Biological essentialism? No thanks

P. Godfrey-Smith (left) and M. Devitt (right)

A few weeks ago my CUNY Graduate Center’s colleague Michael Devitt gave a colloquium entitled “Individual essentialism in biology,” which was followed by a response/commentary by Peter Godfrey-Smith by the title “Modality, essence, and biology.” I thought it was a really interesting example of two top notch philosophers going at each other, respectively defending and criticizing a given central thesis, in the best tradition of analytical philosophy (no, I do not mean this as a sneer). It was also, however, a rather surreal experience for a biologist turned philosopher of science such as myself. I mean, essentialism, seriously?

Essentialism is the notion that there are some attributes that are necessary to the identity or function of a given entity, and in the Western tradition is usually traced back to Aristotle and, before him, Plato. Plato’s idealism, his notion of a realm of abstract Forms of which the world as we experience it is a pale reflection, is a form of essentialism. But the kind of essentialism that has been most debated throughout the last couple of millennia is Aristotle’s, which American linguist George Lakoff characterized as the idea that some properties make the thing what it is, and without which it would not be that kind of thing. An essential property of a triangle, for instance, is that the sum of its internal angles amounts to 180 degrees; the essence of the element oxygen is that it has an atomic number of 8 (i.e., its nucleus is made of 8 protons).

In philosophy, however, that sort of essentialism has gone the way of the dodo, because it applies to very few things, which do not even include chemical elements (given the existence of isotopes). Michael, therefore, wasn’t trying to revive Aristotle and apply him to contemporary biology. What, then, was he trying to do? (If you want a lot of details, here is his full 2008 paper on this topic.)

Michael’s opening shot was to say that Linnaean taxa, and especially (but not only) species, have essences that are at least in part intrinsic, underlying, and genetics. He promptly acknowledged that the consensus among biologists is of a rejection of such talk, but he shrug that off (literally, when I pointed it out to him during the q&a) with a “too bad for biologists, then.” (Incidentally, it is also the consensus among philosophers of biology.)

I find this approach rather troubling. I thought that time was long past when philosophers could tell scientists what to think while ignoring the scientific aspects of the question. In this case, for instance there are no Linnaean taxa “out there” (so to speak). Ever since the 1970s and ’80s the consensus among systematists has been that taxa are simply convenient more or less arbitrary containers, useful to orient the limited human mind among the bewildering variety of biological forms. But what biologists recognize as descriptively and explanatory relevant are clades, that is continuously branching lineages resulting from evolutionary processes. Look, for instance, at this simplified view of the cladogenesis that has given rise, among others, to our own species:

Chimpanzees belong to the genus (a Linnaean taxon) Pan, we belong to the genus Homo, and these two species, together with gorillas, orangutans and gibbons belong to the superfamily (another Linnaean taxon) Hominoidea. But there is no biological sense in which the genus Homo is “equivalent” (meaning, it is the same sort of essential thing) as the genus Pan. And even less so is our “genus” anything like a genus of plants, say Achillea (a member of the family Asteraceae), like this individual (from the species Achillea millefolium, also a taxon not at all equivalent, in essence, to the species Homo sapiens, or to Pan troglodytes):

At any rate, Michael defined his concept of essentialism in this way: “A property P is the essence of being an F if and only if anything is an F in virtue of having P.” While logically crystal clear, Michael not once throughout his talk gave an example of an essential biological property, and when I asked him directly he said that none has been discovered. Yet.

Devitt discriminated among intrinsic essences (like the atomic number that identifies the element oxygen), partly intrinsic and partly extrinsic essences (a pencil is defined by the materials of which it is made, internal, as well as by the function that characterizes it, external), and relational essences (being Australian is a matter of being in a certain relation with a particular geographical location).

He is, of course, aware that both biologists and philosophers of biology reject talk of essentialism, maintaining that biological taxa are best thought of as arbitrary breaks in an underlying continuous evolutionary process, as discussed above. Surprisingly, however, he claims that the consensus among his opponents “says strikingly little, and nothing plausible, about what precisely the historical component [to the identification of taxa] is.” I’m not sure what Michael was looking for, here. Cladistic theory is highly precise and quantitative, and so is evolutionary theory — particularly in the mathematized form known as population genetics. So I’m at a loss even imagining why he thinks there is anything amiss in the consensus view.

Devitt’s next step was to introduce a Kripkean view of individual essentialism. (Saul Kripke was actually sitting in the audience, and when asked about it he said he did not really recognize Devitt’s account of biological essentialism as particularly Kripkean. But I’m no expert on Kripke, so I will sidestep that particular issue.)

