[From Bruce Abbott (960921.1145 EST)]
Given our recent discussions on purpose and evolution, I thought the
following quotation might be of interest:
We might say that in order to maintain the individual or the species as
long as possible, the organs most essential for survival maintain or even
increse their weight at the cost of the less essential organs. This is a
_teleological_ explanation. This type of explanation plays an important
role in biology. The animal behaves as if it knew what was necessary for
survival. As long as the words "as if" are emphasized (Vaihinger,
translated by Rutledge 1935), the reasoning is sound, but they are often
forgotten. Then the implication is that animals and plants, or nature in
general, has divine wisdom and the power to follow this wisdom.
Through this type of teleological reasoning, theology enters into biology.
It is, however, possible to avoid teleology. Those animals which during
the first few hours of starvation katabolize their nerve tissue instead
of their fat stores promptly die. Animals now living are those whose
reactions favor survival and who therefore behave _as if_ they knew what
was good for survival. This explanation is based on natural selection
rather than teleology.
The old Greek philosophers explained not only biological phenomena but
purely physical processes teleologically. _Telos_ is the Greek word for
"aim." Thus water "aims" to reach its "proper level"; a stone thrown
into the air "seeks" its "proper place." To seek a goal, however, implies
the expectation of future events and implies further that present actions
are based on this expectation. Planning, in turn, requires a mind. The
idea that stones and other "dead" objects "expect and plan" has since
been abandoned. Since Galileo, we know that the path of a stone thrown
into the air is determined, not by an expected future, but by conditions
in the past and present, usually called _causes_. In biology, however,
teleological explanations are still used extensively. Few biologicst
actually believe that animals and plants plan their own future, yet some,
like Krebs (1954), feel that our understanding of an animal, like our
understanding of a machine, is improved by knowing its purpose. Kleiber
(1956), however, pointed out that we understand a machine in terms of its
purpose because a designer has a mind essentially similar to our own. A
claim to understand nature teleologically implies an understanding of the
purposes of the creator. The scientist does well to leave such claims to
prophets and priests. A. V. Hill (1956) maintains that the idea of design
is as essential to biology as it is to engineering. He recommends that
those whom conscience forbids the use of a certain amount of teleology
leave biophysics and choose another field, because they will miss most of
what is interesting.
It is not clear why a scientist who is dissatisfied with a teleological
explanation should miss more than one who accepts such an explanation.
On the contrary, where the teleologists accepts an analogy between an
engineer designer and the creator of organisms, the skeptic sees a
problem to be solved. A physiologist who refutes teleological explanations
does not differ from Hill in observation of nature, but he is only more
conscientious than Hill in his use of words. For example, what does Hill
mean by the "purpose of an organ"? If he means only the function of that
organ as part of an organism, why use the word "purpose"? If by "design"
he means only some regular arrangement, why does he use the word "design"?
A design implies a designer, a planning mind.
Max Klieber (1961, Pp. 38-40)
Unfortunately for me, I see merit in both sides of the argument. For clear
communication it is best to use words that do not imply, in the minds of
others, meanings one does not intend to convey. Evolution as described by
Darwin is undirected and apurposeful; "nature" intends nothing: what is,
simply is. The turtle's shell is the product of a "walk" during which
current properties of the organism at any given time, the situations in
which it found itself at those times, blind variation, and selective
retention combined in such as way as to result in the current properties of
turtles. There was no "intention" to produce a shell and, had circumstances
been slightly different during the course of the animal's evolution, a
different arrangement doubtless would have emerged. The shell is not a
"design" in the sense of a planned arrangement, and it has no "purpose" in
the sense of an intended function.
On the other hand, it can be awkward to talk about biological systems while
assiduously avoiding such language. In the final paragraph, Klieber gives
examples of both ways of explaining the conservation of brain-tissue over
fat during starvation:
Teleological argument: The animal aims to survive. Brain is more essential
for survival than fat tissue. Therefore the animal maintains brain weight
at the cost of fat.
Biological argument: Animals which are so organized that in times of
starvation their fat deposits are maintained at the cost of the brain have
less chance of survival than those of animals in which brain is maintained
at the cost of fat deposits, and which are therefore favored as the fittest
by natural selection.
The first statement is inaccurate if taken literally, but it communicates
the essential idea -- that the reason brain is preserved over fat is that
the selective criterion of greater reproductive fittness has resulted in
this pattern being "preserved" over its opposite, and thus represented in
current animals -- clearly and quickly. The second statement is accurate,
but having to repeat all that about survival and selection each time one
wishes to explain why some property of the organism is there gets a little
verbose.
Note also that even Kleiber speaks erroneously of animals being "favored as
the fittest by natural selection," which, if taken literally, suggests that
"natural selection" is a conscious being "favoring" this animal or that on
the basis of its "fittness." Sometimes taking the long way around to avoid
misinterpretation by those who would wish to impose a literal meaning is too
much bother even for one as hard-headed in his use of terms as Kleiber.
The alternative is to avoid terms with excess meaning when possible (e.g.,
use "function" rather than "purpose") and for the rest (where literal
language is awkward and lengthly), explain what you _intend_ by your use of
terms or phrases that might otherwise be misinterpreted. I see no great
difficulty in this approach for general discourse.
As an example, consider the term "design." Although Kleiber would have us
avoid the term when referring to, let's say, the heart, because "design"
implies a "designer," I see no harm in the use of this term as a particular
arrangement of parts that develops in all animals of a given species. There
may be no "planner," but there clearly is a "plan" being followed during
development, a series of steps that culminate in the development of a given
structure with its usual familiar properties. It's a metaphor that leads to
no great errors of conception so long as one has explained it as such, and
it certainly leads to more convenient, clear, and active language than the
alternative.
I'm sure there are others of you who have a different opinion, and you're
entitled to it. And I'm entitled to mine. This is it: I'm very much in
favor of precise language. However, there are times in which it can be
awkward, and under those circumstances I think that speaking a little
metaphorically can add to clarity and brevity, if it's done right, by
explaining what you intend by the words and phrases you use. So I agree
with Kleiber in principle, but would rather not have to wear his
straight-jacket for all occasions.
Regards,
Bruce