Tag Archives: cladistics

Aristotle: Is “Non-feathered” a Genus of Animals?

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In the last post I primarily addressed Aristotle’s objection to dichotomous division, a taxonomic method that Platonists used to determine the kinds of animals there are and where any particular animal kind fits, an enterprise roughly equivalent to the animal-classification that for contemporary biology results in the designation of genus and species.  In particular, amongst Aristotle’s objections to dichotomous division, he says that grouping birds into, say, feathered and non-feathered, results in the absurdity that the latter does not exist

And yet it is necessary to divide by privation, and the dichotomists do divide [in this way].  But there is no difference of a privation qua privation.  For it is impossible for there to be species of what is not, for example of “non-footed” or of “non-winged” just as there are species of “footed” and “winged.”  Furthermore it is necessary that species belong to a generic difference.  For if they do not, why would they belong to a generic difference and not a specific difference? (Aristotle, Parts of Animals, 642b21-26).(1)

The objection substantively amounts to this: because a privation does not exist, e.g. “non-winged,” there cannot be any species subsequently derived from it.  And, as the concluding question makes clear, if in fact no pair of species can be divided from it, then this means that, e.g. “non-winged,” is a species.  This is evidently false, however, because “non-winged” is as indeterminate a species for ancient taxonomy as it would be for modern biology.

However, what if Platonists appealed to Aristotelian privation in making a case for dividing privation?   In his Physics Aristotle says this:

But white comes to be from the non-white, and not from everything [that happens to be non-white] but from black or from something between black and white, and an educated man comes to be from something that is not educated, but not just from anything that is not educated, but rather from an uneducated man, unless this happens incidentally.  Again the white turns into the non-white, and not into the chance non-white but into the black or an intermediate (Physics 188a36-188b6). (2)

Now Aristotle is clearly, in context, discussing how things come to be, and more particularly how this generation comes about from opposites.  A black beard, for example, comes to be white, where this whiteness is explicable by saying it comes to be from “non-white,” yet not just any non-white (as say, the number 1 is non-white), but from the opposite of white, black, or an intermediate, gray.

Nevertheless it seems plausible that this concept of privation, although employed to a very different purpose in the Physics than in our taxonomic concerns, establishes that we can use privation as a faithful ontological characterization of things.  If that is the case, there is no reason we cannot use “non-feathered” as a genus from which we can further dilineate more species.

Would Aristotle accept this understanding of privation from Physics for his work on animal classification?

More broadly, does this eliminate Aristotle’s original objection to privation as a method of division?

(1)
Translation mine:
Ἔτι στερήσει μὲν ἀναγκαῖον διαιρεῖν, καὶ διαιροῦσιν οἱ
διχοτομοῦντες. Οὐκ ἔστι δὲ διαφορὰ στερήσεως ᾗ στέρησις·
ἀδύνατον γὰρ εἴδη εἶναι τοῦ μὴ ὄντος, οἷον τῆς ἀποδίας ἢ τοῦ
ἀπτέρου ὥσπερ πτερώσεως καὶ ποδῶν. Δεῖ δὲ τῆς καθόλου δια-
φορᾶς εἴδη εἶναι· εἰ γὰρ μὴ ἔσται, διὰ τί ἂν εἴη τῶν καθόλου
καὶ οὐ τῶν καθ’ ἕκαστον;

(2)
Translation mine:
ἀλλὰ λευκὸν μὲν γίγνεται ἐξ οὐ λευκοῦ, καὶ τούτου οὐκ ἐκ παντὸς
ἀλλ’ ἐκ μέλανος ἢ τῶν μεταξύ, καὶ μουσικὸν οὐκ ἐκ μου-
σικοῦ, πλὴν οὐκ ἐκ παντὸς ἀλλ’ ἐξ ἀμούσου ἢ εἴ τι αὐτῶν
ἐστι μεταξύ. οὐδὲ δὴ φθείρεται εἰς τὸ τυχὸν πρῶτον, οἷον
τὸ λευκὸν οὐκ εἰς τὸ μουσικόν, πλὴν εἰ μή ποτε κατὰ συμ-
βεβηκός, ἀλλ’ εἰς τὸ μὴ λευκόν, καὶ οὐκ εἰς τὸ τυχὸν ἀλλ’
εἰς τὸ μέλαν ἢ τὸ μεταξύ·

Aristotelian Objections to Platonic Animal Classification

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Deep into his criticism of the dichotomist method of division, Aristotle and his opponents are deciding what genera and species of animals truly exist.  To discover these natural kinds of animals, the appropriate method of division, that is, a way of separating animals from each other into categories precisely representative of species, is under contentious dispute.

