Principal Aristotle: the desire to understand

Aristotle: the desire to understand

This is a philosophical introduction to Aristotle, and Professor Lear starts where Aristotle himself started. He introduces us to the essence of Aristotle's philosophy and guides us through all the central Aristotelian texts--selected from the Physics, Metaphysics, Ethics, Politics and the biological and logical works. The book is written in a direct, lucid style that engages the reader with the themes in an active and participatory manner. It will prove a stimulating introduction for all students of Greek philosophy and for a wide range of others interested in Aristotle as a giant figure in Western intellectual history.
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the desire to understand
This is a philosophical introduction to Aristotle, and
Professor Lear starts where Aristotle himself starts. The
first sentence of the Metaphysics states that all human
beings by their nature desire to know. But what is it for
us to be animated by this desire in this world? What is it
for a creature to have a nature? What is our, human,
nature? What must the world be like to be intelligible,
and what must we be like to understand it systematically? Through a consideration of these questions Professor Lear introduces us to the essence of Aristotle's
philosophy and guides us through the central Aristotelian texts — selected from the Physics, Metaphysics,
Ethics, and Politics and from the biological and logical
The book is written in a direct, lucid style which engages
the reader with the themes in an active, participatory
manner. It will prove a stimulating introduction for all
students of Greek philosophy and for a wide range of
others interested in Aristotle as a giant figure in Western
intellectual history.

the desire to understand
Jonathan Lear
Professor of Philosophy
Yale University



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For Cynthia Farrar
xi ovv KCOXAJEI Xeyeiv etiSai|iova xov icax' 4perf|v
xeXeiav frvepyouvxa Kai xoig Eicxog dcyaOoig
{Kava>g KEXOPTJYT|(IEVOV nf) xov xuxovxa xpovov
d U a xeleiov piov;


page ix

1 The desire to understand


2 Nature
1 Nature as an inner principle of change
z Understanding and'the why'
3 Four fashions
4 The hearts of animals


3 Change
1 The Parmenidean challenge
2 The analysis of change
3 The media of change I: the infinite
4 The media of change II: the infinity of time
5 A paradox of change: Zeno's arrow


4 Man's nature
1 Soul
2 Perception
3 Mind
4 Active mind
5 Mind in action


5 Ethics and the organization of desire
1 The point of the Nicomachean Ethics
2 Happiness and man's nature
3 Virtue
4 Incontinence
5 Freedom and virtue
6 The master-slave dialectic



6 Understanding the broad structure of reality

i Aristotle's logic
2 Aristotle's philosophy of mathematics
3 Metaphysics: the inquiry into being as being
4 The most certain principle of being
5 What is substance?
6 A tourist's guide to Metaphysics VII
7 Mind's place outside of nature
8 Man's place outside of nature



Select bibliography





I wrote this book as a way of saying goodbye. Ifirstwent to Cambridge on a Mellon Fellowship when I graduated from Yale in
1970, and with occasional excursions back to the United States I
ended up staying there for almost twelve of the next fifteen years.
Cambridge is in many ways my intellectual and emotional home: I
had never seen before such a warm, supportive, yet challenging
intellectual environment. Perhaps that is why I stayed so long.
When I decided to return to the U.S. in 1985,1 wanted somehow to
mark, intellectually if not emotionally, the time I had spent in
Cambridge. Most of my research on Aristotle was done while I was
first a student and later a Fellow at Clare College, so I decided to
write an introduction to his philosophy. I liked the idea of an introduction, first, because I thought it would force me to work on a
broad canvas: to elucidate the thoughts of years rather than detail
a single argument. Second, I wanted to write a book that was
accessible to my friends who are not Aristotelian scholars — friends
who would ask me in countless casual conversations, 'What do
you think Aristotle would have thought about this?' I am not going
to mention my many Cambridge friends by name: if you are one of
them and are reading this, suffice it to say that you are very much
in my heart and mind. I would, however, like to mention those
who helped me in my study of Aristotle. First, I would like to thank
that part of my Cambridge life which accompanied me back to
America: my wife, Cynthia Farrar. I won't indulge in the usual
cliche, '... without whose support...', in part because it is a
cliche, in part because I am not sure it is true: even if Cynthia had
not been supportive I think I still would have written this book. I
mention her here solely because she helped me to understand what
is involved in Aristotle's claim that man is by nature a political
animal. It was in attending her lectures on Thucydides in Cambridge and watching her live her life tharl learned how theorizing
about politics and actively living the life of a citizen in a polis might

form a coherent whole. Let me also thank the ancient philosophy
mafia of which I was once part. It is from countless seminars,
classes, individual discussions with Myles Burnyeat, Geoffrey
Lloyd, M. M. Mackenzie, David Sedley, Malcolm Schofield and
(for two years) Gregory Vlastos, that I learned how to read ancient
philosophical texts. Indeed, virtually every week I spent in Cambridge had a day in it which was spent with one or the other of
them translating and interpreting an Aristotelian text. Finally, I
would like to mention Timothy Smiley and Bernard Williams, two
friends from whom I have learned most about how to do philosophy. However, I have no interest in bidding them a fond farewell.
In saying goodbye to a way of life, I do not intend to be saying
goodbye to the people who helped to constitute it.
There is one person I do want to say goodbye to, but I can't.
Charles Parkin, the soul of Clare College, died suddenly of a heart
attack in the fall of 1986. He was one of those modest men who
knew everything and published nothing. He loved the people he
knew and remained a bachelor living in College rooms. The world
did not know him, and the students and Fellows of Clare loved
him. He was an historian of political thought, but his interests
spanned the world. When I first arrived in Cambridge, we would
spend evenings looking at bacteria under his microscope, photographing craters on the moon through his telescope, sitting quietly
and listening to recordings of trains pulling out of various European stations. And we would discuss Aristotle. Just after World
War II, Charles contracted tuberculosis and spent two years in a
sanatorium outside of Cambridge. It was in this period that he had
an epiphany in which he felt he really understood the identity of
subject and object. He once told me that he thought that the rest of
his life was an attempt to recapture that moment. I think he would
have liked this book.
I should like to thank: the National Endowment for the Humanities (U.S.) for a Fellowship for Independent Research in which
some of the research and writing of this book were accomplished;
the Andrew W. Mellon Foundation for administering the Fellowship which first sent me to Cambridge; the Masters and Fellows of
Clare College, Cambridge, for providing the ideal atmosphere in
which to carry out my studies; the Whitney Humanities Center at
Yale for providing a second hide-away office in which I could

write this book undisturbed by the usual demands of the semester.
An earlier draft of this book was read by Alan Code, Geoffrey
Lloyd, Jeremy Mynott, Malcolm Schofield, Timothy Smiley,
Bernard Williams and Michael Woods. They all offered extensive
and valuable comments. Although Code and I talked about Aristotle so often and so long on the transatlantic telephone that I suspect
we supported the launching of a communications satellite, I would
especially like to thank him for his suggestion of Kermit as a candidate for the non-human individual I needed to make the point I
was trying to make about levels of potentiality and actuality.
Christopher Dustin, who was a teaching assistant in a lecture
course I gave at Yale, wrote copious comments on my lectures
which greatly helped me to unify the material I have presented in
this book.
Above all, I would like to thank the undergraduate students at
Cambridge and Yale to whom I have lectured about Aristotle.
They persuaded me that material at this level of difficulty is interesting to them and that a book of this sort would be a help to



The desire to understand
Aristotle's Metaphysics begins:
All men by nature desire to know. An indication of this is
the delight we take in our senses; for even apart from
their usefulness they are loved for themselves; and above
all others the sense of sight. For not only with a view to
action, but even when we are not going to do anything,
we prefer sight to almost everything else. The reason is
that this, most of all the senses, makes us know and
brings to light many differences between things.1
Aristotle is attributing to us a desire, a force, which urges us on
toward knowledge. Of course, for some this desire does not exercise great influence; but for some of us it plays an important role in
our lives. Aristotle no doubt believed it was this desire that motivated him to do the research and thinking that led to his writing the
Metaphysics, and he trusted in this desire to lead others to study it.
It is this desire that is responsible for your reading and my writing
this book.
How did Aristotle know that we have this desire? One does not
know the content of a desire unless one knows what ultimately
satisfies it. By its satisfaction we learn what the desire is a desire
for. That is why Aristotle speaks of the delight we take in our
senses. If the knowledge we pursued were merely a means to a further end, say, power over others or control of the environment,
then our innate desire would not be a desire for knowledge. It
would be a will to power Or an obsessional drive for control. That
we take pleasure in the sheer exercise of our sensory faculties is a
sign that we do have a desire for knowledge. For though we do use
our sensory knowledge to organize ourselves in the world and to
achieve practical ends, this knowledge is also pursued for its own

Metaphysics I.I, 980321-7. The Greek for 'to know* is eidenai.

The desire to understand
Leisure was of the utmost importance to Aristotle. It was only
after men had developed the arts to help them cope with the necessities of life that they were able to turn to sciences which are not
aimed at securing any practical end.2 That is why, Aristotle says,
mathematics was founded in Egypt: for it is there that a priestly
caste had the leisure to pursue knowledge for its own sake. But
then the natural desire to know had to wait upon a historical development, the creation of societies with leisured classes, before it
could find full expression. Before that time an observer might have
been able to detect a delight men took in sensory experience itself,
but he would not have been able to grasp that this pleasure was
only a surface manifestation of a much deeper force within man's
soul. One cannot help but wonder: was Aristotle himself living at a
time appropriate for appreciating the true content of this desire?
Aristotle certainly thought that within an individual's history
the desire to know develops in content: that is, the individual
develops a richer sense of what it is he wants to know. The structures of the world and of our own souls conspire to encourage this
development.3 Man is not born with knowledge, but he is born
with the capacity to acquire it. But the world must cooperate with
him if he is to exercise that capacity. Man starts life with the ability
to discriminate among sensory phenomena, an ability he shares
with other animals. His soul retains a record of its sensory encounters. The world, for its part, offers man repetition and regularity in
his sensory encounters. Through repeated encounters with items in
the world, our sensory discriminations develop into memory and
then into what Aristotle calls 'experience.' Experience Aristotle
characterizes as 'the whole universal that has come to rest in the
soul.'4 From repeated perception of particular men, we form the
concept of a man, and the knowledge that this thing we see is a
man is experience. If the universal, or concept, were not somehow
already embedded in the particular, we could not make the transition from bare sensory discrimination to knowledge of the individual. As Aristotle says, 'though one perceives the particular,
perception is of the universal.'5 The world, then, provides a path

Metaphysics n , 9811513-25; i.x, 98^20-4.
See Metaphysics 1.1, 980327-981811; Posterior Analytics 11.19,
Posterior Analytics 11.19, iooa7.
Posterior Analytics 11.19, iooai7—bi.

