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.