar as they stand in mutual relations to one another: universals as common wholes, and particulars as parts subjected to them.

In the first way, all sciences and arts discourse about universals, as was said at the beginning—not all about all of them, but different sciences about different universals. Physics treats all the genera of animals and plants; moral science treats all the forms of virtues and vices; medicine treats the common differences of all diseases and treatments. In the second and third ways, however, it belongs only to first philosophy and Dialectic to treat universals and particulars. Being universal and particular, and the relations between universals and particulars, are common features of things; they belong no more to the things considered by one science than to those considered by another. They must therefore belong to sciences concerned with all things, such as first philosophy and Dialectic alone—to leave aside sophistry, which is designed not for truth but for deception. Yet the two sciences consider them in different ways. First philosophy treats them as common features of things; Dialectic treats them insofar as knowledge of them contributes to reasoning and its common use. Dialectic’s teaching—and even its practice—depends remarkably on considering universals and particulars and the relations by which universals are related to particulars, and particulars in turn to universals. The relations themselves, however, are held to be less important in both first philosophy and Dialectic than the accounts of universals and particulars explained above.

But three things are considered in the definitions of the universal: the unity of universal things, their aptitude to be in many, and their aptitude to be predicated of many. Although both sciences treat all these matters in some way, it must be understood that the first philosopher, as part of his proper inquiry, discusses only the first two, while the dialectician discusses only the third. The first philosopher treats general modes of predication only so that, guided by them, he may discover general modes of being; he discusses the method of definition only to teach many things about the quiddity and nature of things. The dialectician, by contrast, presents—or rather receives from the first philosopher—certain accounts of the modes of being of things, and of their unity and distinction, in order to gather all the modes of predicating and reasoning. The same judgment applies to the three corresponding conditions of particulars: their unity and their aptitude to be subjected to their universals and to serve as subjects in predication.

One further point must not be passed over: universal things have a twofold unity, one usually called formal unity and the other, in our present terminology, called unity of precision.

Formal unity is nothing other than the indivision of a universal thing in itself—that is, in its nature or account. Such is the indivision of animal insofar as it is animal, and of man insofar as he is man. The senate, the people, and a team of four horses are not indivisible in this way, because in their accounts they are divided and many even in actuality. This unity is called formal because it is communicable to many, just as the universal thing itself, of which it is the unity, is communicable and is its first property.

Unity of precision, by contrast, is the indivision of a universal thing not in itself but in its particulars. Such is the indivision of animal in man and beast, and of man in Socrates and the other individual men. It is called unity of precision because it does not belong to a universal thing in whatever state it is taken. Formal unity belongs to it in every state: before it is contracted to its particulars, while it is already contracted in them, and after it has been abstracted from them and, as it were, plucked away by the intellect. Unity of precision belongs to it only in the state in which it is apt to descend to its particulars and be divided and multiplied in them. For insofar as a thing is apt to be in many and to be divided among them and called many, but has not yet been divided and multiplied in the order of nature, it is individed in relation to them and therefore one by this unity of precision. But if it is taken as it already exists in its particulars, divided and countable in them, it is already many, not one, by this kind of unity.

These two kinds of unity differ chiefly in three respects. First, formal unity is a property of universal things insofar as they are things; unity of precision is a property of them insofar as they are universal, that is, insofar as they are apt to be in many. For the whole essence of universality lies in this aptitude, to the extent that it can be called an essence.

Accordingly, in the earlier definition in which the universal is said to be one thing apt to be in many, the word “one,” which is put in place of the genus and stands for the thing underlying universality, is to be understood as formal unity—or rather as unity common to formal unity and the numerical unity of singular things. Unity of precision is not expressed in that definition, but it necessarily follows from the aptitude to be in many, which completes the account of universality. For, as we just said, while a thing retains its aptitude to be in many, it remains undivided into many and therefore one by this kind of unity.

They also differ in that formal unity is an indivision that is purely negative, whereas unity of precision is privative.

Formal unity presupposes no aptitude in the universal thing to be many within itself: what is undivided in itself cannot in any way be divided in itself. Unity of precision, however, presupposes an aptitude by which a universal thing can be divided and multiplied in its particulars. In the same way, we say that a stone’s lack of sight is a pure negation, because a stone has no aptitude for seeing; but a blind man’s lack of sight is a privation, because a man is by nature apt to see.

