VI. TELEOLOGY
Teleological explanations in ancient biology are of
several kinds. They have
in common the basic meaning
that natural processes occur for the sake of their conse-
quences; they tend towards goals. Traditional religion
ascribed this
tendency to the gods, who send rain to
make the crops grow. This conception
of providential
teleology could vary from its strong form in Judaic
monotheism to the quite unsystematic religious beliefs
of the Greeks.
Opposing the popular ideas of provi-
dence,
the early Greek cosmologists claimed to account
for all phenomena by
“necessity,” that is by automatic
causes like the hot
and the cold. But within their
naturalistic theories there was room for
teleology of
another kind, no longer implying providence or pur-
pose. Anaxagoras included
“Mind” among his natural
causes, to account for
nature's orderliness; Empedocles
included “Love and
Strife” to account for complexity;
Diogenes held that the cosmic
Air is intelligent, to
account for nature's tendency towards goals.
They
were opposed by the atomists, who held that all three
features—orderliness, complexity, and directiveness—
could be explained by random movements of atoms.
These features
have remained the chief talking-points
in the debate over teleology, which
has continued into
modern times.
Plato argued that the cosmologists merely analyzed
the material constituents
of things, and failed to ac-
count for the
characters of whole entities as such: for
a whole has a character which is
not found by adding
together the characters of its parts. He also
criticized
Anaxagoras for not making proper use of his concept
of
Mind, for he did not explain how things tend towards
“the
best,” nor what “the best” means. Plato's
own
concept was a world-soul distinct from the material
elements. He
believed in an overall teleology, namely
that nature is coordinated so that
the “best” for an
individual cannot be distinguished
from the good order
of the cosmos; but control by the world-soul is
not
complete, for there is much failure and evil due to
irrational
material.
This dualism disappears in Aristotle's analysis. He
still uses Plato's
double explanation—material necessity
on the one hand,
directiveness or “the final cause” on
the other
hand—but he emphasizes that both coexist
in natural movements.
Living things contain their own
sources of motion and directiveness. There
is no
world-soul or divine providence outside them. The
“Unmoved Mover” (God) which he posits as the sus-
taining cause of motion in the universe,
does not elicit
the individual “beginnings of motion”
which are all
the time occurring in nature; nor does God originate
or
comprehend nature's forms and species. Again,
within nature itself there is
no overall design nor coor-
dinating
agency, no quasi-conscious purpose. In his
explanations of animal
structures the goal is the ani-
mal's own
complete state, nothing beyond. For con-
venience he personifies “nature who does nothing at
random, but always does what is best out of the avail-
able possibilities,” and speaks of it as a
prudent house-
wife who
“apportions” the materials and
“uses” the
necessary movements of the elements. In so
speaking,
he formulated several principles of nature's economy
which
were adopted by later teleologists, such as: one
function to one organ, no
duplication of defenses, use
of by-products from one tissue in another. But
if taken
literally, these expressions would have to imply an
overall
purposiveness in nature, for which there is no
foundation in his
philosophy. They must therefore be
rhetorical. His frequent comparison
between nature
and craftsman helps to analyze teleological sequences
but does not imply a craftsman in nature. Lucretius
the atomist uses even
more colored language about
natura creatrix, which he could not possibly mean.
The
one or two occasions when Aristotle seems to suggest
that one
animal's advantage is sacrificed to the good
of other species probably mean no more than a general
balance
of nature. He never speaks of “purpose” in
nature.
His expression for the final cause is “the end
for the sake of
which the development occurs,” and
this end is the individual's
perfection and reproduction.
The source of directiveness in an animal or plant
is its soul. Aristotle did
not agree with Plato that the
soul is a separable entity, but argued that
it is the form
of the single body-soul entity. It is both the
structural
pattern of the living body, and the motive force which
makes it grow into that pattern. This difficult concep-
tion is closely related with his conception of
directive
nature. It is natural for the elements to act according
to
their simple properties; but it is equally natural for
them to combine and
become organized in complexes,
and in so doing to act against the simple
properties.
