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Porphyry, Introduction (or Isagoge) to the logical Categories of Aristotle (1853) vol. 2. pp.609-633.

[Translated by Octavius Freire Owen, M. A. of Christ Church, Oxford.  Rector of Burstow, Surrey; and Domestic Chaplain to the Duke of Portland]


Chap. I. --Object of the writer, in the present Introduction.

Since it is necessary, Chrysaorius, both to the doctrine of Aristotle's Categories, to know what genus, difference, species, property, and accident are, and also to the assignments of definitions, in short, since the investigation of these is useful for those things which belong to division and demonstration,2 I will endeavour by a summary briefly to discuss to you, as in the form of introduction, what on this subject has been delivered by the ancients, abstaining, indeed, from more profound questions, yet directing attention in a fitting manner, to such as are more simple. For instance, I shall |610 omit to speak about genera and species, as to whether they subsist (in the nature of things) or in mere conceptions only; whether also if subsistent, they are bodies or incorporeal, and whether they are separate from, or in, sensibles,3 and subsist about these,4 for such a treatise is most profound, and requires another more extensive investigation.5 Nevertheless, how the ancients, and especially the Peripatetics, discussed these and the other proposed subjects, in a more logical manner, I will now endeavour to point out to you.

Chap. II. --Of the Nature of Genus and Species 6

Neither genus nor species appear to be simply denominated, for that is called genus which is a collection of certain things, subsisting in a certain respect relatively to one thing, and to each other, according to which signification the genus of the |611 Heraclidae is denominated from the habitude from one, I mean Hercules, and from the multitude of those who have alliance to each other from him, denominated according to separation from other genera. Again, after another manner also, the principle of the generation of every one is called genus, whether from the generator or from the place in which a person is generated, for thus we say that Orestes had his genus from Tantalus, Hyllus from Hercules, and again, that Pindar was by genus a Theban, but Plato an Athenian, for country is a certain principle of each man's generation, in the same manner as a father. Still, this signification appears to be most ready,7 for they are called Heraclidae who derive their origin from the genus of Hercules, and Cecropidae who are from Cecrops; also their next of kin. The first genus, moreover, is so called, which is the principle of each man's generation, but afterwards the number of those who are from one principle, e. g. from Hercules, which defining and separating from others, we call the whole collected multitude the genus of the Heraclidse.

Again, in another way that is denominated genus to which the species is subject, called perhaps from the similitude of these; for such a genus is a certain principle of things under it, and seems also to comprehend all the multitude under itself. As then, genus is predicated triply, the consideration by philosophers is concerning the third, which also they explain by description, when they say that genus is that which is predicated of many things differing in species, in answer to what a thing is, e. g. |612 animal. For of predicates some are predicated of one thing alone, as individuals, for instance, "Socrates," and "this man," and "this thing;" but others are predicated of many, as genera, species, differences, properties, and accidents, predicated in common, but not peculiarly to any one. Now genus is such as "animal," species as "man," difference as " rational," property as " risible," accident as "white," "black," "to sit." From such things then, as are predicated of one thing only, genera differ in that they are predicated of many, but on the other hand, from those which are predicated of many and from species, (they differ) because those species are predicated of many things, yet not of those which differ in species, but in number only, for man being a species, is predicated of Socrates and Plato, who do not differ from each other in species, but in number, while animal being a genus is predicated of man, and ox, and horse, which differ also in species from each other, and not in number only. From property, moreover, genus differs because property is predicated of one species alone of which it is the property, and of the individuals under the species, as "risible" of man alone, and of men particularly, for genus is not predicated of one species, but of many things, which are also different in species. Besides, genus differs from difference and from accidents in common, because though differences and accidents in common are predicated of many things, different also in species, yet they are not so in reply to what a thing is, but (what kind of a thing) it is. For when some persons ask what that is of which these are predicated, we reply, that it is genus; but we do not assign in answer differences and accidents, since they are not predicated of a subject, as to what a thing is, but rather as to what kind of a thing it is. For in reply to the question, what kind of a thing man is, we say, that he is rational, and in answer to what kind of a thing a crow is, we say that it is black, yet |613 rational is difference, but black is accident. When however we are asked what man is, we answer, an animal, but animal is the genus of man, so that from genus being predicated of many, it is diverse from individuals which are predicated of one thing only, but from being predicated of things different in species, it is distinguished from such as are predicated as species or as properties. Moreover, because it is predicated in reply to what a thing is, it is distinguished from differences and from accidents commonly, which are severally predicated of what they are predicated, not in reply to what a thing is, but what kind of a thing it is, or in what manner it subsists: the description therefore of the conception of genus, which has been enunciated, contains nothing superfluous, nothing deficient.8