Finally, they differ in this: formal unity is multiplied along with the universal things themselves in their particulars, whereas unity of precision is not. There are as many formal unities of the nature of animal in particular animals, and of human nature in individual human beings, as there are particular animals and individual human beings. But there is only one unity of precision for one common nature taken in its commonness, which does not descend together with that commonness into its particulars. This difference shows that formal unity is itself universal, just as the thing whose unity it is is universal; unity of precision is singular, just as the aptitude it presupposes and follows is singular. Hence it is only by unity of precision that we can say animal is one genus in number and man one species in number, and that the number of primary objects of our intellect is the same as the number of universal things.

Since unity taken generally is divided into formal and numerical unity, and formal unity belongs properly to universal things taken absolutely, while unity of precision is their numerical unity insofar as they are universal, it remains that numerical unity taken simply and absolutely belongs properly and peculiarly to singular things. This will suffice for what we have said in general about the five species or forms of universals.

We must now treat each one separately, but first let us warn readers that whatever in this little book has been said so far, or will be said later, that seems harder to understand is not to be explained more precisely here by teachers, still less debated at length and in detail. It should be presented through familiar examples and provisionally taken on trust, so that it may help students understand what is taught throughout the course of philosophy. If students wholly fail to grasp these matters, they will often be led astray and stumble midway through the course. But if they are burdened at the very outset with long and weighty debates so that they may understand them more deeply, they lose heart and give up their undertaking under something like compulsion; or at least they become so weary and disheartened that, needing still greater support in philosophy, they do not finally understand these matters and approach what follows with less interest and zeal. It will therefore be enough at this stage to grasp them as best one can, commit them to memory, and hold them largely on the authority of teachers until they are explained more clearly in their proper places. For, as Aristotle teaches, the learner must believe; this is especially clear of those who are at the very beginnings of the sciences. The same rule should be observed in the treatment of the categories, in the account of future contingents given in On Interpretation, and in similar places. To demand that minds still untrained and little practiced reduce all these matters, as the saying goes, to exact calculation, and to require a precise account of them from new students, is quite inept and unbecoming. It is disgraceful to demand from beginners what even veterans often scarcely manage to provide adequately.

But now let us say what genus is and what force it has.

Taken broadly, “genus” is used in many ways. We often misuse the name of a genus for a species or something like a species, as when we say there are many genera of languages or colors, and generally when we bring something more common down to less common things—even if those less common things have nothing common beneath them but are themselves singulars. Properly speaking, however, “genus” seems to have about four meanings.

First, the continuous and uninterrupted generation of things of the same species is called a genus, as it were a common begetting, without any regard to a first progenitor. The term is also applied in the same sense to the whole multitude of begetters and begotten in an unbroken succession. This is how we use it when we say, “As long as the human race shall endure”—that is, as long as their generation continues, or the succession of begetters and begotten remains unbroken. In this sense they would not be called one genus if the common flood of the whole world had killed all the people then alive and others had been brought forth in some way other than generation from a woman.

“Genus” is also used for the very origin of an uninterrupted line of generation from a single progenitor.

In this sense we say that all men ever born of a woman trace their lineage to Adam, and all those born after the universal flood to Noah; we also speak of Greeks as descended from Graecus and Ionians from Ion. We readily extend this usage to any family, in which we find two relations: one of natural dependence on the first parent and head of the whole group, the other of kinship among all its members. By these two relations we distinguish each such lineage from others of the same kind. Related to this meaning is the use of “genus” for origin from a homeland or nation, since a nation may be called a kind of broader homeland. Aeneas, for example, seeks Italy as his homeland and claims descent from Jupiter; in the same verse the poet recalls both kinds of lineage, that from a homeland and that from a first progenitor. In this way we call Plato Athenian by nation and Aristotle a Stagirite; or, more precisely, Plato an Achaean and Aristotle a Macedonian by nation, but the Stagirite and the Athenian by homeland. For although a homeland has greater force in the generation of each person, a nation contributes more broadly to it.

A third use, proper to philosophers, takes genus as a subject in which various differences are found. Thus surface is called the genus of plane figures and solid the genus of solid figures. Different sciences and arts concern different genera of subjects, and each demonstrates the proper attributes of its own subjects; as Aristotle says, one science may not pass into the genus of another.

