17 Aug 2015

Somers-Hall, (4.5), Deleuze’s Difference and Repetition, ‘4.5 Second Example: The Organism as Biological Idea (184–5/233–4)’, summary

by Corry Shores
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[The following is summary. All boldface, underlining, and bracketed commentary are my own. Proofreading is incomplete, so please forgive my typos and other distracting mistakes. Somers-Hall is abbreviated SH and Difference and Repetition as DR.]

Summary of

Henry Somers-Hall

Deleuze’s Difference and Repetition:
An Edinburgh Philosophical Guide

Part 1
A Guide to the Text

Chapter 4. Ideas and the Synthesis of Difference


4.5 Second Example: The Organism as Biological Idea (184–5/233–4)



Brief summary: 
There are three critical features of “the Idea”: 1) its parts by themselves are undetermined, but 2)  become so through and by their reciprocal relations, of which 3) there is a great variety of possible spatio-temporal actualizations. The second of Deleuze’s three examples is Geoffroy Saint-Hilaire’s homological model of evolutionary anatomy. In Cuvier’s comparative anatomy, parts that are similar have similar names, but when they have dissimilar form and function, they get different names. Yet, as species evolve from other species, they will have certain parts whose form and function have altered, but which maintain the same relational place in the entire system as their prior instantiation did. So when we only classify the parts based on form and function, we lose a sense of their evolutionary descent. Geoffroy’s alternative model of anatomy, however, keeps these evolutionary links. For him, there is a transcendental structure, which is a template not for the parts themselves but rather for their relations. Each instantiation in different species will have different forms and functions, but the parts will also maintain the same relations to the other parts. So for Cuvier, the fin of a fish and the arm of a man are different anatomical parts, given that they look very different and they serve different roles. However, for Geoffrey, they are analogous in their structural relation to the rest of their respective skeletons, and thus his model allows us to see the evolutionary descent. Geoffrey’s model also exhibits the three traits of the Idea, since 1) the parts have no sensible or conceptual determination on their own in the abstract “transcendental” template, but 2) they gain determination when understood in terms of the basic relations between parts, and 3) many possible instantiations of these relations have and still can actualize in the evolution of species. Deleuze thinks that Geoffrey’s model is still too tied to actual instantiations, but that genetics is an improvement, since it is less so.





Previously Deleuze gave his first example of the Idea. The second example

is derived from a nineteenth-century debate over the nature of the organism. This was the debate as to whether comparative anatomy should understand the structure of organisms in terms of what are known as analogies or in terms of homologies
(SH 144-145)

[For more on this topic, see these very excellent sections of Somers-Hall’s Hegel, Deleuze, and the Critique of Representation. Dialectics of Negation and Difference: Pt3.Ch8.Sb6 ‘Deleuze, Geoffroy, and Transcendental Anatomy’ and Pt3.Ch8.Sb7 ‘Teratology and Teleology’. Selected parts and more elaboration can be found in the comments section to the entry for section 1.8 of Deleuze’s Difference and Repetition.] SH explains:

For traditional (and pre-evolutionary) comparative anatomy, the names of the parts of animals are, to a certain extent, derived analogically from other animals, archetypally with man. On a model dating back to Aristotle, we define what an organ is by looking at the functional role it plays in allowing the organism to perpetuate itself. Parts are thus defined by their relationship to the whole. The importance of this relationship is made clear by one of the most important comparative anatomists of the nineteenth century, Georges Cuvier, who claims that ‘it is in this dependence of the functions and the aid which they reciprocally lend one another that are founded the laws which determine the relations of their organs and which possess a necessity equal to that of metaphysical or mathematical laws’ (Cuvier, quoted in Coleman 1964: 67). When the function or form of the parts differ, however, a different term must be assigned to the part in question. Thus, although there is a similarity between the fins of a fish and the arm of man, on a teleological account, the functional and structural differences mean that different terms must be applied to each. This teleological account proves itself to be problematic in terms of evolutionary theory, since evolution often involves the change of function of the same structure between different creatures.

[I might be missing the point, but it seems to be that an evolutionary theory needs to be able to account for the chain of development from one species to another, with (at least some of) the anatomical parts of the descendent being evolutionary variations on those of its ancestor. And, those variant parts may also serve a completely different function. In Cuvier’s system, we would give that anatomical part a different name, but in doing so, we lose a sense of the evolutionary descent from its ancestor. What we  need instead is model of anatomy which allows us to better grasp the lines of evolutionary development despite the stark differences in function and form of the parts from one species to its evolutionary descendent. Geoffroy St. Hilaire had a different way to understand the evolution of the anatomical parts, which proves better for this task. For him, we are to think of a basic template of a structure not for the parts themselves but instead for their relations. Many animals then are variations of this basic template, with drastic variations in the form and function of the parts, while still these parts are analogous to one another. Let us look at a diagram from a book that is making a similar point.

“The hand and the arm of man are similar to the hand and arm of the ape. We find the same plan in the forefoot of the rat, the elephant, the horse and the opossum. We can identify the same parts in the forefoot of the lizard, the frog (fig 3), and even, though less certainly, in the pectoral fins of fishes. Comparison does not end here. We find similarities in the skull and back bones of these same animals; in the brain; in the digestive system; in the heart and blood vessels; in the muscles” (Morton p.8).

