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

408 THE EVOLUTION OF MEANINGS The Quest for Real Meaning 409
his lights, with any evolutionary account of such meanings: they are too
indeterminate. They fail to distinguish, as they ought, between such frog-eye
reports as "fly here now" and "fly or small dark projectile here now" and so
forth. But this is false. We can use the frog's environment of selection (to the
extent that we can determine what it has been ) to distinguish between the
various candidates. To do this, we use exactly the same considerations we
used to settle the questions—to the extent that they were worth trying to
settle—about the meaning of the state in the two-bitser. And to the extent that
there is just no telling what that environment of selection has been, there is
also just no fact of the matter about what the frog-eye report really means.
This can be brought home vividly by sending the frog to Panama— or, more
precisely, sending the frog to a novel selective environment.
Suppose scientists gather up a small population of frogs of some flygrabbing
species, on the brink of extinction, and put them under protective
custody in a new environment—a special frog zoo in which there are no flies
at all but, rather, zookeepers who periodically arrange to launch little food
pellets past the frogs in their care. To their delight, it works; the frogs thrive
by zapping their tongues for these pellets, and after a while there is a crowd
of descendant frogs who have never in their lives seen a fly, only pellets.
What do their eyes tell their brains? If you insist on saying the meaning
hasn't changed, you are in a bind, for this is simply an artificially clear
instance of what happens in natural selection all the time: exaptation. As
Darwin was careful to remind us, the reuse of machinery for new purposes is
one of the secrets of Mother Nature's success. We can drive home the point,
to any who wish some further persuasion, by supposing that the captive frogs
do not all do equally well, because, due to variation in pellet detecting
prowess in their eyes, some eat less heartily than others, and leave less
progeny as a result. In short order there will have been undeniable selection
for pellet detection—though it would be a mistake to ask exactly when
enough of this has occurred for it to "count."
Unless there were "meaningless" or "indeterminate" variation in the triggering
conditions of the various frogs' eyes, there could be no raw material
(blind variation) for selection for a new purpose to act upon. The indeterminacy
that Fodor (and others) see as a flaw in Darwinian accounts of the
evolution of meaning is actually a precondition for any such evolution. The
idea that there must be something determinate that the frog's eye really
means—some possibly unknowable proposition in froggish that expresses
exactly what the frog's eye is telling the frog's brain—is just essentialism
applied to meaning (or function). Meaning, like function, on which it so
directly depends, is not something determinate at its birth. It arises not by
saltation or special creation, but by a (typically gradual) shift of circumstances.
Now we are ready for the only case that really matters to these philosophers:
what happens when we move a person from one environment to
another? This is the notorious Twin Earth thought experiment of Hilary
Putnam (1975). I am reluctant to go into the details, but I have learned that
nothing short of spelling it all out and blocking all the exits will have a prayer
of persuading those whose allegiances lie with original intentionality. So with
apologies, here goes. Armed with our background briefing on the two-bitser
and the frog, we can see exactly what the Twin Earth thought experiment
depends on for its undeniable rhetorical force. Twin Earth, let's suppose, is a
planet almost exactly like Earth, except that there are no horses on Twin
Earth. There are animals that look just like horses, and are called "horses" by
the inhabitants of Twin Boston and Twin London, "chev-aux" by the
inhabitants of Twin Paris, and so forth—that's how similar Twin Earth is to
Earth. But these Twin Earth animals are not horses; they are something else.
Call them schmorses, and if you like, you may suppose they are a sort of
pseudo-mammal, a hairy reptile or whatever—this is philosophy, and you get
to make up whatever details you find you need to make your thought
experiment "work." Now comes the dramatic part. One night, while you
sleep, you are whisked off to Twin Earth. (It is important that you sleep
through this momentous change, for that keeps you in the dark about what
has happened to you—it keeps you "in the same state" you were in on Earth.)
When you awake, you look out the window and a schmorse gallops by. "Lo,
a horse!" you say (out loud or just to yourself, it makes no difference). To
make the case simple, let's suppose Twining, a handy Twin Earth-ling, utters
the very same sounds at the very same time when he, too, sees the schmorse
gallop by. Here is what Putnam and others insist on: Twining says, and
thinks, something true—namely, that a schmorse has just run by. You,
Earthling that you still are, say and think something/alse—namely, that a
horse has just run by. How long, though, would you have to live on Twin
Earth, calling schmorses "horses" (just like all the natives), before the state of
your mind (or what your eye tells your brain ) is a truth about schmorses
rather than a falsehood about horses? (When does the aboutness or intentionality
leap to the new position?—a saltation demanded by these theorists.)
Would you ever make the transition? Would you somehow make it without
knowing it? The two-bitser was forever oblivious of the change of meaning
of its internal state, after all.
I suppose you may be inclined to think that you are quite radically unlike
the frog and the two-bitser. You, it may seem, have intrinsic or original
intentionality, and this marvelous property has a certain amount of inertia:
your brain can't just turn on a dime and suddenly mean something entirely
new by its old state. In contrast, frogs don't have much of a memory, and
two-bitsers none at all. What you mean by the word "horse" (your private
mental concept of a horse) is something like one of those equinish beasts that
we Earthlings like to ride, an epithet anchored in your mind by all your
memories of horse shows and cowboy movies. Let us agree that this memory
matrix fixes the kind of thing to which your concept of horse applies. Ex