Self-Motion

194 Pages·1994·21.16 MB·English

by  Mary Louise Gill

SELF-MOTION
F R O M ARISTOTLE T O NEWTON
Edited by
Mary Louise Gill and James G. Lennox
PRINCETON UNIVERSITY PRESS PRINCETON, NEW JERSEY
Cont ents
Copyright O 1994 by Princeton University Press
Essays by Mary Louise Gill, Lindsay Judson, and Susan Sauvt Meyer,
copyright O 1994 by Mary Louise Gill, Lindsay Judson,
and Susan Sauvt Meyer
Published by Princeton University Press, 41 William Street,
Princeton, New Jersey 08540 Preface vii
In the United Kingdom: Princeton University Press,
Abbreviations ix
Chichester, West Sussex
All Rights Reserved Introduction xiii
Library of Congress Cataloging-in-Publication Data
PART I: ARISTOTLE
Self-motion : from Aristotle to Newton 1 edited by Mary Louise Gill
and James G. Lennox. Chapter 1. Self-Movers
p. cm.
Dauid Furley 3
Includes bibliographical references and index.
ISBN 0-691-03235-1 (alk. paper) Chapter 2. Aristotle on Self-Motion
1. Aristotle. 2. Movement (Philosophy) I. Gill, Mary Louise,
1950- . 11. Lennox, James G. Mary Louise Gill 15
B491.M6S45 1994
Chapter 3. Aristotle on Perception, Appetition, and Self-Motion
116-dc20 93-45882 CIP
Cynthia A. Freeland 3 5
David Furley's essay, "Self-Movers," is reprinted by permission from
Chapter 4. Self-Movement and External Causation
Aristotle on Mind and the Senses, ed. Geoffrey Lloyd and Gwil Owen
(Cambridge: Cambridge University Press, 1978). Susan Sauue* Meyer 65
This book has been composed in Sabon
Chapter 5. Aristotle on the Mind's Self-Motion
Princeton University Press books are printed on acid-free paper and Michael V. Wedin 8 1
meet the guidelines for permanence and durability of the Committee
on Production Guidelines for Book Longevity of the Council Chapter 6. Mind and Motion in Aristotle
on Library Resources
Christopher Shields
Printed in the United States of America
Chapter 7. Aristotle's Prime
Aryeh Kosman
Chapter 8. Heavenly Motion and the
Lindsay Judson
PART 11: THE ARISTOTELIAN TRA
Chapter 9. Self-Motion in Stoic Philos
David E. Hahm 175
Chapter 10. Duns Scotus on the Reality of Self-Change
Peter King 227
V1 CONTENTS
Chapter 11. Ockham, Self-Motion, and the Will
' Preface
Calvin G. Normore
g Chapter 12. Natural Motion and Its Causes: Newton
on the "Vis Insita" of Bodies
J. E. McGuire
THEP APERS in this volume originated in a conference (of the same name),
List of Contributors held February 23-25, 1990, celebrating the expansion of the Program in
Classics and Philosophy at the University of Pittsburgh into the Program in
Bibliography
Classics, Philosophy, and Ancient Science. As the conference progressed, it
Index Locorum became clear that the papers told a remarkably unified story of the develop-
ment of the concept of self-motion from Aristotle, through Hellenistic and
General Index
medieval philosophy, to Newton's natural philosophy. It was also clear that
the commentators had gone far beyond their assigned roles, offering alter-
native, sometimes complementary, interpretations to those of the speakers.
The conference organizers, Mary Louise Gill, James G. Lennox, and Steven
K. Strange, therefore decided to ask both speakers and commentators to
contribute papers, based on their presentations, for inclusion in a volume
devoted to the conference theme. This volume is the result.
Neither the conference nor this volume would have been possible with-
out the support of many, and it is a pleasant responsibility to thank them.