Species indeed is predicated of every form, according to which it is said, "form is first worthy of imperial sway;"9 still that is called species also, which is under the genus stated, according to which we are accustomed to call man a species of animal, animal being genus, but white a species of colour, and triangle of figure. Nevertheless, if when we assign the genus, we make mention of species, saying that which is predicated of many things differing in species, in reply to what a thing is, and call species that which is under the assigned genus, we ought to know that, since genus is the genus of something, and species the species of something, each of each, we must necessarily use both in the definitions of both. They assign, therefore, species thus: species is what is arranged under genus, and of which genus is predicated in reply to what a thing is: moreover, thus species is what is predicated of many things differing in number, in reply to what a thing is. This explanation, however, belongs to the most special, |614 and which is species only, but no longer genus also,10 but the other (descriptions) will pertain to such as are not the most special. Now, what we have stated will be evident in this way: in each category there are certain things most generic, and again, others most special, and between the most generic and the most special, others which are alike called both genera and species, but the most generic is that above which there cannot be another superior genus, and the most special that below which there cannot be another inferior species. Between the most generic and the most special, there are others which are alike both genera and species, referred, nevertheless, to different things, but what is stated may become clear in one category. Substance indeed, is itself genus, under this is body, under body animated body, under which is animal, under animal rational animal, under which is man, under man Socrates, Plato, and men particularly. Still, of these, substance is the most generic, and that which alone is genus; but man is most specific, and that which alone is species; yet body is a species of substance, but a genus of animated body, also animated body is a species of body, but a genus of animal; again, animal is a species of animated body, but a genus of rational animal, and rational animal is a species of animal, but a genus of man, and man is a species of rational animal, but is no longer the genus of particular men, but is species only, and every thing prior to individuals being proximately predicated of them, will be species only, and no longer genus also. As then, substance being in the highest place, is most generic, from there being no genus prior to it, so also man being a species, after which there is no other species, nor any thing capable of division into species, but individuals, (for Socrates, Plato, Alcibiades, and this white thing, I call individual,) will be species alone, and the last species, and as we say the most specific. Yet the media will be the species of such as are before them, but the genera of things after them, so that these have two conditions, one as to things prior to them, according to which they are said to be their species, the other to things after |615 them, according to which they are said to be their genera. The extremes on the other hand, have one condition, for the most generic has indeed a condition as to the things under it, since it is the highest genus of all, but has no longer one as to those before it, being supreme, and the first principle, and, as we have said, that above which there cannot be another higher genus. Also, the most specific has one condition, as to the things prior to it, of which it is the species, yet it has not a different one, as to things posterior to it, but is called the species of individuals, so termed as comprehending them, and again, the species of things prior to it, as comprehended by them, wherefore the most generic genus is thus defined to be that which being genus is not species, and again, above which there cannot be another higher genus; but the most specific species, that, which being species is not genus, and which being species we can no longer divide into species; moreover, which is predicated of many things differing in number, in reply to what a thing is.11

Now, the media of the extremes they call subaltern species and genera, and admit each of them to be species and genus, when referred indeed to different things, for those which are prior to the most specific, ascending up to the most generic, are called subaltern genera and species. Thus, Agamemnon is Atrides, Pelopides, Tantalides, and lastly, (the son) of Jupiter, yet in genealogies they refer generally to one origin, for instance, to Jupiter; but this is not the case in genera and species, since being is not the common genus of all things, nor, as Aristotle says, are all things of the same genus with respect to one summum genus. Still, let the first ten genera be arranged, as in the Categories, as ten first principles, and even if a person should call all things beings, yet he will call them, so he says, equivocally, but not synonymously, for if being were the one common genus of all things, all things would be synonymously styled beings, but the first principles being ten, the community is in name only, yet not in the definition |616 also belonging to the name: there are then ten most generic genera. On the other hand, the most specific they place in a certain number, yet not in an infinite one, but individuals which are after the most specific are infinite; wherefore, when we have come down to the most specific from the most generic, Plato exhorts us to rest,12 but to descend through those things which are in the middle, dividing by specific differences; he tells us however to leave infinites alone, as there cannot be science of these. In descending then, to the most specific, it is necessary to proceed by division through multitude, but in ascending to the most generic, we must collect multitude into one, for species is collective of the many into one nature, and genus yet more so; but particulars and singulars, on the contrary, always divide the one into multitude, for by the participation of species, many men become one man; but in particulars and singulars, the one, and what is common, becomes many; for the singular is always divisive, but what is common is collective and reductive to one.13

