Thursday, December 27, 2012
Nagel's Neoaristotelian Teleology
In Chapter 4, Section 6 of Mind and Cosmos, Thomas Nagel adds a fourth kind of explanation for the existence of organisms, consciousness, reason, and value. The first three I have considered in previous posts: chance, non-intentional biasing, and intentional biasing.
Nagel considers all three to be inadequate. He accepts the apparent consensus that the appearance of the original, proto-biological self-replicators cannot be explained by random processes. He accepts Robert White’s argument that non-intentional biasing is not indicated because, while it can explain non-random patterns, it cannot explain a bias “towards the marvelous.” This is to say that non-intentional biasing is no more likely to produce creatures or traits of creatures that look designed than mere chance. Finally, he rejects intentional biasing in large part because he is an atheist.
So what is left? Nagel proposes a naturalistic teleology
that is distinct from all three of the other candidate explanations: chance, creationism, and directionless physical law.
What does a “naturalistic teleology” mean? When we try to understand any natural event, we look for ways in which the initial state of the system limits subsequent states. A beaker of water can be frozen or heated to a boil, but not transformed into gold. Lava under the earth can produce a volcano, but not Godzilla.
Given any initial state of a system, some subsequent states are more likely than others. It is rare, but not unprecedented, for mammalian evolution to move toward the development of wings and flight. Some mammals returned to the sea and began to look a lot like fish; however, they did not develop gills. This is what Daniel Dennett meant when he talked about “design space”. At any point in the history of life on earth, a range of future organisms is possible. As environments change, evolution will explore the possibilities in design space. A population of lizards may change color to blend in better with new local vegetation, but the lizards will not acquire the power of genuine invisibility.
Nagel proposes that the laws of physics underlying the appearance of life are biased towards “the formation of more complex systems”.
Teleological laws would assign higher probability to steps on paths in state space that have a higher velocity toward certain outcomes.
In other words, there is something in inorganic matter that is biased toward the development of something like human beings. It smoothed the path toward the appearance of the Ur-replicators, and then toward the development of genuine organisms. It has operated in evolution up to the appearance of philosophers.
All I would add at this point is that Nagel has become an Aristotelian, if not a Platonist. The Socratics clearly believed in an embedded teleology. It is not, or not so much, that some God intervenes to govern the course of organic development. It is that mind is already present in the forces that mold living things.
That is a shockingly bold proposal. How it can be maintained and/or squared with a scientific scheme seems to me to be a challenging question. I don’t know if we can make sense of such an embedded teleology without a divine intention biasing the cosmos; however, if we forget about that question for a moment, this is a plausible picture of the history of life on earth.