The desire to understand
along which man's curiosity can run. Because the universal is
embedded in particulars, a person's first explorations among particulars will naturally lead him toward a grasp of the embodied
universal. Having acquired experience, or knowledge of individuals, we are able to formulate more abstract forms of knowledge, the arts and sciences (technai and epistemai).6 Each stage of
cognitive development is grounded in the previous stage and the
structure of the world itself helps us to ascend from the Cave of Ignorance. It is only because the world offers a course along which
man's inquiries can run that his desire to know has any hope of
being satisfied.
But the world does not 'grab us by the throat' and yank us out of
the Cave. There must be something in us that drives us to take
advantage of the world's structure. From earliest childhood
humans display an innate curiosity. Indeed the British psychoanalyst Melanie Klein once called this childhood curiosity
epistemophilia — love of episteme.7 But curiosity is not, I believe,
the best way to conceptualize what drives men on. Perhaps it is
better to think of man's natural capacity to be puzzled. We tend to
take this capacity for granted. Yet it is a remarkable fact about us
that we cannot simply observe phenomena: we want to know why
they occur. We can imagine beings who simply watched the sun set
and the moon rise in the heavens: they might come to expect the
regular transitions, but they would lack curiosity as to why the
changes occur. We are not like that. The heavenly motions cry out
{to us) for explanation.
It is out of wonder, Aristotle says, that men first began and even
now begin to philosophize.8 That is, philosophy grows out of
man's natural capacity to feel puzzlement and awe. We cannot
remain content - we are literally discontented - until we have an
explanation as to why the heavens are as they are. This discontent
is of a piece with the desire to know: it propels us toward exploration and the formation of explanations. Even myths, Aristotle
recognizes, are manifestations of man's propensity for puzzlement: they are designed to allay our unease by offering expla6

Metaphysics I.I, 98iai-bio.
Melanie Klein, Lofe, Guilt and Reparation, e.g., pp. 87,188,190-1,217-8,416,
Metaphysics i.z, 98zbii-ii.

The desire to understand
nations of the phenomena. Of course, myths offer at best
temporary relief, for the explanations they offer are unsatisfying.
We are ultimately led, by our own natural makeup, to the honest
pursuit of explanations for their own sake.
In searching for explanations, men inevitably encounter difficulties.9 There are of course conflicting opinions on most serious
subjects; and the opinions themselves express persuasive, though
differing, accounts of the phenomena. These difficulties are, for
Aristotle, the starting-point of philosophy. It is by working one's
way through the puzzles or difficulties that philosophical wisdom
grows. Hence Aristotle devotes an entire book of the Metaphysics
simply to cataloguing the puzzles surrounding the question of
what are the basic elements of reality.10 As he says, 'one should
have surveyed all the difficulties beforehand ... because people
who inquire without first stating the difficulties are like those who
do not know where they have to go.' 11 Aristotle uses the metaphor
of a knot. When we are confronted with difficulties we do not
know how to solve, our thought is all tied up. We are constrained,
we cannot go forward in our search, the desire to know is frustrated. Hence the frustration we feel when we repeatedly return to
a problem we cannot solve, and the relief and pleasure when suddenly we understand how to solve the problem and move on.
According to the Oxford translation, Aristotle says that when we
have solved the difficulties we enjoy the 'free play of thought.'12
The Greek, euporia, literally means 'easy passage or travel.' Its opposite, aporia, is Aristotle's word for difficulty, but it literally
means difficulty or impossibility of passage.
Aristotle typically begins a treatise by listing the difficulties
which previous thinkers encountered when they first began to
think about the issue at hand. To a reader fresh to Aristotle, these
opening chapters can seem extremely boring. Because one is ignorant of the setting of the intellectual stage in Aristotle's time, the
problems can seem obscure, lifeless and dull. However, even if the
difficulties which Aristotle lists do not immediately come to life,
one should not lose sight of the significance of his philosophical
' Metaphysics 111.1,995315-^3.
Metaphysics m.
Metaphysics m.i,
euporesai: Metaphysics m.i, 995317 (old and revised translation - see note 14

The desire to understand
method. For Aristotle, philosophy begins with questions and puzzles'. We are led to the pursuit of explanations for their own sake
both by our natural makeup — the desire to know - and because it
is part of our nature to find the world puzzling. It is misleading to
say that the world is inherently puzzling: rather, the world presents
itself as puzzling to beings like us, But as soon as we formulate
questions about the world, philosophy (at least in embryonic form)
is already under way. By posing and answering questions we do
what we can to render the world intelligible to us: and rendering
the world intelligible is what, for Aristotle, philosophical activity
Although it is difficult to reach the truth, in another sense, Aristotle says, the truth is easy.13 Almost every belief is a stab at the
truth. Beliefs are formed on the basis of interaction with the world,
and Aristotle thinks it very rare that a belief has no drop of truth in
it. Not only is knowledge accumulated by the humble efforts of
many thinkers and researchers, but even false beliefs are usually
formed reasonably. Aristotle describes the truth as 'the proverbial
door which no one can fail to hit.' Thus there is a point to investigating men's beliefs - even the false ones — for by seeing how men
have stumbled, we may gain a clearer grasp of the truth.
The reason the truth is difficult lies not in the world, Aristotle
thinks, but in us: 'For as the eyes of bats are to the blaze of day, so
is the reason in our soul to the things which are by nature most evident of all.'14 What is it for things to be by nature most evident of
all? Aristotle distinguishes that which is most understandable
without qualification from that which is most understandable to
us.15 Because we begin life in ignorance and must work our way
from experience of particulars to knowledge of general truths, the
route we take is a tortuous one, and as we move toward these
truths we are unaccustomed to them. Yet, though what is initially
most understandable to us and what is simply most understandable are distinct, they are essentially related. For it is from our current state of knowledge (or ignorance) and our puzzlement that we
are led along, as though on a path, toward discovering what the
world is really like. And once we have grasped basic truths about

Metaphysics u.i, 993330-615.
Metaphysics i n , 993b8-9.
See, e.g., Metaphysics 1.1, 981830-^30.

The desire to understand
the world and the structure of reality, we realize that there is nothing so clear as they. Our job, as systematic inquirers, is to turn that
which is most clear into that which is most clear to us. It is that
which satisfies the desire to know. The basic truths of reality no
longer confront us like the blaze of day.
Thus, although philosophy begins in wonder, it ends in lack of
wonder.16 We may, for example, be surprised to discover that the
diagonal of a square is incommensurable with its sides, but once
we have learned the theory of incommensurable magnitudes, it
would seem bizarre if the diagonal were not incommensurable.
For the theory teaches us why the diagonal must be as it is. The
man who has achieved this appropriate lack of wonder is a man
who has achieved wisdom (sophia), and the pursuit of wisdom for
its own sake is philosophy (philosophia) - literally, love of
wisdom. The desire to know achieves its deepest satisfaction in the
philosopher who understands the principles and causes of the
But if philosophy is the ultimate goal of our original innate
desire, perhaps we have to re-think what that desire is. We are not
satisfied to know, for example, that the heavens move in such a
way; nor will we be satisfied to know a vast array of such facts
about the phenomena. We want to know why the heavens move
that way, why the phenomena are as they are. We are after more
than knowledge, we are after understanding. Aristotle was, I believe, aware of this. Although 'to know' is an adequate translation
of the Greek 'eidenai,' Aristotle used this term generically to cover
various species of knowing. 17 One of the species is 'epistasthaf
(literally, to be in a state of having episteme) which has often been
translated as 'to know' or 'to have scientific knowledge,' but which
ought to be translated as 'to understand.' For Aristotle says that we
have episteme of a thing when we know its cause.18 To have episteme one must not only know a thing, one must also grasp its
cause or explanation. This is to understand it: to know in a deep
sense what it is and how it has come to be. Philosophy, says Aristotle, is episteme of the truth.19

Metaphysics i.i, 983313-11.
See M. F. Burnyeat, 'Aristotle on Understanding Knowledge.'
See, e.g., Posterior Analytics 1.1, 7 i b 8 - n .
Metaphysics n.i, 993619-10.

The desire to understand
Aristotle uses 'episteme' in two ways: first, to refer to an organized body of knowledge, like geometry; second, to refer to the state
of the soul of a person who has learned this body of knowledge.
This is not an equivocation or ambiguity. For a person who has
learned geometry has the episteme as part of his soul. Indeed, it is
because his soul has become the episteme- has actually become an
organized body of knowledge — that he can be said to be a geometer. Note that what the geometer has is not just knowledge, but an
organized body of knowledge. The geometer knows not merely
that the interior angles of a triangle are equal to two right angles,
he knows why a triangle must have such interior angles. For he can
supply a proof. Understanding is by its nature completely general.
The geometer's proof, for example, does not explain why this particular figure has interior angles equal to two right angles (except,
as Aristotle would say, incidentally). The proof explains why all
triangles have such interior angles.20 As we seek understanding we
move away from particular facts toward the general principles,
causes, explanations which underlie them.