Genus then, and species, being each of them explained as to what it is, since also genus is one, but species many, (for there is always a division of genus into many species,) genus indeed is always predicated of species, and all superior of inferior, but species is neither predicated of its proximate genus, nor of those superior, since it does not reciprocate. For it is necessary that either equals should be predicated of equals, as neighing of a horse, or that the greater should be predicated of the less, as animal of man, but the less no longer of the greater, for you can no longer say that animal is man, as you can say that man is animal. Of those things however whereof species is predicated, that |617 genus of the species will also be necessarily predicated, also that genus of the genus up to the most generic; for if it is true to say that Socrates is a man, but man an animal, and animal substance, it is also true to say that Socrates is animal and substance. At least, since the superior are always predicated of the inferior, species indeed will always be predicated of the individual, but the genus both of the species and of the individual, but the most generic both of the genus or the genera, (if the media and subaltern be many,) and of the species, and of the individual. For the most generic is predicated of all the genera, species, and individuals under it, but the genus which is prior to the most specific (species), is predicated of all the most specific species and individuals; but what is species alone of all the individuals (of it), but the individual of one particular alone.14 Now, an individual is called Socrates, this white thing, this man who approaches the son of Sophroniscus, if Socrates alone is his son, and such things are called individuals, because each consists of properties of which the combination can never be the same in any other, for the properties of Socrates can never be the same in any other particular person;15 the properties of man indeed, (I mean of him as common,) may be the same in many, or rather in all particular men, so far as they are men. Wherefore the individual is comprehended in the species, but the species by the genus, for genus is a certain whole, but the individual is a part, and species |618 both a whole and a part; part indeed of something else, but a whole not of another, but in other things, for the whole is in its parts. Concerning genus then, and species, we have shown what is the most generic, and the most specific, also what the same things are genera and species, what also are individuals, and in how many ways genus and species are taken.

Chap. III. -- Of Difference.

Difference may be predicated commonly, properly, and most properly: for one thing is said to differ from another in common from its differing in some respect in diversity of nature, either from itself, or from something else; for Socrates differs from Plato in diversity of nature, and himself from himself when a boy, and when become a man, also when he does any thing, or ceases to do it, and it is always perceived in the different ways in which a thing is somehow effected. Again, one thing is said to differ properly from another, when one differs from another by an inseparable accident; but an inseparable accident is such as blueness, or crookedness, or a scar become scirrhous from a wound. Moreover, one is most properly said to differ from another, when it varies by specific difference, as man differs from horse by specific difference, i. e. by the quality of rational. Universally then every difference acceding to a thing renders it different, but differences common and proper render it different in quality, and the most proper render it another thing. Hence, those which render it another thing are called specific, but those, |619 which make it different in quality, are simply (called) differences, for the difference of rational being added to animal, makes it another thing, (and makes a species of animal,) but difference of being moved makes it different in quality only from what is at rest, so that the one renders it another thing, but the other only of another quality.16

According then, to the differences which produce another thing do the divisions of genera into species arise, and the definitions arising from genus and such differences are assigned. On the other hand, as to those which only make a thing different in quality, diversities alone consist, and the changes of subsistence of a thing; beginning then, again, from the first, we must say that of differences some are separable, others inseparable, thus to be moved, and to be at rest, to be ill, and to be well, and such as resemble these, are separable, but to have a crooked, or a flat nose, to be rational, or irrational, are inseparable differences. Again, of the inseparable, some exist per se, others by accident, for rational, mortal, to be susceptible of science, are inherent in man per se, but to have a crooked or flat nose, accidentally, and not per se. Wherefore, such as are present per se, are assumed in the definition of substance, and effect a different thing, but what are accidental arc neither taken in the definition of substance, nor render a thing another, but of another quality. Those too, which are per se, do not admit of the more and less, but the accidental, even if they be inseparable, admit of intention and remission, |620 for neither is genus more and less predicated of that of which it is the genus, nor the differences of genus according to which it is divided. For these are such as complete the definition of each thing, but the essence of each is one and the same, and neither admits of intention, nor remission; to have however a crooked or a flat nose, or to be in some way coloured, admits both of intension and remission. Since then, there are three species of difference considered, some indeed separable, but others inseparable, again, of the inseparable, some are per se, but others accidental, moreover of differences per se, some are those according to which we divide genera into species, but others according to which the things divided become specific:--thus of all such differences per se of animal as these, animated and sensitive, rational and irrational, mortal and. immortal, the difference of animated and sensitive is constitutive of the essence of animal, for animal is an animated substance, endued with sense, but the difference of mortal and immortal, and that of rational and irrational, are the divisive differences of animal, for through these we divide genera into species: yet these very differences which divide the genera are constitutive and completive of species. For animal is divided by the difference of rational and irrational, and again, by the difference of mortal and immortal; but the differences of rational and mortal are constitutive of man, but those of rational and immortal of God, those again, of mortal and irrational, of irrational animals.17 Thus also, since the differences of animate and inanimate, sensitive and void of sense, divide the highest substance, animate and sensitive added to substance, complete animal, but animate and deprived of sense, form plant; since then, the same  |621 differences taken in one way become constitutive, but in another divisive, they are all called specific.

These indeed are especially useful for divisions of genera, and for definitions, yet not with regard to those which are inseparable accidentally, nor still more with such as are separable.18 And indeed defining these, they say that difference is that by which species exceeds genus, e. g. man exceeds animal in being rational and mortal, for animal is neither any one of these, (since whence would species have differences?) nor has it all the opposite differences, (since otherwise the same thing would at the same time have opposites,) but (as they allege) it contains all the differences which are under it in capacity, but not one of them in energy, and so neither is any thing produced from non-entities, nor will opposites at the same time subsist about the same thing.

