Aristotle: Biology

aristotle

Aristotle (384-322 BCE.) may be said to be the first biologist in the
Western tradition. Though there are physicians and other natural
philosophers who remark on various flora and fauna before Aristotle,
none of them brings to his study a systematic critical empiricism.
Aristotle's biological science is important to understand, not only
because it gives us a view into the history and philosophy of science,
but also because it allows us more deeply to understand his
non-biological works, since certain key concepts from Aristotle's
biology repeat themselves in his other writings. Since a significant
portion of the corpus of Aristotle's work is on biology, it is natural
to expect his work in biology to resonate in his other writings. One
may, for example, use concepts from the biological works to better
understand the ethics or metaphysics of Aristotle.

This article will begin with a brief explanation of his biological
views and move toward several key explanatory concepts that Aristotle
employs. These concepts are essential because they stand as candidates
for a philosophy of biology. If Aristotle's principles are insightful,
then he has gone a long way towards creating the first systematic and
critical system of biological thought. It is for this reason (rather
than the particular observations themselves) that moderns are
interested in Aristotle's biological writings.

1. His Life

Aristotle was born in the year 384 B.C. in the town of Stagira (the
modern town Stavros), a coastal Macedonian town to the north of
Greece. He was raised at the court of Amyntas where he probably met
and was friends with Philip (later to become king and father to
Alexander, the Great). When Aristotle was around 18, he was sent to
Athens to study in Plato's Academy. Aristotle spent twenty years at
the Academy until Plato's death, although Diogenes says Aristotle left
before Plato's death. When Plato was succeeded by his nephew,
Speusippus, as head of the Academy, Aristotle accepted an invitation
to join a former student, Hermeias, who was gathering a Platonic
circle about him in Assos in Mysia (near Troy). Aristotle spent three
years in this environment. During this time, he may have done some of
the natural investigations that later became The History of Animals.

At the end of Aristotle's stay in Mysia, he moved to Lesbos (an
adjacent island). This move may have been prompted by Theophrastus, a
fellow of the Academy who was much influenced by Aristotle. It is
probable (according to D'Arcy Thompson) that Aristotle performed some
important biological investigations during this period.

Aristotle returned to Athens (circa 334-5). This began a period of
great productivity. He rented some grounds in woods sacred to Apollo.
It was here that Aristotle set-up his school (Diog. Laert V, 51).

At his school Aristotle also accumulated a large number of manuscripts
and created a library that was a model for later libraries in
Alexandria and Pergamon. According to one tradition, Alexander (his
former pupil) paid him a handsome sum of money each year as a form of
gratitude (as well as some exotic animals for Aristotle to study that
Alexander encountered in his conquests).

At the death of Alexander in 323, Athens once again was full of
anti-Macedonian sentiment. A charge of impiety was brought against
Aristotle due to a poem he had written for Hermeias. One martyr for
philosophy (Socrates) was enough for Aristotle and so he left his
school to his colleague, Theophrastus, and fled to the Macedonian
Chalcis. Here in 322 he died of a disease that is still the subject of
speculation.
2. The Scope of Aristotle's Biological Works

There is some dispute as to which works should be classified as the
biological works of Aristotle. This is indeed a contentious question
that is especially difficult for a systematic philosopher such as
Aristotle. Generally speaking, a systematic philosopher is one who
constructs various philosophical distinctions that, in turn, can be
applied to a number of different contexts. Thus, a distinction such as
"the more and the less" that has its roots in biology explaining that
certain animal parts are greater (bigger) among some individuals and
smaller among others, can also be used in the ethics as a cornerstone
of the doctrine of the mean as a criterion for virtue. That is, one
varies from the mean by the principle of the more and the less. For
example, if courage is the mean, then the defect of excess would be
"foolhardiness" while the defect of paucity would be "cowardice." The
boundary between what we'd consider "biology" proper vs. what we'd
think of as psychology, philosophy of mind, and metaphysics is often
hard to draw in Aristotle. That's because Aristotle's understanding of
biology informs his metaphysics and philosophy of mind, but likewise,
he often uses the distinctions drawn in his metaphysics in order to
deal with biological issues.

In this article, the biological works are: (a) works that deal
specifically with biological topics such as: The Parts of Animals
(PA), The Generation of Animals (GA), The History of Animals (HA), The
Movement of Animals, The Progression of Animals, On Sense and Sensible
Objects, On Memory and Recollection, On Sleep and Waking, On Dreams,
On Prophecy in Sleep, On Length and Shortness of Life, On Youth and
Old Age, On Life and Death, On Respiration, On Breath, and On Plants,
and (b) the work that deals with psuche (soul), On the Soul—though
this work deals with metaphysical issues very explicitly, as well.
This list does not include works such as the Metaphysics, Physics,
Posterior Analytics, Categories, Nicomachean Ethics, or The Politics
even though they contain many arguments that are augmented by an
understanding of Aristotle's biological science. Nor does this article
examine any of the reputedly lost works (listed by ancient authors but
not existing today) such as Dissections, On Composite Animals, On
Sterility, On Physiognomy, and On Medicine . Some of these titles may
have sections that have survived in part within the present corpus,
but this is doubtful.
3. The Specialist and the Generalist

The distinction between the specialist and the generalist is a good
starting point for understanding Aristotle's philosophy of biology.
The specialist is one who has a considerable body of experience in
practical fieldwork while the generalist is one who knows many
different areas of study. This distinction is brought out in Book One
of the Parts of Animals (PA). At PA 639a 1-7 Aristotle says,

In all study and investigation, be it exalted or mundane, there
appear to be two types of proficiency: one is that of exact,
scientific knowledge while the other is a generalist's understanding.
(my tr.)