Epistemophilia' — love of episteme — turns out to be a remarkably apt expression for the inner drive which motivates a child's
first explorations of the world. But if the true content of a desire is
revealed only by what ultimately satisfies it, then it is too constricting to conceive of epistemophilia as innate curiosity or even desire
for knowledge: the desire is for episteme, or understanding.
And yet there must be more to episteme than mere understanding. For episteme binds man to the world in a much deeper and
more significant relation than the concept of understanding on its
own would suggest. First, the world is not merely the object of our
understanding, it is the occasion for it. The world prompts us to
inquiry by presenting itself (to us) as puzzling, and then it obligingly yields up its truths in response to our patient investigations.
The world as such is meant to be known (by beings like us) and it
invites man to fulfill his role as a systematic understander of the
world. Imagine how frustrating it would be to be born with the
desire to understand in a world which did not cooperate! The
world would remain incomprehensible, and yet we would obsessionally keep bumping our heads against it. Aristotle had great faith

I discuss this in detail in section 6.1 below.

The desire to understand
in the world: indeed, his philosophy is an attempt to give the world
back to creatures who desire to understand it.
Second, it is by gaining understanding of the world that man
comes to understand who he is. The project of understanding the
world lies at the bottom of who we are. Until we have pursued that
project all the way, it is not just that we do not yet fully know what
the desire to understand is a desire for, we do not yet know who we
really are. That is, we don't yet fully understand what it is to be a
systematic understander of the world. Therefore, we cannot gain
self-knowledge merely by turning our gaze onto ourselves. Because
we desire to understand, because we are at bottom systematic
understanders, self-understanding must to some extent be indirect.
When we first come to Aristotle, much of what he is doing does not
seem to be anything remotely like what we would now consider to
be philosophy. He seems to us a scientist engaged in earnest exploration of the natural world. But this dichotomy between philosophy and science would seem, in Aristotle's eyes, to rest on a
superficial understanding of the relation between inside and outside. It is by looking out to the world that man's soul maps the
structure of the world. Once he has come to understand the world,
not only has he become what he most fundamentally is, a systematic understander, but he can also look to the world to see the
structure of his soul mapped there. (This is not, as a modern idealist might think, because man constitutes the world in his image,
but because man's nature is such that the world is able to impress
its image on him.)
In any case, what we do easily recognize to be philosophy is, for
Aristotle, a natural outgrowth of man's exploration of the world.
For episteme is by its nature reflective: one cannot understand the
world unless one understands the place of understanding within it.
In a similar way, the desire to understand and the desire to understand that desire must be one. There is, therefore, no additional
step required, no change in perspective needed, to move from 'ordinary' understanding of the world to an attempt to understand that
very understanding - or, indeed, to understand the nature of philosophical thought itself.
What one comes to understand, Aristotle thought, is that the understanding of first principles and causes is divine.21 No doubt the

Metaphysics 1.1, 981818-983311. See also Metaphysics xn.7,9, and Nicomachean Ethics x.7.

The desire to understand
early discovery of basic principles underlying the disparate
phenomena must have seemed so marvelous as to be a God-given
gift: it is, after all, unlikely that Prometheus could have stolen all
this from jealous, hoarding gods. We are such and the world is
such that understanding comes to us almost as a loving bequest.
But Aristotle had a more hard-headed reason for considering this
understanding to be divine. God is himself thought to be among
the causes of all things and a first principle. Thus in knowing first
principles we come to an understanding of God. For God, this
knowledge would be self-understanding. It is absurd to suppose
that we mortals can have insight into God's nature while God himself remains ignorant. It is more reasonable to suppose that we are
partaking of something divine.
This plausible train of thought has two very remarkable consequences. First, since God is a first principle of all things, and is (at
least partially) constituted by self-understanding, it would seem
that this understanding is itself a cause or principle of all things.
Understanding is itself a force in the world. Second, when man
acquires this understanding, he is not acquiring understanding of a
distinct object which, as it turns out, is divine: the understanding is
itself divine. Thus in the acquisition of this understanding - in
philosophical activity — man partially transcends his own nature.
Aristotle explicitly recognized this consequence:
... it is not insofar as he is man that he will live [a life of
contemplation], but insofar as something divine is present in him... If mind is divine, then in comparison with
man, the life according to it is divine in comparison with
human life. But we must not follow those who advise us,
being men, to think of human things and, being mortal,
of mortal things, but must, so far as we can, make ourselves immortal, and strain every nerve to live in accordance with the best thing in us; for even if it be small in
bulk, much more does it in power and worth surpass
All men by nature have a desire which leads them to transcend

Nicomachean Ethics x.7, H 7 7 b i 6 - i i 7 8 a z . The old Oxford translation uses
'reason' as a translation for nous; the revised translation uses 'intellect.' The
reason I use 'mind' is given in section 4.3 below.

The desire to understand
their own nature. Paradoxically, it is in this divine transcendence
of his own nature that man most fully realizes himself:
[Mind] would seem, too, to be each man himself, since it
is the authoritative and better part of him. It would be
strange men if he were to choose not his life but that of
something else ... that which is proper to each thing is
by nature best and most pleasant for each thing; for
man, therefore, the life according to mind is best and
pleasantest, since mind more than anything else is
Man has a desire to understand which, if satisfied, pulls him right
up out of human life into a divine existence. Yet man is most fully
realizing himself when he does this. This is a view of human nature
which is, to say the least, not easy to understand.
The aim of this book is to come to a deeper understanding of
Aristotle's claim that all men by their nature desire to know. To
understand this one line of the Metaphysics we will have to work
through much of Aristotle's philosophy. For there is both a broad
and a narrow sense in which one can study the desire to understand. In the broad sense, we must come to understand Aristotle's
own attempt to understand the world. For only once we comprehend the world according to Aristotle can we comprehend what,
for him, the desire to understand was a desire for. And, as we have
seen, if one wants to appreciate man's place in nature one must,
Aristotle thinks, work hard at understanding nature itself: for it is
only through a serious study of nature for its own sake that man
can ultimately achieve self-understanding. It is toward that goal
that the desire to understand is urging us all along. That brings us
to the narrow sense: we must inquire into the place the desire to
understand occupies within Aristotle's world. In this book I try to
keep both perspectives alive. I try to give a wide-ranging picture of
Aristotle's world, but one designed to illuminate the significance of
his claim that man by his very nature desires to know. If we do not
know what it is to have a nature at all, we cannot understand what
it is for man by nature to do anything. Therefore chapters 2 and 3

Nicomachean Ethics x.7, i i 7 8 a z - 7 (old translation; my emphasis).

The desire to understand
present Aristotle's conception of nature in general. In chapters 4
and 5,1 focus on Aristotle's account of man's nature. Chapter 4 is
about the human soul: the capacity for sense perception, for thinking about and understanding the world, for desiring, and for deliberating, on the basis of those desires, how to act. Man also has
the ability to organize and shape his desires, and chapter 5 is about
man's ability to shape himself into a being who derives genuine
happiness from an ethical life within society. Man, says Aristotle,
is by nature a political animal. If we are to comprehend Aristotle's
world, we must see how the natural desire to understand coexists
with the natural imperative for leading an ethically virtuous life
within political society. Finally, in chapter 6,1 give a rather sweeping account of what the desire to understand is a desire for. Aristotle discovered the possibility of conducting a very broad inquiry
into the structure of reality. He called this study 'first philosophy';
later commentators called it 'metaphysics.' Ifirstpresent an introduction to Aristotle's logic, for he conceived it as an important
tool for laying out the broad structure of reality. Then I present
what I take to be some of the central ideas and arguments of the
mature metaphysics and theology, while trying to assess the significance of the fact that this is where the desire to understand
leads us.
I believe this dual approach to Aristotle - tracking the desire to
understand in its broad and narrow senses - recapitulates the essence of his philosophy. This approach can help a reader understand what Aristotle is doing at any particular point in the
exposition of his account of the world and why he is doing it. Thus
this book can serve as an introduction to Aristotle's philosophy. I
speak of helping a reader, for I do not think it is possible to be
seriously interested in Aristotle without trying to read him.
Anyone who has tried to read him will know that it is not easy. The
Greek is written in a dense style (it is, I admit, an acquired taste:
after a while one comes to like it), and though the English translations do a remarkable job, they are nevertheless difficult to read.
Occasionally, the translators compensate for the dense style by
supplying an interpretation of what they think Aristotle is saying.
This can be helpful, but it can sometimes be misleading, even to an
intelligent and otherwise well-educated reader. In this book I make
an effort to render Aristotle's writing more accessible. Each section

The desire to understand
begins with a list of texts to be discussed, and when I quote Aristotle I regularly offer comments upon the translation.24 My hope in
writing this book is that a reader who works both with it and with
an English translation will then be able to go on and read Aristotle
for himself. My hope is that a great work which has, for many,
remained almost unreadable can be transformed into a source of
intellectual sustenance and joy.
Because I am trying to shed a particular light on Aristotle's philosophy as well as to provide an introduction to it, this book has
certain definite limitations. For instance, this is not a comprehensive introduction. That is, I do not attempt to summarize in a stepby-step fashion all the major positions Aristotle occupied. This is,
rather, a philosophical introduction: an attempt to work with
Aristotle's concepts and arguments and bring them to life. This
requires that much time and energy be spent elucidating a single
concept or argument. Although I do cover a wide range of Aristotelian texts, and I do try to present a large-scale picture of Aristotle's world, this picture could not be comprehensive without
losing claim either to being philosophical or to being an introduction. Moreover, I make virtually no effort to defend my interpretation of Aristotle against rivals. Aristotle may well be the most
commented-upon thinker in the history of the world. The reader
ought to be aware that for virtually every claim I make in this
book, there is a conflicting claim by a thoughtful, serious student
of Aristotle who would offer a different interpretation. Although I
could defend my claims at greater length, I cannot do so here
without abandoning the book's claim to be an introduction. But I
do not mind. The point of this book is neither to give the reader a
boiled-down summary of each of Aristotle's works nor to give him
an absolutely definitive interpretation, but to enable him to go on
and read these works himself.
As we begin this study, I think that we can conceive ourselves as
standing in a similar relation to Aristotle's world - that is, to his

In this book I shall rely for quotations on The Complete Works of Aristotle, The
Revised Oxford Translation, since it is a significant improvement on the original
Oxford translation, The Works of Aristotle Translated into English. However
the original translation is nevertheless pretty good, and an abridged version of it,
The Basic Works of Aristotle, is readily available. I shall occasionally revert to
the original translation in my quotations, and I shall also make occasional emendations and translations of my own. These will be noted.

