Isagoge: Chapter 4 — Of Property

The remaining chapters are fairly short, and this is no exception. I’ve used the word property in the previous blog posts on the Isagoge; here, Porphyry defines it. The word has four senses:

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:

1. Properties peculiar to a species though not to every member, such as writing blog posts: only human beings do it, but not all human beings.

…that also which happens to a whole species, though not to that alone, as to man to be a biped:

2. Properties shared by all members of the species, but not confined to that species, as being bipedal.

…that again, which happens to a species alone, and to every (individual of it), and at a certain time, as to every man to become grey in old age:

3. Properties shared by all members of the species at some point in their history. This strikes me as a subset of sense #2.

…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.

4. Properties shared by all members of a species, and only by members of that species, as the ability to laugh.

Sense #4 is the narrowest sense:

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.

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