The conference was generously supported by the Center for Philosophy of
Science (with the help of funding from the R. K. Mellon Foundation), and
the Departments of Classics, Philosophy, and History and Philosophy of
Science at the University of Pittsburgh. The conference ran smoothly be-
cause of the incomparable organizational skills of Linda Butera, ably as-
sisted by Katherine Nolan and John Quilter, Ann Himmelberger Wald,
Philosophy Editor at Princeton University Press, has been supportive and
encouraging from the outset. VVe are grateful to Sherry Wert, our copy
editor, and to Beth Gianfagna and Colin Barr and the nlembers of the staff
at the Press for their assistance. The readers for the I"1-ess, David Sedley and
Sarah Broadie, provided valuable comments, both on the volume as a
whole and on the individual contributions. Oxford University Press, Cam-
bridge University Press, and Blackwell's allowed us: to use material pub-
lished by their presses. To all of these individuals and institutions, we the
editors say a heartfelt "Thank you."
One final thank-you is in order. During the conference out of which this
collection grew, the extent of the influence of David Furley's paper "Self-
Movers" became apparent to all. Originally invited as a speaker, he agreed
to comment on one paper that took his own as a starting-point. We felt that
this volume should begin, as many of the papers on Aristotle did, with his
original paper (making this the third occasion of its reprinting!). We were
leased
very that he acceded to our wishes. The editors (no doubt on behalf
of our contributors as well) delight in taking this opportunity to give
Abbreviations
thanks for the inspiration, both specific and general, David Furley has
given to those working at the interface of classical philosophy and science.
lames G. Lennox
Mary Louise Gill
WORKSC ITED in this volume are abbreviated as listed here. Full references
to these works and to other texts cited appear in the Bibliography.
Alexander of
Aphrodisias De anima cum mantissa De an. man.
De mixtione De mixt.
Aristoteles Latinus AL
Aristotle Categories Cat.
De anima De an.
De caelo De cue.
De interpretatione De int.
De iuuentute et senectute De iuu.
De longetudine et De long.
brevitate vitae
De memoria De mem.
De respiratione De resp.
Eudemian Ethics EE
Nicomachean Ethics EN
Generation of Animals GA
On Generation and
Aulus Gellius Noctes Atticae Noct. Att.
[author disputed] Centiloquium Cent.
Ci'c ero De oratore De or.
De inventione rhetorica Inu. rhet.
De natura deorum ND
Clement of Alexandria Stromateis Stromat.
X ABBREVIATIONS ABBREVIATIONS X1
Diels and Kranz Die Fragmente der DK In Libros Aristotelis De In De an.
Vorsokratiker anima commentaria
Duns Scotus Opus Oxoniense Op. ox. In Aristotelis Physi- h ~hys.
Ordinatio Ord. corum libros octo
Quaestiones QQ commentaria
quodlibetales Von Arnim Stoicorum veterum SVF
Quaestiones subtilis- QSM fragmenta
simae super Aristotelis
Metaph ysicorum
Reportata Parisiensia Rep. Par.
Vatican edition Vat.
Wadding-VivCs edition WV
Epictetus Dissertationes D iss .
Long and Sedley The Hellenistic LS
Philosophers
Liddell, Scott, Jones, and A Greek-English LSJ
McKenzie Lexicon
Nemesius De natura hominis De nat. hom.
Ockham Exposition in libros Exp. Phys.
Physicorum Aristotelis
Opera philosophica OP
Scriptum in librum pri- Ord.
mum Sententiarum
Opera theologica OT
Tractatus de Praed.
praedestinatione
Quodlibeta septem Quod.
Quaestiones in librum Sent.
quartum Sententiarum
Petrus Olivi Quaestiones in se- Olivi Sent.
cundem librum
Sententiarum
Origen De oratione De orat.
De principiis De princ.
Philoponus In Aristotelis Physica In Phys.
commentaria
Seneca Epistulae EP.
Naturales quaestiones Nat. quaest.
Sextus Empiricus Adversus mathematicos Adv. math.
Simplicius In AAstotelis De caelo In Cae.
commentaria
In Aristotelis Categorias In Cat.
comrnentarium
Introduction
THEO RGANIZING THEME of this volume, the problen~o f sclf-motion, is
clearly defined for the first time in Plato's Phaedrus, in a passage whose
echoes ring throughout Aristotle's physical, metaphysical, and cosmologi-
cal works:
All soul is immortal. For that which is always moving is immortal. But that
which moves something else and is moved by something else, since it has a
cessation of motion, has a cessation of life. Evidently only that which moves
itself never stops moving, because it does not abandon itself; and this is the
(&ex()
origin (nqyfi)a nd source of motion for other things that are moved as
well. (245~5-9)
Plato immediately goes on to prove that such a self-moving source of
motion can neither be created or destroyed, and he argues that this is the
nature of soul, a claim that seems to be flatly contradicted in the Tzmaeus.