Aristotle does not mean to denigrate or to exalt either. Both are
necessary for natural investigations. The generalist's understanding
is holistic and puts some area of study into a proper genus, while
scientific knowledge deals with causes and definitions at the level of
the species. These two skills are demonstrated by the following
example:

An example of what I mean is the question of whether one should
take a single species and state its differentia independently, for
example, homo sapiens nature or the nature of Lions or Oxen, etc., or
should we first set down common attributes or a common character (PA
639a 15-19, my tr.).

In other words, the methodology of the specialist would be to observe
and catalogue each separate species by itself. The generalist, on the
other hand, is drawn to making more global connections through an
understanding of the common character of many species. Both skills are
needed. Here and elsewhere Aristotle demonstrates the limitations of a
single mode of discovery. We cannot simply set out a single path
toward scientific investigation—whether it be demonstrative (logical)
exactness (the specialist's understanding) or holistic understanding
(the generalist's knowledge). Neither direction (specialist or
generalist) is the one and only way to truth. Really, it is a little
of both working in tandem. Sometimes one half takes the lead and
sometimes the other. The adoption of several methods is a cornerstone
of Aristotelian pluralism, a methodological principle that
characterizes much of his work.

When discussing biological science, Aristotle presents the reader two
directions: (a) the modes of discovery (genetic order) and (b) the
presentation of a completed science (logical order). In the mode of
discovery, the specialist sets out all the phenomena in as much detail
as possible while the generalist must use her inter-generic knowledge
to sort out what may or may not be significant in the event taking
place before her. This is because in the mode of discovery, the
investigator is in the genetic order. Some possible errors that could
be made in this order (for example) might be mistaking certain animal
behaviors for an end for which they were not intended. For example, it
is very easy to mistake mating behavior for aggressive territorial
behavior. Since the generalist has seen many different types of
animals, she may be in the best position (on the basis of generic
analogy) to classify the sort of behavior in question.

In the mode of discovery one begins with the phenomenon and then seeks
to create a causal explanation (PA 646a 25). But how does one go about
doing this? In the Posterior Analytics II.19, Aristotle suggests a
process of induction that begins with the particular and then moves to
the universal. Arriving at the universal entails a comprehensive
understanding of some phenomenon. For example, if one wanted to know
whether fish sleep, one would first observe fish in their environment.
If one of the behaviors of the fish meets the common understanding of
sleep (such as being deadened to outside stimulus, showing little to
no movement, and so forth), then one may move to the generalization
that fish sleep (On Sleeping and Waking 455b 8, cf. On Dreams 458b 9).
But one cannot stop there. Once one has determined that fish sleep
(via the inductive mode of discovery), it is now up to the researcher
to ferret out the causes and reasons why, in a systematic fashion.
This second step is the mode of presentation. In this mode the
practitioner of biological science seeks to understand why the
universal is as it is. Going back to the example of sleeping fish, the
scientist would ask why fish need to sleep. Is it by analogy to humans
and other animals that seem to gather strength through sleep? What
ways might sleep be dangerous (say by opening the individual fish to
being eaten)? What do fish do to avoid this?

These, and other questions require the practitioner to work back and
forth with what has been set down in the mode of discovery for the
purpose of providing an explanation. The most important tools for this
exercise are the two modes of causal explanation.
4. The Two Modes of Causal Explanation

For Aristotle there are four causes: material, efficient, formal, and
final. The material cause is characterized as "That out of which
something existing becomes" (Phys. 194b 24). The material has the
potential for the range of final products. Within the material is, in
a potential sense, that which is to be formed. Obviously, one piece of
wood or metal has the potential to be many artifacts; yet the
possibilities are not infinite. The material itself puts constraint
upon what can be produced from it. One can execute designs in glass,
for example, which could never be brought forth from brass.

The efficient cause is depicted as "that from whence comes the first
principle of kinetic change or rest" (Phys. 194b 30). Aristotle gives
the example of a male fathering a child as showing an efficient cause.
The efficient cause is the trigger that starts a process moving.

The formal cause constitutes the essence of something while the final
cause is the purpose of something. For example, Aristotle believed the
tongue to be for the purpose of either talking or not. If the tongue
was for the purpose of talking (final cause), then it had to be shaped
in a certain way, wide and supple so that it might form subtle
differences in sound (formal cause). In this way the purpose of the
tongue for speaking dovetails with the structural way it might be
brought about (P.A. 660a 27-32).

It is generally the case that Aristotle in his biological science
interrelates the final and formal causes. For example Aristotle says
that the efficient cause may be inadequate to explain change. In the
On Generation and Corruption 336a Aristotle states that all natural
efficient causes are regulated by formal causes. "It is clear then
that fire itself acts and is acted upon." What this means is that
while the fire does act as efficient cause, the manner of this action
is regulated by a formal/final cause. The formal cause (via the
doctrine of natural place—that arranges an ascending hierarchy among
the elements, earth, water, air and fire) dictates that fire is the
highest level of the sub-lunar phenomena. Thus, its essence defines
its purpose, namely, to travel upward toward its own natural place. In
this way the formal and final cause act together to guide the actions
of fire (efficient cause) to point upward toward its natural place.