The desire to understand
system of beliefs - as Aristotle stood to the world in which he lived.
It is the desire to understand that motivates us all. In Aristotle's
case it was a desire to understand the world in its entirety; in our
case (at the moment) it is a desire to understand one very small part
of the world: namely, Aristotle's beliefs and outlook. Thus, as
students of Aristotle, we need not conceive of ourselves as engaged
in a fundamentally different type of activity from that which
Aristotle was himself engaged in. Aristotle endeavored to make the
world intelligible and believed in its ultimate intelligibility; we are
trying to render Aristotle's account of the world intelligible, and,
perhaps, have even more grounds for believing in its ultimate intelligibility. For even if Aristotle was mistaken in his belief that the
world was meant to be understood, surely we cannot be mistaken
in our belief that Aristotle's philosophy was meant to be understood. It is therefore a mistake to think that we can learn about
Aristotle only by making him an object of our study. Because our
form of inquiry is not fundamentally different from his, we ought
to be able to re-enact at least some of the intellectual problems
which bothered him and thus gain non-observational insight into
the type of activity he took philosophy to be.
Since I am primarily concerned with the truth about Aristotle,
not the truth of Aristotle's views per se, I spend little time locating
him within the history of science. I do occasionally contrast an
Aristotelian concept, say of cause, with the modern conception.
But the point of such contrasts is to bring to light how different
Aristotle's world is from the modern, not to show how Aristotle's
beliefs fall short of what we now take to be the truth. This is the
price of restricting the world of our inquiry to Aristotle's world,
but there are two humbler reasons why I accept this limitation.
First, I am not competent to discuss Aristotle's role within the
history of science: others have, can, and will make a better job of
that than I could. Second, it is not my place to tell a reader of this
book - perhaps a working scientist - that the Aristotelian ideas he
encounters will be of no use to him. Books which do deal with the
seventeenth-century scientific revolution tend to treat Aristotelianism as an objet ntort: a specimen worthy of inspection, but certainly dead. But if science is still a living enterprise, full of problems
of interpretation and conceptualization, there is no telling from
what quarter a working scientist may draw inspiration. So, rather

The desire to understand
than describe in detail why, say, Aristotle's concept of final cause is
(now thought to be) false, I try to present the concept in as living a
form as possible: to show what within Aristotle's system motivates
and sustains this concept.
One last remark. Aristotle believed that to understand ourselves
we must understand the world. He also believed that to understand the world one must understand oneself. In particular, one
cannot understand the world if one remains ignorant of the role
the desire to understand plays in one's own soul as well as in the
world at large, if one remains ignorant of the human mind and its
capacity to understand, if one remains ignorant of the cost to oneself and to others of pursuing one's desire. Aristotle tried to raise
himself and his students out of this ignorance. Though the modern
world may have left the details of his account behind, his insistence
that understanding and self-understanding are each dependent on
the other is, I believe, a truth whose depth we have only begun to

2.1 Nature as an inner principle of change1

If we are to understand what it is for man by nature to desire to
understand, we must understand what it is for something to exist
by nature (phusei).1 Aristotle begins Physics 11 by saying that
existent things can be divided into those which exist by nature and
those which exist from other causes.3 The Greek word which is
translated as 'cause' does not mean cause in the modern sense:
namely, an antecedent event sufficient to produce an effect.
Rather, it means the basis or ground of something. Aristotle later
says that we do not understand something until we know why it is
what it is: and the cause gives us 'the why.'4 We shall discuss
Aristotle's conception of cause later. For the moment, the important point is that Aristotle thinks that to say that something exists
by nature is to cite its cause.
Aristotle thinks he can unproblematically identify the things
that exist by nature. The paradigms are living organisms - animals
and plants — but he also includes their parts and the 'simple bodies'
- earth, air, fire, and water. The task, for Aristotle, is to find the
characteristic feature which distinguishes natural items from
everything else. 'Each of them,' he says, 'has within itself a principle of change and rest.'5 The ability to grow is obvious in plants
and animals, and animals can move about their environment, but
even the simple elements have tendencies to move in fixed directions. For example, fire has the tendency to move toward the circumference of the universe, and will do so unless it is hindered.
When it reaches the circumference, the fire's 'upward' motion will

Appropriate reading for this section: Physics n . i - z .
See Physicsji.i, I92b38.
di' alias aitias: Physics II.I, i9zb8-9.
to dia tt: Physics 11.3,1941)17-10.
Physics II.I, 1 9 1 ^ 3 - 1 4 (my translation).
Cf. Physics II.I,

One might wonder: if nature is an internal principle of change,
how could nature be a cause? Nature would seem to be too much a
piece of the thing itself to be its cause. One way to begin is to think
of the contrast Aristotle has in mind when he divides reality into
natural objects and things that exist from other causes. The paradigmatic case of a thing that exists from another cause is an artefact. Artefacts depend for their existence on an external source, a
craftsman, who constructs the artefact out of certain material.
Now it is obvious that the craftsman is a cause of the artefact he
produces. But why should we isolate this creative principle as a
cause only if it is external? The wondrous fact about natural
objects is that they seem to have this creative force internalized,
and thus it seems right that one should focus on it if one wants to
know why something is what it is. This seems to be Aristotle's
reasoning, for he concludes that 'nature is a principle or cause of
change or rest in that to which it primarily belongs.'7
We as yet know almost nothing about this inner principle. One
suggestion, made by some of Aristotle's predecessors, is that a
thing's nature is the material stuff which constitutes it. According
to Aristotle, Antiphon argued that if you planted a bed what would
emerge from the rotting bed would not be another baby bed, but a
shoot which would grow into wood. This, Antiphon allegedly
thought, showed that the real nature of the bed was wood and that
the form of the bed was merely an attribute imposed on it.8 Given
this use of the craft analogy, it is appealing to think of the form as
superficial: a passing mark on a plastic and changeable reality.
But, for Aristotle, this appeal depends on a misuse of the analogy
between art and nature. Artefacts are of interest to him as much for
their differences from natural objects as for their similarities. Precisely because an artefact has an external principle of change, the
form imposed on the matter has an air of superficiality. But it is the
nature of a young boy to grow into a man. Thus we cannot think of
the manhood of a man as an incidental property superficially
imposed on flesh and bones. And if you, so to speak, 'planted a
man' - that is, let him go through the natural processes of generation, reproduction and decay — what would grow up would be
another man, not mere flesh and bones. If we are to make correct

Physics II.i, I9zbzi (my translation).
Physics H.I, 19389-17.

Nature as an inner principle of change
use of the craft-nature analogy, Aristotle thinks, we must get away
from thinking of the form of a bed as superficially imposed on
wood. Instead, we must think of the bed as having its own integrity
and ask: what is it to be a bed? Here the answer cannot be: to be
wood. As Aristotle says, a pile of wood is at best a bed only potentially:9 that is, the wood is such that it could be formed into a bed
by a competent craftsman. To be a bed, the wood must actually
have the form imposed on it. Thus if we are to think of a bed as
having a nature at all, it is more appropriate, Aristotle thinks, to
identify the bed's nature with its form. Indeed, if a bed were a natural object, then when planted it would grow up into a bed. That a
bed does not reproduce other beds shows that the bed does not
have a nature. For the form of a bed is not a principle internal to
the bed. On this Aristotle and Antiphon agree. They disagree only
to the extent that Antiphon thinks that this reveals something important about the nature of natural objects, whereas Aristotle
thinks it reveals an important difference between natural objects
and artefacts.
Yet if the form is internal to a natural object, how can one distinguish a natural object's form from its matter? After all, with an
artefact there is a straightforward sense in which there is matter
which exists before the artisan crafts it and which may persist after
the artefact has broken down. But (i) if the nature of a natural
object is an internal principle which makes the natural object a
natural object and (1) the form is a candidate for being this nature,
it would seem that form would have to be a part of a natural object
from the beginning. The form, then, cannot be defined in terms of
properties superimposed on a matter which.exists before and
(maybe) after the natural object exists.10
Aristotle, I believe, relies on the analogy between art and nature
to give one some idea of the form of a natural object. A craftsman
can impose a form on various bits of matter: he can make a bed
from this wood and from that, he can shape a sphere in wax or in
bronze.11 In each case there is a process in which the matter comes
to take on a particular form. Now with all living things there is a
process by which each thing comes to be. This natural process of
' Physics ii.i, 193334-5.
See J. L. Ackrill, 'Aristotle's Definitions of Psuche;' and see section 4.1 below.
" See also Metaphysics vn.7-9, which is further discussed in section 6.5 below.


generation Aristotle conceptualizes as a process in which the organism comes to realize its (natural) form. Surely, we do see a level of
organization in mature living organisms which is the outcome of a
process of growth and maturation. It was not there before the
organism grew to maturity. And we can give at least minimal sense
to the idea of matter persisting through change in form. Immediately after an organism dies it lacks a principle of change and rest;
what remains is the matter. However, this is at best an attenuated
characterization, for the matter begins to decay simultaneously
with death. The matter seems to be dependent on the form to be the
matter that it is.
And, indeed, the form seems to be in some sense dependent on
the matter: with natural organisms, unlike many artefacts, there is
only one type of matter in which a form can be realized. Human
form cannot be realized in froggy material or in iron. In short, with
natural organisms we lack the clear-cut criteria which we have
with artefacts for distinguishing matter and form. Yet if, as Aristotle believes, art does imitate nature, we can reason backwards
from the imitation to that which it is an imitation of.12 Aristotle
would, I suspect, endorse the following counterfactual conditional: 'If there were a Divine Craftsman, he would impose the
form of natural organisms on the appropriate matter.' Of course,
Aristotle would deny the antecedent: there is, he thinks, no Divine
Craftsman. However, since art does imitate nature, it is possible to
view natural organisms as though they were created. From this
perspective the creation consists in the imposition of form on
There is a, perhaps apocryphal, story about a young child asking
Einstein how a radio works. Einstein asked the child to imagine a
big cat which stretches from New York to Chicago. Someone in
New York bites on the cat's tail and the cat yelps in Chicago.
'Radio waves are just like that,' Einstein reportedly said, 'except
that there is no cat.'
Natural form is precisely that which a Divine Craftsman would


mimeitai: Physics n.z, 194321. For a further discussion of the idea of reasoning
backward in order to determine the form/matter distinction in natural objects,
see section 4.1! below.
Indeed, Aristotle believes that neither matter nor form is ever created. See Metaphysics VII.7—9. Creation, for Aristotle, is the creation of a compound of form
and matter; and the creation consists in the imposition of the form on the matter.
See section 6.5 below.

