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

Friday, July 16, 2004

The uneasy relation between philosophy and biology 2

Not only do biologists have problems with philosophers, but philosophers have had trouble with biology and biologists for a long time. The practice has been, for the bulk of the modern period, but all the way back to Plato, to treat biological things as examples of more general philosophical categories: the Dog, the Horse, the Chicken, as well as the more indirect examples of living kinds - Man, Unicorn, Monster. As Umberto Eco notes:
The history of research into the philosophy of language is full of men (who are rational and mortal animals), bachelors (who are unmarried adult males), and tigers (though it is not clear whether we should define them as feline animals or big cats with a yellow coat and black stripes). [Umberto Eco, Kant and the Platypus (Vintage, 1999) page 9]

This is, in a way, old news. Biologists have been complaining about how philosophers treat variation in the living world since Mayr announced that essentialism is dead in taxonomy:
Typological thinking finds it easy to reconcile the observed variability of the individuals of a species with the dogma of the constancy of species because the variability does not affect the essence of the eidos [the Greek term translated as "species"] which is absolute and constant. Since the eidos is an abstraction derived from human sense impressions, and a product of the human mind, according to this school, its members feel justified in regarding a species "a figment of the imagination," an idea. [Mayr, Ernst. 1957. Species concepts and definitions. In The species problem: A symposium presented at the Atlanta meeting of the American Association for the Advancement of Science, December 28–29, 1955 (Publication No 50, edited by E. Mayr. Washington DC: American Association for the Advancement of Science), page 12])

He then of course affirmed that "species" in biology is quite different, a gene pool rather than a class of objects. Ironically, the early nineteenth century writers, such as Mill, knew from their Locke that real species had variation that logical classes did not. One widely used textbook was that of the Archbishop of Dublin, Richard Whatley, The Elements of Logic, published in 1826, and by the time of the Origin in its 9th edition. Whatley notes, for example, that the logical sense of "species" is quite distinct from the sense in which naturalists use it of “organized beings" (Bk IV, ch. 5 §1), for they are real things, “unalterable and independent of our thoughts" (p183):
... if anyone utters such a proposition as ... "Argus was a mastiff," to what head of Predicables would such a Predicate be referred? Surely our logical principles would lead us to answer, that it is the Species; since it could hardly be called an Accident, and is manifestly no other Predicable. And yet every Naturalist would at once pronounce that Mastiff, is no distinct Species, but is only a variety of the Species Dog. ...

... the solution of the difficulty is to be found in the peculiar technical sense ... of the word "Species" when applied to organized Beings: in which case it is always applied (when we are speaking strictly, as naturalists) to individuals as are supposed to be descended from a common stock, or which might have so descended; viz. which resemble one another (to use M. Cuvier’s expression) as much as those of the same stock do.

Whatley knew that species varied in ways logical species didn't. So why is it that modern philosophers are so ill-equipped to deal with biology? It has to do, I believe, with the development largely in English-speaking philosophy of logical empirical method, primarily in Russell and Moore (see Suzanne Cunningham's review for a comprehensive look at how this arose).

British philosophy had been idealist up until this point, and in reaction to it, Russell and Moore drew on Hume, who had been brought to the attention of the philosophical community again by a review by Thomas Henry Huxley (yes, that Huxley), published in 1879. The philosophical method used was one of logical argument, begun afresh by any rational enquirer. It was therefore ahistorical - Plato was treated as if he had just now made his arguments, along with Aristotle, Berkeley, Spinoza and so on. And science was not the foundation of any philosophy, but philosophy was to be the foundation for science.

In part this was also a reaction to the over-simplistic appeal to science, including evolutionary biology, by a number of philosophers such as Herbert Spencer, who blithely assumed that "more evolved" meant "better", and for which George E. Moore developed his characterisation of the "Naturalistic Fallacy", the idea that any natural (that is, physical) property was to be identified with The Good that Socrates had said was the aim of philosophy to characterise.

