Darwin's Dangerous Idea - Evolution and the Meaning of Life

128 THREADS OF ACTUALITY IN DESIGN SPACE
might get wildly different answers on different planets, but it does not betray
a "geocentric"—let alone "anthropocentric"—assumption.
What about vision? We know that eyes have evolved independently many
times, but vision is certainly not a necessity on Earth, since plants get along
fine without it. A strong case can be made, however, that if an organism is
going to further its metabolic projects by locomoting, and if the medium in
which the locomoting takes place is transparent or translucent and amply
supplied by ambient light, then since locomoting works much better (at
furthering self-protective, metabolic, and reproductive aims) if the mover is
guided by information about distal objects, and since such information can be
garnered in a high-fidelity, low-cost fashion by vision, vision is a very good
bet. So we would not be surprised to find that locomoting organisms on other
planets (with transparent atmospheres) had eyes. Eyes are an obviously good
solution to a very general problem that would often be encountered by
moving metabolizers. Eyes may not always be "available," of course, for
QWERTY reasons, but they are obviously rational solutions to this highly
abstract design problem.
2. FORCED MOVES IN THE GAME OF DESIGN
Now that we have encountered this appeal to what is obviously rational under
some general set of circumstances, we can look back and see that our case of
necessity, having an autonomous metabolism, can be recast as simply the
only acceptable solution to the most general design problem of life. If you
wanna live, you gotta eat. In chess, when there is only one way of staving off
disaster, it is called a forced move. Such a move is not forced by the rules of
chess, and certainly not by the laws of physics (you can always kick the table
over and run away), but by what Hume might call a "dictate of reason." It is
simply dead obvious that there is one and only one solution, as anybody with
an ounce of wit can plainly see. Any alternatives are immediately suicidal.
In addition to having an autonomous metabolism, any organism must also
have a more or less definite boundary, distinguishing itself from everything
else. This condition, too, has an obvious and compelling rationale: "As soon
as something gets into the business of self-preservation, boundaries become
important, for if you are setting out to preserve yourself, you don't want to
squander effort trying to preserve the whole world: you draw the line"
(Dennett 1991a, p. 174). We would also expect the locomoting organisms on
an alien planet to have efficiently shaped boundaries, like those of organisms
on Earth. Why? (Why on Earth?) If cost were no object, one might have no
regard for streamlining in organisms that move through a relatively dense
fluid, such as water. But cost is always an object—the Second Law of
Thermodynamics guarantees that.
Forced Moves in the Game of Design 129
So at least some "biological necessities" may be recast as obvious solutions
to most general problems, as forced moves in Design Space. These are
cases in which, for one reason or another, there is only one way things can be
done. But reasons can be deep or shallow. The deep reasons are the
constraints of the laws of physics—such as the Second Law of Thermodynamics,
or the laws of mathematics or logic. 2 The shallow reasons are just
historical. There used to be two or more ways this problem might be solved,
but now that some ancient historical accident has set us off down one
particular path, only one way is remotely available; it has become a "virtual
necessity," a necessity for all practical purposes, given the cards that have
been dealt. The other options are no longer really options at all.
This marriage of chance and necessity is a hallmark of biological regularities.
People often want to ask: "Is it merely a massively contingent fact that
circumstances are as they are, or can we read some deep necessity into
them?" The answer almost always is: Both. But note that the type of necessity
that fits so well with the chance of random, blind generation is the
necessity of reason. It is an inescapably teleological variety of necessity, the
dictate of what Aristotle called practical reasoning, and what Kant called a
hypothetical imperative.
If you want to achieve goal G, then this is what you must do, given the
circumstances.
The more universal the circumstances, the more universal the necessity.
That is why we would not be surprised to find that the living things on other
planets included locomotors with eyes, and why we would be more than
surprised—utterly dumfounded—if we found things scurrying around on
various projects but lacking any metabolic processes. But now let us consider
the difference between the similarities that would surprise us and the
similarities that would not. Suppose SETI struck it rich, and established
communication with intelligent beings on another planet. We would not be
surprised to find that they understood and used the same arithmetic that we
do. Why not? Because arithmetic is right.
Might there not be different kinds of arithmetic-like systems, all equally
good? Marvin Minsky, one of the founders of Artificial Intelligence, has
2. Are the constraints of pure logic deep or shallow? Some of each, I guess, depending on
their obviousness. A delicious parody of adaptationist thinking is Norman Ellestrand's
"Why are Juveniles Smaller Than Their Parents?" (1983 ), which explores with a heroically
straight face a variety of "strategic" reasons for JSS (Juvenile Small Size). It ends
with a brave look towards future research: "In particular, another juvenile character is
even more widespread than JSS and deserves some thoughtful theoretical attention, the
fact that juveniles always seem to be younger than their parents."