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?
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;
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·