And yet it is necessary to divide by privation, and the dichotomists do divide [in this way].  But there is no difference of a privation qua privation.  For it is impossible for there to be species of what is not, for example of “non-footed” or of “non-winged” just as there are species of “footed” and “winged.”  Furthermore it is necessary that species belong to a generic difference.  For if they do not, why would they belong to a generic difference and not a specific difference? (Aristotle, Parts of Animals, 642b21-26).(1)

Some say that species should be divided into two with each of the two branches always branching off into two more, until the point where a termination results in an actual species.  For example, if we begin by dividing animals into footed and non-footed, and then the footed into bi-pedal and poly-pedal, we can then divide bi-pedal into split-toed and web-toed, etc.  Advocates of this process of dichotomy are called dichotomists.

Aristotle, on the other hand, advocates opening more than one line of division, not limiting himself to the dichotomist method which follows only one of two branches at every step.  In this section of the text, Aristotle, believing that dichotomists commit themselves to “privation” as well, argues that privation is incompatible with dichotomy.  By privation Aristotle simply means a negation of some difference, such as in the example above, “non-footed” as contrasted with “footed.”  The privation objection demonstrates Aristotle’s characteristic subtlety and insight as he, perhaps ironically, forces his opponents into a logical dichotomy: Either the privation is an actual species of animal or it is not, and further division must continue.

Now if we continue with the first option, that there is an actual species of privative animal, say, non-footed, then this seems precluded for the following reasons.  Most obviously, something which is not cannot be said to be.(2) It is also the case that being non-footed would not pick out a species, as it could generically apply to a worm, a whale and a snake, not to mention the variations of each animal.  And yet, even if it were that case that “non-footed” faithfully picked out only a single animal (pretend that earthworms are the only non-footed animals), it is unclear how non-footed is an essential property of earthworms.  After all, earthworms are also furless, wingless, knuckle-less, eyelash-less, and money-less, to name just a few things.

On the other hand, if the privation is not a species, but must be further divided, then Aristotle clearly precludes this possibility in the above text.  Why this is so is unclear, but I will have a preliminary answer in the next post, as well as offer up a Platonic solution which could perhaps stand up under Aristotle’s scrutiny.

 

REFERENCES:

 

(1)
Translation mine:
Ἔτι στερήσει μὲν ἀναγκαῖον διαιρεῖν, καὶ διαιροῦσιν οἱ
διχοτομοῦντες. Οὐκ ἔστι δὲ διαφορὰ στερήσεως ᾗ στέρησις·
ἀδύνατον γὰρ εἴδη εἶναι τοῦ μὴ ὄντος, οἷον τῆς ἀποδίας ἢ τοῦ
ἀπτέρου ὥσπερ πτερώσεως καὶ ποδῶν. Δεῖ δὲ τῆς καθόλου δια-
φορᾶς εἴδη εἶναι· εἰ γὰρ μὴ ἔσται, διὰ τί ἂν εἴη τῶν καθόλου
καὶ οὐ τῶν καθ’ ἕκαστον;

(2)
I assume A. would approve this, for he says something logically analogous in the case where we suppose that privations are divided into further species.

Problems with Plato: Animal Diversity and Robust Division

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Yesterday, I brought up some difficulties that occur in the first method of division presented in Aristotle’s Parts of Animals.

“Some construe the individual species by dividing the group into two differentiae.  In one way this is not easy, in another impossible.  For of some there will be only one differentia, but the other terms will be superfluous, such as in the case of footed, two-footed, footed with parted toes.  For this last differentia alone is proper” (Parts of Animals, 642b5-9)?

Before discussing the difficulties again, it must be taken into consideration, of course, that since he is embarking on a criticism of Academic methodology, any philosophical difficulties arising from this process of division might in fact owe to chinks in the armor which Aristotle himself was trying to illuminate.  He might very well be bringing some of these difficulties to light without proceeding to explain them.

A couple of the difficulties I brought up yesterday were:

“It is not true that the concept of “footed with parted toes” includes “two footed” and “footed.” viz. lizards

It is also clear from his use of the term elsewhere, that “footed with parted toes (σχιζόπους)” is not meant to designate any particular species alone, such as humans (cf. HA 593a28, concerning birds).”

A mistake one could make, at least in Aristotle’s construal of the division, is failing to recognize that at every point of the division a particular animal is being guided through each step of the division.  So, in this example, one has to have in mind a particular animal which one leads through each “gate” of the division.  There is no abstracted “two-footed,” in other words; differentiae always belong to real animals.  (This is one reason why Aristotle says shortly that there cannot be divisions of non-being, for no animals correspond to such a division.)

In fact, Aristotle will return to this division at 643b29 ff.  He says there two interesting things.  He affirms that with this method both (a) that only one differentia will be arrived at (b) it is impossible for one differentia to be adequate for a species.  In light of this he brings up the same “footed, two-footed, footed with parted toes,” tri-partite division.  Only this time he applies it to “man” (ἄνθρωπος).  He points out that man is many other things besides possessing parted toes.

Both of these judgments merge into a single criticism: there is a need for there to be multiple differentia, although the Academic method cannot allow for it, it is not so much wrong, as it is inadequate.  One reason for a need for more lines of division is that there are many homologous features in animals.  Similar body plans, parts, and functions means that there will be many animals with split-toed feet.  Because of this diversity there will be a corresponding need for a robust method of division.