Aristotle and Darwin on species. A Note

An anonymous commenter on Edward Feser’s blog asked for his comments on two quotations from Stephen Mayer:

“Since Aristotle, most biologists had believed that each species or type of organism possessed an unchanging nature or form; many believed that these forms reflected a prior idea in the mind of a designer. But Darwin argued that species can change-or “morph”-over time.”

and

“If Darwin was right, then it was futile to maintain rigid distinctions in biology based on ideas about unchanging forms or natures.”

The first quotation is a historical claim. Now since there are about two millennia of interpreters from Aristotle to Darwin,  speaking about “most interpretations” of Aristotle by biologists is no easy thing, and even within Aristotle himself there is more than one method and approach to looking at natural species. But for the sake of simplicity, let’s take Mayer’s account of a single Aristotelian vs. Darwinist account of species for granted. Mayer’s general account is that  Aristotle- inspired accounts of species are essentialist or static whereas Darwin- inspired interpretations are dynamic. There is a real truth that Meyer is aware of, but I think he is interpreting it in a way that gets “most interpreters of Aristotle” wrong.

Almost all the interpreters from Aristotle to Darwin were stymied by the question of whether the universe was eternal or not. By wondering whether the world was “eternal” they didn’t just wonder whether there was an unlimited amount of time going backwards, but also whether the very structure of the universe- or more modestly, our earth- was the sort of thing that developed over time. Put in our terms, most of the interpreters after Aristotle weren’t sure that the earth had a history at all. Most interpreters after Aristotle not only did not know whether the earth had a developmental story to tell, they even doubted whether human reason could discern the story if it had one. This is an easily overlooked aspect of the Medieval debates about whether reason could discern whether the world was eternal or not.

By Darwin’s time, a good deal of work had been done to show that human reason could figure out that the earth had a developmental story to tell. Darwin’s account of species as arising at some point in time from various causes is occurring within this framework. But the question of how species arise is posterior to the question of whether they arise at all- which is exactly what most interpreters after Aristotle were neither sure happened nor, if it did happen, that they could know about it. Since most interpreters after Aristotle didn’t know whether there was any point in asking about the origin of the species, they didn’t treat of the question and asked other sorts of questions about species. This is the crucial point- and even if one wants to give a summary account of the difference between Aristotle and Darwin, they can’t miss this.

When Aristotle looked at “species” (which, again, means more than one thing which Aristotle examined in far more than one way) he wanted to answer questions like “what must be true of species, if there is science about them?” or what must be true of species, if species are natural and nature is mobile?” These were extremely heated and controversial questions in his time, and these sorts of questions about species set the tone for the science and philosophy that followed. Darwin is not interested in these questions, nor were his followers. This is not to say that the questions are not relevant- it is only to say that they are not asked, nor is there much controversy about them. Modern people take for granted that things move and are intelligible, and so they don’t bother asking what must be true in order that this be so. Even if we did ask questions of this sort, we would demand that they be expressible in some kind of metrical way, which again would require us to ask the question in a different way than Aristotle or most of his interpreters would have asked it.

Mayer is seeing a truth and expressing it in the wrong way. The truth he is seeing, said rightly, is this:

“Most interpreters of Aristotle were interested in answering questions about species that would explain how they were intelligible and natural, and this led them to posit an unchanging element in the species themselves. After Darwin, biologists became much more interested in other sorts of questions about species, and so they lost interest in this unchanging element, and since they are more interested in answering questions about the development of the species- questions which the Aristotelian did not even know could be asked- they considered the dynamic nature of the species. The question of how the Aristotelian and Darwinian perspectives of nature relate to each other- if at all- is a third point over and above the various differing questions that they ask about one and the same thing, namely species.

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