Sunday, August 4, 2013
Pross Proves Plato
It is a commonplace in the academy that we learn as much or more from intelligent errors than from the modestly correct. Addy Pross’ book What is Life? has utterly failed to convince me that the title of his penultimate chapter is correct; i.e., that biology is chemistry. What he has convinced me of is that Plato was closer to the truth than Aristotle.
The basic problem that Pross addresses is how to reconcile our understanding of non-living, non-replicating nature (governed by the second law of thermodynamics) with our understanding of organisms and their prebiotic (but replicating) chemical ancestors. Pross finds the solution in a distinction between two kinds of stability: static stability and dynamic stability. Water molecules are statically stable: they remain stubbornly what they are over long periods without change. Bacteria are dynamically stable. They remain what they are by a process of constant change that keeps bringing the form back into existence.
Just as the second law of thermodynamics is the driving force that governs all chemical reactions, so all dynamically stable systems like organisms and replicating molecules are governed by a similar law:
Replicating chemical systems will tend to be transformed from (dynamically) kinetically less stable to (dynamically) kinetically more stable.
Once diverse populations of replicators get going in the history of life, more dynamically stable replicators out compete less dynamically stable competitors. This law governs the evolution of all life up to the present and, presumably, for the duration.
Here’s where Aristotle and Plato come in. While they had no viable chemistry, they were very good at thinking about biological form. Aristotle famously rejected his teacher’s theory of forms as independent entities in favor of the view that form is an abstraction from existing organisms. How do we understand a horse? This horse, here, is the real thing. It consists of a certain collection of materials that realize a certain form. The form of the horse is an abstraction from really existing horses, but it allows us to sort horses out from other organisms. Thus it is a species form.
Aristotle was later drawn to the view that the real thing is not the individual horse but the species, since the one comes and goes but the latter persists. What persists over time is more robustly real than what does not. Still, the form is an abstraction from something really embodied now (and always) whether the embodied thing is a horse or all the horses. The laws that govern the existence and development of each species are specific; there is nothing more general than the species that controls their natures.
Plato looked at the problem the other way round. Form was primary; individual organisms (and presumably populations of organisms) are derivative. Plato’s view was rooted in an analysis of human intelligence. When we view a tree from a great distance, it looks very small. As we approach it, it seems to grow larger. Near the tree, it is very large indeed. Yet the tree has not changed; what has changed is our perspective. There is one thing, the individual tree, behind the shifting perspectives and that one thing is more real than the appearances.
Plato’s great innovation was to extend this analogically to understand what a species is. When we move from one tree to another, we recognize both of them as in some sense the same thing‑different examples of tree, just as we recognized the various views of a single tree as the same objective thing. Perhaps this is because there is one thing behind all the individual trees that our minds are getting a dim grasp of. That is the idea of a tree and it is more real than individual trees because it is not susceptible to change or decay. It defines what a tree is for all actual trees and for all trees that may or may not come to be in the future.
This account has been subject to a lot of derision over the millennia, but Plato’s Socrates was always careful to advance it as provisional. It is not necessarily this, he would say, but something more or less like this. It is unclear whether he really believed in the idea of a complex object like a tree, or whether the true ideas were more like mathematical principles.
It strikes me that Pross’ law of dynamic kinetic stability looks a lot like a Platonic form. It is not a mere abstraction from actual organisms or populations. It is a logical rule that (if valid) governed all the emergence of all replicators from the Ur-replicating molecules to the replicating elephants. It will govern all organisms that emerge in the future.
Aristotle laid down a very good foundation for biology. I have argued that modern biology is now coming round to his view on a lot of things. It may be, however, that Plato’s view was correct at a deeper level.