The fourth and principal meaning, most familiar to philosophers, calls genus that to which species are subjected. Some features of the two preceding meanings resemble this one. Genus in this sense is a kind of principle and source of its species, into which it is, as it were, propagated; in the composition of its species it plays, as it were, the role of matter and of a subject for opposed differences. In describing it, Aristotle says that a genus is what is predicated of many things differing in species in answer to “What is it?” To express all that this description implies, and to arrange its terms so that things alien to the account of genus are excluded in the proper order, genus should be said to be a certain universal predicated necessarily and essentially, in answer to “What is it?”, of things differing in species—that is, as a complete expression of their common nature. Once genus is explained in this way, individuals are first excluded, since they are furthest from the account of genus; next accidents, which are the lowest class of universals; then properties, which belong necessarily; then differences, which already pertain to essence; and finally species, which alone among the universals completely contain the common nature of singular things.

These are not, however, several differencee by which a genus is constituted in the order of generation, such as those used to define man when we say that he is a corporeal, corruptible, living, sensitive, rational substance. Rather, they indicate a single difference, whatever it may be, with the full force conveyed by those several terms taken separately. It follows that we should not look for intermediate species between the universal and its five familiar species, into which those five might be divided—any more than we look for intermediate species of colors between color and the lowest colors—even though some of the latter agree more closely with one another than with others. This account differs from the deeper definition of genus only in using the word “predicated” in place of the verb “to be,” which signifies the basis of predication. It can therefore serve, in its own way, as an essential definition: Genus is a universal that is necessarily and essentially, or quidditatively, in many things differing in species. These two points should be recalled when considering the similar definitions of the other universals.

Genus is divided, by reference to the things called genera, into supreme and subaltern genera. A supreme genus has no genus above it and, though it is a genus, is not also a species; substance, quantity, and quality are examples. A subaltern or intermediate genus has another genus above it and, while a genus, is also a species; corporeal substance and continuous quantity are examples.

If we are speaking of real and complete things, there are ten supreme genera: substance, quantity, quality, relation, action, passion, where, when, position, and possession. They are regarded as the first principles and, as it were, sources of the categories. Being, which might seem to be the common genus of all things, does not have the account of a genus. For, as Aristotle teaches, although it is not altogether equivocal, it is not univocal either; it is something intermediate, which is called analogical. We will treat more conveniently, in the explanation of species, the multitude of subaltern or intermediate genera, since they are both genera and species.

“Species” commonly means the outward form of things presented to sight, from which things are called beautiful, deformed, or neither. Hence Euripides’ line, “The first in beauty is worthy to rule,” to which Aristotle alludes when he says that if human beings excelled in bodily form as much as the images of the gods, everyone would judge them worthy to be served by the rest.

Among philosophers, however, “species” often names certain natural likenesses by which the senses and intellect perceive the things presented to them. We called these sensible and intelligible species above. The form that completes the substance of each natural thing is also sometimes called its species; philosophers classify this form under the genus of causes.

Their most common use of the term is for a part subjected to a genus that is itself common. In this way man is a species under animal, and laurel a species under tree. They define species as that which is subjected to a genus in answer to “What is it?” and of which the genus is predicated in answer to “What is it?” More explicitly and in a more fitting order, species is a particular that is immediately subjected to a genus in answer to “What is it?”—or, equivalently, of which the genus is predicated in this way. Man, for example, is a species subjected to animal, and animal is predicated of man in answer to “What is it?”, not “What sort of thing is it?” This subjection is immediate, without the intervention of another species.

No one should be surprised that species is used in defining genus, and genus in turn in defining species. Since genus and species are defined as universal and particular, it is useful and straightforward in defining them to indicate their mutual relation. It is therefore necessary for each to appear in the definition of the other. Otherwise it would have been enough for Aristotle to say that genus is what is predicated in answer to “What is it?” of many things that share a common nature and essence but differ among themselves.