Again, they define it (difference) also thus: difference is that which is predicated of many things differing in species in answer to the question, of what kind a thing is,19 for rational and mortal being predicated of man, are spoken in reply to what kind of thing man is, and not as to the question what is he. For when we are asked what is man, we properly answer, an animal, but when men inquire what kind of animal, we say properly, that he is rational and mortal. For since things consist of matter and form, or have a constitution analogous to matter and form, as a statue is composed of brass, matter, but of figure, form, so also man, both common and specific, consists of matter analogous to genus, and of form analogous to difference, but the whole of this, animal, rational, mortal, is |622 man, in the same manner as the statue there. They also describe it thus, difference is what is naturally adapted to separate things which are under the same genus, as rational and irrational separate man and horse, which are under the same genus, animal. Again, they give it in this way: difference is that by which each singular thing differs, for man and horse do not differ as to genus, for both we and horses are animals, but the addition of rational separates us from them; again, both we and the gods 20 are rational, but the addition of mortal separates us from them. They however who more nicely discuss what pertains to difference, say that it is not any casual thing dividing those under the same genus, but such as contributes to the essence, and to the definition of the essence of a thing, and which is part of the thing. For to be naturally adapted to sail is not the difference, though it is the property of man, since we may say that of animals, some are naturally adapted to sail, but others not, separating man from other animals; yet a natural ability to sail does not complete the essence, neither is a part of it, but only an aptitude of it, because it is not such a difference as those which are called specific differences. Wherefore specific differences will be such as produce another species, and which are assumed in explaining the very nature of a thing: and concerning difference this is sufficient.

Chap. IV. --Of Property.

Property they divide in four ways: for it is that which happens to some one species alone, though not to every (individual of that species), as to a man to heal, or to geometrize: that also which happens to a whole species, though not to that alone, as to man to be a biped: that again, which happens to a species alone, and to every (individual of it), and at a certain time, as to every man to |623 become grey in old age: in the fourth place, it is that in which it concurs (to happen) to one species alone, and to every (individual of it), and always, as risibility to a man; for though he does not always laugh, yet he is said to be risible, not from his always laughing, but from being naturally adapted to laugh, and this is always inherent in him, in the same way as neighing in a horse. They say also that these are validly properties, because they reciprocate, since if any thing be a horse it is capable of neighing, and if any thing be capable of neighing it is a horse.

Chap. V. -- Of Accident.

Accident is that which is present and absent without the destruction of its subject. It receives a two-fold division, for one kind of it is separable, but the other inseparable, e. g. to sleep is a separable accident, but to be black happens inseparably to a crow and an Ethiopian; we may possibly indeed conceive a white crow, and an Ethiopian casting his colour, without destruction of the subject.

They also define it thus; accident is that which may be present and not present to the same thing; |624 also that which is neither genus, nor difference, nor species, nor property, yet is always inherent in a subject.

Chap. VI. --Of Things common and peculiar to the Five Predicates.

Having discussed all that were proposed, I mean, genus, species, difference, property, accident, we must declare what things are common, and what peculiar to them. Now it is common to them all to be predicated, as we have said, of many things, but genus (is predicated) of the species and individuals under it, and difference in like manner; but species, of the individuals under it; and property, both of the species, of which it is the property, and of the individuals under that species; again, accident (is predicated) both of species, and individuals. For animal is predicated of horse and ox, being species, also of this particular horse and ox, which are individuals, but irrational is predicated of horse and ox, and of particulars. Species however, as man, is predicated of particulars alone, but property both of the species, of which it is the property, and of the individuals under that species; as risibility both of man, and of particular men, but blackness of the species of crows, and of particulars, being an inseparable accident; and to be moved, of man and horse, being a separable accident. Notwithstanding, it is pre-eminently (predicated) of individuals, but secondarily of those things which comprehend individuals.

Chap. VII. --Of the Community and Distinction of Genus and Difference.

It is common to genus and difference to be comprehensive of species, for difference also comprehends species, though not all such as the genera; |625 for rational, though, it does not comprehend irrational, as animal does, yet it comprehends man and divinity, which are species. Whatever things also are predicated of genus as genus, are predicated of the species under it, and whatever are predicated of difference as difference, will be also of the species formed from it. For animal being a genus, substance is predicated of it as of a genus, also animated, and sensible, but these are predicated of all the species under animal, as far as to individuals. As moreover, rational is difference, the use of reason is predicated of it, as of difference, yet the use of reason will not be predicated of rational only, but also of the species under rational. This too is common, that when genus or difference is subverted, the things under them are also subverted, for as when animal is not, horse is not, nor man, thus also, when rational is not, there will be no animal which uses reason. Now, it is the property of genus to be predicated of more things than difference, species, property, and accident are, for animal (is predicated) of man and horse, bird and snake, but quadruped of animals alone, which have four feet; again, man of individuals alone, and capacity of neighing of horse alone, and of particulars. Likewise, accident of fewer things: yet we must assume the differences by which the genus is divided, not those which complete, but which divide the essence of genus.