Aristotle (at least in the biological works) invokes a strategy of
redundant explanation. Taken at its simplest level, he gives four
accounts of everything. However, in the actual practice, it comes
about that he really only offers two accounts. In the first account he
presents a case for understanding an event via material/kinetic means.
For the sake of simplicity, let us call this the ME (materially-based
causal explanation) account.

In the second case he presents aspects of essence (formal cause) and
purpose (final cause). These are presented together. For the sake of
simplicity, let us call this the TE (teleologically-based causal
explanation) account. For an example of how these work together,
consider respiration.

Aristotle believes that material and efficient causes can give one
account of the motions of the air in and out of the lungs for
respiration. But this is only part of the story. One must also
consider the purpose of respiration and how this essence affects the
entire organism (PA 642a 31-642b 4). Thus the combination of the
efficient and material causes are lumped together as one sort of
explanation ME that focus upon how the nature of hot and cold air form
a sort of current that brings in new air and exhales the old. The
final and formal causes are linked together as another sort of
explanation TE that is tied to why we have respiration in the first
place.

In Aristotle's account respiration we are presented with a partner to
TE and ME: necessity. When necessity attaches itself to ME it is
called simple or absolute necessity. When necessity attaches itself to
TE it is called conditional necessity. Let us return to our example of
respiration and examine these concepts in more detail.

First, then there is the formal/final cause of respiration.
Respiration exists so that air might be brought into the body for the
creation of pneuma (a vital force essential for life). If there were
no respiration, there would be no intake of air and no way for it to
be heated in the region of the heart and turned intopneuma—an element
necessary for life among the blooded animals who live out of water.
Thus the TE for respiration is for the sake of producing an essential
raw material for the creation of pneuma.

The second mode of explanation, ME, concerns the material and
efficient causes related to respiration. These have to do with the
manner of a quasi-gas law theory. The hot air in the lungs will tend
to stay there unless it is pushed out by the cold incoming air that
hurries its exit (cf. On Breath 481b 11). (This is because 'hot' and
'cold' are two of the essential contraries hot/cold & wet/dry). It is
the material natures of the elements that dictate its motions. This is
the realm of the ME.

ME is an important mode of explanation because it grounds the
practitioner in the empirical facts so that he may not incline himself
to offer mere a priori causal accounts. When one is forced to give
material and kinetic accounts of some event, then one is grounded in
the tangible dynamics of what is happening. This is one important
requirement for knowledge.

Now to necessity. Necessity can be represented as a modal operator
that can attach itself to either TE or to ME. When it attaches itself
to TE, the result is conditional necessity. In conditional necessity
one must always begin with the end to be achieved. For example, if one
assumes the teleological assumption of natural efficiency, Nature does
nothing in vain (GA 741b 5, cf. 739b20, et. al.) then the functions of
various animal parts must be viewed within that frame. If we know that
respiration is necessary for life, then what animal parts are
necessary to allow respiration within different species? The
acceptance of the end of respiration causes the investigator to
account for how it can occur within a species. The same could be said
for other given ends such as "gaining nutrition," "defending one's
self from attack," and "reproduction," among others. When the
biologist begins his investigation with some end (whether in the mode
of discovery or the mode of scientific presentation), he is creating
an account of conditional necessity.

The other sort of necessity is absolute necessity that is the result
of matter following its nature (such as fire moving to its natural
place). The very nature of the material, itself, creates the
dynamics—such as the quasi gas law interactions between the hot and
cold air in the lungs. These dynamics may be described without
proximate reference to the purpose of the event. In this way ME can
function by itself along with simple necessity to give one complete
account of an event.

In biological science Aristotle believes that conditional necessity is
the most useful of the two necessities in discovery and explanation
(PA 639b 25). This is because, in biology, there is a sense that the
entire explanation always requires the purpose to set out the
boundaries of what is and what is not significant. However, in his
practice it is most often the case that Aristotle employs two complete
accounts ME and TE in order to reveal different modes of explanation
according to his doctrine of pluralism.
5. Aristotle's Theory of Soul

The word for 'soul' in Aristotle is psuche. In Latin it is translated
as anima. For many readers, it is the use of the Latin term
(particularly as it was used by Christian, Moslem, and Jewish
theologians) that forms the basis of our modern understanding of the
word. Under the theological tradition, the soul meant an immaterial,
detached ruling power within a human. It was immortal and went to God
after death. This tradition gave rise to Descartes' metaphysical
dualism: the doctrine that there are two sorts of things that exist
(soul and matter), and that soul ruled matter.

Aristotle does not think of soul as the aforementioned theologians do.
This is because matter (hyle) and shape (morphe) combine to create a
unity not a duality. The philosopher can intellectually abstract out
the separate constituents, but in reality they are always united. This
unity is often termed hylomorphism (after its root words). Using the
terminology of the last section we can identify hyle with ME and
morphe with TE. Thus, Aristotle's doctrine of the soul (understood as
hylomorphism) represents a unity of form and function within matter.

From the biological perspective, soul demarcates three sorts of living
things: plants, animals, and human beings. In this way soul acts as
the cause of a body's being alive (De An 415b 8). This amalgamation
(soul and body) exhibits itself through the presentation of a
particular power that characterizes what it means to be alive for that
sort of living thing.