Michael’s concern, as he put it, was with “what timeless properties could an object not have failed to have, and what properties could it have lacked while still timelessly existing?” For a biologist, the answer to this question is an empty set: there are no timeless properties in the contingent world of biology, pace recent attempts at mathematical Platonism that I have previously criticized.

Kripke comes into play because according to him — as recounted by Devitt — both the origin and the substance of which an object is made are essential to it (that, and something to do with the idea of modality, see below). In this spirit, Michael added, “it is essential to the Queen’s zygote not just that it is constituted of human genetic material of some sort, but of the particular genetic material of that zygote.”

Let’s set aside that there is no such thing as “the Queen’s zygote,” but at most a zygote that, through a particular combination of historical accidents and cultural influences will, eventually give us a female individual of the human species that some misguided Brits will refer to as “the Queen.” What Michael is saying here presents no problem whatsoever for the anti-essentialist consensus: a particular zygote is the result of a particular series of evolutionary and developmental events, which could have gone otherwise, thus originating another zygote (which in turn may or may not have given rise to a Queen). End of the story, no essence required.

Devitt then continued by providing two arguments, one in favor of intrinsic individual essentialism, the other in favor of historical individual essentialism. Right there, however, we run into yet another problem. Michael is following biologist Ernst Mayr’s sharp distinction between proximate and ultimate causes: the proximate cause of, say, a tiger’s stripes is the particular genetic makeup of tigers; the ultimate cause of the stripes is whatever evolutionary (i.e., historical) series of processes led to that phenotype (e.g., adaptation by natural selection, if it turns out that it is advantageous to have stripes in a typical tiger environment).

But plenty of people have convincingly argued that Mayr’s distinction is far too sharp: genetic-developmental processes affect evolutionary trajectories while at the same time also being a result, generation by generation, of those trajectories. Development is an evolutionary mechanism, the basis of the incredibly fertile field of research known as “evo-devo” (evolution of development). Thus the very distinction between these two types of individual essentialism that Michael makes is, again, based on a shaky appreciation of both biology and philosophy of biology. (Here, incidentally, is my take of the proximate-ultimate distinction.)

At any rate, Devitt considers the case of Benji the (hypothetical) tiger to explain his views on intrinsic and historical individual essentialism. He says that: “the essential nature of Benji, probably unknown, causes him, in his environment, to be striped. What nature? If our concern is structural, an intrinsic nature … The same intrinsic nature or essence that (partly) makes something Benji (partly) explains both why he is striped and being Benji is explanatory.” (The latter part means that the fact that a particular tiger is striped, in Devitt’s account, is due to the fact that he is Benji, a particular individual.)

I find this to be entirely unhelpful. First, notice that Michael admits that he has no clue to what the essential nature of Benji is to begin with. Second, we actually have a pretty darn good account of what makes not just Benji, but most tigers, striped: structurally speaking, it is their particular genetic makeup in interaction with their particular environment, throughout the process of development. While the details may be difficult to fill in, there is absolutely no mystery here. Moreover, this account also explains the exceptions, that is, those individual tigers who are not striped: they either have a mutation that inhibits the formation of stripes during normal development or, less likely in this specific example, have experienced developmental environments that were not suitable to the formation of stripes, given the present genetic background.

What about historical individual essentialism? For Devitt, “if our concern is historical, with what led to there being Benji with those properties, the explanatory nature must be historical. The same history that (partly) makes the organism Benji causes Benji to be striped. That’s why Benji is explanatory.”

Fine, but that “same history” is, in fact, nothing other than a sequence of gene-development-environment interactions that are also explanatory in the structural sense. Once more: no mystery, no need for talk of essences. The latter simply does not add anything to either a biological or a philosophical account of what is going on, it simply obfuscates things by introducing an as yet unknown, and highly vaguely defined “essence.” Why?

Next, Michael moves from individual essentialism to what he calls essential membership. He says: “[consider] Benji and his property of being striped, a property typical of tigers in their environment. A part of the intrinsic component of Benji’s essence explains why he has the property of being striped. That part of the intrinsic component of the essence of tigers also explains why tigers have that property of being striped. The ‘sum’ of all such parts of Benji’s essence, is the intrinsic component of the essence of tigers.” And moving from structural to historical concerns: “organisms of a certain intrinsic kind evolve into organisms of another intrinsic kind, until we reach the taxon in question” (emphasis in the original).