Moreover, genus comprehends difference in capacity, for of animal one kind is rational, but another irrational, but differences do not comprehend genera. Besides, genera are prior to the differences under them, wherefore they subvert them, but are not co-subverted with them. For animal being subverted, rational and irrational are co-subverted, but differences no longer co-subvert genus, for even if all of them should be subverted, yet we may form a conception of animated, sensible substance, which is animal. |626 

Yet more, genus is predicated in reference to what a thing is, but difference in reference to what kind of a thing it is, as was observed before; besides there is one genus according to every species; e. g. of man, animal (is the genus), but there are many differences, as rational, mortal, capable of intellect and science, by which he differs from other animals. Genus also is similar to matter, but difference to form: however since there are other things common and peculiar to genus and difference, these will suffice.

Chap. VIII. --Of Community and Difference of Genus and Species.

Genus and species possess in common, (as we have said,) the being predicated of many things, but species must be taken as species only, and not as genus, if the same thing be both species and genus. Moreover, it is common to them both to be prior to what they are predicated of, and to be each a certain whole; but they differ, because genus indeed comprehends species, but species are comprehended by, and do not comprehend genera, for genus is predicated of more than species. Besides, it is necessary that genera should be presupposed, and when formed by specific differences, that they should consummate species, whence also genera are by nature prior. They also co-subvert, but are not co-subverted, for species existing, genus also entirely exists, but genus existing there is not altogether species; genera too, are indeed univocally predicated of species under them, but not species of genera. Moreover, genera exceed, from comprehending the species which are under them, but species exceed genera by their proper differences; |627 besides, neither can species become most generic, nor genus most specific.

Chap. IX. --Of Community and Difference of Genus and Property.

Both to genus and to property it is common to follow species, for if any thing be man, it is animal, and if any thing be man, it is risible. Likewise to genus, to be equally predicated of species, and to property, (to be equally predicated) of the individuals which participate it; thus man and ox are equally animal, and Anytus and Melitus risible.21 It is also common that genus should be univocally predicated of its proper species, and property of the things of which it is the property; still they differ, because genus is prior, but property posterior, for animal must first necessarily exist, afterwards be divided by differences and properties. Also genus indeed is predicated of many species, but property of one certain species of which it is the property. Besides property is reciprocally predicated of that of which it is the property, but genus is not reciprocally predicated of any thing, for neither if any thing is an animal, is it a man, nor if a thing be animal is it risible, but if any thing is a man it is risible, and vice versa. Moreover, property is inherent in the whole species, of which it is the property, in it alone, and always, but genus in the whole species indeed of which it is the genus, and always, yet not in it alone; once more, properties being subverted do not co-subvert genera, but genera being subverted, co-subvert species, to which properties belong; wherefore, also those things of which there are properties, being subverted, the properties themselves also, are co-subverted. |628 

Chap. X. -- Of Community and Difference of Genus and Accident.

It is common to genus and accident to be predicated, as we have said, of many things, whether they (the accidents) be separable or inseparable, for to be moved is predicated of many things, and blackness of crows, and of Ethiopians, and of certain inanimate things. Genus however differs from accident, in that genus is prior, but accident posterior to species, for though an inseparable accident be assumed, yet that of which it is the accident is prior to the accident. Also the participants of genus participate it equally, but those of accident do not equally; for the participation of accidents accepts intension and remission, but not that of genera. Besides, accidents primarily subsist about individuals, but genera and species are by nature prior to individual substances. Moreover, genera are predicated of the things under them, in respect to what a thing is, but accidents in respect to what kind of a thing it is, or how each thing subsists; for being asked, what kind of man an Ethiopian is, you say that he is black; or how Socrates is, you reply that he is sick or well.

Chap. XI. --Of Community and Difference of Species and Difference.

We have shown then, wherein genus differs from the other four, but each of the other four happens also to differ from the rest, so that as there are five, and each one of the four differs from the rest, the five being four times (taken), all the differences would appear to be twenty. Nevertheless, such is not the case, but always those successive being enumerated, and two being deficient by one difference, from having been already assumed, and the three by two differences, the four by three, the five by four; all the differences are ten, namely, four, three, two, one. For in what genus differs from difference, species, property, and accident, we have shown, wherefore, there are four differences; also we explained in what respect |629 difference differs from genus, when we declared in what genus differs from it. What remains then, viz. in what respect it differs from species, property, and accident, shall be told, and three (differences) arise. Again, we declared how species differs from difference, when we showed how difference differs from species; also we showed how species differs from genus, when we explained how genus differs from species; what remains then, viz. in what species differs from property and from accident, shall be told: these, then, are two differences. But in what respect property differs from accident, shall be discovered, for how it differs from species, difference, and genus, was explained before in the difference of those from these. Wherefore, as four differences of genus with respect to the rest, are assumed, but three of difference, two of species, and one of property with regard to accident, there will be ten (differences altogether), of which, four we have already demonstrated, viz. those of genus, with respect to the rest.

Chap. XII. --The same subject continued.