The soul is the form of a living body thus constituting its first
actuality. Together the body and soul form an amalgamation. This is
because when we analyze the whole into its component parts the
particular power of the amalgamation is lost. Matter without TE, as we
have seen, acts through the nature of its elements (earth, air, fire,
and water) and not for its organic purpose. An example that
illustrates the relationship between form and matter is the human eye.
When an eye is situated in a living body, the matter (and the motions
of that matter) of the eye works with the other parts of the body to
present the actualization of a particular power: sight. When governed
by the actuality (or fulfillment) of its purpose, an eyeball can see
(De An 412b 17). Both the matter of the eyeball and its various neural
connections (hyle, understood as ME) along with the formal and final
causes (morphe, understood as TE) are necessary for sight. Each part
has its particular purpose, and that purpose is given through its
contribution to the basic tasks associated with essence of the sort of
thing in question: plant, animal, human.

It is important not to slip into the theological cum Cartesian sense
of anima here. To say that plants and animals have souls is not to
assert that there is a Divine rose garden or hound Heaven. We must
remember that soul for Aristotle is a hylomorphic unity representing a
monism and not a dualism. (The rational soul's status is less clear
since it is situated in no particular organ since Aristotle rejected
the brain as the organ of thinking relegating it to a cooling
mechanism, PA652b 21-25). It is the dynamic, vital organizing
principle of life—nothing more, nothing less.

Plants exhibit the most basic power that living organisms possess:
nutrition and reproduction (De An 414a 31). The purpose of a plant is
to take in and process materials in such a way that the plant grows.
Several consequences follow (for the most part) from an individual
plant having a well-operating nutritive soul. Let's examine one sort
of plant, a tree. If a plant exhibits excellence in taking in and
processing nutrition it will exhibit various positive effects. First,
the tree will have tallness and girth that will see it through
different weather conditions. Second, it will live longer. Third, it
will drop lots of seeds giving rise to other trees. Thus, if we were
to compare two individual trees (of the same species), and one was
tall and robust while the other was small and thin, then we would be
able to render a judgment about the two individual trees on the basis
of their fulfillment of their purpose as plants within that species.
The tall and robust tree of that species would be a better tree
(functionally). The small and thin tree would be condemned as failing
to fulfill its purpose as a plant within that species.

Animals contain the nutritive soul plus some of the following powers:
appetite, sensation, and locomotion (De An 414a 30, 414b 1-415a 13).
Now, not all animals have all the same powers. For example, some (like
dogs) have a developed sense of smell, while others (like cats) have a
developed ability to run quickly with balance. This makes simple
comparisons between species more difficult, but within one species the
same sort of analysis used with plants also holds. That is, between
two individual dogs one dog can (for example) smell his prey up to 200
meters away while the other dog can only detect his prey up to 50
meters. (This assumes that being able to detect prey from a distance
allows the individual to eat more often.) The first dog is better
because he has fulfilled his soul's function better than the second.
The first dog is thus a good dog while the second a bad example of
one. What is important here is that animals judged as animals must
fulfill that power (soul) particular to it specifically in order to be
functionally excellent. This means that dogs (for example) are
proximately judged on their olfactory sense and remotely upon their
ability to take in nutrition and to reproduce.

Humans contain the nutritive soul and the
appetitive-sensory-locomotive souls along with the rational soul. This
power is given in a passive, active, and imaginative sense (De An III
3-5). What this means is that first there is a power in the rational
soul to perceive sensation and to process it in such a way that it is
intelligible. Next, one is able to use the data received in the first
step as material for analysis and reflection. This involves the active
agency of the mind. Finally, the result (having both a sensory and
ratiocinative element) can be arranged in a novel fashion so that the
universal mixes with the perceived particular. This is imagination (De
An III.3). For example, one might perceive in step-one that your door
is hanging at a slant. In step-two you examine the hinges and ponder
why the door is hanging in just this way. Finally, in step-three you
consider types of solutions that might solve the problem—such as
taking a plane to the top of the door, or inserting a "shim" behind
one of the hinges. You make your decision about this door in front of
you based upon your assessment of the various generic solutions.

The rational soul, thus understood as a multi-step imaginative
process, gives rise to theoretical and practical knowledge that, in
turn, have other sub-divisions (EN VI). Just as the single nutritive
soul of plants was greatly complicated by the addition of souls for
the animals, so also is the situation even more complicated with the
addition of the rational soul for humans. This is because it has so
many different applications. For example, one person may know right
and wrong and can act on this knowledge and create habits of the same
while another may have productive knowledge of an artist who is able
to master the functional requirements of his craft in order to produce
well-wrought artifacts. Just as it is hard to compare cats and dogs
among animal souls, so it is difficult to judge various instantiations
of excellence among human rational souls. However, it is clear that
between two persons compared on their ethical virtues and two artists
compared on their productive wisdom, we may make intra-category
judgments about each. These sorts of judgments begin with a biological
understanding of what it means to be a human being and how one may
fulfill her biological function based on her possession of the human
rational soul (understood in one of the sub-categories of reason).
Again, a biological understanding of the soul has implications beyond
the field of biology/psychology.
6. The Biological Practice: Outlines of a Systematics

Systematics is the study of how one ought to create a system of
biological classification and thus perform taxonomy. ("Systematics" is
not to be confused with being a "systematic philosopher." The former
term has a technical meaning related to the theoretical foundations of
animal classification and taxonomy. The latter phrase has to do with a
tightly structured interlocking philosophical account.) In Aristotle's
logical works, he creates a theory of definition. According to
Aristotle, the best way to create a definition is to find the
proximate group in which the type of thing resides. For example,
humans are a type of thing (species) and their proximate group is
animal (or blooded animal). The proximate group is called thegenus.
Thus the genus is a larger group of which the species is merely one
proper subset. What marks off that particular species as unique? This
is the differentia or the essential defining trait. In our example
with humans the differentia is "rationality." Thus the definition of
"human" is a rational animal. "Human" is the species, "animal" is the
genus and "rationality" is the differentia.

