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Dictionary of the History of Ideas | ||
BIOLOGICAL CONCEPTIONS
IN ANTIQUITY
The ancients did not distinguish between being
alive
and having a soul, which was conceived in various ways
as
something that organizes and controls the body.
Lacking optical
instruments, they had no concept of
the living cell, nor did they think of
flesh or wood as
possibly different from the constituents of nonliving
things. Life was given by the soul, both in animals and
in plants. Biology,
as the study of the living, is a modern
concept; when we speak of ancient
biology, we mean
the study of the ensouled. At the same time, the differ-
ence between living and nonliving
things was less
marked, because the ancients tended to assume that
all
matter possesses power and mobility and is quasi-
alive (the assumption that the material world is alive
is known
as “hylozoism”).
The early biological conceptions seem to originate
in pre-philosophical
reflection upon everyday experi-
ence. A
great deal of data was available concerning
husbandry, stockbreeding,
hunting, nutrition, medicine
and poisons, childbirth and dying, to which
was added
special information from Persian game reserves, from
the
wild animals of India, Egypt, and Libya, from the
Babylonian gardens where
the fertilization of fig and
from ritual crafts like root-cutting for drugs. From this
variety of data there arose certain common ideas which
can be conveniently grouped under the topics of the
four elements (Earth, Air, Fire, Water), the mysterious
extra element (aether), heredity, species, classification,
and teleology. But these ideas did not acquire precision
until philosophical argument came to sharpen them.
Agriculture and medicine were conducted by tradi-
tional rule of thumb. It was the early philosophers who
used these data to illustrate and justify their own cos-
mological arguments, and thereby evolved biological
theories which were then taken over by the agricultural
and medical writers (especially the Hippocratics). The
theoretical influence therefore ran mostly from philos-
ophy to biology rather than the other way. Zoology
and botany were not separated from cosmology until
Aristotle departmentalized the sciences; and even he
did not set up autonomous principles in biology, but
applied a conceptual framework from his general phi-
losophy. The earlier biological theories therefore need
to be understood in the context of larger physical
theories. Inevitably Greek philosophy is the best place
to study these ideas. Not that the other ancient civili-
zations lacked biological speculation; but we do not
find there any major biological idea that does not also
appear in the richer and fuller Greek discussions.
I. THE FOUR ELEMENTS
The soul was traditionally associated with blood,
breath, semen, the warmth
of life, and the persona.
Each of these retained significance as theorizing
de-
veloped. The most universal was the
conception of vital
warmth, which was regarded as one aspect of the
role
played by heat in the cosmos. Here the early cosmol-
ogists combined three traditional ideas: vital
warmth;
the seasonal powers of hot, cold, wet, and dry; and
the four
world-masses of fire, air, water, and earth.
Vital warmth was extended from
warm-blooded ani-
mals to all animals and even
to plants. It clearly meant
more than temperature, for pine wood (which is
not
hotter to touch than other timber) was thought to
contain more
heat and therefore to burn better. Hotter
plants have better fruit; hotter
animals are more intel-
ligent. Animal
droppings may still contain the warmth
of life, enabling them to generate
maggots. This is the
concept of heat as a stuff, not merely a quality
and
not necessarily perceptible, which survived into the
eighteenth-century theory of phlogiston. It was com-
mon ground among ancient scientists, even those who
did not consider
heat to be an element. The atomist
Democritus, for instance, who argued
that heat is
merely a sensation, nevertheless gave it an objective
basis by saying that it is the round atoms that feel
hot and that form the soul; that the heart contains the
fire of
life; that stags grow horns because their bellies
are hot and send the
nourishment upwards; that the
owl sees in the dark because she has fire in
her eyes.
These views are typical of the age.
As heat is necessary to life, so cold brings death:
it is not mere absence
of heat, but a stuff with its own
powers. Wet and dry also figure in early
theorizing,
more commonly than other powers, as being necessary
in
various forms of liquid and solid. These four were
assimilated to fire,
air, water, and earth. The two sets
do not exactly match, but Aristotle
eventually recon-
ciled them by a formula of
cross-pairing: fire is hot
plus dry, air is hot plus wet, and so on. He
held that
hot, cold, wet, and dry are the primitive qualities of
matter but cannot exist in isolation, while fire, air,
water, and earth are
the simplest separable elements,
capable of transformation into each other.
