My slow reading of the full paragraph on pg. 31 of DR was incomplete in my last slow reading post. Let's look at the closing sentences:
In effect, the quality of the essence [of a species] is sufficiently special to make the genus [under which is falls] something other, and not simply of another quality. It is thus in the nature of genera to remain the same in themselves while becoming other in the differences which divide them. Difference carries with itself the genus and all the intermediary differences. The determination of species links difference with difference across the successive levels of division, like a transport of difference, a diaphora (difference) of diaphora, until a final difference, that of the infima species (lowest species), condenses in the chosen direction the entirety of the essence and its continued quality, gathers them under an intuitive concept and grounds them along with the term to be defined, thereby becoming itself something unique and indivisible [atomon, adiaphoron, eidos]. In this manner, therefore, the determination of species ensures coherence and continuity in the comprehension of the concept. (31, original brackets in italics)
Goodness. Let's try to unpack Deleuze's thinking.
I don't really want to go back over my summary of (Deleuze's summary of) Aristotle (see here and here), so suffice it to say that Deleuze is dramatizing whether or not his ancient predecessor's notion of "specific difference meets . . . the requirements of a harmonious concept and an organic representation." And what are these requirements? According to the sentences early in the paragraph, these requirements include purity, intrinsic-ness, quality, synthesis, mediation, and productivity. I'm not sure if Deleuze is referencing Aristotle's own notion of conceptual harmony here, but the categories he offers make sense as virtues of a representational metaphysical system. For a concept to be in harmony and in organic concert with other concepts, for instance, it must relate to the form of the thing it purports to represent (since the thing's content may differ in small, insignificant ways from other species-identical things). Thus, purity. It must also capture the essence of the thing (not mere accidental features of the thing's matter). Thus, intrinsic-ness and quality. It must unify various predicates into one complex notion. Thus, synthesis. It must relate the sense of the thing in language or thought. Thus, mediation. It must participate in the ever-growing representation of existing things. Thus, productivity.
But specific difference, following Aristotle's logic closely, does more than just meet these requirements. It meets them reflexively. It does not just refer to form, for instance; it is form. It does not just relate to quality; it is the quality of the essence ("a very special quality"). It does not merely mediate. For (Deleuze's) Aristotle, "it is itself mediation, the middle term in person" (31). Specific difference—as a harmonious concept—is the key to conceptual harmony itself; it is "a synthetic and constitutive predicate . . . that . . . carr[ies] with itself that which it attributes." Attributive rather than attributed. Additive rather than added. Rather than merely being a concept that refers to and mediates the idea of all the essences of all things in themselves, Aristotle's specific difference constitutes the activity of representational organicism and harmony.
The long passage above continues to dramatize this idea and to think through the activity of specific difference. This form of difference does not just provide the proper context of contrariety between species (as I state in my previous post), for the essential qualities of all genus-identical species—the differences between them, difference which synthesize and produce our concepts of them—act retroactively on the genus that purportedly contains, precedes, and relates them to one another. In the bodies of two things from two different species, the genus they share simultaneously "remain[s] the same"—it is the condition that makes them comparable in the first place—and "becom[es] other" than itself "in the differences which divide" it from itself. This is to say that a genus is not just a neutral relation or category but a mutable occasion and re-occasioning of specific difference, which Aristotle (remember) has defined as the greatest and most perfect form of difference. A genus is carried along by "a transport of difference, a diaphora (difference) of diaphora" (a metadifference? a second-order difference?). This differential transport lends "coherence and continuity in the comprehension of the concept" of different species under a single genus—species which can no longer be divided (infirma species)—as well as the reflexive, peculiar, special concept of "specific difference" in itself.
Deleuze places an endnote after the first sentence of the long passage above ("In effect, the quality of the essence is sufficiently special to make the genus something other, and not simply of another quality"). Here is the endnote:
Porphyry, Isagoge, para. 9, pp. 42-43: 'The difference 'rational' added to animal makes another essence [allo], but the difference 'moving' only make something qualitatively different from resting, so that the one makes a difference-in-essence, the other only a difference-in-quality.' (308n3)
He includes no explanation, so what are we to make of it?
Let's try to dramatize this example, using Deleuze's exemplary dramatization of Aristotle's specific difference. "Rational" is not just a difference that helps us determine the concept of a species (is a tiger rational or irrational? is it capable of rationality?). Moreover, it alters the genus "animal," which categorizes both rational and irrational species. What we understand animal to be fundamentally changes when "rational" or "irrational" is added to the determination of a species because this distinction hits upon the essence of tiger or human or jellyfish in ways that "mobile" or "immobile" do not. Thus the greatest and most perfect difference—specific differences, differences in the essences of things, differences in our concepts of things (rational vs. irrational, not mobile vs. immobile or black vs. white)—does not just contribute qualities to genera that remain fundamentally the same. Deleuze's Aristotle implicitly invents—through this notion of specific difference—a concept of genera as multiplicities that are intuitively coherent but essentially diverse and dispersed. They are sustained by the transport of a (meta)difference that actively divides, distributes, and links specific differences and that is conceptually and organically pure, intrinsic, synthetic, qualitative, mediate, and productive.
As fun as this dramatization is, Deleuze will go on to challenge how coherent its concept of specific difference actually is. How, for instance, does the definition of contrariety as the most perfect difference jive with Aristotle's definition of contradiction as the primary form of opposition? How can something "perfect" also be secondary? How can a "perfect" thing, in other words, simultaneously be "most" and relatively perfect?
Reading on . . .