Isagoge: Chapter 7 — Of the Community and Distinction of Genus and Difference

I confess, I’ve been bogging down in Porphyry, not because he’s hard as because he’s dull; and I’ve been spending time on other books. But I want to finish the things I start, especially in this arena, so once more into the breach!

So: Genus and Difference, compare and contrast. Let’s go.

It is common to genus and difference to be comprehensive of species, for difference also comprehends species, though not all such as the genera; 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.

Discounting the species “divinity”, as we’ve had to do in the previous parts of the Isagoge, this is straightforward. All species of animal are animals; all species rational beings are rational. Thus, genus and difference both comprehend species. Given that a species is the combination of a genus and a difference, this only makes sense.

When we say that they both comprehend species, what does that mean?

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.

Simply, I can predicate animal of all animal species; I can predicate rational of all rational species.

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.

Right. If I can’t predicate animal of a being, I can’t predicate any animal species of it; and if I can’t predicate rational of a being, I can’t predicate any rational species of it.

So, now, what are the differences?

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.

Genus is predicated of more things than difference–than any difference within that genus, anyway. (A genus like animal is simply a species defined by the parent genus and difference, e.g., animate body; and so the difference animate will have the same extension as animal. But the extension of rational is clearly much less than the extension of animal. The same is true of species, property, and accident.

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.

The genus comprehends all of the differences within it, that is, all of them include the genus within their meaning; but none of the differences comprehend the entire genus. And if I should say, this being is not a member of this genus, then I’ve said that none of the differences in this genus can be predicated of it, but not the other way around. The genus still has meaning and can be conceived of, even in all of the differences which apply to it are denied.

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.

Here, he seems to be using difference in the wider sense, not merely as the specific difference.

How useful it is to know any of the above is, I can’t say.

2 Responses to “Isagoge: Chapter 7 — Of the Community and Distinction of Genus and Difference”

  1. If this is dull, don’t forget that it is a commentary to help introduce (Isagoge is literally “introduction”) the Categories of Aristotle, making things more precise and explicit. Because it is so basic, you have probably picked up a lot from reading the works of St Thomas and his disciples/commentators.

    That said, if you feel bogged down, I would skip it and move to something that grabs your interest. “Pleasure in the doing puts perfection in the work”, Aristotle writes. There is of course a place for discipline, but in an area of self-study such as this, keep your interest as keen as possible.

    Just my $0.02.

    Sorry I disappeared for a while, lost my job at the beginning of Christmas and then had my family in town.

  2. I’ve picked up one or two things from ol’ Porphyry, so I don’t want to give up yet. Part of the reason I’ve been moving slowly is that I’ve been hitting other books in addition, including (just starting) the Sertillanges book mentioned on Just Thomism. (And I’ve felt like my brain is running at about 50% speed this week.)