He takes this development from simple to complex as
a
datum, for which he offers no extra-physical cause.
Even where he posits
the soul as the cause of develop-
ment, this
soul is not something over against the com-
plex
of materials: it is the form of the whole complex,
its essential nature as
a unity. Where Plato regarded
necessity and directiveness as arising from
separate
sources, Aristotle regarded them as arising simulta-
neously within nature. An animal
is a process (a “road
to nature” in his words)
consisting of many movements,
all natural, which by natural coordination
tend towards
the animal's complete form.
There is therefore no “extra factor” such as modern
teleologists posit, no “conatus” (innate striving) irreduc-
ible to the laws of physics.
Aristotle's physics no doubt
made it easier to accommodate directiveness,
for he
was some way from the concept of an exactly quanti-
tative science, nor had he the theory that bodies
are
naturally inert. He may also have been unconsciously
influenced by
traditional hylozoism, which represented
nature as behaving like a living
being. At any rate,
soul is not enough to account for all of nature's direc-
tiveness, for Aristotle explicitly
says that nature pro-
ceeds without a break
from the soulless to the ensouled
(P.A. 681a 12, H.A. 588b 4).
When he defends teleology he does not argue pri-
marily from directiveness, like later teleologists, but
from the
fact that forms and species exist; from this
fact he then infers
directiveness. The object to be
explained is a living animal and its
structures. If it were
an artifact—for example a
chair—it would not be
enough to define it as
“something made of wood,” but
its form must be
included. In an animal there is the
further point that it is able to
function (for a dead man's
hand is no longer strictly a hand). Therefore
the first
thing to grasp is the form and function of the whole
living
animal, and only then can one understand its
growth. The parts are
“for the sake of the whole”; and
just as a whole differs from the sum of its parts, so
an end
differs in kind from the process leading to it.
From the fact that nature
regularly produced these
forms, he infers that natural processes tend
towards
them.
After Aristotle the Epicurean atomists produced a
counter-theory to make
teleology unnecessary. Atoms
have all kinds of shapes, and those that
happen to fit
together must tend to interlock when they meet in
random
collisions. In this way complexes can be
formed, which may grow very large.
Within them
movements will necessarily become restricted to cer-
tain patterns. Having been formed by pure
chance,
such a system will become stabilized, so long as it does
not
conflict with neighboring systems. For as atoms
continually flow in and out
of it, a successful system
will automatically perpetuate itself by
rejecting atoms
of incompatible shape, while retaining those that fit.
Furthermore, if a complex part of the system comes
away, it will consist of
atoms linked in the same con-
formation as
in the parent system. One such system
will be an animal. Innumerable
unsuccessful animals
will doubtless be formed, lacking essential organs
and
so unable to feed or defend themselves. But sometimes
a successful
one will appear, able to survive. Its off-
spring will naturally be of the same conformation.
Teleological
explanations are therefore vacuous: the
eye is not produced for the sake of
sight, but having
been produced by chance it then creates its own use.
This hypothesis of course could not be an inference
from data; spontaneous
generation was the only sup-
porting evidence
available. It was a theoretical con-
struction designed to show that random atomic move-
ments would originate complex and stable systems,
which would then reproduce themselves. The atomists'
explanation of the
survival of the fittest systems was
indeed a conception of random natural
selection. It
was not, however, linked with an evolutionary theory,
though it would have readily lent itself to one if it
had been suggested.
A new kind of teleology appeared in Stoicism, which
was a materialistic
theory of divine providence. The
divine pneuma,
consisting of warm air, is a continuum
that permeates the whole of nature.
Not only souls,
but all forms and abstract constructions, are parts of
the divine, and are somatic; they penetrate natural
objects and hold them
in tension. Hence every detail
in nature is continuously controlled by
providence,
which coordinates all goals in a predestined design.