In a similar way, Aristotle adapts his logical theory of genus and
species to biology. By thinking in terms of species and their
proximate genus, Aristotle makes a statement about the connections
between various types of animals. Aristotle does not create a
full-blown classification system that can describe all animals, but he
does lay the theoretical foundations for such.

The first overarching categories are the blooded and the non-blooded
animals. The animals covered by this distinction roughly correspond to
the modern distinction between vertebrates and invertebrates. There
are also two classes of dualizers that are animals that fit somewhat
between categories. Here is a sketch of the categorization:

I. Blooded Animals

A. Live bearing animals

1. Homo Sapiens2. Other mammals without a distinction for primates

B. Egg-laying animals

1. Birds2. Fish

I. Non-Blooded Animals

A. Shell skinned sea animals: testaceaB. Soft shelled sea
animals: Crustacea

C. Non-shelled soft skinned sea animals: Cephalopods

D. Insects

E. Bees

I. Dualizers (animals that share properties of more than one group)

A. Whales, seals and porpoises—they give live birth yet they
live in the seaB. Bats—they have four appendages yet they fly

C. Sponges—they act like both plants and like animals

Aristotle's proto-system of classification differs from that of his
predecessors who used habitat and other non-functional criteria to
classify animals. For example, one theory commonly set out three large
groups: air, land, and sea creatures. Because of the functional
orientation of Aristotle's TE, Aristotle repudiates any classification
system based upon non-functional accidents. What is important is that
the primary activities of life are carried out efficiently through
specially designated body parts.

Though Aristotle's work on classification is by no means comprehensive
(but is rather a series of reflections on how to create one), it is
appropriate to describe it as meta-systematics. Such reflections are
consistent with his other key explanatory concepts of functionalism
(TE and ME) as well as his work on logic in the Organon with respect
to the utilization of genus and species. Though incomplete, this again
is a blueprint of how to construct a systematics. The general
structure of meta-systematics also acts as an independent principle
that permits Aristotle to examine animals together that are
functionally similar. Such a move enhances the reliability of analogy
as a tool of explanation.
7. "The more and the less" and "Epi to polu"

"The more and the less" is an explanatory concept that is allied to
the ME account. Principally, it is a way that individuation occurs in
the non-uniform parts. Aristotle distinguishes two sorts of parts in
animals: the uniform and the non-uniform. The uniform parts are those
that if you dumped them into a bucket and cut the bucket in half, they
would still remain the same. For example, blood is a uniform part.
Dump blood into a bucket and cut it in half and it's still the same
blood (just half the quantity). The same is true of tissue, cartilage,
tendons, skin, et al. Non-uniform parts change when the bucket test is
applied. If you dump a lung into a bucket and cut it in half, you no
longer have a proper organ. The same holds true of other organs:
heart, liver, pancreas, and so forth, as well as the skeleton (Uniform
Parts—PA 646b 20, 648b, 650a 20, 650b, 651b 20, 652a 23; Non-Uniform
Parts—PA 656b 25, 622a 17, 665b 20, 683a 20, 684a 25.)

When an individual has excess nutrition (trophe), the excess
(perittoma) often is distributed all around (GA 734b 25). An external
observer does not perceive the changes to the uniform parts—except,
perhaps, stomach fat. But such an observer would perceive the
difference in a child who has been well fed (whose non-uniform parts
are bigger) than one who hasn't. The difference is accounted for by
the principle of the more and the less.

How does an external observer differentiate between any two people?
The answer is that the non-uniform parts (particularly the skeletal
structure) differ. Thus, one person's nose is longer, another stands
taller, a third is broader in the shoulders, etc. We all have noses,
stand within a range of height and broadness of shoulders, etc. The
particular mix that we each possess makes us individuals.

Sometimes, this mix goes beyond the range of the species (eidos). In
these instances a part becomes non-functional because it has too much
material or too little. Such situations are beyond the natural range
one might expect within the species. Because of this, the instance
involved is characterized as being unnatural (para phusin).

The possibility of unnatural events occurring in nature affects the
status of explanatory principles in biology. We remember from above
that there are two sorts of necessity: conditional and absolute. The
absolute necessity never fails. It is the sort of necessity that one
can apply to the stars that exist in the super lunar realm. One can
create star charts of the heavens that will be accurate for a thousand
years forward or backward. This is because of the mode of absolute
necessity.

However, because conditional necessity depends upon its telos, and
because of the principle of the more and the less that is
non-teleologically (ME) driven, there can arise a sort of spontaneity
(cf. automaton, Phys. II.6) that can alter the normal, expected
execution of a task because spontaneity is purposeless. In these cases
the input from the material cause is greater or lesser than is usually
the case. The result is an unnatural outcome based upon the principle
of the more and the less. An example of this might be obesity.
Nourishment is delivered to the body in a hierarchical fashion
beginning with the primary needs. When all biological needs are met,
then the excess goes into hair, nails and body fat. Excess body fat
can impair proper function, but not out of design.