Just as genus, by reference to the things called genera, is divided into supreme and intermediate, or subaltern, genera, so species in this sense is divided into subaltern and lowest species. Subaltern species are species that are also genera and have other species beneath them; animal, for example, is a species under living body and also a genus of man and beast. Lowest species are species of higher kinds but are not genera of lower species, and have no species beneath them; man, for example, is a species under animal but is not a genus of individual men, since human beings do not differ from one another in species, but only in number. All this has concerned species insofar as they are particulars, or parts subjected to a genus.

But since the lowest species of higher kinds are not genera of lower species, yet are predicated of them in answer to “What is it?”, another kind of universal arises. The ancients also chose to call it “species.” This is the fourth and more proper meaning of “species” for our present discussion. It is usually defined as what is predicated in answer to “What is it?” of many things differing in number. More explicitly and in a more fitting order, species is a universal that is predicated necessarily, essentially, and in answer to “What is it?” only of things that differ in number alone. In other words, it is predicated completely—or, if you prefer, immediately—of things differing only in number. In this way man is predicated only of individual human beings.

This species of universal is the most perfect of all, both with respect to the things called universals and with respect to universality or commonness itself. It is most perfect with respect to the things involved because all things called lowest species are more perfect than all the genera and differences of which they are composed, and than any of their properties and accidents. It is most perfect with respect to commonness because the unity and identity of universals with their particulars show that no other universal is as one in itself, or has as much identity with its particulars, as a lowest species has with its individuals. This is why Plato and all the other philosophers judged that one should stop at the lowest species when dividing, defining, and demonstrating: the perfection of all universal things is evident in them. Individuals are indeed more perfect and more beings than lowest species, as Aristotle teaches, but they are rightly left aside, partly because their great multitude cannot be reckoned by a determinate number so as to fall within our science, and partly because all things under the same lowest species have equal perfection of nature. Thus someone who has learned about even one of them need not investigate the others. Species are contrary to individuals in both these respects. With a few exceptions—which arise either from unusual natural unions of animals, from the arts of grafting and of applying active agents to passive subjects as these are gradually discovered, or from the chance combination of several natural causes, knowledge of which in time enriches the arts and sciences—all other species are fixed and determinate in number, though most are unknown to us. The same is true of subaltern genera.

Thus, under the supreme genus substance, we count corporeal and incorporeal substance; under corporeal substance, corruptible and incorruptible; under corruptible, living and nonliving; under living, sensitive and non-sentient, which we call animal and plant; under animal, man and brute animal; but under man there is no determinate number of individuals. In the same way we can descend through the species we pass over here until we reach the lowest species in each order. It is not always necessary to divide a genus in two. Although corruptible substance is divided into simple and mixed, simple substance is divided among the four species of the elements, and plants into three genera of plants—trees, shrubs, and herbs. The same occurs in many other genera, which are divided into more than two species but still into a finite number. Thus, whether one descends from the supreme genera or proceeds across the divisions, one will never encounter an infinite number of true and genuine species. We set aside those that could exist in nature only by God’s absolute, rather than ordinary, power, since we are not concerned with their number.

Everyone agrees that no species can be entirely equal to another in perfection. For, as Aristotle teaches, species of things are like species of numbers: just as no species of number is equal to another in its multitude of units, so no species of things is equal to another in perfection. Aristotle’s statement applies properly to species of which some are higher and others lower; in its own way it applies to the others as well, since all, as he also teaches, hold among themselves an order of prior and posterior according to their own natures. Thus colors nearer to the first and most perfect color are held to be more perfect, and animals nearer to the first and most perfect animal must likewise be more perfect.

Moreover, just as genera are naturally prior to their species in the order of generation, so species are prior to their genera in the order of perfection. It follows that one may proceed from species to genera by a consequence of either being or existence, but neither consequence runs in reverse, from genera to their species.

Likewise, just as species are better known to us in the order of discovery, genera are better known in the order of exact understanding. In investigating common natures, we customarily proceed from lower kinds, which are closer to the senses, to higher ones; but in dividing, defining, and demonstrating them, we descend from higher to lower.

Finally, by ascending from species to genera and from individuals to species, we gather one from many; by descending from genera to species and from species to individuals, we make many from one. Through participation in a species, many men are one man; but what is one and common becomes many through the addition of particular conditions. The same can be said of animal in relation to man and its other species. This is enough about genus and species.

