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.