In
such a conception Aristotle's primary defense of
teleology (that forms
cannot be explained by material
causes) is irrelevant. The Stoics based
their case on
directiveness, and it was therefore important to ac-
count for every detail teleologically. Galen's exhaustive
treatise On the Use of the Parts (second
century A.D.)
shows the difference from Aristotle's conception.
Writing under Stoic influence, Galen analyzes bodily
structures to the
smallest detail of tissue and arrange-
ment,
to show their uses. Where some detail carries
a disadvantage, he shows that
it is for an ulterior
advantage (for example, the skull's thinness aids
the
brain's efficiency); positive evils, like disease, are there
for
moral training. Aristotle on the other hand depends
upon conceiving the
animal as a coherent pattern of
activity, not upon piecemeal explanations
of utility,
and he recognizes that “while many things are for
the
sake of ends, much else occurs of necessity”: if you
have bone for the sake of rigidity, you must expect
it also to be
breakable.
In this way the Stoics contributed the first thorough-
going conception of providential teleology, within
a
naturalistic philosophy. This at once creates a problem
of evil; in
biology it means that all the inessentials and
imperfections which
Aristotle could attribute to “ne-
cessity” must now be shown to be purposed. The Stoic
answer to this problem was unsatisfactory (as were
their answers to the
allied ethical problems of free will
and wrongdoing). They confused the
issue by trying
to equate providence and nature. And by trying to
treat
immaterial things (such as abstract ideas) as if they
were
material, they confused design and directiveness.
Subsequent developments,
however, clarified the real
issues in the teleological arguments.
The first step was the return of Stoicism to a non-
materialistic theology. With the Neo-Platonists of
the
third century A.D., they held that forms are thoughts
in God's
mind, from which they emanate into matter
or are imposed upon it. Hence
nature exhibits a ra-
tional design which is
blurred by matter's intractability.
This was a return to Plato's view and
restored the
distinction between abstract and material. The next
step
was due to the impact of Judeo-Christian theology,
which introduced the
idea (not found in Greek philos-
ophy) that
God is not part of the universe, is omnip-
otent, and has created the universe out of nothing.
From this it
follows that matter of itself is inert, and
its motion is imparted to it.
Natural and supernatural
were now categorically distinguished.
Providential
design could no longer be confused with a natural
directiveness. At first indeed Aristotle's conception of
natural teleology
seemed impossible, for all movements
in nature must be imparted by God
alone. The problem
of evil now became critical, but was answered at
this
stage by theological doctrines (such as the Fall of Man)
which do
not concern teleology. But as the concept
of inertia developed in physics
during the later Middle
Ages, a contrast came to be drawn between the auto-
matic orderly movements of physical bodies
and the
supernatural guidance leading to goals. This brought
out a
distinction which had been latent but obscure
in Greek physics, between
orderliness and directive-
ness. The
orderliness of nature had been claimed in
evidence both by Aristotle and by
his opponents, the
atomists. But now, and especially after Newton, it
seemed to support only the anti-teleologists: they now
developed a concept
of nature working like a machine
by the “laws” of
physics, while teleologists had to
produce evidence of God's interference
in the causal
nexus. Then in the nineteenth century the Epicurean
conception of random natural selection appeared anew
in association with
the Darwinian theory of evolution.
The concept of rigid laws of nature
became modified
into a concept of statistical probability.
Teleologists
opposed the notion of randomness, but began to argue
less
from design and more from directiveness, so mov-
ing closer to Aristotle's natural teleology. But modern
teleology
still differs from his insofar as it relies upon
directiveness first,
rather than upon forms, and insofar
as it posits an “extra
factor” that is not reducible to
physics and chemistry. It is
therefore less simple, and
to that extent less rational, than Aristotle's.
But al-
though teleology has taken so many
different forms,
and has been opposed on different grounds, never-
theless the debate has in a way always
been between
the same contestants.
