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1. University of Iowa
From the SelectedWorks of David J Depew
2002
Aristotle, Naturalist.” Invited Review Essay of
James Lennox, Aristotle’s Philosophy of Biology
David J Depew, University of Iowa
Available at: https://works.bepress.com/david_depew/70/

2. ESSAYREVIEW
Aristotle, Naturalist
James G. Lennox, Ariswtle's Philosophy of Biology:
Studies in the Origins of Life Science. Cambridge, UK:
Cambridge University Press, 2001. Pp. xxiii + 321.
US$64.95 HB, $22.95 PB.
By DavidJ. Depew
p osterior Analytics (APo) is Aristotle's only thorough treatment of
scientific method. This granddaddy of all philosophies of science
takes mathematics as its model. Its meta-language--deduction
of necessary truths from axioms, hypotheses, and definitions--is close
to what we find in Euclid, probably because Peripatetic philosophy of
science somehow went into making geometry a 'finished' science in
Hellenistic Alexandria. For Aristotle all genuine sciences (mathematics
included) move from establishing that an attribute holds of a subject to
finding middle terms that reveal why it holds. These middle terms meet
the necessity required for scientific knowledge (episteme) when the con-
nection they secure between premises and conclusion is both definitional
and explanatory (APo 1.2b19-23). We know why a predication holds when
we know what the subject essentially is. We know, for example, why
eclipses happen as soon as we learn that an 'eclipse is screening by the
earti~' (APo 2.8.93b6-7).
A sr.rong consensus has held that Aristotle's prolific biological re-
searches (which on some accounts he undertook during an exile that
occurred after he had formulated his mathematical model) are the grave-
yard of'the scientific ideal set out in Apo--a not inconsiderable claim,
given that twenty-five percent of the extant corpus consists of treatises we
would call biological. The primafacie difficulty is that in APo (and even in
the presumably mature Metaphysics Z [12]; see 1038a9-30) we are told
that explanatory middle terms are to be found by dividing a subject genus
until we find a single defining differentia. That is also Plato's assumption
in Statesman and other late dialogues about how definitions are to be
found; successive dichotomous divisions will presumably result in a final,
unique differentiation of any real entity within a larger genus. Yet in Parrs
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3. ESSAYREVIEW
of Animals (PA) I, Aristotle's treatise on method in biology, a new trans-
lation of which by Lennox has recently appeared (Oxford, 2001), we
learn that it is impossible to use this method to explain why animals have
their traits (PA 1.3.644a2-8). An animal kind integrates many lines of
differentiation, not one (PA 1.3.643b 14-15). If you follow the method of
successive dichotomous divisions you will end up 'breaking up' these
natural kinds. Moreover, even if by following this method you happen to
hit upon a feature that uniquely picks out a species--bipedality with knees
that bend in the opposite direction from birds in the case of humans, for
example--there is often no reason to think that you will have hit on a
feature that explains other properties. On the contrary, one expects that
human bipedality must be explained by something more essential: ration-
ality, for example (PA 4.10.687a5-23).
Many students of Aristotle's biological works have thought that this
difficulty greatly hinders Aristotle's efforts to bring his model of scientific
method to bear on living things. Aristotle's methodological model has
two steps. The first ascends to explanatory first principles, usually essen-
tial definitions, by what Aristotle calls epagoge (correctly, but misleadingly
translated 'induction'). The second step resolves issues found on the way
up by deductively demonstrating their solutions from these first prin-
ciples. It has been widely assumed that this second leg must be syllogistic
in form (a requirement most fully defended in recent decades by Jaako
Hintikka). For some time, however, a consensus has existed that, in view
of his apparent inability to bring biological complexity under the control
of this model, as well as by the plentiful lack of actual syllogisms to be
found in his biological works, Aristotle must have contented himself in
these treatises with mucking about in search of first principles, not with
making demonstrative scientific knowledge (episteme) out of them. This
consensus has been reinforced in recent decades by G. E. L. Owen's
influential view that first principles are to be found, not by dividing a
subject matter into its least proper parts and assembling these into a
synthetic definition, but by dialectically sorting through what has been
said (legomena) about a subject by 'the many or the wise' in order to find
generalisations that will preserve the majority of these opinions (endoxa).