Because of the possibility of spontaneity and its unintended
consequences, the necessary operative in biological events
(conditional necessity) is only "for the most part" (hôs epi to polu).
We cannot expect biological explanatory principles to be of the same
order as those of the stars. Ceteris paribis principles are the best
the biological realm can give. This brute fact gives rise to a
different set of epistemic expectations than are often raised in the
Prior Analytics and the Posterior Analytics. Our expectations for
biology are for general rules that are true in most cases but have
many exceptions. This means that biology cannot be an exact science,
unlike astronomy. If there are always going to be exceptions that are
contrary to nature, then the biologist must do his biology with
toleration for these sorts of peripheral anomalies. This disposition
is characterized by the doctrine of epi to polu.
8. Significant Achievements and Mistakes

This section will highlight a few of Aristotle's biological
achievements from the perspective of over 2,300 years of hindsight.
For simplicity's sake let us break these up into "bad calls"
(observations and conclusions that have proven to be wrong) and "good
calls" (observations and conclusions that have proven to be very
accurate).

We begin with the bad calls: let's start with a few of Aristotle's
mistakes. First, Aristotle believed that thinking occurred in the
region around the heart and not in the brain (a cooling organ, PA 652b
21-25, cf. HA 514a 16-22). Second, Aristotle thought that men were
hotter than women (the opposite is the case). Third, Aristotle
overweighed the male contribution in reproduction. Fourth, little
details are often amiss such as the number of teeth in women. Fifth,
Aristotle believed that spontaneous generation could occur. For
example, Aristotle observed that from animal dung certain flies could
appear (even though careful observation did not reveal any flies
mating and laying their eggs in the dung. The possibility of the eggs
already existing in the abdomen of the animal did not occur to
Aristotle.) However, these sorts of mistakes are more often than not
the result of an a priori principle such as "women being colder and
less perfectly formed than men" or the application of his method on
(in principle) unobservables—such as human conception in which it is
posited that the male provides the efficient, formal, and final cause
while the woman provides merely the material cause.

Good Calls: Aristotle examined over 500 different species of animals.
Some species came from fishermen, hunters, farmers, and perhaps
Alexander. Many other species were viewed in nature by Aristotle.
There are some very exact observations made by Aristotle during his
stay at Lesbos. It is virtually certain that his early dissection
skills were utilized solely upon animals (due to the social
prohibition on dissecting humans). One example of this comes from the
Generation of Animals in which Aristotle breaks open fertilized
chicken eggs at carefully controlled intervals to observe when visible
organs were generated. The first organ Aristotle saw was the heart.
(In fact it is the spinal cord and the beginnings of the nervous
system, but this is not visible without employing modern staining
techniques.) On eggs opened later, Aristotle saw other organs. This
led Aristotle to come out against a popular theory of conception and
development entitled, "the pre-formation theory." In the pre-formation
theory, whose advocates extended until the eighteenth century, all the
parts appear all at once and development is merely the growth of these
essential parts. The contrary theory that Aristotle espouses is the
epigenetic theory. According to epigenesis, the parts are created in a
nested hierarchical order. Thus, through his observation, Aristotle
saw that the heart was formed first, then he postulated that other
parts were formed (also backed-up by observation). Aristotle
concludes,

I mean, for instance, not that the heart once formed, fashions the
liver, and then the liver fashions something else; but that the one is
formed after the other (just as man is formed in time after a child),
not by it. The reason of this is that so far as the things formed by
nature or by human art are concerned, the formation of that which is
potentially brought about by that which is in actuality; so that the
form of B would have to be contained in A, e.g., the form of liver
would have to be in the heart—which is absurd. (GA 734a 28-35, Peck
trans.)

In epigenesis the controlling process of development operates
according to the TE plan of creating the most important parts first.
Since the heart is the principle (arche) of the body, being the center
of blood production and sensation/intelligence, it is appropriate that
it should be created first. Then other parts such as the liver, etc.
are then created in their appropriate order. The
epigenesis-preformation debate lasted two thousand years and Aristotle
got it right.

Another interesting observation by Aristotle is the discovery of the
reproductive mode of the dog shark,Mustelus laevis (HA 6.10, 565b
1ff.). This species is externally viviparous (live bearing) yet
internally oviparous (egg bearing). Such an observation could only
have come from dissections and careful observations.

Another observation concerns the reproductive habits of cuttlefish. In
this process of hectocotylization, the sperm of the Argonauta among
other allied species comes in large spermataphores that the male
transfers to the mantle cavity of the female. This complicated
maneuver, described in HA 524a 4-5, 541b 9-15, cf. 544a 12, GA 720b
33, was not fully verified by moderns until 1959!

Though Aristotle's observations on bees in HA seems to be entirely
from the beekeeper's point of view (HA 625b7-22), he does note that
there are three classes of bees and that sexual reproduction requires
that one class give way. He begins his discussion in the Generation of
Animals with the following remark, "The generation of bees is beset
with many problems" (GA 759a 9). If there are three classes and two
genders, then something is amiss. Aristotle goes through what he feels
to be all the possibilities. Though the observations are probably
second-hand, Aristotle is still able to evaluate the data. He employs
his systematic theory using the over-riding meta-principle that Nature
always acts in an orderly way (GA 760a 32) to form his explanation of
the function of each type of bee. This means that there must be a
purposeful process (TE) that guides generation. However, since neither
Aristotle nor the beekeepers had ever seen bee copulation, and since
Aristotle allows for asexual generation in some fish, he believes that
the case of bees offers him another case in which one class is sterile
(complies with modern theory on worker bees), another class creates
its own kind and another (this is meant to correspond to the Queen
bee—that Aristotle calls a King Bee because it has a stinger and
females in nature never have defensive weapons), while the third class
creates not its own class but another (this is the drone).