All of this is a fancy, unclear, and consequently not very helpful way to say what every biologist would say. I’ll rephrase it precisely to make the point: “[consider] Benji and his phenotypic property of being striped, a property typical of tigers in their environment. The genetic component of Benji’s developmental system explains (in part) why he has the property of being striped. That genetic component (variable within the species) also explains (in part) why tigers have that property of being striped. … Organisms of a certain average genetic makeup evolve into organisms of another average genetic makeup, until we reach the (provisional) current state of affairs.”

See? No essences, no mysteries.

Time now finally to turn to Peter Godfrey-Smith’s response to Michael Devitt’s talk.

Peter began by taking on Michael’s reference to Kripke’s philosophy of modality (see this section of a larger essay on modal epistemology in the Stanford Encyclopedia of Philosophy). Peter’s take is that modality — the way or mode in which something exists — plays a role in our talk of causation, and makes sense of our intuition that we see events as “surrounded by a cloud of possibilities.” For instance: the window broke because I accidentally kicked a soccer ball in its direction. But it was possible that I had not kicked the ball in such a manner, and that therefore the window would still be intact. But what does “possible” mean here? If you are a determinist in metaphysics, it cannot mean that I could have done otherwise, at the least not without violating the laws of cause and effect in this universe. But surely there is a logical sense in which I could have done otherwise, meaning that it was not a logical necessity that I thus kicked the ball. Kripkean modal talk then helps us both to organize the actual, as Peter put it, and of making sense of unrealized possibilities: there are nearby worlds (we shall leave their ontological status undecided) in which I did not kick the ball in a manner that led to the breaking of the window.

That, Godfrey-Smith said, is a good use of modality. A bad use, by contrast, includes talk of essences. That, of course, is precisely the use of Kripkean modality made by Devitt (and to which, as I said above, Kripke himself, who was present at the talk, seemed to object).

Peter then moved to consider Michael’s concept of essence. As we have seen, Michael rejects the rigid Aristotelian idea of essences, and would “like to be as thin as possible on the modal front. [For Devitt] essences have a certain explanatory role.” One immediate problem, then, is that “explaratoriness is a matter of degree. A matter of more or less. [It is] also relative — explanatory in this context but not that one. [And] essences are not like this.” Exactly. It seems at times that Devitt’s concept of essence is so “thin” that it is hard to see why it would count as an essence.

[Michael’s refrain here is that he is not wedded to talk of essence, and that something like “nature” (of a thing) would do. But Peter points out that he uses the word “nature” very much in the sense of an essence, and I would further add that if Michael really did drop that talk there would be little left to disagree with him and we could all go out for a beer.]

Peter continued: “If you have a scholastic view of the world, it is a reasonable project to try to sort through the clutter of different sorts of importance of properties, to find essences. If you don’t have a view like that, it makes less sense. You just have various explanatory roles, and facts about how we talk: ‘if it lacked F we would not call it an F.'” This is a rephrasing of my objection above that one could simply drop the word “essence” from what Michael is saying about stripes and tigers, replace it with an account of gene-development-environment interactions, and be done with it, nothing lost in terms of explanation, much gained in terms of clarity. (Also notice that in contemporary philosophy the word “scholastic” is not a complimentary one…)

More from Peter, referring to Michael’s example of Benji the tiger and his stripes: “the tiger’s stripes are not themselves essential. They are conspicuous accidental features. Easy for that tiger to never have had stripes. [This type of] properties are caused by a mix of external and internal, but with a big role for internal specifics — the genome. Why is the cause of those features an essence? What is lost by denying that it is?” Precisely nothing, I’d say.

And more, along the same lines: “In the tiger quote [from Devitt] remove ‘essential’ and the quote is fine. Understand ‘nature’ in terms of ‘its actual make-up.’ … The properties Devitt calls ‘essences’ are good explainers, in certain contexts, mixed in with other properties that explain other things.”

Godfrey-Smith concludes with an analogy between species, like Pan troglodytes (the chimpanzee) and human lineages, say the Churchills.

What sort of things is the Churchill family, Winston & co.? “A scattered particular, it seems. We have a sense of other possibilities surrounding their actual features and activities. Winston might not have been PM. The Churchills left London on Friday but they could have decided to stay in town.” And so on. “Had they lived in another century would they have not been the Churchills? Even if they came out similar looking-ancestors, in that other century?”

“Think of the chimps as like the Churchills,” said Peter. “Being a chimp is analogous to being a Churchill. They are the same sort of thing. Whatever sort of modal cloud surrounds the Churchills, the chimps get something similar. … The chimps present at a later time — the slice of the chimps at time t — can be very different with respect to the properties of the individual animals than the chimps at an earlier time. Evolution is open-ended.”

Exactly. And in order to understand evolution, and to describe its products at any given time, we need no talk of essences, at all.

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