(The canonical formulation is Owen's frequently reprinted essay, 'Tithenai
ta phainomena'.)
The essays collected in this volume (all but one previously published,
but sometimes in technical venues) represent the fruits of a sustained
effort to overturn this consensus. Lennox is convinced that PA I does not
fret about the inapplicability of the APo model, or fudge it to fit anom-
alous cases. He does not seem to agree even with Richard McKirahan's
modest proposal that Aristotle's adventures with animals led him to
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4. ESSAYREVIEW
'change his mind' about scientific explanation, but that he subsequently
failed to revise Apo to 'integrate the views [of PA I] on division and
definition', although he might easily have done so. According to Lennox,
Aristotle never changed his mind at all. 'Peppering [APo] with biological
examples' (p. 6), his intention was to show 'how the Analytics model of
science is to apply to Aristotle's paradigm of natural substances, animals'
by adding concepts, such as the matter-form distinction and a distinction
between hypothetical and unconditional necessity, neither of which is
overt in APo (p. 99, my italics). Since Lennox acknowledges that APo
does indeed take mathematics as its paradigm, he sees Aristotle as facing
'problems analogous to those of contemporary philosophy of biology'
(p. 109). A possible interpretation of this remark is that, considering how
well Aristotle the biologist managed to get along with his formalist
metascience, we might not have to reject our own received mathematical-
physics-oriented philosophy of science in order to accommodate the
peculiarities of biology, as some contemporary philosophers of biology
(Robert Brandon, Elizabeth Lloyd) and philosophising biologists (Ernst
Mayr, Stephen Jay Gould) have urged.
A key to Lennox's view is his spin on the late David Balme's demon-
stration that Aristotle's History ofAnimals (HA) is aimed not at classifying
species, but at identifying and classifying traits, both morphological and
behavioural, and at establishing the width of their co-extension. This
does not mean that Aristotle's is a 'zoology without species', as Pierre
Pellegrin has claimed. Where a large number of traits co-vary, are differ-
entiated from other groupings by analogy (fish : live-bearing quadrupeds
:: gills : lungs), and are themselves varied into many species, we are
entitled to recognise 'great kinds' (megista gene) at least as good as those
mankind has informally hit upon, such as bird or fish (PA 1.3.643b10-
13). Clustering around these great kinds are the 'lesser' kinds that we call
species, which are marked off from other gene within the same great kind
quarititatively; for instance, all birds have two legs and feathers, but one
kind will have legs just so much longer than another, combined with
split, say, rather than unsplit feathers (PA 1.3.642b25-30; Chapter 7).
Kinds construed in this way, both great and small, lie in the background
of Aristotle's biological works. The focus, however, is on getting these
'differences and attributes' (HA 1.1.487a1-12) properly named, differenti-
ated, predicated of kinds and, ultimately, explained. In HA the focus is
on finding the exact range of co-extended traits, so that we can determine
whether the joint possession of A, B, and so forth applies to all, some, or
no animals of a given genos.
Doing this constitutes an exercise in what Lennox calls 'pre-
demonstrative science' (Chapter 2). It is conducted by using a revised
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5. ESSAYREVIEW
method of division, outlined in APo 2.14-17, to establish scientific (not
dialectical) problemata--propositions ready for the demonstrative move
from 'that' to 'why' (Chapter 3). For example: 'all viviparous quadrupeds
have kidneys and bladders; no non-quadrupedal ovipara have them... ;
but the sea turtle alone among oviparous quadrupeds has them' (HA
505b25-8; 22). The crucial point is that these distributions of traits are
explained in PA II-IV not species-by-species, but at their highest level of
co-extension (p. 62). The relevant explanations have only to reveal, there-
fore, that peregrine falcons, to use Lennox's (not Aristotle's) example,
have hooked beaks not because they are peregrine falcons, but because
they are crook-taloned birds, all of which (according to Aristotle) have
hooked beaks. Seen this way, PA resonates with APo's claim that every
isoceles triangle has two right angles because it is a triangle, not because
it is an isosceles triangle (Apo 1.1.71a17-29).