Some medical theorists at first opposed the concept
of four elements,
arguing that there are other equally
basic powers in the body, such as the
sweet, bitter,
salty, acid, astringent, insipid, and that the body con-
tains separate essential liquids (later
“humours” from
the Latin translation). After
controversy the humors
were agreed to be four—blood, black bile,
yellow bile,
phlegm—which were accommodated to Aristotle's ele-
ments by similar cross-pairing: blood is hot
plus wet
plus sweet, phlegm is cold plus wet plus salty.... Each
humor
was associated with a season and a human
temperament. This systematization
lasted through the
Middle Ages.
Heat always seemed the chief active force. Its char-
acteristic action was to concoct materials, to bring
them to fruition, to energize, sometimes to volatilize
or dissolve. Cold
caused condensing, coagulation, so-
lidifying. When Aristotle called hot and cold the chief
instruments
of nature, he was expressing a universal
view, whose details clearly
originated from kitchen and
garden. Water and earth were the materials
upon
which hot and cold worked; Aristotle analyzed them
into various
kinds of liquid and solid.
The importance of a fruitful balance among ele-
ments, a harmony of opposites, impressed the Greeks
perhaps more
than other peoples, and came from them
into medieval European thought. The
idea of symmetry
and proportionate blending dominated their medicine,
their art and architecture, their social and political
thinking. The
cosmologist Alcmaeon, who was also a
physician, made it his first cosmic
principle under the
political metaphor isonomia
(“equality of rights”).
When applied to mixtures of
materials, it led the way
from a qualitative assessment towards a
quantitative
chemistry. But the ancients did not go far in that
direction. Aristotle held that if the proportions of a
(kratein) the others. Wine and water can form a mix-
ture; but a single drop of wine, put into an ocean,
would be overcome and would lose its nature entirely.
Both concepts, proportion and mastery, are important
in his biology, particularly in genetics.
II. PNEUMA
The notion of a mysterious extra element in the
living body began to appear
in Aristotle's time, espe-
cially among those
inclined towards a materialistic
explanation. Aristotle believed in a
special fifth ele-
ment, the aether, but he confined it to the heavens.
In biology he uses a
concept of innate breath (pneuma),
which is mingled
with vital heat and is present even
in nonbreathing animals. It transmits
sensation, and is
the conveyor of soul in the semen. At one point he
compares its generative power with the aether, but
otherwise he defines it as warmed air, which the body
replenishes by
respiration.
After Aristotle the pneuma concept spread widely,
with different applications according to the different
philosophical
positions. Among medical writers it was
the residuary legatee of
unattributed functions, psychic
and sensory. The Stoics equated it with the divine
Logos that permeates nature, identifying pneuma and
aether (which remain confused in the medieval
concept
of the fifth element or quinta
essentia). Even the atom-
ists
posited a special kind of atom to account for the
soul, which Epicurus said
consists of atoms of fire, air,
wind, and a nameless fourth
kind—thus reducing his
opponents' pneuma
to wind but replacing its mysteri-
ous
functions with a new mystery.
Aristotle's predecessors had debated whether the
brain or the heart is the
center of sensation, and
whether the heart or the liver is the source of
the blood.
He decided for the heart in both cases. But in the third
century B.C. the Alexandrian anatomists distinguished
arteries from veins,
and isolated the nervous system
with the brain as its base. This led to an
elaboration
of pneuma theory: venous blood is formed
in the liver,
where it is charged with the lowest grade of pneuma
(Latin spiritus
naturalis, “natural spirits” in Renais-
sance medicine); some venous blood
flows to the heart,
where it is mixed with “pneuma necessary for life”
(“vital
spirits”) and so becomes arterial blood; this flows
to the
brain, where its pneuma is purified into “pneuma
used by the soul” (spiritus animalis, “animal
spirits”).
