Evolving Thoughts

Evolution, culture, philosophy and chocolate! John Wilkins' continuing struggle to come to terms with impermanence... "Humanus sum, nihil humanum a me alienum puto" - Terence

Wednesday, March 22, 2006

Essentialism revisited

In my long-delayed book on the species concept, I find myself concurring with historians like Polly Winsor and Ron Amundson that there never was an "essentialist" view of species before Darwin. In fact it is my opinion that essentialism in biology postdates Darwin, and was in fact due to the revival of Thomism among German and French speaking Catholic biologists who were reacting to the metaphysical views of people like Herbert Spencer and Ernst Haeckel. Thomism, or neo-scholasticism as it was called at the time, relied upon the doctrines of Aristotle as interpreted by Thomas Aquinas, particularly in his text
De ente et essentia (On being and essence). As such the essence of a thing was that which was necessary to be that sort of thing. So species had, said these revisionists, an essence that could not change, and so they denied evolution. This was not a majority view even among Catholic scholars, but it is the first appearance of essentialism as a justification for species fixism I can find.

So why did the story arise that prior to Darwin everyone was an essentialist? There are two reasons - one a matter of history, the other a matter of, well, the uses of history by biologists. Ernst Mayr, the main architect of this essentialist myth, studied in Germany as an undergraduate in the early 1920s, under an ornithologist named Erwin Streseman. This was the high water mark of Thomist inspired essentialism and anti-evolutionism, although I have a book dated 1955 by a Jesuit arguing this line. It's my opinion that Mayr overgeneralised his undergraduate experience, and then read the prior literature through those spectacles.

The second reason is that biologists often use history in a triumphalist manner, to indicate that they or their school is the apex of thinking on a topic. In this case, Darwin acts as the John Baptist of biology, and before him, all was in darkness. The apex is, of course Ernst Mayr (he's rather shameless about declaring this).

But were there essentialists before Darwin? Why does this myth seem to hold up? The reason is that history-plundering evolutionists misread the literature. There most certainly was a diagnostic essentialism before Darwin - if you specify a set of identification key characters, then that is a kind of essence. It's just not a substantive one. Even Darwin himself contributed to that, although it derives basically from the way Linnaeus set up the "definitions" of species in Systema Naturae and other works. Darwin was a member of the so called Strickland Committee, which determined how classification was to be done in 1842, and from which modern taxonomic codes derive. It's a very harmless kind of essentialism, based on practice rather than scientific ontology. And every systematist who had a number of specimens had to deal with the increasing problem of variation, code or no code.

The reason why I mention this is that there have been a number of interesting blogs lately on the matter, based on what psychologists like Susan Gelman call "essentialism". This is a matter of cognitive behaviour - we tend to select a single criterion or property as the way to identify kinds, and deal with the variation later, as the early nineteenth century systematists did.

The first blog is from Mixing Metaphors, on a paper by Andrew Shtulman on the differences between naive and informed views of evolution. The conclusion is (rightly) that our predilections to average across variation to generate a "type" inhibits our ability to understand class concepts like species and their evolution.

Sirus takes this up and develops what he calls Minimum Classificatory Essentialism. In the first of four blogs, he starts by discussing the difference between type essentialism and shared-nature essentialism. It is the latter that Mayr targeted, incidentally, but it is the former that was actually employed by pre- and post-Darwinian biologists. In the second, he discusses the nature of creationist kinds attacked by Darwin. I actually think Darwin chose this target to make the line of argument easier - the competing Platonist morphology of Owen and Oken was a harder target to identify, let alone attack. In blog three, Sirus discusses whether Darwin was an essentialist, and notes a confusion between type and essence in Mayr.

I'd like to comment on this for a minute. A "type" can be a number of things. It can be a definition. It can be a generalised description. or it can be an exemplar. Mayr often attacked cladism as being "typological" (I don't have my notes to hand, but I think this was a term introduced by George Gaylord Simpson, and adapted by Mayr). It is - it uses a single instance as a type for the species. So what? The likelihood is that if you select enough characters, the specimen/s used will cover the consensus characters of the species (or taxon), so individual idiosyncracies will average out. Types are pretty harmless. If you use types as exemplars, then you might be led to make poor inferences, I guess, but there are all kinds of safeguards used by biologists, and they have been with a few failures all the way back to Linnaeus. Most of the time type specimens were pretty representative of the taxon, even if sexual morphs got mistaken once in a while for different species or, like (my favourite case) the seal Arctocephalus pusillus, so named because the type specimen was small, turn out to be a juvenile.

Types do not need to, and did not have as far back as they were used, essences. Everybody was aware of deviation from the type. Locke even has a discussion in the Essay for heaven's sake, and when philosophers know this, it isn't secret specialist knowledge. The book by Peter F. Stevens, The development of biological systematics: Antoine-Laurent de Jussieu, nature, and the natural system (New York: Columbia University Press 1994) discusses how types were not fixed or essentialistic in some detail.

Enough. Back to Sirus' discussion. He mistakenly claims that Darwin was a "type" essentialist. He was not. But he was a typologist, as were and are all biologists, even those who study variation (or else how do you know you are studying variation in the same taxon?).

The remainder of the series, blog four, discusses how Shtulman investigated attitudes of people to evolution based on (psychological) essentialism, and it is a worthy study. I'll let you go read it for yourself. Sirus graciously links to my presentation on the history of essentialism. I only add self-servingly that you can listen to my talk as well.

How to conclude? I believe that essentialism is not the boogieman it is claimed to be. It is even philosophically respectable to say that species have essences in Aristotle's sense of the what-it-is-to-be that the Latins gave the translation of "essentia" to. Of course they do (although I think it is more likely to be the nature of the species as a whole rather than a shared essence in each organism). And this doesn't thereby make species intensional classes of the kind that cannot evolve. Individuals have essences too (contra Aristotle) - I am whatever it is that makes me who I am. So are species. And like them I can change...