Difference in one way is called any diversity; by which signification we also say those things to differ among themselves which are diverse in whole genus, as substance and quality. Properly, however, difference is the diversity of those things which otherwise are of one altogether reason: by which difference those things alone are said to differ among themselves which are the same either in genus, or in species, or in number; as man from horse, Socrates from Plato, and the same old man from himself young.

It is noted of difference taken in this pact into common, proper, and most proper distinction. Common is called that which can truly be separated, as to sit, to stand, youth, and similar. Proper, which although truly inseparable is; nevertheless does not pertain to the essence of the thing, as a scar when covered by a callus, the gray color of the eyes, and properties of common natures. Most proper truly is that which makes the essence diverse, as rational; for this is the cause that man is of diverse essence from horse and the other brute animals. Therefore common and proper make the thing otherwise affected, or at least having it in another way; but most proper makes it to be another according to essence.

Difference is also divided first into separable and inseparable: then inseparable into difference per se and per accidens. Difference per se is the same as most proper, and is called difference per se because it is per se divisive of some superior, and constitutive of some inferior; in which way sensitive is divisive of living, and constitutive of animal; rational however divisive of animal, and constitutive of man. Difference per accidens, if taken absolutely, not as a member dividing inseparable difference, comprehends common and proper, and is called per accidens because by accidental alone it divides and makes to differ.

Those things therefore dismissed, difference per se is twofold, one specific, the other individual. Specific is that which with genus constitutes species, whether mediate namely or infima; individual however which with infima species constitutes individual or one in number. Hence it comes about that whatever properly differs from another by difference per se and not per accidens, all that either differs in species or in number alone.

Nor are those to be heard who acknowledge no difference per se among individuals of the same infima species, but wish them to be distinguished only by accidents. For no predicament is there which per se itself and without aid of another predicament is not sufficient for the constitution of its species and individuals, since all predicaments are unmixed from supreme genera to individuals, nor are differences to be sought in one predicament by which species or individuals of another are constituted. But just as from the power of each genus the differences productive of species are in a certain way born, so from the power of each infima species its own differences of individuals arise in its own way.

Specific difference is also said to be that by which species exceeds genus. By the same pact individual difference can be said to be that by which individual exceeds infima species. For just as man in its common essence has this more than animal, that it is participant of reason; so Socrates in his singular essence surpasses the common essence of man, that he is this singular and determinate.

Difference per se is also commonly divided into divisive and constitutive. But these are rather various offices of difference, insofar as difference is (which is already clear from things said) than genera of differences, just as that third which is to make to differ. For no difference per se is there which does not execute these three in that order in which they are numbered, since it both divides something superior, and constitutes something inferior, and makes that differ from this, others of the same division. Although if divisive and constitutive differences are taken with respect to one and the same common nature, no same difference is there which can perform these three, but it is necessary that another or others constitute it and make it differ from another or others, others divide; in which way another is that which constitutes corporeal substance and makes it differ from incorporeal; others which divide incorruptible and exempt from corruption; others also which constitute animal and make it differ from incorporeal substances, incorruptibles, simples, and plants; others which distribute into various species.

Finally specific difference is divided into general and special. General is that which constitutes a species which itself is also a genus; as sensitive. Special which constitutes a species which is not likewise a genus; as rational. But these things are said of difference insofar as it is difference, not insofar as it is the third species of universals, although all things conduce not a little to this posterior consideration.

Difference is also usually described as a certain universal in this manner. Difference is that which is predicated of many differing in species in the question what kind it is; and this (as is understood) according to essence. And this indeed is the explanation of difference drawn from Aristotle, which agrees only in general differences; and this is not given as a fault because special differences are less known and less used. They are called general in this posterior consideration of differences because they are predicated of things differing in species; special however because of things differing in number alone: which genera of differences neither differ in species among themselves, nor are they genera, but are distinguished by more or less universal reason alone.

The common description of all specific differences is nevertheless this: by which difference is said that which is predicated of many in the question what kind it is, according to essence. For it comprehends both general and special differences; and excludes in apt order singulars and other universals. If this is so understood. Difference is a universal which necessarily and according to essence is predicated of many in the question what kind it is. Which all things from those things said above remain clear.

