II. Essentialisms in Biology
III. Essentialism in Darwin
Now, one might think from my having to go into all this background that I'm gearing up for some major criticism of the Shtulman paper (for the basic argument of the paper, see Chris's post again). But I'm not. The basic points of the paper seem to me to be very plausible. The background is primarily (1) for me to be more clear about essentialism; and (2) to emphasize just how careful we need to be when talking about essentialism. (See below for a few sources I've found since that do a better job than I at making one or two of my points.)
And we do need to be careful. For instance, what sort of essentialism does Shtulman have in mind when he talks about essentialism? It seems clear that he must be talking about type essentialism, since he thinks of it as being the positing of an ideal member of the family. He thinks of this as a sort of average (following Gould), and although type essentialists haven't generally seen the type as an average, this can be taken as correct for at least crude purposes. But the mechanisms he associates with essentialists in evolution -- transformationists, as he calls them -- are more like shared nature essentialism. This was why my first reaction on looking at one of Shtulman's diagrams (which Chris exhibits in his post) was, "Does that even make sense?" Remember, things are constrained by natures but constrained to types. Because of this, if a population is continuously changing it is quite reasonable to regard the type as being in more or less smooth transition throughout the change of the population: it depends on precisely how you think the type is determined (which has always been the trickiest issue in type essentialism), but it's a plausible first conclusion. However, types are not related to generations of a population by any sort of inheritance; you don't inherit a type, you resemble it. You do, however, inherit shared natures (that's precisely the point of inheritance, that you share something in common with the previous generation). So in the diagram Shtulman gives we find an implausible amalgam of type and shared nature essentialisms.
I haven't decided whether this is a lack of clarity in Shtulman, or a common confusion that he is faithfully reporting, or both. A confusion between shared nature and type is exactly the sort of confusion that one might expect of the general public; and, I suspect, it wouldn't be difficult to set up fairly basic situations in which people fail to distinguish properly between classifying by paradigm or type and classifying by features. So it is entirely possible that Shtulman is right that his transformationalists are committed to the sort of position his diagram suggests, in which essential types are given the job of natural essences. The result is a weird view in which things are caused to be what they are by their (independently changing) type. Perhaps this can be regarded as a form of vitalism. But, as Shtulman points out, his results suggest that transformationists actually haven't thought things through very carefully.
Shtulman doesn't use the term 'vitalism' but transformationism as he characterizes it involves the following characteristics:
1. Variation: Individual differences are nonadaptive or maladaptive deviations from type.
2. Inheritance: Organisms inherit any trait adaptive to the species as a whole.
3. Adaptation: Death of individuals prior to reproducitve maturity not important for adaptation.
4. Domestication: Domestication occurs not by selection but by manipulation of individuals over many generations.
5. Speciation: Morphologically distinct species do not share a common ancestor; morphologically similar species are linearly related.
6. Extinction: Background extinction (slow extinction over many generations) is not common.
Shtulman's results ended up dividing the evolutionary stance of the participants into three groups.
Transformationists tended to hold the above views.
Variationists tended to reject the above views and provide a view closer to standard scientific theory.
Pre-variationists tended to provide transformationist answers to the questions, but diverged from pure transformationists by tending somewhat variationist. The primary places where this variation tended to occur were inheritance and adaptation (p. 181):
Because the pre-variationists produced fewer ambiguous responses than the transformationists did...these diverences cannot be attributed to confusion or laziness on the part of the pre-variationists. Rather, they suggest that the pre-variationists held two variational beliefs that the transformationists did not: (1) that organisms inherit the traits of their parents regardless of their adaptive value and (2) that differential survival is relevant to species adaptation.