To explain the blood's route, Galen in the second
cen-
tury A.D. postulated minute passages
leading from right
to left ventricle in the heart, for which later
anatomists
searched in vain. After Harvey had demonstrated the
circulation of the blood, the whole hypothesis of
pneuma was gradually discarded.
III. GENETICS
It was an ancient question whether the male or the
female contributes the
seed which grows into the em-
bryo; the answer to
it partly determined a society's
view of blood-kinship and legal
inheritance. In classical
Greece the father was thought to be the primary
con-
tributor, but they disputed whether
the mother pro-
vides merely nutrition (as in
the dramatic decision in
Aeschylus' Oresteia) or a
second seed which unites with
the father's. Aristotle's analysis of current
theories in
his Generation of Animals shows that
discussions were
particularly lively in this field, where much
evidence
was quoted, some seriously misleading—for example,
that fishes swallow the milt, or that wound-scars have
been inherited (G.A. I. 17-18, III. 5, IV. 1). He himself
opposed
the concept of female seed, but it was ac-
cepted by Galen, Avicenna, and the Renaissance scien-
tists, until finally it was superseded by Von
Baer's
demonstration of the mammalian ovum. Among many
diverse
theories held by the atomists, “pangenesis”
was
important: that seed is drawn from every part of
both parents' bodies, to
account for resemblances. An-
other was
“preformationism”: that every part of the
embryo must
preexist in the seed (“for how could hair
grow from
non-hair?” said Anaxagoras). Some argued
that males must develop
from the father's seed and
females from the mother's; others attributed
sex-
differentiation to
differences of heat or position in the
uterus. Multiple births, monstrous
growths, superfeta-
tion, sterility, were
regularly quoted in evidence: to
some they suggested disproportion between
two seeds,
to others they suggested excess or deficiency of heat.
A Persian tradition connecting the semen with the
brain and spinal marrow
was followed by those who
held the brain to be the center of psychic
activity.
Those who held the heart to be the center argued that
semen
must come from the blood. A Greek tradition
associated it with foam (aphros, as in Aphrodite). Aris-
totle rationalized this idea in terms of pneuma, which
emulsifies the semen, being present in
it as the vehicle
of soul.
Aristotle gathered together these trains of thought
in a formulation based
on his own theory of matter
and form. The male seed transmits soul, which
is form
and movement; but its somatic part is sloughed away.
The
female contributes only the material (the cata-
menia). Among his arguments, he points out that fishes'
eggs do not
develop unless sprinkled with the milt,
yet this does not change them
quantitatively; and that
certain insects (as he thought) can receive the
male
impulse without a transmission of seed. Using his con-
cept of “mastery” he argues that
family likeness de-
pends upon the extent to
which the male impulse
controls the female material. Malformations, redun-
After Aristotle, the concept of female seed was re-
vived by the Alexandrian anatomists, who demon-
strated the genital connections of the ovaries and con-
cluded that these are channels for seeds
coming from
the blood. Later Galen demonstrated the oviduct in
sheep;
but instead of moving to a concept of mam-
malian ovum, he tried to reconcile this new datum with
Aristotle's
view, arguing that the female seed contrib-
utes only nutrition and the allantois, while the male
seed forms the
other embryonic membranes (chorion,
amnion) and bodily parts.
It was a universal belief (until Pasteur) that many
insects and plants grow
out of rotting materials without
seed. The early cosmologists used this to
argue that
life must have begun in that way. A typical account
occurs
in the History of Diodorus Siculus in the first
century B.C. In the primeval mud (that is, cold dry
earth
mixed with wet rain and the sun's heat) there appear
membranes containing embryo
animals of every kind,
which grow up and then reproduce themselves sexu-
ally. There was no ancient theory of
evolution out of
simpler forms, and therefore one problem was to ex-
plain how young animals, having appeared sponta-
neously, could survive in the mud
long enough to
become mature.
Those like Aristotle, who held that the universe had
no beginning, still had
to account for spontaneity. He
argued that pneuma
containing vital warmth is some-
times present
in water and earth mixed; a foamy bubble
is then formed, out of which may
arise eels and certain
of the fishes, testaceans and insects. He would
not
however allow that rottenness is a cause, for rottenness
is
disintegration whereas only concoction by heat can
generate new life.