Morgan. Geoffrey homology p8 or so

“Fig. 3. Limb skeletons of extinct and living animals, showing the homologous bones: 1, salamander; 2, frog; 3, turtle; 4, Aetosaurus; 5, Pleisiosaurus; 6, Ichthyosaurus; 7, Mesosaurus; 8, duck. (After Jordan and Kellogg.)” (Morton p.8)

In this original text, the author is making a point about comparative anatomy, which it seems is different from Geoffrey’s model. However, we still see in this diagram how the anatomical parts each themselves are different in form and function, but their overall relations to one another are maintained in each case. Thus, the same part that becomes a fin on a fish also becomes an arm or leg on a human.]

Now, one of the key conceptual developments that made the theory of evolution possible was Geoffroy St. Hilaire’s positing of homologies between different parts of organisms. Rather than seeing an organism as defined by the form or function of parts, Geoffroy, a contemporary of Cuvier, saw it as defined by the relations between parts. By focusing on relations rather than functions, Geoffroy was able to provide an account that explains one of the key results of evolutionary theory – that the same structure can change its function in different organisms (fins becoming arms, for instance). Geoffroy didn’t relate organisms to one another directly to generate his account of homologies, but rather posited a transcendental structure of an ideal organism that other organisms were instantiations of (he called his approach ‘transcendental anatomy’).(SH 145)

[SH then moves to what Deleuze sees in Geoffroy’s model. I do not follow it perfectly well, so I will quote it below. It seems the point is that the transcendental structure is somehow like a field of differential relations, and as a whole the model has the three traits of an idea: 1) On the abstract level of the “transcendental structure,” each of the “parts” is really like a juncture of relations between possible instantiations. So in the transcendental model there is a relation which would be between parts that in the instantiation of the human is the relation between the arm bones and the rest of the skeleton, while in the instance of the fish the relation stands between the fin and the rest of the skeleton. But these abstract place-holders in the transcendental structure have no meaningful “content” by themselves. Thus the parts are indeterminate on their own, but have some sensible meaning when understood in terms of how they form relations. And so, 2) the elements are determinable only in their reciprocal relations. And 3) there are countless evolutionary variations of these same differential relations. The last point about genetics I am not grasping so well. It seems that Deleuze is saying that for Geoffroy, since the homologies are always actual, that they are too much about the actual to constitute a good example for the Idea. However, the field of genetics perhaps is somehow more about the field of differential variation on the level of coding and thus is a better example for the Idea. Please read to be sure of the meaning:]

Deleuze’s interpretation of Geoffroy’s work rests on what he calls Geoffroy’s dream, ‘to be the Newton of the infinitely small, to discover “the world of details” or “very short distance” ideal connections beneath the cruder play of sensible and conceptual differences and resemblances’ (DR 185/233). He claims that what Geoffroy is aiming at with his emphasis on connections is a field of differential elements (the ideal correlates of the bones) forming specific types of relations (the connections | which are central to Geoffroy’s account). On this basis, Deleuze claims that Geoffroy’s transcendental anatomy functions like an Idea, with its three characteristics. The elements of the Idea ‘must have neither sensible form nor conceptual signification’, and transcendental anatomy fulfils this requirement due to the fact that what is important is not the sensible properties of the bones, which vary in different creatures, but their relations. Second, ‘these elements must be determined reciprocally’, which means that what is central is not the bones themselves, but the connections they hold with other bones, what Geoffroy calls the ‘unity of composition’. Third, ‘a multiple ideal connection, a differential relation, must be actualised in diverse spatio-temporal relationships, at the same time as its elements are actually incarnated in a variety of terms and forms’. Deleuze emphasises that homologies do not exist directly between actual terms, ‘but are understood as the actualisation of an essence, in accordance with reasons and at speeds determined by the environment, with accelerations and interruptions’ (DR 184/233). That is, we discover a homology between two creatures by recognising that the actual parts of both organisms are actualisations of the same transcendental essence, the unity of composition, rather than by an analogical correlation of actual terms, as in comparative anatomy. As Deleuze notes, this approach finds its parallels in genetic theory, where genes gain their significance from their relations to one another. In fact, genetics represents an advance over Geoffroy’s account in that for him the transcendental correlates of bones, according to Deleuze, ‘still enjoy an actual, or too actual, existence’ (DR 185/233–4). The Idea in this case therefore allows us to determine in what way diverse phenomena (different organisms) are related to one another.

Citations from:

Somers-Hall, Henry. Deleuze’s Difference and Repetition. An Edinburgh Philosophical Guide. Edinburgh: Edinburgh University, 2013.

Or if otherwise noted:

Deleuze, Gilles. Difference and Repetition, trans. Paul Patton, New York: Columbia University Press, 1994/London: Continuum, 2004.

Somers-Hall, Henry (2012) Hegel, Deleuze, and the Critique of Representation. Dialectics of Negation and Difference. Albany: SUNY.


Coleman, William (1964), Georges Cuvier: Zoologist, Cambridge, MA: Harvard University Press.

Morgan, Thomas Hunt. A Critique of the Theory of Evolution. Princeton/London: Princeton University Press / Humphrey Milford Oxford University Press, 1916.
Available at the Internet Archive:




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