However, is it really true, as Shtulman says, that what is misleading the non-variationist groups is the same thing that led earlier biologists, like Lamarck, Cope, and Haeckel, astray, namely, that species have essences and that the essences of species change over time? Well, if we are talking about a minimal essentialisms like the MCE I suggested in my first post, we certainly aren't wrong to say that species have essences and that the essences of species change over time; because species are kinds of things that change over time, and they become different kinds of things. It can only be a narrower sort of essentialism that is at stake here. What is more, it isn't clear whether we are really dealing with essential types or natural essences. And, more importantly, it seems very unlikely that some of the biologists who were not variationists were 'led astray' by assumptions possessed by the transformationalists in Shtulman's study. For one thing, what led Lamarckians astray (and even Darwin) was not any position about essences; rather they were led astray by the apparent plausiblity of the claim that the actual use or disuse of organs by individuals always causes heritable changes in them. Further, this mistake gives a general view of natural history that is very similar to Darwin's. It is true that Lamarck has no real place for extinction (instead of becoming extinct, species transform into other species) and he did hold that evolution had a direction (from the simple to the complex). Haeckel had (very roughly) similar views. But it doesn't seem, at least on first glance, to be any particular position about essences that leads to it. Perhaps there is some such position (I certainly haven't studied Lamarck and Haeckel very extensively), but it's certainly not obvious that there is. The reason for these positions were apparent facts, not assumptions about essences. (And Haeckel was certainly nothing even vaguely like a vitalist; nor does he seem a particularly likely candidate for a strong form of essentialism, although, again, it depends on exactly what you mean.)
The issue is complicated; my point here is primarily that it seems misleading to say that earlier thinkers about evolution were misled by assumptions about essences.
Incidentally, having taken the trouble to struggle through the previous posts on my own, I came across a few things that could have helped. These presentation notes by John Wilkins (PDF) make some points similar to ones I had made, and a few in clearer ways (and he also gives the sense in which a modern biologist would be inclined to deny that species have essences, i.e., shared natures, which I did not). Levit and Meister have an interesting paper called The history of essentialism vs. Ernst Mayr's "Essentialism Story": A case study of German idealistic morphology (PDF). Ron Amundson has a paper called Typology Reconsidered: Two Doctrines on the History of Evolutionary Biology (PDF); it makes the important point, which I was trying to make in discussing Mayr but only gestured at, that in Darwin's era the typical 'type essentialist' (to use my term) or typology was in direct opposition to any robust theory of biological teleology; our bizarre tendency to conflate the two (and to conflate them both with independent special creation) is a result of historical events since then. And it must be recognized as a genuinely bizarre tendency.
It occurs to me, in reflection on these sources, that I should say something briefly about an assumption I was making about 'essentialism' in biology; namely, that it is closely connected to classification. In fact, it's only really because of classification that types and natures (essences) have ever been talked about in biology at all. However, it occurs to me that many people may not make this assumption. If 'essentialism' is closely connected to classification, it follows that even a very skeptical biologist must admit a lot of essentialism, and it becomes weird why anyone would make such a fuss about essentialism -- it can only be done if you are thinking about a very, very particular form of essentialism. So, if people aren't beginning their thinking about 'essentialism' from classification, where are they beginning it? It would seem from modern creationists (in the usual sense of the term 'creationist'). This is not, however, a good template for examining either the history of biology or our cognitive tendencies with regard to biology.
I've gotten away somewhat from Shtulman's paper, in part because, as I said, there's very little I find to disagree with in it. I'm still left uneasy about it, for the reason I gave above: we need to be very sophisticated when we talk about 'essentialism', because failure to do so brings in a perpetual danger of distortion. Above I questioned whether it was quite so clear that 'species have essences that change over kind' was really quite so problematic in the history of biology as Shtulman suggests; and that leaves another question, namely, whether it is doing quite as much work in the transformationist errors as Shtulman suggests. It's much more plausible there, I think, and just by what can be told from a mere amateur's glance, something like Shtulman's conclusions are suggested by his data. Nonetheless, I would be happier if a study like this were done with a greater sophistication about essences. From Shtulman's own analysis it's very difficult to see what's going on. Is it the use of typological thinking? Is it the use of natural-kind thinking? Is it the bizarre mixture of the two, trying to get types to do what only natures could do? Or is there something more fundamental that makes people engage in apparently silly errors (like treating types as natures)? I don't know and I can't tell. It would be nice if further studies in this area would take a more sophisticated approach to this whole issue of intuitive essentialism.
UPDATE: John Wilkins has an excellent post in response called Essentialism Revisited. (Unlike me, Wilkins actually does work on this sort of subject). He also notes that you can listen to the talk (mp3) that goes with the presentation linked to above.
Were I to change a few things in the argument of these four posts, I would, besides incorporating the above sources more adequately, have been more careful about the issue of typology, since, as Wilkins notes, I muddle a few type-relevant issues together.