Aristotle, as a number of the following essays will argue, agrees with very
little of the above argument. But there can be virtually no doubt that it, and
similar passages in Plato's Laws 10, are at the root of much of his physical
theory.
As in so many other areas of science and philosophy, Aristotle domi-
nated the scientific study of motion and its causes through the sixteenth
century. Although there were alternative views in the ancient world and
intelligent critics among his Greek, Arabic, and Latin commentators, the
basic concepts and problems of the field were those that Aristotle posed. At.
the very center of the Aristotelian approach to tht: study of motion is the
distinction between self-movers and objects moved by others. Aristotle
employs and discusses this basic opposition in lrtany di rent contexts, and
it is by no means clear that his various discussions are mutually consistent.
So his followers and critics had ample room to develop and apply the
distinction in a variety of ways.
A number of classic works in the history of science have made it an
orthodoxy that there was a revolutionary replacement of Aristotle's dis-
tinction in the seventeenth century, which was represented paradigmat-
ically by Sir Issac Newton's Mathematical P&ciples of Natural Philoso-
phy. This orthodoxy deserves reassessment. Indeed, the last essay in this
volume, which treats the thought of Issac Newton, challenges a fundamen-
tal myth of the scientific revolution by suggesting that Newton, far from
rejecting the problem context of the ancients, was himself deeply immersed
in it.
xiv INTRODUCTION INTRODUCTION XV
The essays presented in Part I constitute a systematic study of self- of physics, some of these thinkers allowed it in contexts involving non-
motion in Aristotle's natural philosophy, psychology, ethics, and meta- physical causes, such as the will. As we sce in the paper on William of
physics. Those in Part I1 examine how Aristotle's theory was developed, Ockham by Calvin Normore, the tradition that the will is a self-mover
criticized, and transformed by the Stoics, by the scholastic Aristotelians, developed, not from a consideration of Aristotle's argutncnts for self-
and finally by Issac Newton. motion, but from Plato's argument in the Phaedrus and elsewhere that the
Our initial question is whether Aristotle admitted the existence of self- soul is a self-mover. William of Ockham, at the end of the Middle Ages,
movers at all. Although he frequently calls animals self-movers, on several argued that the will is a self-mover and that physical bodies depend for
occasions he appears to deny that they are. The first four papers in Part I their motion on an external cause. As Normore points out, this view set the
examine this discrepancy. stage for the early modern distinction between free spirits and inert matter.
A second question is, What types of self-motion did Aristotle envisage? And although, as McGuire argues, Newton's view that bodies have an
Is self-motion restricted to animals, or are simple inanimate bodies- internal force, a vis insita, hearkens back to Aristotle's theory of self-
earth, water, air, and fire-also self-movers? What about the heavenly movers, this was not a part of his theory that subsequent thinkers pursued.
bodies and their spheres? And the Prime Mover? The consensus among the
authors in Part I is that Aristotle's theory excluded the four elements as self-
movers, but views differ on the status of celestial objects and the Prime PART I
Mover.