IV. SPECIES
In folklore the animals and plants had clear-cut
natures, including moral
characterizations such as we
find in Aesop and in the Oriental and African
fables.
The ancients believed that some types regularly meta-
morphose into each other, for example,
cuckoo hawk
and hoopoe interchange, and wheat can become darnel.
By
this they meant a change of identity, not an ambi-
guity between these types, nor a seasonal change (as
stoat to
ermine).
Plato was the first to apply a philosophical technique
to the conception of
animal types. According to his
theory of Forms, we identify natural
qualities by com-
paring them with ideal
qualities which may not appear
exactly in nature but are known directly to
the mind.
The animal type is an aggregate of characters which
approximate to ideal Forms. The Forms therefore are
an absolute reference
point.
Aristotle inverts this analysis, by taking the animal
type as the exact
object of knowledge, while its char-
acters
vary in precision. Some characters are essential,
some not (for instance,
the eye may be essential, and
an eye must have a color, but its actual
color is ines-
sential and imprecise). The
animal type, namely its
species, is a unified pattern of essential
characters and
functions. It is identical in all members of the
species.
The variations between individuals are due to their
material
makeup, not to their form.
There have been so many conceptions of species in
modern times that it is
perhaps useful to say what
Aristotle's conception is not. It is not a
statistical aver-
age, not a population, not an
approximation, not an
arbitrarily selected type-specimen. On the other
hand,
it is not a form imposed by God. It is a type-pattern
that
exists in nature as an objective datum: it is there
to be detected within
individuals. It differs from any
one individual as absolutely as the
mathematical circle
differs from a drawing of a circle. It is this species-
pattern that Aristotle believes
to be eternally repro-
duced in nature, for
that is the nearest that sublunary
beings can get to the eternal cyclic
movement of the
stars. The fact that it may never be exactly
reproduced
does not affect his point, which is that nature tends
to
reproduce it.
This conception could easily become a belief in fixed
species, but Aristotle
did not consider that point; there
was in fact nothing in his biology that
was incompatible
with an evolutionary theory, had the question ever
arisen. He accepted reports of new species resulting
from miscegenation (he
quotes dog and fox, dog and
wolf, several fishes and birds). He makes only
the pro-
viso that interbreeding is limited to
animals that are
alike in species, size, and length of gestation, and
that
in any case there could not be indefinite production
of new
species, because that would defeat nature's
teleology (meaning that there
would be no goals, for
the goal is the reproduction of the parent's form).
He
emphasizes that the ladder of nature is continuous, and
that many
types overlap the borders of classifications.
Moreover his theory of
reproduction is aimed at ex-
plaining how the
father's form is transmitted and how
the family likeness may come to be
disturbed: the
precise goal is that the animal should “beget
another
like itself,” and its specific form is something
wider
that is only latent in it. There is a contradiction in
his
doctrine here: for he says theoretically that species
is the object of
science while individual differences are
due to matter and are unknowable,
but in practice he
brings to scientific account many characters that
are
below specific level—not only family likeness but ines-
sential attributes such as coloration
and voice. Just
occasionally he suggests that individuals differ not only
individualize them could be stated generally; but he
does not follow this up. (It was followed up by some
medieval scholastics, who thereby removed this diffi-
culty from his theory of individuation.)
Aristotle therefore could have accommodated an
evolutionary theory of
species; but he had no need of
it. He had no paleontology, no obsolete
species to
consider; similarity of species could be covered by his
theory; and believing that the world had no beginning,
he had no problem of
the origins of species. By the
third century A.D. some Stoic and
Neo-Platonist theo-
logians had developed
the idea that forms and species
are thoughts in the mind of God. It was
this idea, rather
than Aristotle's theory, that led later scientists
like
Linnaeus to posit the fixity of species.
V. CLASSIFICATION
Animals were traditionally grouped into Birds,
Beasts, and Fishes, air,
land, and sea creatures, and
some of them into subgroups like
cloven-hoofed,
horned, carnivorous. Plants were grouped as trees,
shrubs, fruiting, leguminous, and others that Theoph-
rastus reports. Popular classification did not go far,
and
was unsystematic in that some classes cut across each
other.