It is common then to difference and species to be equally participated, for particular men partake equally of man, and of the difference of rational. It is also common always to be present to their participants, for Socrates is always rational, and always man, but it is the property of difference indeed to be predicated in respect to what kind a thing is of, but of species in respect to what a thing is, for though man should be assumed as a certain kind of thing, yet he will not be simply so, but in as far as differences according to genus constitute him. Besides, difference is often seen in many species, as quadruped in many animals, different in species, but species is in the individuals alone, which are tinder the species. Moreover, difference is prior to the species which subsists according to it, for rational being subverted, co-subverts man, but man being subverted, does not co-subvert rational, since there is still divinity. Further, difference is joined with another difference, |630 (for rational and mortal are joined for the subsistence of man,) but species is not joined with species, so as to produce some other species; for indeed a certain horse is joined with a certain ass, for the production of a mule, but horse simply joined with ass will not produce a mule.

Chap. XIII. -- Of Community and Difference of Property and Difference.22

Difference also and property have it in common to be equally shared by their participants, for rational are equally rational, and risible (equally) risible (animals). Also it is common to both to be always present, and to every one, for though a biped should be mutilated, yet (the term biped) is always predicated with reference to what is naturally adapted, since also risible has the "always" from natural adaptation, but not from always laughing. Now, it is the property of difference, that it is frequently predicated of many species, as rational of divinity and man, but property (is predicated) of one species, of which it is the property. Difference moreover follows those things of which it is the difference, yet does not also reciprocate, but properties are reciprocally predicated of those of which they are the properties, in consequence of reciprocating.

Chap. XIV. --Of Community and Difference of Accident and Difference.

To difference and accident it is common to be predicated of many things, but it is common (to the former) with inseparable accidents to be |631 present always and with every one, for biped is always present to man, and likewise blackness to all crows. Still they differ in that difference indeed comprehends but is not comprehended by species; for rational comprehends divinity and man, but accidents after a certain manner comprehend from their being in many things, yet in a certain manner are comprehended from the subjects not being the recipients of one accident, but of many. Besides, difference indeed docs not admit of intension and remission, but accidents accept the more and less; moreover contrary differences cannot be mingled, but contrary accidents may sometimes be mingled. So many then are the points common and peculiar to difference and the others.

Chap. XV. --Of Community and Difference of Species and Property.

In what respect species differs from genus and difference, was explained in our enunciation of the way in which genus, and also difference, differ from the rest; it now remains that we should point out how it (species) differs from property and accident. It is common then to species and property, to be reciprocally predicated of each other, since if any thing be man, it is risible, also if it be risible, it is man, still we have frequently declared that risible must be assumed according to natural adaptation to risibility. It is also common (to them) to be equally present, for species are equally present to their participants, and properties to the things of which they are properties, but species differs from property, in that species indeed may be the genus of other things, but property cannot possibly be the property of other things. Again, species subsists prior to property, but property accedes to species, for man must exist, in order that risible may: besides, species is always present in energy with its subject, but property sometimes also in capacity, for Socrates is a man always in energy, but he does not always laugh, though he is always naturally adapted to be risible. Once more, things of |632 which the definitions are different, are themselves also different, but it is (the definition) of species to be under genus, and to be predicated of many things, also differing in number, in respect to what a thing is, and things of this kind, but of property it is to be present to a thing alone, and to every individual and always.

Chap. XVI. --Of Community and Difference of Species and Accident.

To species and accident it is common to be predicated of many, but other points of community are rare, from the circumstance of accident, and that to which it is accidental, differing very much from each other. Now, the properties of each are these: of species, to be predicated of those of which it is the species, in respect to what a thing is, but of accident, in reference to what kind a thing is of, or how it subsists.23 Likewise, that each substance partakes of one species, but of many accidents, both separable and inseparable: moreover, species are conceived prior to accidents, even if they be inseparable, (for there must be subject, in order that something should happen to it,) but accidents are naturally adapted to be of posterior origin, and possess a nature adjunctive to substance. Again, of species the participation is equal, but of accident, even if it be inseparable, it is not equal; for an Ethiopian may have a colour intense, or remitted, according to blackness, with reference to an(other) Ethiopian.

Chap. XVII. -- Of Community and Difference of Property and Accident.24

It remains to speak of property and accident, for how property differs from species, difference, and |633 genus, has been stated. It is common then to property and inseparable accident not to subsist without those things in which they are beheld, for as man does not subsist without risible,25 so neither can Ethiopian subsist without blackness, and as property is present to every, and always, so also is inseparable accident. Nevertheless, they differ, in that property is present to one species alone, as the being risible to man, but inseparable accident, as black, is present not only to an Ethiopian, but also to a crow, to a coal, to ebony, and to certain other things. Moreover, property is reciprocally predicated of that of which it is the property, and is equally (present), but inseparable accident is not reciprocally predicated, besides, the participation of properties is equal, but of accidents one (subject partakes) more, but another less. There are indeed other points of community, and peculiarity of the above-mentioned (predicables), but these are sufficient for their distinction, and the setting forth of their agreement.