A further question is, What types of organic motion does Aristotle treat The volume opens with David Furley's classic paper, "Self-Movers." This
as self-motion? Is self-motion restricted to locomotion, or does it have a essay poses the interpretive question that remains central for any evalua-
much wider extension? After the opening paper by David Furley, which tion of Aristotle's theory of self-motion. Aristotle sometimes calls animals
poses the general question about Aristotle's commitment to self-motion, self-movers, but in two crucial passages in Phys. VIII,h e appears to deny
the papers in Part I examine the various levels of self-motion, which corre- that they are. Is this apparent inconsistency due to Aristotle's philosophical
spond roughly to the types of Aristotelian soul. Thus, the simplest type of development, or is his position as a whole consistent? Furley defends Aris-
self-motion, which is explored by Mary Louise Gill, is that involving nutri- totle's commitment to self-movers, and he argues that the conflict between
tive soul, the faculty common to plants and animals, which accounts for this commitment and the mechanical model in Phys. v111 reflects, not a
the basic life functions of survival and organic development. Next are the change of mind, but a clash of motives. Aristotle wants to preserve the
functions proper to animals-perception, desire, and locomotion-which intuition that animals have an internal source of their own movement, but
depend on perceptive soul. Self-motions involving these functions are dis- he also sees the risk that the cosmos itself might have originated its own
cussed in the papers by Cynthia Freeland and Susan SauvC Meyer. We turn movement on analogy with animals. Zi, avoid this possibility, Aristotle
then to the function proper to human beings-reason. Mental self-motion argues in Phys. v111 that even the self-motiotx of animals clepead on some
is treated in the papers by Michael Wedin and Christopher Shields. Aryeh previous motion. According to Furley, animals are self-mtwers because
Kosman and Lindsay Judson turn finally to the Prime Mover, the cause of they pursue objects in their environment under certain descriptions. So the
all motion, a being whose life is the activity of thinking. external object of de&&h:ch the animal exerts itself to obtain, cannot be
The papers in Part I1 indicate that later thinkers transformed Aristotle's identified independently of the animal's psychic faculty of desire. Because
theory in various ways. Some philosophers believed that even the elements the object of desire is ari intentional object, the sorrree of motion can be said
are self-movers. David Hahm argues that the Stoics developed a compre- to be "inside" the agent.
hensive theory of self-motion that included the motions of inanimate ob- In "Aristotle on Self-Motion," Mary Louise Gill examines Aristotle's
jects, as well as the three levels of animate motion discussed in connection account of self-motion within the framework of his general theory of
with Aristotle. This view of the elements reemerges in the work of Duns change and of active and passive potencies, and she focuses her discussion
Scotus and Isaac Newton, as Peter King and J. E. McGuire show. But a quite on self-motion in its simplest manifestation-organic survival and devel-
different position was also defended by some scholastics prior to Scotus- opment controlled by nutritive soul. She argues that the discrepancy, to
that self-motion is impossible in the physical world-and these thinkers, which Furley called attention, disappears if we recognize that Aristotle is
who included in their number Thomas Aquinas, claimed Aristotle's au- asking two sorts of question. First, why is an animal's motion of a particu-
thority for their position. Although they excluded self-motion in the realm lar sort and sustained in a particular direction? And second, what triggers
xvi INTRODUCTlON INTRODUCTION xvii
the motion, and why is it sometimes impeded? Gill argues that all living comprises two levels. Actual thinking emerges at the higher level when, at
things are self-movers because they have an active source of change, which the lower level, productive mind gives rise to the object of thought in
is internal. But because this source is an unmoved mover, it cannot account receptive mind. This proposal satisfies one of thc tmic constraints on self-
for the initiation of motion. To explain why motions start, Aristotle ap- motion set in Phys. v111.5, that an active part of an object cause change in a
peals to factors in the organism's environment, which are themselves ex- passive part. But why, asks Wedin, is thinking up to us? I'he moctcl of self-
plained by the motions of the heavenly spheres, and ultimately by the Prime motion in Phys. v111 seems to conflict with this idea, for it treats mind as a
Mover. paradigm of things that move unless prevented. Wedin points out, howcver,
Cynthia A. Freeland, in "Aristotle on Perception, Appetition, and Self- that thought differs from the lower-level self-motions-nutrition, percep-
Motion," treats the next higher level of self-motion, involving perceptive tion, and desire-in two relevant respects. First, the object of thought is a
soul, and she offers another response to the problem posed by Furley. product of the noetic system itself, brought about by productive mind in
Freeland defends Aristotelian self-motion, not by appeal to the inten- receptive mind. Second, the mover is not, in any sense, external to the
tionality o s lper ception, desire, and ac7tlon (as Fu rley suggqsts), ,but. mind. According to Wedin, thinking is thus "up to us" in a more unqual-
by appeal to the objective goal-directedness of animal motionsfihe pre- ified way than is perceiving or desiring, the objects of which are external.
sents a general account of the teleolog-y. of animal movements and shows Christopher Shields's "Mind and Motion in Aristotle" starts from the
that self-motion is not restricted to animals capable of imagination but is same apparent conflict: Do we think only if we wish, or unless prevented?