Plato developed in several dialogues the logical
technique of
“Division,” whereby a large concept is
analyzed into
its varieties—for example, the concept
“living on
land” is divisible into walking and flying,
and walking is
further divisible into quadruped, biped,
and polypod. With it he combined
the complementary
technique of “Collection,” whereby
data are sorted
into groups by common concepts, and these groups are
further grouped under more general concepts; for ex-
ample, biped and quadruped share the concept walk-
ing, and walking, flying, and swimming share the con-
cept locomotion. Collection is the inductive
process
which Division follows and confirms deductively.
Plato's aim
was to “track down” and identify concepts
by showing
their relationships in a Division.
Plato intended his method to reveal the actual divi-
sions in nature, but when applied to animal characters
it split
up natural groups. Aristotle therefore took as
initial data not characters
but animal types (which have
multiple characters). Class the species by
likeness, then
class the classes by more general likenesses, until you
arrive at the class Animal itself. Then reconsider what
are the most
significant distinguishing characters, and
re-divide the classes
accordingly down to the individual
species again. You now have an orderly
hierarchy of
genera and species, enabling you to define species by
group-characters, to classify new species as they ap-
pear, and to predict characters not yet observed. This
is the same conception that Ray and Linnaeus success-
fully developed, but Aristotle
lacked enough data to
make it workable. He also handicapped it
unnecessarily
by laying down that within a genus the member-species
must have characters differing only in degree (for ex-
ample, wings of various shapes), whereas between
genera the
comparison must be one of “analogy” (as
wing to fin).
He began with a division of Animal into
“blooded”
(that is, red-blooded) and “bloodless,” and
divided
these into (1) man, viviparous quadrupeds,
oviparous quadrupeds, cetaceans,
birds, fishes and (2)
crustaceans, testaceans, mollusks, insects. But he
points
out that this scheme omits some types (snakes, sponges),
and
that below this level the natural subgroups cut
across each other: for
example, the classes solid-hoofed,
hornless, ruminant are defeated by the
“overlapping”
types pig and camel.
He therefore preferred to arrange the species in an
order of
“perfection.” This too was inspired by Plato,
who had
set out a rough scala naturae running down-
wards from man, through bipeds,
quadrupeds,
polypods, serpents, to fishes; his indices were intelli-
gence and posture. Aristotle took
vital heat as his index
of perfection, as shown not only by intelligence
and
posture but also by respiration, method of repro-
duction, and state at birth. This method better
suited
his view that nature is continuous from plant to animal
(the
testaceans and sponges being in both categories).
In his actual practice he
often argues from this order
of perfection, but makes almost no use of
genus-species
classification.
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—
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
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
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.
BIBLIOGRAPHY
A. L. Peck's editions (Loeb Classical Library, London and
Cambridge,
Mass.) of Aristotle's Parts of Animals (1955),
Generation of Animals (1953), and Historia Animalium
(1965) contain expository
introduction, English translation
and notes, including a short
bibliography of modern sec-
ondary
literature on ancient Greek biology. E. Lesky, Die
Zeugungs- und Vererbungslehren der Antike und ihr
Nachwirken (Vienna, 1950) describes ancient genetic theo-
ries. O. Keller, Die antike Tierwelt, 2 vols. (Leipzig, 1909-13)
collects
information under each animal. Ernest H. F. Meyer,
Geschichte der Botanik, 4 vols.
(Königsberg, 1854-59) dis-
cusses
authors chronologically from classical times. E. L.
Greene, Landmarks of Botanical History, Smithsonian Mis-
cellaneous Collections 54
(Washington, D.C., 1909) and A.
Arber, The Natural
Philosophy of Plant Form, (Cambridge,
1950) analyze Greek
views, especially of Theophrastus.
F. S. Bodenheimer, The History of Biology (London, 1958)
includes English
translations of ancient non-Greek texts.
D. M. BALME
[See also Atomism; Causation; Chain of Being; Classificationof the Sciences; Evolutionism; Genetic Continuity; God;
Platonism; Stoicism.]
Dictionary of the History of Ideas | ||