Specific difference is compared with genus; which divides as substantial form with its proper matter; with the species itself which it constitutes, as such form with natural substantial composite; yet neither form nor matter, which are parts truly component of the whole, are predicated of the natural composite. Genus however and difference, which with species are one and the same thing in whatever individual, are said of the species. These are the things concerning universals which are predicated essentially of their particulars.

The usurpation of proper is also not the same, by which reason it is proper, and by which a certain species of universals. For insofar as it is proper, it agrees to one alone, to that namely of which it is proper; but insofar as universal, it is said of many.

The vocabulary of proper, insofar as it is proper, is founded, if it is taken altogether generally, not only to those things which accrue to things, but also to those which are contained in their essences, whether those universals are universal or singular (for nothing is in the nature of things which does not have something proper to itself) nor does it comprehend only simple or incomplex things, but complex also. By which general consideration even the specific and individual differences themselves are called proper to species and individuals which are proximately constituted from them; and not rarely with Aristotle even definitions of whatever kind are comprehended under the name of proper by comparison of things which are defined.

Those proper things, however, dismissed which pertain to essences of things, and all complex ones; which indeed pertains to simple and accidentary things, in the mouth of all is that fourfold division of proper, by which proper is said either to accrue to the species alone, but not to all or the whole; as to man to be lisping from birth, or a grammarian: or to all, but not to the species alone; as to be biped, or participant of intelligence: or to all and to the species alone, but not always; as to grow gray: or to all and to the species alone, and always; as to be capable of discipline or laughter. Which distinction is apt if it is partly explained rightly, partly corrected. For that which accrues to all but not to the species alone, that truly, if one must speak simply and absolutely, cannot be called proper, as Aristotle teaches; nor does the handed-down explanation of proper, insofar as it is proper, agree with it generally. It can, however, be called proper to something (as the same speaks) namely by comparison of those things to which it does not accrue, which is to be proper according to something; in which way proper is of man by comparison of quadrupeds or serpents, to be biped: and by comparison of plants or brute animals, to have intelligence; since otherwise to have two feet agrees with birds; intelligence truly with substances separated from matter.

The division will be corrected if by the name of species, by which infima is commonly understood, any universal thing whatever is conceived. For all species, whether infima or subaltern, and also all supreme genera, have their own accidentary properties.

Therefore a more accurate division will be if simple and accidentary proper is distinguished: first into proper simply, which agrees absolutely to the thing alone of which it is said to be proper: and into proper according to something or comparatively, which is already explained. Then proper simply into proper perfectly and imperfectly. Perfectly that is proper which lays claim to those three conditions, that it accrue to all and to the species alone and always.

For whatever is of this kind reciprocates with the thing of which it is proper, and has in it an adequate cause why it so agrees. Imperfectly, however, to which either the first condition alone is lacking, as lisping from birth with respect to man; or first and third; as grammarian of the same habit; or third alone; as growing gray. For if the second is lacking, that already will not be proper simply, but according to something. Thus another four-membered division of proper simply alone can be used, as either it accrues to the species alone and always, but not to all; or to the species alone indeed, but neither to all nor always: or to all and to the species alone, but not always; or to all and to the species alone and always, of which examples from things said are patent. By this truly the second mode of the prior division is rejected, because it is proper according to something; the first however is divided into the first and second of the posterior; the third and fourth truly are the same in both. And let these things about proper, insofar as it is proper, according to the first imposition of the name and reason, have been enough.

Insofar, however, as the name of proper is accommodated to the fourth species of universals, others thought it to be defined thus, that in the question what kind it is, it is said of those alone which differ in number alone. By which pact although the prior part of the definition rightly excludes genus and species; the posterior however does not rightly reject difference and accident, since these two do not always predicate of things differing in species, but often also of those which differ in number alone. The definition is usually corrected, the posterior part rejected, and substituted with these other words. Proper is the universal, or that which is predicated of many in the question what kind it is, accidentally and necessarily: so that by the first part individuals are rejected; second, genus and species; third, difference; fourth truly accident. Examples are properties of laughing, of undertaking disciplines, of sensing, of generating, of walking, of understanding, and other such; although some of these do not recur with any genus or species. Moreover by the name of necessary in this matter, not any necessity is understood, but that which is drawn from the very nature of the subjects.