Lennox is confident about the fit between APo and PA because he
believes that explanations of this sort, as they move from the pre-demon-
strative to the demonstrative stage, will conform to one of two fully
accredited models of deductive explanation in APo (Chapter 1). One is
the top-down method of inferring the necessity of having this or that trait
from knowledge of essential definitions. This is Aristotle's ideal, but the
required definitions are hard to come by. The other approach is far more
tractable. It works upward from 'the predication of a feature which
belongs to its subject necessarily, but to other subjects as well... The
predication is explained by showing that the subject is an instance of the
kind to which the predication belongs primitively' (p. 10).
Lennox blunts the objection that this is not very explanatory by draw-
ing a surprising implication from the fact that the paired terms genos and
eidos do not mean genus and species in Aristotle (p. 128), but kind (either
great or lesser) and 'determinate realization' of a kind (p. 168), as the
genos peregrine falcon is a 'determinate realization' of bird. By translating
eidos as determinate realization, Lennox is pointing out that the eidos, or
form, of a lesser genos is reached when the process of quantitative trait
division reaches a point which, were it to go any further, would reveal
nothing that can be assigned a teleological rationale in terms of the life of
the genos in question, but must be chalked up instead to the functionless
accompaniments of material causation (Chapter 7, esp. p. 168). From
this claim Lennox infers that a trait is 'essential or incidental only relative
to a kind' (p. 144). Having a hooked beak is incidental to a being a
peregrine falcon; however it is in the essence of crooked-taloned birds,
which include peregrine falcons. This interpretation makes the task of
demonstrative explanation more manageable, and has the advantage of
showing why Aristotle asks the little particle he (qua in Latin) to do such
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6. ESSAYREVIEW
a prodigious amount of work. It is only qua this or that genos-eidos rela-
tion that explanations can be deductively demonstrative.
How, someone might ask, can the deductive nature of Aristotle's zoo-
logical program be squared with his teleology? Aristotle's 'bottom up'
explanations of trait distributions are teleological in the sense that their
middle terms refer to what we would call adaptationist rationales for why
kinds must have the traits they do if they are to develop their natures in
the particular environments that mark them off. Both the 'must' and the
'if' are important. They refer to what Aristotle calls hypothetical necessity--
the kind of necessity that tells you that if you want a knife that cuts,
you had better make it out of material that takes and keeps an edge (P~/
1.1.642a 10-11). Hypothetical necessity is necessity enough to meet the
demand that scientific truths be necessary truths, but falls short of the
unconditional necessity that would assure you that such and such an
animal has to exist, and therefore has these traits. To apply this distinc-
tion, Lennox shows that for Aristotle organisms have two natures, one
material, one formal, and that the hypothetical necessity that figures
in his teleology applies to their material natures (Chapter 8). Material
natures make use of the inherent dispositional properties of the organic
and inorganic materials from which body parts are formed in order to
carry out the functions that define the formal nature of a kind, such as
living, breathing, feeding, and reproducing.
Here Lennox gives us an Aristotle who poses few challenges to a
disposition-based analysis of teleological explanations such as that advoc-
ated, for example, by Ernest Nagel. Aristotle's teleology is rooted in
the law-governed properties of matter; it does not risk wrecking its
movement from premise to conclusion by predicating through intentional
contexts, as design teleology (courtesy of Plato, Chapter 13) does. There
is much to be said for this argument. For Aristotle there are no teleolo-
gical explanations of functional parts that do not rest on the independent
availability of disposition-rich materials. Aristotle's acknowledgement of
spontaneous generation shows how causative these properties can be
(Chapter 10, although Lennox professes new doubts about the argument
republished here while only gesturing at an alternative; see p. 226.) More-
over, too strong an emphasis on Aristotle's hylomorphism--in which
material natures take a back seat to formal, or are swallowed whole by
them--has long obscured what Lennox takes to be a fact: that the maxim
'Nature does nothing in vain' is an APo-style supposition or hypothesis,
and hence an explanatory first principle (p. 208), according to which the
nature of each individual organism does the best it can with the materials
available to it (Chapter 9). PA is full of cases in which some quirk in the
resource base of a kind requires that an abnormal amount of the
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7. ESSAYREVIEW
dispositional properties on hand be given to one part and so are duly
taken from another. Aristotle explains why horn-bearing animals lack
upper dentition, for example, by saying that 'the nourishment given to
the upper front teeth is expended in the growth of the horns' (p. 193; PA
664al-2). This is what Lennox means when he says that material natures
'place constraints on the operation of [an organism's] formal nature in
achieving its ends, and thus play an explanatory role in the operation of
hypothetical necessity' (p. 196).