Nature as an inner principle of change
impose if there were a Divine Craftsman; but there is no such
Craftsman. The development of form, as an organism grows to
maturity, is a process internal to the organism itself. But an organism's internal principle of change is its nature. An object's nature
would thus seem to be a developmental force which impels it
toward the realization of its form. How then can Aristotle identify
an organism's nature with its form? The answer, which we shall
investigate in detail later, is that form can exist at varying levels of
potentiality and actuality. A young organism's form should not be
identified with its current organization and structure. In addition
to the structural articulation which the immature organism has so
far achieved, it has within itself a force for future growth and development. This force is the form, though at this stage Aristotle thinks
the form should be thought of as a potentiality or power
(dunamis). The form in the young healthy organism is an internal
force propelling it toward the realization of its form. This is not as
paradoxical as it might initially appear, for when the organism has
reached maturity, its form will no longer be a potentiality. In the
mature organism, the form exists as a full-fledged actuality. In the
growth of an organism, form is itself developing from potentiality
to actuality, and it is directing this process. One cannot, therefore,
identify natural forms with an organism's structure. Structure
helps to constitute the form, but forms are also dynamic, powerful,
active. They are a force for the realization of structure.
Form also provides the link between the mature and the immature organism. The growth of an organism is, for Aristotle, a process directed toward an end (telos): the mature functioning
organism. The mature organism is 'that for the sake of which' the
process of growth has occurred.14 And yet Aristotle also identifies
an organism's nature with the end or the 'that for the sake of
which.'15 Again there is an air of paradox. If an organism relies on
its internal principle of change in order to reach its end, how could
this end, which did not exist during the process of growth, be identified with the organism's nature? Aristotle's answer is that we
should conceive the end as being the [fully actualized) form. For
the form is and has been its nature throughout its development.
The form is both that toward which the process is directed - 'that

Physics ii.i, 194817 (to hou heneka).
Physics u.i, 194318-9.

for the sake of which' the growth occurs - and that which is directing the process. It is an immature organism's nature to grow into a
mature member of the species, and it is a mature organism's nature
simply to be a member of that species in the fullest, most active
sense. This, for Aristotle, is one and the same nature: the active,
dynamic form which, at varying levels of potentiality and actuality, is at work in the appropriate matter.
Since the seventeenth century Western science has moved steadily
away from conceiving forms as part of the basic fabric of the universe. It is thought that if we understand all the properties of the
matter we will see form as emerging from these properties. It is important to realize that Aristotle's world is not like that. In Aristotle's world, forms cannot be understood in terms of matter. Forms
must occupy a fundamental ontological position: they are among
the basic things that are.
Aristotle had, I suspect, a family of reasons for his belief in the
irreducibility of form. If art imitates nature, then form must be a
principle additional to the matter. A bed does not come to be from
wood alone; there must be a craftsman who imposes a form on the
wood. A natural object has this principle internalized, but that
does not diminish the fact that the principle must be additional to
the matter. No doubt Aristotle also thought he could support his
belief in the irreducibility of form on the basis of empirical observation. Matter, for Aristotle, is indefinite, lacking order. As one
moves toward the basic elements - earth, air, fire, and water - it
appears incredible that an organized unity like flesh, let alone a
living organism, should be completely explained by these elements
alone. Aristotle also had theoretical reason for thinking this impossible.16 For each of the basic elements themselves have (primitive) natures: fire to move upward to the circumference of the
universe, earth to move toward the center, air and water to occupy
intermediate positions. Were there no additional organizing principle, there would be nothing to hold the elements together: in the
absence of external constraints, the elements would goflyingoff in
the disparate directions of their natural places.
An organized unity, Aristotle believes, can always be dis16

See Sarah Waterlow (Broadie), Nature, Agency and Change in Aristotle's Physics.

Nature as an inner principle of change
tinguished from the matter which constitutes it. For an organized
unity, to be organized requires a principle responsible for the organization. Aristotle contrasts a heap and a syllable.17 A heap is
not really a unity at all and thus may be thought of as a mere agglomeration of its material constituents. The syllable ba, by contrast,
cannot be thought of as a mere heap of its constituents b and a. To
be a syllable rather than a mere concatenation of the shapes b, a, it
must have been formed either in writing or in speech, by a person
who also understands the language. This person - or the linguistic
knowledge in his soul - functions as a principle of organization: he
forms the syllable into the syllable that it is.
Matter, Aristotle says, is a relative item.18 What he means by this
is that the matter of a given thing must be understood in relation to
the form that it is the matter of. The matter will always be less organized than the form, but it may itself have a certain organization.
Indeed, there may be a hierarchy of matter and form. For example,
Aristotle says that the matter of animals is their parts: heart, lungs,
brain, liver, limbs, etc. But these parts of animals are themselves
composites of form and matter: they are made up of homogeneous
matter - flesh, viscera, and bone - organized in certain ways.19 So
while human lungs, liver, hands, etc., are the matter of a human
being, a human is not a mere heap of liver and lungs. He is liver,
lungs, etc., organized in such a way: there is thus required, in addition to the organization already manifested in the liver, lungs,
and limbs, a principle responsible for organizing human organs
and limbs into human form. This type of reasoning is applicable all
the way down. Flesh and bones are the matter of human organs
and limbs, but an arm is not a mere heap of flesh and bones. It is
flesh and bones organized in such a way: there is thus required, in
addition to the organization already manifested in the flesh and
bones, a principle which is responsible for organizing thefleshand
bones into an arm. And, to take this reasoning one step further:
flesh does have a certain organization, but flesh is itself a composite of form and matter. The organization offleshcannot be understood solely in terms of the organization already manifested in
its matter, fire and earth. Flesh is not a mere heap of earth, water,

See, e.g., Metaphysics vn.17, iO4ibn-3Z.
Physics 11.z, 1 9 ^ 9 (pros ti he hule).
See Generation of Animals 1.1, 71589-11.

and heat: this matter must be organized by an additional principle.
Thus organized, the flesh can stand as matter for the limbs of a
human being: that is, in need of an additional principle to organize
It. 20

Both Aristotle and a modern biologist would agree to the following subjunctive conditional: 'If this young child were allowed to
live in a supportive environment, it would grow into a mature,
healthy adult.' However, for the modern biologist the truth of this
conditional would be grounded in the already achieved material
structure of the young child. The child already has a structure
which ensures that, in supportive conditions, the child will grow
into a healthy adult. For Aristotle, by contrast, the actual material
structure of the child is in itself insufficient to guarantee normal development. Yet Aristotle does endorse the subjunctive conditional.
And he does not think that the conditional is brutely true: that is,
true, but not in virtue of anything actual. The fact that the child
would in a healthy environment grow to a mature adult is
grounded in the actual presence of form in the child. This form is
the additional principle, responsible both for the already achieved
material structure of the child and for the child's future development. It is not merely a functional state of material structure. Nor,
as it exists, is the form in the child in its fully developed state. It
exists in the child as a power or potentiality for attaining this fully
developed state.
However, if this power is not a functional state of material structure, how can its presence be observed? Are natural powers
beyond the realm of empirical inquiry? No, they are not; but it
takes some care to spell out the conditions under which they can be
observed. Obviously, powers are not immediate items of sensory
perception. Nor can they be seen under a microscope. If an intelligent scientist were permitted to observe only one immature natural
organism in his life, having been kept in ignorance of the general
facts of generation and destruction, then there would be no way he
could detect the presence of a power in the organism. The first
dawning of the idea that a power is present could only occur in
retrospect. From the perspective of the fully developed organism
we realize that there was a force present in the immature organism
which directed its growth and activity toward this mature state.

1 discuss this further in section 2.3 below.

Nature as an inner principle of change
However, although the original idea of the presence of power is
necessarily backward looking, this does not imply that powers are
Aristotle attached much significance to the regularity of natural
processes of generation and decay. If a teleological process of generation did occur only once, one would have to wait until the end
to comprehend the antecedently existing powers which brought it
about.21 Because natural processes of growth occur with such
dependable regularity - the exceptions can be dismissed as degenerate or crippled - there is empirical evidence for the presence
of a power in an immature organism. Moreover, the form of an
immature organism is not present merely as a power toward development. It is also manifest in its structure and organization. So,
while the form is not merely a functional state of the young organism's material structure, it is nevertheless responsible for that
structure. And, while that immature structure on its own is not
itself sufficient to ensure the development of a more complex and
mature structure, the immature structure is a manifestation of
form which (given the proper setting) is sufficient to ensure development.
Since the seventeenth century it has been customary to treat socalled virtus dormitiva explanations with scorn. A virtus dortnitiva explanation gets its name from Moliere's play Le Malade
imaginaire, in which a foolish doctor is asked how a certain
powder induces sleep. He replies that it has a virtus dormitiva - a
power of inducing sleep. The heart of the objection to virtus dormitiva explanations is that they are not explanations at all. To say
that a powder causes sleep because it has a power to bring on sleep
is to explain nothing: it is just to repeat that the powder causes
There is no doubt but that Moliere's doctor is a fool and his 'explanation' a sham. But his legacy to Western culture is, I believe, a
mistaken conception of adequate explanation. It is widely believed
that if any explanation has the structure of a virtus dormitiva explanation, it must therefore be circular and non-explanatory. Thus

Hegel believed that one such unique process was human history. Thus philosophy was, for Hegel, essentially retrospective. For the full meaning of human activity could only be fully understood from the vantage-point of the realized end.
As Hegel put it, 'the Owl of Minerva spreads its wings only with the falling of the
dusk' (Philosophy of Right, Preface, p. 13).