Aristotle has got some of this right and some of it wrong. What he has
right is first, bees are unusual in having three classes. Second, one
class is infertile and works for the good of the whole. Third, one
class (the Queen) is a super-reproducer. However, in the case of bees
it is Aristotle's method rather than his results that stirs
admiration. Three meta-principles cause particular note:

1. Reproduction works with two groups not three. The quickest
"solution" would have been to make one group sterile and then make the
other two male and female. [This would have been the correct
response.] However, since none of the beekeepers reported anything
like reproductive behavior among bees and because Aristotle's own
limited observations also do not note this, he is reluctant to make
such a reply. It is on the basis of the phainomena that Aristotle
rejects bee copulation (GA 759a 10).
2. Aristotle holds that a priori argument alone is not enough. One
must square the most likely explanation with the observed facts.
3. Via analogy, Aristotle notes that some fish seem not to
reproduce and even some flies are generated spontaneously. Thus,
assigning the roles to the various classes that he does, Aristotle
does not create a sui generis instance. By analogy to other
suppositions of his biological theory, Aristotle is able to "solve" a
troublesome case via reference to analogy. (Aristotle is also
admirably cautious about his own theory, saying that more work is
needed.)

What is most important in Aristotle's accomplishments is his
combination of keen observations with a critical scientific method
that employs his systematic categories to solve problems in biology
and then link these to other issues in human life.
9. Conclusion

Since Aristotle's biological works comprise almost a third of his
writings that have come down to us, and since these writings may have
occurred early in his career, it is very possible that the influence
of the biological works upon Aristotle's other writings is
considerable. Aristotle's biological works (so often neglected) should
be brought to the fore, not only in the history of biology, but also
as a way of understanding some of Aristotle's non-biological writings.
10. References and Further Reading
a. Primary Text

* Bekker, Immanuel (ed) update by Olof Gigon , Aristotelis Opera.
Berlin, Deutsche Akademie der Wissenschaften, 1831-1870, rpt. W. de
Gruyter, 1960-1987.

b. Key Texts in Translation

* Barnes, Jonathan (ed). The Complete Works of Aristotle: the
Revised Oxford Translation. Princeton, NJ: Princeton University Press,
1984.
* The Clarendon Series of Aristotle:
* Balme, David (tr and ed). Updated by Allan Gotthelf, De Partibus
Animalium I with De Generatione Animalium I (with passages from II
1-3). Oxford: Clarendon Press, 1993).
* Lennox, James G. (tr and ed) Aristotle on the Parts of Animals
I-4. Oxford: Clarendon Press, 2002.
* The Loeb Series of Aristotle (opposite pages of Greek and English).