It might be thought that Aristotle's modernism is compromised by his
claim that the formal natures (souls) of organic kinds are eternal. Lennox
addresses this question in Chapter 6, his longest. The trick here is to find
the mean between Platonism, in which organisms are treated as exem-
plars of eternal species forms (even if this Platonism is often disguised by
a pseudo-Aristotelian principle stipulating that such forms must always
be enmattered) and the view that the persistence of species is too contin-
gent on the reproductive prowess of organisms to count as a necessary
truth. The first view allows a metaphysical guarantee to stray into scient-
ific territory. Lennox brushes it aside by pointing out that for Aristotle,
unlike Plato, there are no (typological) species-forms (eide) at all, only
kinds (gene) that are maintained by repeated acts of reproduction (p. 136).
He skirts the other horn of the dilemma by arguing that the natural desire
of each animal for personal (not species) immortality is oriented toward
'making a copy of itself which is indistinguishablefrom it with respect to
those [teleologically explanatory] characteristics which contribute directly
to its life' (p. 146). It is the formalnature of the parent (read: father), not
its material nature, that is passed on to its offspring in the cyclical pattern
of birth, growth, and replication that constitutes the genos of anthropos
(p. 139). If this natural urge is not to be frustrated (perish the thought!),
Lennox argues, its fulfillment must not be a matter of hypothetical, but
unconditional necessity. Whether this argument succeeds in rescuing the
persistence of animate form from merely contingent behavior by treating
the maxim 'Nature does nothing in vain' as an hypothesis that serves as
an explanatory first premise, I am unable presently to judge.
One of the attractive features of these essays is that Lennox shoulders
all relevant burdens of proof, acknowledging colleagues who dissent from
his conclusions as generously as those who have worked closely with him
over the decades, such as Gotthelf. To G. E. R. Lloyd's objection, for
example, that we would see far more syllogisms in the text of P,Zl if it
were modeled on APo, Lennox replies, 'the Analytics demands only that
a good scientific explanation be capable of syllogistic recasting, not that it
actually be written as a syllogism' (p. 5). Scholars of APo who are either
implicitly or explicitly under the spell of logical empiricism fail to see that
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reducing teleological rationales to syllogistic would 'leave the mode of
causation implicit' (p. 6). (Does this reply concede too much?) They also
wrongly assume that APo models a 'finished science' rather than being a
treatise on how to do good science. For Lennox's Aristotle, the way to do
good biological science is to use the method of division, albeit appropri-
ately, to find explanatory first principles. In this connection, Lennox
makes a strong case for rejecting the received view which holds that,
having perceived difficulties in applying the APo model of a 'finished'
science, Aristotle retreated to dialectics in his search for explanatory first
principles. By distinguishingdialectical from scientific problems (Chapter
3), Lennox implies that the rival versions of Owen's dialectical approach
offered by Terry Irwin and Martha Nussbaum are both so much wasted
effort.
If Aristotle's work was so good, we may ask, why did only a cartoon
version of it survive to influence subsequent history of biology? Lennox's
answer is that Aristotle's biological works were reshuffled in antiquity
into species-by-species epitomes, yielding the sense of 'natural history'
that Buffon, for example, inherited from Pliny (Chapter 5). As a result,
Aristotle's explanatory program in zoology disappeared until something
as good, or better, started to appear with Harvey in embryology and with
Cuvier in comparative anatomy. Aristotle's last faithful scholar was his
first, Theophrastus, who did for plants what Aristotle did for animals--
and even he wavered by suggesting that Aristotle was too generous in
handing out teleological, rather than material, explanations (Chapter 12).