Aristotelian powers are viewed as inevitably suspect. This, I think,
is a mistake. There may be a valid objection to certain explanations
which have a virtus dormitiva structure, but the objection is not
one of principle. Even if we do not live in Aristotle's world, it is not
absurd to imagine that our world is as he described. In such a
world we could not explain the organism's ability to develop in
terms of its material microstructure. In such a world this ability is
form, and form is one of the basic constituents of the universe: it
cannot be explained in terms of anything more fundamental.
In Aristotle's world form as a potentiality or power does help to
explain the growth, development, and mature functioning of living
organisms. And there are empirical tests for the presence of form.
Were there no structure in an immature organism or regularity in
the processes of development there would, in Aristotle's eyes, be
no basis for the attribution of a power, regardless of the outcome.
The absurdity of Moliere's doctor is manifested not merely by his
virtus dormitiva explanation but, first, by the fact that he has not
noticed that he is not living in Aristotle's world (and by that time in
the history of science he should have); second, by the evident fact
that he merely cites the virtus without having any understanding of
how it might work as an explanation; third, by the fact that he has
done nothing to determine whether the powder actually has the
power. (He could have devised tests to distinguish accidental onset
of sleep from genuine inducement.)
Each thing which has a nature is, Aristotle says, a substance
(ousia).22 Reality, for Aristotle, forms a hierarchy of dependencies.
The color white, for example, may exist, but it can only exist as the
color ofsomething.23 Substance stands at the base of the hierarchy:
it is that on which the reality of other things depends, while it is not
dependent on anything else. This characterization of substance is
very abstract. As a result, we may know that substance is ontologically independent yet remain ignorant of what in the world fits this
characterization. Indeed, Metaphysics vn, which represents the
mature Aristotle's search for substance, is probably the most difficult text in the entire Aristotelian corpus. Fortunately we do not

Physics ii.i, I9ib33. It is worth noting at the outset that Aristotle's conception
of substance will develop over time.
See, e.g., Metaphysics vn.i.

Nature as an inner principle of change
have to work our way through that text in order to understand
Aristotle's claim that everything that has a nature is a substance.
For Aristotle distinguished substance in the primary sense from
various other things we call substance because they have some
degree of ontological independence. Whatever finally emerges as
primary substance, we can appreciate right now that things which
have a nature enjoy at least some degree of ontological independence.
Natural organisms are loci of reality and self-determination.
Because each has in itself a principle of change, there is an objective
basis for distinguishing it from the rest of the environment. It is not
just that we observers are minded so as to perceive certain functional organizations as salient and thus select out certain bits of a
relatively homogeneous reality as objects of interest. Natural
forms are ontologically basic, and each thing having a nature has
such a principle within itself. Moreover, the principle which
directs the growth, development, and characteristic activity of a
natural organism exists in the organism itself. The environment
only supplies a backdrop against which an organism acts out the
drama of its life. The environment may be benign or hindering, but
beyond that it plays no significant role in the development and life
of the organism.24 Further, this inner principle is not like an extra
silicon chip which is plugged into an already existing computer. It
is rather the clearest expression of what the organism itself is. An
organism is thought to be most fully what it is when it has reached
maturity: thus it is most fully what it is when its form is fully developed.25 The principle directing the change, growth and characteristic activity expresses the organism's self-determination.
It is by virtue of its nature, then, that each natural organism is a
substance.26 Because it has a nature, an organism is relatively independent of the environment and self-directing. It provides a subject
for properties to belong to, and it does not itself depend on another
subject for its existence.27 Yet there is a problem here. It seems odd
to say that a natural organism is a substance because of its form.


For a discussion of how the modern conception of the importance of the environment differs from Aristotle's, see Sarah Waterlow (Broadie), Nature, Agency and
Change in Aristotle's
Physics i i . i , i 9 3 b 6 - 7 Cf. Physics I I . I , 1 9 x ^ 3 3 - 4 .
See also Metaphysics v . 8 , 1 0 1 7 6 1 3 - 1 4 .

This would seem to imply that it depends on its form to be the
substance that it is. And this would seem to threaten the idea that
an organism is ontologically independent. How could a natural
organism be a substance if it depends on its form? One can say that
the form expresses what the organism most truly is. Form is not a
property true of the organism; form is constitutive of the organism's very being. One can also point out that an organism does not
depend on its form in the way that a property depends on a subject.
But the fact remains that the organism is a composite of form and
matter, and the form is ontologically prior to the composite.28
Such reasoning will eventually convince Aristotle to dismiss natural organisms as candidates for primary substance - as we shall
see. We can continue to call them substances, however, for within
the natural world they do exercise a certain type of ontological
2.2 Understanding and 'the why'29
We do not think we understand something, Aristotle says, until we
have grasped the why of it.30 The expression 'the why' is awkward
even if it is a literal translation, but this is one of those cases where
awkwardness is of value. For it is often thought that Aristotle is
saying that a cause is anything which answers a why-question.
This is anachronistic. It looks as though Aristotle is relativizing
causes to our interests and curiosities. In fact the situation is the
reverse. 'The why' is an objective feature of the world: it is that
about which we ought to be curious if we wish to understand a
thing. The expression 'the why' is suggestive of the intimate link
Aristotle saw between man and world. Man is by nature a
questioner of the world: he seeks to understand why the world is
the way it is. The world for its part reciprocates: it 'answers' man's
questions. 'The why' performs a curious double duty, as interrogative and indicative, suggesting both question and answer.
And the world's 'answers' are not merely responses to man's
probings: they manifest the ultimate intelligibility of the world.
'The why,' therefore, penetrates to the world's most basic reality.

See Metaphysics v n . 7 - 9 , and section 6.6 below.
Appropriate reading: Physics 11.3, 7 - 8 ; 111.1-3.
to dia ti: Physics 11.3, 194818-19; cf. Postertor Analytics 1.2, 7ib8-i2.

Understanding and 'the why'
To grasp the why of a thing, Aristotle says, is to grasp its primary cause.31 From what we have learned so far one would expect
Aristotle to identify the why with a thing's nature. For the form,
which is the thing's inner principle of change, provides us with the
best understanding of what the thing most truly is and why it is the
way it is. This expectation is, I believe, realized: Aristotle did identify the why with an object's nature or form. This will seem surprising only if you have heard that Aristotle isolated four distinct
causes: material, formal, efficient, andfinal.What he actually cites
are not four causes but four fashions in which we cite the cause.32
Of course, Aristotle was proud to have identified the four distinct
ways in which cause is cited. Nevertheless, he believed that for the
generation of natural organisms and for the production of
artefacts there were at most two causes - form and matter. And
matter ultimately has to be relegated to a secondary position, for it
is ultimately unintelligible: at each level of organization what we
come to understand is the principle of organization or form. The
matter provides the brute particularity of an object: it can be perceived, but not understood.33 Unintelligible matter cannot, in a
strict sense, give us the why of anything. The so-called formal, efficient, and final causes are (at least in the wide variety of events
that occur within the natural world) three different aspects of form
itself. Aristotle says that these three causes 'often converge on one
thing.'34 The one thing is form, and 'often' covers all cases of natural generation and creation of artefacts.3S So although Aristotle
can talk about the three causes which coincide, he can also talk
about the primary cause. He is not then picking out one of four
causes for special honor: he is citing the one item, form, which can
be considered either as the form it is or as the efficient cause or as
the final cause. The form really is the why of a thing.



he prote attia: Physics 11.3, 1 9 4 8 2 0 .
tropot: Phystcs 11.3, 1 9 4 6 2 3 - 4 , bz6, b29, b32.
See, e.g., Physics i n . 6 , 2 0 7 8 2 4 - 3 2 . For the attenuated sense in which matter can
be considered intelligible, see the discussion of final cause in section 2.3 below,
and the discussion of the hierarchy of matter and form in section 2.4 below.
ets hen pollakts: Physics 11.7, 198825.
It does not cover the causal influence of an unmoved mover. It also does not
cover mathematical objects like geometrical objects and numbers. Cf. Physics
11.7, 198828-9.

2.3 Four fashions
Aristotle does think that there are four ways in which we cite the
cause of a thing. The first is the matter: or 'that out of which a
thing comes to be and which persists.'36 The paradigmatic case is
the matter of artefacts: for example, bronze may be shaped into a
bowl, then melted down and beaten into a sword. The bronze is the
matter, first of the bowl and later of the sword. The remaining
three ways in which we state the cause are three different ways of
specifying the same thing, the form.
The second fashion is the form - that is, it is the form specified as
such. Since this cause is not distinct from the ones which will
follow, what we learn here is how Aristotle characterizes form. He
calls it 'the logos of the essence.'37 'Essence' is a customary translation for what is literally rendered as 'the what it is to be.' 38 An
organism's nature, its inner principle of change, gives us what it is
to be that thing. Indeed, the fact that an organism has a nature provides a metaphysical basis for distinguishing among what we
moderns would think of as the properties of the organism. Those
properties which are part of an organism's essence should not be
conceived as true of the organism. These properties express what
the organism is. Other properties - like being pale, walking, being
six feet tall — are true of the organism; and they depend for their
existence on the organism which acts as the subject to which they
The Oxford translation of 'the logos of the essence' is 'the definition of the essence.'40 While 'definition' is sometimes an appropriate translation for logos, in this context it cannot be correct.
Aristotle is here trying to characterize the form as cause, and a
cause is not a definition, but a real item in the world. Logos is a
protean word: it can also mean proportion, ratio, order. The logos
of the essence need not be a linguistic item; it can be the order,
arrangement, proportion instantiated by the essence itself.
'Logos of the essence' brings home that the essence - what it is

* to ex hou gignetai ti enuparxontos: Physics 11.7, 1 9 ^ 2 4 .
ho logos, ho tou ti en einai: Physics 11.7,19^27.
to ti en einai.
I began discussing this distinction in section 2.1. It will be discussed in greater
detail in sections 6.5-6.6 below.
*° The old Oxford translation is 'statement of the essence.'