c. Selected Secondary Sources

* Balme, David. "Aristotle's Use of Differentiae in Zoology."
Aristote et les Problèms de Méthode.Louvain: Publications
Universitaires 1961.
* Balme, David. "GENOS and EIDOS in Aristotle's Biology" The
Classical Quarterly. 12 (1962): 81-88.
* Balme, David. "Aristotle's Biology was not Essentialist" Archiv
Für Geschichte der Philosophie. 62.1 (1980): 1-12.
* Bourgey, Louis. Observation et Experiénce chez Aristote. Paris:
J. Vrin, 1955.
* Boylan, Michael. "Mechanism and Teleology in Aristotle's
Biology" Apeiron 15.2 (1981): 96-102.
* Boylan, Michael. "The Digestive and 'Circulatory' Systems in
Aristotle's Biology" Journal of the History of Biology 15.1 (1982):
89-118.
* Boylan, Michael. Method and Practice in Aristotle's Biology.
Lanham, MD and London: University Press of America, 1983.
* Boylan, Michael. "The Hippocratic and Galenic Challenges to
Aristotle's Conception Theory" Journal of the History of Biology 15.1
(1984): 83-112.
* Boylan, Michael. "The Place of Nature in Aristotle's Biology"
Apeiron 19.1 (1985).
* Boylan, Michael. "Galen's Conception Theory" Journal of the
History of Biology 19.1 (1986): 44-77.
* Boylan, Michael. "Monadic and SystemicTEleology" in Modern
Problems in Teleology ed. Nicholas Rescher (Washington, D.C.:
University Press of America, 1986).
* Charles, David. Aristotle on Meaning and Essence. Oxford: Oxford
University Press, 2000.
* Deverreux, Daniel and Pierre Pellegrin. Eds. Biologie, Logique
et Métaphysique chez Aristote. Paris: Éditions du Centre National de
la Recherche Scientifique,1990.
* Düring, Ingemar. Aristotles De Partibus Animalium, Critical and
Literary Commentary. Goeteborg, 1943, rpt. NY.: Garland, 1980.
* Ferejohn, M. The Origins of Aristotelian Science. New Haven, CT:
Yale University Press, 1990.
* Gotthelf, Allan and James G. Lennox, eds. Philosophical Issues
in Aristotle's Biology. NY: Cambridge University Press, 1987.
* Grene, Marjorie. A Portrait of Aristotle. Chicago: University of
Chicago Press, 1963.
* Joly, Robert. "La Charactérologie Antique Jusqu' à Aristote.
Revue Belge de Philologie et d'Histoire40 (1962): 5-28.
* Kullmann, Wolfgang. Wissenscaft und Methode: Interpretationen
zur Aristotelischen Theorie der Naturwissenschaft. Berlin: de Gruyter,
1974.
* Kullmann, Wolfgang. Aristoteles und die moderne Wissenschaft
Stuttgart: F. Steiner, 1998.
* Kullmann, Wolfgang. "Aristotles' wissenschaftliche Methode in
seinen zoologischen Schriften" in Wörhle, G., ed. Geschichte der
Mathematik und der Naturwissenschaften. Band 1 Stuttgart: F. Steiner,
1999, pp. 103-123.
* Kullmann, Wolfgang. "Zoologische Sammelwerk in der Antike" in
Wörhle, G., ed. Geschichte der Mathematik und der Naturwissenschaften.
Band 1 Stuttgart: F. Steiner 1999, pp. 181-198.
* Kung, Joan. "Some Aspects of Form in Aristotle's Biology" Nature
and System 2 (1980): 67-90.
* Kung, Joan. "Aristotle on Thises, Suches and the Third Man
Argument" Phronesis 26 (1981): 207-247.
* Le Blonde, Jean Marie. Aristote, Philosophie de la Vie. Paris:
Éditions Montaigne, 1945.
* Lesher, James. "NOUS in the Parts of Animals." Phronesis 18 (1973): 44-68.
* Lennox, James. "Teleology, Chance, and Aristotle's Theory of
Spontaneous Generation" Journal of the History of Philosophy 20
(1982): 219-232.
* Lennox, James. "The Place of Mankind in Aristotle's Zoology"
Philosophical Topics 25.1 (1999): 1-16.
* Lennox, James. Aristotle's Philosophy of Biology: Studies in the
Origins of Life Sciences. NY: Cambridge University Press, 2001.
* Lloyd, G.E.R. "Right and Left in Greek Philosophy" Journal of
Hellenic Studies. 82 (1962): 67-90.
* Lloyd, G.E.R. Polarity and Analogy. Cambridge: Cambridge
University Press, 1966.
* Lloyd, G.E.R. Aristotle: The Growth and Structure of his
Thought. Cambridge: Cambridge University Press, 1969.
* Lloyd, G.E.R. "Saving the Appearances" Classical Quarterly. n.s.
28 (1978): 202-222.
* Lloyd, G.E.R. Magic, Reason, and Experience. Cambridge:
Cambridge University Press, 1979.
* Lloyd, G.E.R. The Revolutions of Wisdom. Berkeley, CA:
University of California Press, 1987
* Lloyd, G.E.R. Methods and Problems in Greek Science. Cambridge:
Cambridge University Press, 1991.
* Lloyd, G.E.R. Aristotelian Explorations. Cambridge: Cambridge
University Press, 1996.
* Louis, Pierre. "La Génération Spontanée chez Aristote" Congrèss
International d'Histoire des Sciences (1968): 291-305.
* Louis, Pierre. La Découverte de la Vie. Paris: Hermann, 1975.
* Owen, G.E.L. "TITHENAI TA PHAINOMENA" Aristote et les Problèms
de Méthode. Louvain, 1975.
* Owen, G.E.L. The Platonism of Aristotle. London: British
Academy: Dawes Hicks Lecture on Philosophy, 1965.
* Pellegrin, Pierre. La Classification des Animaux chez Aristote:
Statut de la Biologie et Unite de l'Aristotélisme. Paris: Societé
d'édition "Les Belles Lettres," 1982.
* Pellegrin, Pierre. "Logical Difference and Biological
Difference: The Unity of Aristotle's Thought" in Gotthelf, Allan and
James G. Lennox, eds. Philosophical Issues in Aristotle's Biology. NY:
Cambridge University Press, 1987, pp. 313-338.
* Pellegrin, Pierre. "Taxonomie, moriologie, division" in
Deverreux, Daniel and Pierre Pellegrin. Eds.Biologie, Logique et
Métaphysique chez Aristote. Paris, 1990, 37-48.
* Preus, Anthony. "Aristotle's Parts of Animals 2.16 659b 13-19:
Is it Authentic?" Classical Quarterly18.2 (1968): 170-178.
* Preus, Anthony. "Nature Uses. . . ." Apeiron 3.2 (1969): 20-33.
* Preus, Anthony. Science and Philosophy in Aristotle's Biological
Works. NY: Olhms, 1975.
* Preus, Anthony. "Eidos as Norm" Nature and System 1 (1979): 79-103.
* Solmsen, Friedrich. Aristotle's System of the Physical World: A
Comparison with his Predecessors.Ithaca, NY: Cornell University Press,
1960.
* Sorabji, Richard. Necessity, Cause, and Blame. Ithaca, NY:
Cornell University Press, 1980.
* Thompson, D'Arcy. Aristotle as Biologist. Oxford: Oxford
University Press, 1913.
* Thompson, D'Arcy. Growth and Form. Cambridge: Cambridge
University Press, 1917.
* Ulmer, K. Wahrheit, Kunst und Natur bei Aristotles. Tübingen: M.
Niemayer, 1953.
* Witt, Charlotte. Substance and Essence in Aristotle: An
Interpretation of Metaphysics VII-IX.Ithaca, NY: Cornell University
Press, 1989.
* Wörhle, Georg and Jochen Althoff, eds. Biologie in Geschichte
der Mathematik und der Naturwissenschaften (series). Band 1 Stuttgart:
F. Steiner, 1999.