Tuesday, August 13, 2013
Modern Biology As A Series of Footnotes to Plato & Aristotle
While Addy Pross failed to convince me that biology is chemistry, he has confirmed my long held opinion that modern biological science has largely come back around to Plato and Aristotle. I provided one example in my last post. Here is another.
Pross’ book centers on what one may call the central problematic of modern biology: the fact that, while biological processes are and must be perfectly consistent with the natural laws that govern all physical substance, organisms seem to have sets of rules that are entirely their own and they seem to go in the opposite direction from all inorganic chemistry. Organisms move uphill toward greater degrees of complexity rather than move downhill toward simplicity.
As I have detailed in previous posts, Pross deals with this by distinguishing between static complexity (which governs everything below the level of molecular replicators) and dynamic kinetic stability, which is displayed by replicators. Whether this in any way moves toward a solution rather than merely restating the problem, I will ignore here.
It does seem to me that this question maps back onto the history of ancient Greek philosophy quite well. For the ancients, the central problematic was how to explain coming to be and change. Let us state it in its simple form:
If something new can come to be, it must come to be either out of what is or out of what is not. It cannot come to be out of what is, because what already exists cannot come to be. It cannot come to be out of what is not, because there is nothing there to come to be out of.
That this is not mere word play is evident by the emergence of two schools of pre-Socratic thought. One was that of the monists. They argued that, in fact, nothing ever does come to be or change at all. That is because there is really only one thing and it never changes. Consider, by way of analogy, a pyramid. It is wide at the base but narrow at the top. This does not mean that it changes, but only that it offers different aspects to different points of view. Likewise, the small tree in my yard seems to become bigger as time goes on. This is an illusion. It is always one thing at one time, and time is just another dimension along which different aspects are offered to the observer.
If this seems implausible, it is well to consider that it is the view of most modern physicists. Time is just another dimension, analogous to the three dimensions of space. At time T1 I am at position X1, Y1, and Z1. This fact is always true and does not change. At T2, I have moved to X2, etc. Reality viewed as a whole is nothing more or less than the sum total of all such facts. None of the facts ever changes.
A less radical solution was offered by the ancient atomists. They posited that the only real things are the uncut particles out of which everything else is composed. The atoms (uncut things) are eternal. They never come to be nor do they ever decompose, since they aren’t composed of anything except themselves. All those things that appear to come to be, like stars and people, are mere aggregates of atoms. Complex things do not exist in any real way and so it is unnecessary to account for their coming to be.
Aristotle cut the Gordian knot first by positing three principles: potentiality, actuality, and a substratum. How does an iron skillet come to be? It comes to be from a lump of iron which is potentially a skillet. The iron is heated, becoming red and hot from what was black and cold. It is then shaped into an actual skillet. Thus it comes to be from what is not: the iron that was potentially but not yet actually a skillet. It also remains what it is, still iron after the shaping.
Contrary to the atomists, something new has come to be beyond the mere aggregation of the materials. The skillet has powers that the lump of iron did not have (for example, holding a few lamb chops in hot oil). Contrary to the monists, there is no necessity to dispense with the element of time. As the iron was potentially a skillet, it was also potentially something else (a hammer?) or might just have continued its career as a lump. Potentially suggests an open future.
This account of coming to be and change is hylomorphic, from the Greek words for matter and form. It recognizes form as something real, but requires a material substratum underlying the processes of generation and change. Let us map this back onto Pross’ categories. In simple chemical reactions, the nature of the materials controls all the action. Forms and formal processes are entirely derivative from the elements and the downhill pressure of the second law of thermodynamics. Hylomorphic explanations recognize that the same material can have very different powers in different arrangements. This is true even of the inorganic world. A cloud behaves differently from a pool of water.
Aristotle made a leap beyond simple hylomorphism when he recognized individual organisms as substances. A substance (ousia in Greek) functions as a bearer of properties and as the substratum of change. This horse over here is so large and of a certain color. It persists as what it is while it grows from a foal to a yearling to a filly to a mare. This kind of persistence is what Pross means by dynamic kinetic stability. The horse continual communicates its being over time, for as long as it lives. This kind of substance apparently emerges on earth with the first genuine replicators, presumably the ancestors of RNA molecules.
At some point in his thinking, Aristotle began to recognize the species as a substance. If what persists over greater periods of time is more real than what persists over shorter terms, then the species is more substantial than the individual organism. By taking this step, Aristotle was getting at something that has stirred the pot of the modern philosophy of biology. What is the unit of selection in evolution? The most obvious answer is the individual organism. A less obvious but very robust answer is that it is the genes. The individual may be viewed as a vehicle for the genes, discarded as they mechanically pursue immortality. At least two philosophers of biology (Michael Ghiselin and David Hull) have argued that conspecific populations are genuine individuals. They are following the track laid down by the philosopher.
That, as rich and rewarding as it is, is the limit of Aristotle’s approach. Aristotelian substances, however large, exist as visible objects at some present moment. Modern Darwinian biology can conceive of a species as an object that extends backwards into the past. When Darwin spoke of the origin of the species, he might have meant a single species consisting of all the organisms on earth. Such an object, if we choose to recognize it, is Platonic rather than Aristotelian. All existing organisms and populations of organisms are buds and branches of one great, invisible tree.
Or we might consider that what really persists over geological time is not the vast number of replicators but replication. Genes, after all, are more ephemeral than the organisms they underwrite. They must be constantly recreated. Replication is an idea, but not merely a nominal idea. It logically enables and constrains the processes of ontogeny and evolution.