Four fashions
to be a thing - instantiates an order, or proportion, in the matter.
Precisely because the essence does instantiate an order, it is intelligible. Mind can grasp the order manifested in an essence, and
thus we can give an account or definition of it. Aristotle is translated as saying that what is potentially flesh has not yet its own
nature until it receives 'the form specified in the definition.'41 A
more literal rendering would be: until it receives 'the form according to the logos'. Here again 'definition' is the wrong translation.
For Aristotle does not mean that the potentialfleshis in the process
of conforming to a linguistic entity. It is rather that the potential
flesh is in the process of realizing a certain order, and this order is
the logos. Yet Aristotle does move from the order of a form to its
definability. For example, he says that the form according to the
logos is that 'by which we, when defining, say what flesh or bone
is.' 42 This is not an equivocation. Aristotle thinks the very same
logos present in the form and in the definition: that is why the definition is a definition. It is a logos which gives the logos: the definition states the essence. Aristotle thinks that order is ultimately
intelligible: it is that which is realized over and over again in natural organisms, it is that which a single definition can capture as the
essence of these organisms, it is that which the mind can apprehend. Because the form of a natural organism or artefact gives us
what it is to be that thing, the why and the what converge. We tend
to envision philosophical activity as concerned at least as much
with essential charaterization - what there really is - as with explanation - why things are the way they are. For Aristotle, a single
inquiry will reveal both, for the why of something is its essence.
The third way we specify the cause is as the primary source of
the change or rest.43 The father is cause of the child, in this sense, as
is the craftsman of what he makes - and, generally, that which
brings about a change is the cause of what is changed.44 The Greek
for 'primary source of change' is often translated as 'efficient
cause.' For the primary source or principle is that which brings
about a change. Yet this translation is misleading for two reasons.



H.I, i93bi-2.
H . I , 193hz (my translation).
H.3, 1 9 ^ 2 9 - 3 0 .

First, it suggests anachronistically that Aristotle had isolated the
modern conception of cause; second, it suggests that this is a different cause from the form rather than a different way of specifying
the same cause. Let us consider these reasons in turn.
Aristotle's primary principle of change differs dramatically from
the modern conception of efficient cause. The most obvious difference is that on the modern, post-Humean conception, the efficient cause is an event which is regularly followed by its effect,
whereas Aristotle tends to cite things - the father, the builder, the
doctor - as paradigms of his primary principle. This difference is
so great that it would immediately destroy any resemblance between efficient cause and primary principle were it not for the fact
that Aristotle does distinguish between the potential and the actual
cause.45 The builder is the potential cause of the house, the builder
building is the actual cause. Those who have wanted to assimilate
Aristotle's cause to the modern conception have insisted that the
actual cause - the builder building, the doctor doctoring, the father
fathering - is an event; indeed, it is an event which brings about its
effect, and thus it should be treated as the efficient cause. This line
of reasoning fails, I believe, to capture the significance of Aristotle's insistence that it is the builder building which is the actual
To see this, let us consider for a moment why the modern conception of cause focusses on events at all. Hume argued that transitive agency in nature is empirically unobservable. All one can ever
observe is one event following another. One can never observe the
causing which, as it were, glues the two events together. When there
is a regular pattern of one type of event following another we tend
to see the first event as causing the second; but, Hume argued, we
never see the causing, we only witness the events. Hume did not
think we should abandon the language of causation, but Humeans
do have to reconstrue what is meant by 'cause.' To isolate an event
as a cause must be construed as shorthand for claiming that the
event occupies a certain place in a larger regularity of events. To
say that a particular event x causes an event y is to say that x is an
event of type X and y is an event of type Y and, in general, when
an event of type X occurs it is followed by an event of type Y. We
may even say that X-type events bring about Y-type events,

Physics 11.3,

Four fashions
but all we can mean by this is that if an X-type event were to
occur a Y-type event would follow. Strictly speaking, though,
all connotation of transitive agency should be expunged.
One reason why we moderns focus on events as causes is
that we want to get away from appealing to anything that is
empirically unobservable, and we take the actual causing to be
Aristotle, by contrast, thought that the actual causing was
clearly observable: the builder building is the actual causing and
one can see his activity of building. For Hume the causing is not
itself a particular event: it is that which would occur between the
antecedent and the subsequent event, if anything did, but nothing
(at least, nothing empirically observable) does occur. What is at
issue is a disagreement not only about causes but about what constitutes an event. It is important to realize that events are not
unproblematically given. It is easy for us to overlook that, because
we think we can locate any space-time point and call what is going
on there an event. But Aristotle had no such matrix to isolate and
identify events. He did not have a watch, and when he specified the
place of an object it was not in terms of its location in a unique allencompassing field. The place of an object was characterized in
terms of the boundary of the body which contained it.46 The way
Aristotle chose to identify events instead was via the actualizing of
potentialities: the potentialities of substances to cause and suffer
One way to characterize the difference between Hume and Aristotle is to say that while for Hume causation must be understood in
terms of a relation between two events, for Aristotle there is only
one event - a change. Aristotle can pick out the single event of a
change: and causation must be understood as a relation of things
(or things doing their thing) to that event. A change, for Aristotle,
is the actualizing of potentiality.47 For example, a pile of bricks
may be a house potentially and a builder may be able to build the
house. The actualization of these potentialities is the building of
the house. Indeed, Aristotle says that change can be understood as

See Physics iv.4.
Physics III.I, z o i a i o - n . This will be discussed in more detail in chapter 3

the actualizing of the potential agent and the patient.48 Thus we
can think of a change in terms of a builder actualizing his potential
by becoming a builder building and the bricks having their potential actualized by becoming a house being built. However, the
actualizing of these two potentialities is not two separate events.
The actualizing of the agent and the actualizing of the patient are,
for Aristotle, one and the same event.
In Physics 111.3, Aristotle argues that there is but a single activity
in a given change, and it occurs in the patient. Aristotle is concerned to show that not every cause of change need itself undergo
change when it acts as a cause - that there is at least a possibility of
an unmoved mover. Thus when he confronts the question 'Where
does one locate the agency which is the actualizing of the agent?' he
is willing to bite the bullet and say, 'in the patient.' If we think of a
teacher teaching and a student learning we should not, according
to Aristotle, think of two activities which are related to each other:
'teacher teaching' and 'student learning' are two different ways of
characterizing the very same happening. One description captures
the perspective of the agent, the other captures the perspective of
the patient. Although there may be various ways to characterize
this activity, Aristotle argues that there is nevertheless only one activity and it is occurring in the student. It may sound odd at first to
think of the teacher's teaching as occurring in the student, but for
Aristotle if it is happening anywhere at all, this is where it would
have to be. And, on second thoughts, the idea is not so odd: where
else could teaching be occurring? We can imagine a teacher going
through the motions in an empty classroom, or lecturing to a flock
of geese, but Aristotle would deny that he was teaching. Unless a
student is learning a teacher cannot be teaching.
Similarly with the builder: 'the builder building' and 'the house
being built' refer to one and the same event from two different perspectives. The activity of the builder building is occurring in the
bricks and mortar that are becoming a house. And, again, were the
builder not performing his characteristic activity on the appropriate material, he would not be a builder building. At best, he
would be a builder doing something else. Thus it is futile to specify
the builder building as an antecedent event which might serve as efficient cause in the modern sense. The event which 'the builder
"s Physics ui.3, ioibi6.

Four fashions
building' refers to is every bit as much the effect as it is the cause.
Indeed, it is because there is only one event for Aristotle that the
vocabulary of cause is ineliminable. The language of cause requires
one to note that there are two distinct 'objects' involved in a
change - an agent and a patient - without allowing what Aristotle
must deny: that there are two distinct events. (A Humean, by contrast, can always cease using the shorthand language of cause in
favor of (what for him is) a more accurate description of general
regularities and of the place of particular events within those patterns.)
So far we have shown that 'the primary principle of change'
should not be conceived in terms of the modern conception of
efficient cause. But what reason is there for thinking that it should
be identified with form? Has not Aristotle identified a distinct
We have already seen that there are two features of forms which
Aristotle is concerned to stress: first, that they are immanent in
natural objects and, second, that they are dynamic. Forms are
instantiated in natural organisms - they are the inner principles of
change - and they act as a force within the organization for the realization (and reproduction) of the form.49
There are at least three ways in which forms are transmitted in
the natural world: by sexual reproduction, by the creation of
artefacts, and by teaching. The creation of artefacts remains a
paradigm. The craftsman has his art or techne in his soul: that is,
the form which he will later impose on external matter first resides
in his soul. We have already seen that form can exist at varying
levels of potentiality and actuality. The form of an artefact, as it
resides in a craftsman's soul, is a potentiality or power. It is in
virtue of this power in his soul that we can say that he is a craftsman. The full actuality of the craftsman's art is his actually making
an artefact. Thus the builder building is actually the form of the
house in action. And, as we have seen, this activity is occurring in
the house being built. In short, the primary principle of change is
the form in action.
When Aristotle cites the builder building or the teacher teaching
as the actual cause of change it is not because he is trying to focus
on an antecedent causal event - i.e. on what for us would be the ef49

See section 2.1 above.



ficient cause. It is because he is trying to cite the primary principle
of change: the form in its highest level of actualization. Aristotle
identifies the agent of change with that which determines the form:
'The changer will always introduce a form ... which, when it
moves, will be the principle and cause of the change. For instance,
an actual man makes what is potentially a man into a man.'50 But
he also says that if we are being more precise we must think of the
cause as being the form itself: 'In investigating the cause of each
thing it is always necessary to seek what is most precise ... thus
man builds because he is a builder, and a builder builds in virtue of
his art of building. This last cause then is prior; and so generally.'sx
Aristotle could not conceive the primary source of change as a
mere antecedent event. It must be something - the form - which
persists and determines the form in the change. Even in art there is
a sense in which form is responsible for its own realization. When
we specify the builder as the primary source of change we are not
simply citing him as the cause: we are concerned with what eventually constitutes him as a builder. This is the form (of a house, say)
which, as a potentiality, is the builder's art. It is the builder's capacity to be a builder. The art of building at its highest level of activity is the builder building. This is occurring in the house being
built and is identical to the activity of the house being built. As
Aristotle says, 'architecture is in the buildings it makes.'52 Thus in
Aristotle's world, there is no event antecedent to this activity
which might be isolated as the efficient cause. If we are to isolate
anything antecedent to this activity which might help to explain its
occurring, we have to specify a thing - a builder - or perhaps a
form which exists as a potentiality or power in the builder's soul.
Teaching is very much like the creation of an artefact, though
the 'matter' on which the teacher imposes his form is the student's
soul. A teacher, in teaching, is able to pass on his knowledge to his
student: this, for Aristotle, is to impart the (relevant) forms or essences in his soul to the student's soul. The teacher teaching is the
activity of form - a form which constitutes the knowledge the
teacher is passing on. If the teaching is successful, the student's


Physics III.Z, z o i a 9 - n (my emphasis). I use the words 'changer' and 'change,'
where the Oxford translation uses 'mover' and 'motion.' Aristotle does not stick
to this consistently throughout the Physics, but it at least serves as a paradigm.
Physics 11.3, i 9 5 b n - 4 (my emphasis).
Generation of Animals 1.12, 73ob7-8.