And if proper is taken as proper is, and even as perfectly proper (for no account of imperfectly proper is proposed in this consideration of division) that is commonly called general which reciprocates with some genus; special which with some infima species. If truly as it is the fourth species of universals, general is called that which is predicated of many differing in species. Special, of those alone which differ in number alone. Whether they reciprocate with some genus or species, or not at all, as was said. For those which do not reciprocate, although they are not proper simply, as proper they are, they are nevertheless insofar as universals. So it comes about that it is not necessary that every universal of this species reciprocate with some first subject.

Finally the name of accident is commonly accepted in three ways principally. One for a thing which by its own nature inheres in a subject, such as color and taste of milk, and similar. Another for any attribute not pertaining to the essence of the thing of which it is said; in which way not only all contingent attributes accrue to things, as to iron to be hot, and to man to be white or a grammarian, but also very many necessary ones; nor by any necessity alone, but drawn from the very nature of the subjects, as to man to be capable of laughter or of disciplines. By which signification we used a little before in the verb Accidit, where we explained the fourfold division of proper. Third for an attribute which neither pertains to the essence of the thing, nor flows from it as it were by necessary emanation: in which way by another reason it accrues to man to be black, another to be capable of disciplines, because this in the very nature of man insofar as he is man has whence to arise, that from another source comes forth. And this is the proper and peculiar reason of accident, which makes it the fifth, extreme species of universals; provided accident is taken not as this or that in number, but as it is common to many. For although the name of accident carries nothing universal before itself, it can be accepted for singulars equally as for universals: from the very use of philosophers, however, it is accommodated to signify this extreme species of universals, of which the rest remains for us to speak.

It is usually defined accident taken in this way, that it is present and absent without corruption of the subject. Likewise, that it chances to be in and not to be in. And finally that it is neither genus, nor species, nor difference, nor proper, but inheres in the thing: the sense of which explanations is the same. In which definitions the place of genus is understood universal, so that the first definition may have this: Accident is a universal which can be present and absent, be affirmed and denied of subjects without their overthrow. And in the same way the second definition can be understood. The third truly thus can be exposed: That which indeed can agree with many by the same reason, but not as genus, nor species, nor difference, nor proper. So that in all these definitions the contingent is put in the last place as the constitutive difference of accident. More explicitly, however, accident will be defined if it is said: universal, or that which is predicated of many in the question what kind it is, accidentally and contingently; in apt order: first place individuals are excluded; then genera and species; then truly differences; lastly properties.

This genus of universals comprehends not only real accidents, but also attributes of reason and negations which are said contingently of many, and even substances themselves circumposed after the manner of accidents, as to be a predicate, a subject, blind, dark, clothed, adorned, gilded, fortified. For all these can contingently agree with many and be affirmed of things not destroyed of which they are said.

Accident is further divided into that which is truly separable, and that which is inseparable. For although every accident of this species of predicables can by thought, and even by negative thought, be separated with the subject preserved, since in its nature considered in itself nothing repugns it to lack it; not all however can be separated in reality, but some can, some not. For to sit is separable both by thought and in reality; to be snub-nosed, blind, and similar are separable by thought, not however in reality. In which thing a broad distinction is seen between accident and proper, which neither in reality nor by negative thought can be separated with the subject preserved. For if, for example, you deny man to be capable of disciplines, by the very negation you are forced to confess him not even to be a man, since from the very nature of man necessarily follows aptitude and propensity for undertaking disciplines.

Accident can also be divided into general and special, just as difference and proper; as general indeed is said of species differing, as white, to watch, to sleep; special truly of those differing in number alone, as to laugh, to be a grammarian.

Now if accidents are compared with properties, and the discourse is of true and real accidents and properties, that is usually observed how properties first agree with universals, then through universals are communicated to singulars; so accidents first agree with singulars, then through singulars are attributed to universals.

But if accident is compared with all four superior genera of universals, this distinction, besides others already said, is seen between them, that those four always have the act of being in many conjoined with aptitude, whether they themselves or their particulars exist or not (for it was always true that Socrates is man and animal and participant of reason and capable of disciplines even before he and such predicables existed in the nature of things; true it is now after he closed his extreme day; perpetually true it will be) accident truly although from all eternity it had aptitude to be in many; it does not have the act, however, unless both it itself exists and the particulars in which it exists; as heat existing in water and wood existing.