[This translation appears in volume 2 of The Organon, or logical treatises of Aristotle, with the introduction of Porphyry, published by Henry G. Bohn in London in 1853.

Note that only selected footnotes are included and no marginalia.  The urge to write a commentary on this text appears to overwhelm most translators, but since much of the material is either references to other pages in the book or refers to long obsolete texts on logic it has been omitted.]

1. 1  At the request of Chrysaorius, his pupil, who had recently met with the Categories of Aristotle, Porphyry wrote this introduction, in order to his comprehension of that treatise: nearly the whole of it is composed from the writings, and often almost in the very words of Plato. As philosophers reduced all things under ten common natures, as grammarians also, with respect to eight words, so Porphyry has comprehended every significant word, except such as are significant of individuals, under five terms. The five heads of predicables therefore, taken from this Isagoge, which was written in the third century, are an addition to the Aristotelian Logic, in part of which, (the Topics,) the doctrine laid down differs from that enunciated here, in several points, as Porphyry's view also differs from that of Aldrich. Upon the subject generally, the reader may compare Albertus Magnus de Praedicab. Aquinas. Occam Logica. Abelard de Gen. et Spec. ed Cousin. Trendelenb. Elem. Crakanthorpe's, Whately's, Hill's, and Wallis' Logics, also Boethius de Divisione.

2. 2   Dialectic, according to Plato, consists of four parts, division, definition, demonstration, and analysis; hence a treatise adapted to the formation of these, will be evidently useful to the dialectic of Plato. The difference between the dialectic of Plato and that of Aristotle, is noticed in the subsequent notes upon the Organon, and the reader will find the subject ably discussed in the introduction to Mansel's Logic; here we need only observe that Aristotle in the Topics, looks to opinion (in his treatment of dialectic), while Plato disregards it, and the former delivers many arguments about one problem, but the latter, the same method about many problems. Cf. Proclus. MSS. commentary on the Parmenides, Philip., Schol. p. 143, ch, 4; Waitz, vol. ii. p. 137.

3. 1  On the metaphysical part of this question, the opinions of philosophers are as vague as (I may add) they are unprofitable, hence the term "universals," is the best to be employed, as least liable to commit the logician to any metaphysical hypothesis; since the realist may interpret it of "substances," the nominalist of "names," the conceptualist of "notions." Cf. Occam, Log. p. 1, Albertus Magnus, Abelard. The agreement between the first and last, proves that there is no real difference between nominalism and conceptualism, since they were both. Vide also Mansel, Appendix A, where the authorities upon each side will be found quoted.

4. 2  Genus and species, in short all forms, have a triple subsistence, for they are either prior to the many, or in the many, or posterior to the many. Taylor. Philoponus, in his extracts from Ammonius, illustrates this as follows: Let a seal-ring be conceived, having the image of Achilles upon it, from which seal let there be many impressions taken in pieces of wax, afterwards let a man perceiving the pieces of wax to have all the impression of one seal, retain such impression in his mind: then the seal in the ring is said to be prior to the many; the impression in the wax to be in the many, and the image remaining in the conception of the spectator, after the many, and of posterior origin. This he applies to genus and species.

5. 3  Viz. metaphysics; it is, in fact, psychological. Cf. Leibnitz Meditat. de Cognit. Ver. opera. ed Erdmann. and Mansel's Prolegomena Logica.

6. 4  With this chapter compare ch. 5, of the Categories, and Top. i. 5 and 8, whence the discrepancies between the account of the predicables given by Arist. and this by Porphyry will appear, upon which see Mansel's comment. Log. App. A, p. 9. Cf. also Albertus Mag. de Predicab. Trac. 11, cap. 1, Metap. iv. 28.

7. 1 Ammonius remarks that, "It is worth while to doubt why Porphyry says that the first signification of genus appears to be the one easily adopted, and not the second signification, which is the habitude of one thing to one; since this nature first knows, for she first produces one thing from one, and thus many from many." But as Taylor observes, the second signification of genus, which is second with reference to us, is first to nature; for from Hercules, one man is first produced, and thus afterwards the multitude of the Heraclidae. Universally, whatever is first to nature is second to us, and vice versa, e. g. she begins with form and matter, then flesh and bone; we begin from man, so that things prior to nature are posterior to our knowledge, wherefore the first signification is clearer than the second.

8. 1 Porphyry does not recognise the distinction between "quale quid" and "quale," (cf. Aldrich, Abelard de Gen. et Spe. ed. Cousin,) but makes difference, property, and accident to be all predicated ἐϝ τῷ ὁποῖόν τὶ ἐστιν: Boethius distinguishes quale in substantia, from quale non in substantia. Moreover, Porphyry makes difference to be always predicated de specie differentibus; upon his consideration of property, vide note to ch. 4, Isagog.

9. 2 Athenaeus attributes this verse to Euripides. Vide Ath. lib. xiii. ch. 7.