Moore's and Russell's student, friend and ultimately successor was Ludwig Wittgenstein. As part of the "logicist" movement, developed by Gottlob Frege, in which mathematics was to be founded on the fundamental terms of logic (meaning, symbolic logic) Wittgenstein wrote what is now the most famous modern philosophical text, the Logische-Philosophische Abhandlung, translated into English as the Tractatus Logico-Philosophicus, which similarly used the ahistorical reflective method. In it, he said:
Darwin's theory has no more to do with philosophy than any other hypothesis in natural science. (Tractatus 1922 4.1122)

But he maintained this position even when he developed his later thoughts, which he considered to be a rebuttal of the Tractatus. Just before that comment, he had said "Psychology is no nearer related to philosophy, than is any other natural science", but this view he did change, and his remarks on psychology became the foundation for his entire later thought. So, why did evolution continue to remain philosophically off-limits?

The answer is to be found in a work he tried to produce in concert with the logical positivist Frierich Waismann - entitled Logik, Sprache, Philosophie. We'll look at this next. It has some interesting resemblances - family resemblances? - to issues of modern systematics in biology.

Cunningham, Suzanne. 1996. Philosophy and the Darwinian legacy. Rochester: University of Rochester Press.
Huxley, T.H. 1879. Hume. London: McMillan and Co.

Sunday, July 11, 2004

Finishing Cooper

Well, I think I should put this to bed now.

Cooper has a schematic for "life strategies". They look like this:

The way to think of this is to regard it as a branching diagram of the probabilities of outcomes in a population. An organism - say, a vole - that faces predation has, say, two alternative strategies - to dig and hide or to flee its predators. If it flees, it has a .1 likelihood of getting away, and if it survives it has 1.4 progeny per survivor, the average for this vole. So the fitness of the FLEE branch is 1.4 times .1 = .14. Of course, those that are eaten have a fitness of 0 in this artificial example.

But the other strategy is DIG, and here .36 are consumed anyway, while .64 escape. The fitness that results from DIG is therefore .64 times 1.4 progeny, or .9. So, the DIG strategy is the one that will take over the vole population, because eventually all the FLEEing voles will be eaten. [Note that this population is doomed anyway, because the replacement of voles once all the FLEEers have been eliminated is 9/10 per generation. Selection can drive populations to extinction.]

Now Cooper want to use these diagrams as a basis for deriving, first decision theory, then inductive logic, then deductive logic, mathematics, and so on. Why this? Well, he believes as others have before him that logic evolved (Wigner and Hamming's point) and that therefore the logic must be somehow a subset of evolution.

I disagree with the motivation. Logic evolved - so too did over-optimism (those who are unduly optimistic about their abilities achieve beyond their skills more than those who have a realistic self-assessment). That doesn't mean that evolution is over-optimistic. Moreover, the "logic" of evolution is the mathematics of populations genetics - so are we just describing a circular relation here?

And that logic includes stochastic processes as well - drift in particular, but also peripheral population founder-effect sampling (atypical distributions of alleles in populations at the edge of a range of a species) - are all these to be characterised in terms of the selective fitness of strategies? Perhaps we should recall Ghiselin's comment and move on.

The diagrams are, however, rather an elegant way of representing selectively biased processes. While it is hardly a major revelation that a population's allele frequencies are iteratively added, as a flow diagram it is a useful way to make the implications of larger and more complex situations easy to follow.

A logic of evolution is yet to be worked through. I think that it will be many-valued (continuously as Cooper has shown it - the "truth-value" of an evolutionary trait ranges from 0 (false, or totally unfit) through to 1 (true, or totally fit). However, this sort of truth is merely an indexical way to keep track of the eventual outcomes of the things symbolised. As Wimsatt once said, genes are a way of "bookkeeping" in evolution. Truth is a way of doing the same thing in reasoning.

Read the book if you have an interest in logic and evolution. Let me know if I have been unfair to Cooper. I very much wanted him to succeed, but I very much doubt that he has, at least in doing what I wanted him to do. We have to naturalise logic and reason, for they must be natural. But this is not the way to do it, I think.