A related factor may also have been at play in the disappearance of
Aristotle's program in zoology, which Lennox characterizes as 'a Hellen-
istic mystery'. As I-Ieinrich yon Staden has argued, a decided turn toward
mechanistic materialism followed the post-Aristotelian, but probably Peri-
patetic, discovery of the nervous system in third-century BCE Alexan-
dria. Material natures thereupon pushed aside formal natures and
teleological explanations until a reaction set in with Galen in the second
century CE. But Galen's deeply influential sort of teleology, propounded
in Aristotle's name, turned the principle that 'Nature does nothing in
vain' into a materially unconstrained Panglossianism that was ripe for
attack by modern mechanists and materialists.
There can be little doubt that 'bottom-up' explanations of the sort
Lennox analyses play a role in Aristotle's zoology. My only qualm is
whether an approach that privileges what we would call comparative
anatomy is sufficiently rounded off and autonomous to define Aristotle's
program in zoology. Aristotle says that 'formal nature is more important
than material' (PA 1.1.640b28-30) and that, since the form of living
substances is their soul (psyche), 'the physicist [read: zoologist] must
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9. ESSAYREVIEW
know about soul' (641a22-23). In HA, this kind of inquiry is focused on
the dispositions (ethe), actions (praxeis), and ways of life (bioz) that are
subserved by body-parts. These differential (which are divided by the
'more and the less' by proportional degrees of intensity rather than by
discrete enumeration) are affections that express how life-functions rang-
ing from feeding, growing, and reproducing to memory, imagination,
experience, and conceptually--and linguistically--mediated cognition, are
realized by animals having particular material natures in particular envir-
onments. This being so, it has seemed to some scholars that Aristotle's
zoology, cannot be complete until it has produced top-down explanations
that derive these affections, as well as the bodily parts whose material
dispositions realize them, from essential psychological functions. Scholars
of this 'traditional' persuasion worry about Aristotle's success when
measured by this standard. They worry, for example, that Aristotle's
inability unambiguously to classify animal kinds, and to identify the
single differentia which, according to the Metaphysics, is required to make
members of each kind into the unified substances that they are, will put
a glass ceiling on Aristotle's ability to reach his explanatory ideals--even
if the relatively circumscribed sphere of explanations that relate body
parts to material natures through dispositional properties is successful in
its own terms. These worries have been most fully expressed by Lloyd
and by David Charles.
Be that as it may, with impressive control of the texts, elegant argu-
ments, and clear prose, Lennox has done more than anyone since the
late David Balme to ensure that scholars who continue to insist on the
primacy of soul-talk cannot do so effectively if they retain even a trace of
the neo-Platonist and scholastic pieties that have too long passed as
.~-istotelianian.
105 Becker Communication Studies Building.
University of Iowa,
Iowa City, IA 52242, USA.
References
Charles, D. (1997). 'Aristotle and the Unity and Essence of Biological Kinds', in
Kullmann, W. and F611inger, S. (eds), Aristotelische Biologie. Stuttgart: Steiner
Verlag.
Irwin, T. (1988). Aristotle's First Principles. Oxford: Oxford University Press.
Lloyd, G. E. R. (1996). Aristotelian Explanations. Cambridge, UK: Cambridge
University Press.
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McKirahan, R. (1992). Principles and Proofs. Princeton: Princeton University Press.
Pellegrin, P. (1985). 'Aristotle: A Zoology Without Species,' in Gotthelf, A. (ed.),
Aristotle on the Nature of Living Things. Bristol: Bristol Classical Press.
Nussbaum, M. (1986). 'Saving Aristotle's Appearances,' in Nussbaum, M., The
Fragility of Goodness. Cambridge, UK: Cambridge University Press.
yon Staden, H. (1997). 'Teleology and Mechanism in Aristotelian Biology and
Early Hellenistic Medicine', in Kullmann and F611inger (eds.), op. cir.
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