10. 1 An infima species can be maintained by none consistently but a Realist. Vide Mansel, p. 21

11. 1 For the exemplification of the above, see the "Arbor Porphyriana," (sometimes called by the Greek logicians, the "ladder," κλίμαξ,) given at page 7, ch. 5, of the Categories, with the note.  [Note to the online text: vol. 1 can be found online at]

12. 1  See notes to pp. 6 and 8, Categor. An infima species implies a notion so complex as to be incapable of further accessions, the Realist maintains it to be the whole essence of the individuals of which it is predicated. Cf. Boethius; also Wallis, lib. i. 13, et seq.; Whately, b. ii. ch. 5, sect. 3 and 5.

13. 2  Cf. Mansel, pp. 18 and 21, note; Whately, p. 52, 138; Outline of Laws of Thought, p. 44; Stewart, Philo. of Human Mind, part i. ch. 4.

14. 1   Properly speaking, there cannot be more than one highest genus, which is a cognate term to every substance and quality supposed to exist; yet a subaltern genus may be relatively considered as a highest genus. Species, when resolved into its component parts, is found to be combined of genus and difference, and in different points of view, may be referred to different genera, also many species have no appropriate name, but are expressed by the combination of their constituent parts, genus and difference, e. g. "rectilinear-figure," " water-fowl;" indeed, some are denoted by the difference alone, as " repeater" (a watch which strikes the hour). Cf. ch. 3, Cat. note; Crakanthorpe, Log. lib. ii. Any singular term (denoting one individual) implies, (vide Whately, b. ii. ch. 5, 5,) not only the whole of what is understood by the species it belongs to, but also more, namely, whatever distinguishes that single object from others of the same species, as London implies all that is denoted by the term " city," and also all that distinguishes that individual city. Cf. Wallis, ch. 2.

15. 2   Hence, in describing an individual, we do not employ properties (which belong to a whole species), but generally, inseparable accidents, i. e. such as can be predicated of their subject at all times.

16. 1 According to Porphyry, difference is always predicated "de specie differentibus," and he recognises only a relative difference between two given species; thus "rational" is not the difference of man per se, but of man as distinguished from brutes. ...

17. 1 Porphyry's definition of man, "animal rationale mortale," was adopted by Abelard, Albertus Magnus, and Petrus Hispanus, though sometimes with the saving clause, that it must be understood with reference to the Stoical notions of the gods. Aquinas first removed the genus animal rationale from the Arbor Porphy., and limited rationality to man, distinguishing angels as intellectuales. Cf. Summa, p. 1; Qu. lviii. 3; Opusc. xlviii. Tract 1. In the Aristotelian definition of man, ζῷον πέζον δίπουν, the last would be regarded by him as a difference.

18. 1   Boethius agrees with Porphyry, that accidents, properly so called, are useless in definition, (vide Opera, p. 3,) accidental definition is, in fact, merely a description. Cf. Albert. 1. c. Occam, pt. i. ch. 27. The only proper definition is by genus and differentiae, hence all definable notions will be species. The definition here given of difference, as to its being the excess of species over genus, is clear, from a reference to what was stated in the last note of the preceding chapter.

19. 2   "Ratione ejus, quale quid est predicatur." Buhle; so Aldrich. There is no warranty, as we have observed, by Porphyry, for distinction between "quale quid" and "quale."

20. 1 "Rationales enim sumus et nos et Dii," vetus interpres Latinus. Commonly the word ἄγγελοι was substituted here, probably, as Casaubon conjectures, from the emendation of some Christian: Ammonius and Boethius (Comment, v.) attest that Porphyry wrote θεοὶ.

21. 1  The property of a subaltern genus is predicated of all the species comprehended in that genus; that of a lowest species is predicated of all the individuals which partake of the nature of that species: thus,

"Shape is the generic property of body, 
Growth is the generic property of living body, 
Voluntary motion is the generic property of animal, 
Risibility, the specific property of man." 

Vide Hill's Logic.

22. 1  Whately observes, "It is often hard to distinguish certain properties from differentia, but whatever you consider as the most essential to the nature of a species, with respect to the matter you are engaged in, you must call the differentia, as rationality to man, and whatever you consider as rather an accompaniment (or result) of that difference, you must call the property, as the use of speech seems to be a result of rationality. He adds also, that the difference is not always one quality, but is frequently compounded of several together, no one of which would alone suffice." Vide also Huyshe's Log., pp. 33, 34.

23. 2  Buhle retains the distinction here, between quid and quale quid, upon which, see notes on ch. 2 and 3. The reading is that of Julius Pacius, whom all later editors have followed: the Latin interpretation renders it, "accidentis vero in eo, quod quale quiddam, vel quomodo se habens."

24. 4  Accidents may be distinguished from properties by the very definitions given of them. The latter belong necessarily, and therefore universally, to an essence, whereas the former are those qualities which do not of necessity belong to any essence, but are mere contingencies. Huyshe. Vide also note ch. 4, and cf. Albert de Predicab. Tract, vi. cap. I.

25. 1   Risibility is considered to be so dependent upon rationality, as that the latter could not exist without the former, and if this were not so, the term risible would not be a property of man, but only an inseparable accident. Cf. Whately and Mansel.

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