Four fashions
mind takes on the form that is in the teacher's mind. It is as though
the student's mind is the successful teacher's artefact.
Similarly with sexual reproduction. Consider, for example, the
human species. It is of the essence of the human soul that members
of the human species be able to reproduce their kind. To be a father
is to have the power to pass on the human form to another member
of the species. This power helps to constitute the human form
itself. The father fathering is just the actualization of this power:
namely, active human form.
Therefore, the primary source of change is form. The actual primary source is form in an active state.
The last way in which we cite the cause is the end (telos) or 'that
for the sake of which' something is done.53 For example, plants
grow leaves in order to protect their fruit and send roots downward for nourishment, swallows build nests for protection, and
spiders build webs for the sake of nourishment.54 In each case such
activities of plants and animals are for the development, maintenance, or protection of form: 'Since nature is twofold, the matter
and the form, of which the latter is the end, and since all the rest is
for the sake of the end, the form must be the cause in the sense of
"that for the sake of which."'55 The 'final cause' is not a different
cause, it is a different way of referring to nature. Aristotle concludes his discussion of final cause by saying: 'It is evident then
that nature is a cause, a cause that operates for a purpose.'56 Our
task is to understand how nature or form can operate as a final
In Aristotle's world form exists not merely as a realized state, it
also exists as a striving toward that state. This striving is a basic
ontological entity: it is an irreducible force in the young organism
directed toward an end. The end, the form in its realized state, is
none other than a successful striving.57 Since a striving is not
merely the expression of an actual material state, we cannot make
sense of strivings unless we understand what they are strivings

Physics i i . 3 , 1 9 ^ 3 2 — 3 . Appropriate reading: Physics H . 3 - 9 .
Physics 11.8, 1 9 9 3 1 0 - 3 0 .
Physics 1 1 . 8 , 1 9 9 3 3 0 - 2 (my emphasis).
Physics 11.8, i 9 9 b 3 2 - 3 .
Compare this to the account of human action as successful trying. Action o n this
analysis is not trying plus bodily movement, a successful trying is an action. See
Brian O'Shaughnessy, The Will.


toward. We need to cite form as final cause in order to make the
whole range of developmental activities - form as potentiality - intelligible.
In the twentieth century much work has been done by philosophers to show that teleological explanations are compatible with
mechanical explanations.58 For example, one can say that the
spider builds its web in order to secure nourishment, but one can
also explain its orderly activity via its neuro-physiological makeup
and genetic inheritance. That is, actual physical structure grounds
teleological behavior. It is important to realize that Aristotle does
not believe in any such compatibility.59 For Aristotle, the reason
one has to cite the form in its final, realized state is that it is only by
reference to that form that one can understand teleological behavior.
This comes out most clearly in Aristotle's discussion of chance
and spontaneity.60 Chance (tuche) and spontaneity (to automaton)
are important for they provide cases of apparent teleology. A spontaneous event is one which (i) might have occurred for the sake of
something, (z) as it happens did not, but (3) was instead brought
about by some external cause.61 For example, the stone which
struck the man did so spontaneously, for it might have been the
weapon of his enemy, though in fact it just rolled off the cliff.62
Note that a spontaneous event is not a disturbance of the causal
order. The stone falls because of its own weight - or, in Aristotelian terms, because it seeks its natural place and is unhindered. An
event counts as spontaneous not because it interrupts a causal
chain or because it literally emerges from nowhere, but because it
appears as though it is happening for an end even though it really is
not. The stone did not really drop in order to strike the man,
though it might appear so.
Chance, like spontaneity, is a case of apparent purposiveness,

See, e.g., Charles Taylor, The Explanation of Behavior, and 'The Explanation of
Purposive Behavior;' Hilary Putnam, 'Philosophy and our Mental Life,' Jonathan Bennett, Linguistic Behaviour.
See John Cooper, 'Aristotle on Natural Teleology.' For attempts to make
Aristotle out to be a compatibilist, see, e.g., Wolfgang Wieland, 'The Problem of
Teleology,' and Die aristotelische Physik; and Martha Nussbaum, Aristotle's De
Motu Animalium, Essay 1.
*° Physics 11.4-8.
See Physics n.6, especially I97bi8-io.
Cf. Physics n.6, i97b3O-z; for other examples: bi5~i8.

Four fashions
but it is restricted to men's activities.63 For example, a man goes to
the market to buy a chicken and encounters a debtor.64 If he had
known the debtor was in the market, he would have gone there for
the sake of meeting him. An observer who was ignorant of what
the creditor did and did not know might easily conclude that he
went to the market in order to meet his debtor. But the observer
would be mistaken. The creditor formed no such intention, for he
was ignorant of the debtor's whereabouts. Thus the observer's
teleological explanation, though tempting, would be false. Again,
chance is not a disturbance of the natural order, it is just that in the
regular affairs of men events occur which look as though they
occurred for a certain purpose when they did not. They may well
have occurred for another purpose: for example, both the creditor
and the debtor came to the market in order to buy a chicken.
So, if an end-like state were the inevitable outcome of a process
which depended solely on the material state of the organism,
Aristotle would call this state spontaneous. Far from being a compatibilist, Aristotle explicitly contrasts processes which occur by
necessity and genuinely teleological processes.65 He even considers
a type of natural selection only to reject it. Might it not be, he asks,
... that our teeth should come up ofnecessity - the front
teeth sharp, fitted for tearing, the molars broad and
useful for grinding down the food - since they did not
arise for this end, but it was merely a coincident result;
and so with all other parts in which we suppose that
there is purpose? Wherever then all the parts came to be
just what they would have been if they had come to be
for an end, such things survived, being organized spontaneously in afittingway,..66
It is odd to a modern eye to see Aristotle link necessity and spontaneity. For one is inclined to think that if an event occurs as the outcome of an inevitable, determining process that is just what it is for
the event not to be spontaneous. But for Aristotle a spontaneous
event is one that appears to be for an end. That is why he is able to

See, e.g., Physics 11.5, 19735-8; 11.6,
See Physics 11.5,196^33-19735,197815-18.
See, e.g., Physics 11.8.
Physics 11.8, 198IH3-31. (I use the expression 'came to be' where the Oxford
translation uses 'came about'.)


link the necessary and the spontaneous. If an organism or its functioning parts were the inevitable outcome of material processes
that would be what it was to be occurring spontaneously.
Spontaneity is thus a serious threat to Aristotle's world-view.
For it undermines the candidacy of form to be primary cause. If
form is the inevitable outcome of necessary processes, then form
would be merely supervenient upon these necessities.67 Form could
not then supply the why; an account of the necessary interactions
would supply it. Aristotle answers his hypothesis of necessary processes and natural selection as follows:
It is impossible that this should be the true view. For
teeth and all other natural things either invariably or for
the most part come about in a given way; but of not one
of the results of chance or spontaneity is this true ... If
then, it is agreed that things are either the result of coincidence or for the sake of something, and these cannot
be the result of coincidence or spontaneity, it follows
that they must be for the sake of something ... Therefore action for an end is present in things which come to
be and are by nature.68
Aristotle's argument seems to have the following structure:
1i) natural things, like teeth, come about always or at least
regularly in a certain way;
(2) spontaneous or chance events occur rarely;
and since
(3) things occur either for an end or spontaneously [by
(4) natural things cannot occur spontaneously [by (1) & (2)],
it follows that
(5) natural things must be for an end [by (3) & (4)]
This argument is more powerful than it might at first appear to a
modern reader. To a modern reader, the fact that teeth invariably
occur in a certain pattern is testimony to the existence of necessary

Aristotle does believe that certain lowly species come to be through spontaneous
generation, but in general the generation of living things is dependent on form.
Physics 11.8, I98b34-i99a8.


Four fashions
processes, not to their absence. How could Aristotle invoke invariability in an argument against necessity? Is his argument not
obviously fallacious? At first it seems so. It looks as though Aristotle is relying on two distinct criteria of the spontaneous:
apparent purposiveness and rarity of occurrence. Necessary processes turn out to be spontaneous because they are only apparently
teleological. But then the alleged rarity of spontaneous events is
used to rule out the existence of necessary processes. Might one not
object that if there genuinely are necessary processes which produce apparently purposeful results, then it is simply a mistake to
assume that spontaneous events are rare? That is, should we not
reject premiss (2)? If the necessary processes are ubiquitous, then
so too are the spontaneous events.
The argument is not that bad. But to appreciate it, one must see
it against a backdrop of Aristotle's conception of order. There are
two theses about order which Aristotle believed and argued for
with some vigor. If one accepts these theses, this argument is a
good one. The first thesis is:
(I) order is an expression of form all the way down.
As we have already seen, Aristotle believed that matter was a relative item. Though flesh and bone may be the matter of human
limbs, once we consider flesh itself we see that it is a compound of
form and matter, the form being the order and arrangement of the
matter which constitutes flesh. And so on. The second thesis is:
(II) the order which exists at any level of matter is insufficient to generate the order required at the next level of organization.
What is needed in addition is form as a basic irreducible force - a
developmental power - which, Aristotle believes, the statically
given material structure could not possibly account for. The form
of a developing organism, remember, is not merely its achieved
structure, it is a force in the organism for attaining ever higher
levels of organization until the organism achieves its mature form.
Aristotle finds the idea of structure em