also displayed in the behavior of simpler organisms. According to Free- And the agreement between Shields and Wedin extends two steps further:
land, the periodic movements of cicadas, which Furley claimed Aristotle both take it that Aristotle is committed to an internal, unmoved source of
would explain me~hanisticalle~x,h ibit an objective goal-directedness. She motion that transforms the possession of knowledge into its exercise; and
further argues that the self-motion of animals, although explained tele- both take the object of thought to be that source of motion. Shields, how-
ologically, is also compatible with causal determinism by efficient causes. ever, sees problems with each side of this apparent conflict, even when this
Susan Sauvk Meyer, in "Self-Movement and External Causation," looks much is agreed to. First, if the object of thought is a universal, shared by a
again at the fundamental question of whether self-motion is possible, given number of minds, in what sense is it an internal unmoved mover? If, as
Aristotle's claim that animal motion requires an external cause. Whereas Aristotle claims, part of the reason why we can think when we wish is that
Freeland solves the problem by appeal to the objectively teleological nature the objects of thought are in us, answering this question is crucial. In
of animal perception and appetite, Meyer examines the relationship be- Shields's view, the answer is that each individual mind that knows p stands
tween two types of efficient causation-that by an unmoved mover within in a stable dispositional relation to p, and that disposition is internal to it,
the animal, and that by external moved movers. Meyer contends that though p itself is common. Second, how can thinking be up to us if minds
although external causes precipitate animal movement, such factors do not contemplate their objects unless something prevcnrs them from doing so?
undermine the animal's claim to be a self-mover, because they are acciden- Shields avails himself of J. L. Mackie's account of causes in insisting that
tal rather than intrinsic causes of its motion. An accidental cause, such as Phys. v111.4 specifies only that the removal of impediments to thinking is
an object that enters an animal's visual field, may trigger a response in the among its relevant necessary conditions. This ctrnclusion is analogous to
animal, but it does not explain why the animal responds in the way that it Michael Wedin's view that Phys. vm.4 providcs only 3 pslrrial model of the
does. The origin of animal movement is an intrinsic cause, which Meyer mind's self-motion.
identifies as the specific dispositions of the animal. The intrinsic cause, If minds are the highest form of self-mover, then something that thinks
whose causal efficacy is continual, regulates the animal's desires and other eternally would seem to be the premier self-mover. But making this claim
capacities. Because external causes trigger some response in the agent, but on behalf of Aristotle's Prime Mover is because, at least in the
not a particular response, Meyer can argue that Aristotle's claims about Physics and the Metaphysics, the Prime Mover is an unmoved mover,
voluntary action are compatible with causal determinism. characterized by an active aspect only. A traditional, developmental solu-
The highest and rarest form of self-motion is that possessed by the mind, tion to this problem holds that Aristotle moves from the view in De caelo
and it is to the mind's self-motion that the papers of Michael Wedin and that the outermost sphere is a naturally moving Prime Mover, to the view in
Christopher Shields attend. In "Aristotle on the Mind's Self-Motion," Phys. v111 that the Prime Mover is an unmoved source of the movement of
Michael Wedin argues that in Aristotle's view, the mind or "noetic system" the outermost sphere, and finally to that in the Metaphysics that the Prime
xviii INTRODUCTION INTRODUCTION xix
Mover is a transcendent, eternally active being, imitated by the eternal
rotation of the outermost sphere. On this traditional conception, the major PART I1
shift in Aristotle's thought on the Prime Mover comes between the De caelo
and the Physics. Part I1 opens with David E. Hahm's paper, "Self-Motion in Stoic Philoso-
Aryeh Kosman's "Aristotle's Prime Mover" challenges this developmen- phy." Hahm argues that the types of self-motion treated by Aristotle were
tal account in two respects. First, he argues that both the De Caelo and the drawn together by the Stoics into a single systematic theory, with one
Physics leave room for the Prime Mover to be both an unmoved mover and striking addition to Aristotle's scheme: the inclusion of inanimate objects
a self-mover. Second, he argues that the major development in Aristotle's as self-movers. The Stoic extension is reasonable, given their general view
conception of the Prime Mover, if there is a development, occurs in Meta. of the constitution of corporeal bodies. According to the Stoics, all bodies
A.6-8. This text replaces the negative description of the Prime Mover as consist of a passive and an active principle-a passive matter and an active
"unmoved" with a positive description of it as essentially active being. material source called pneuma. On this view, even the elements should
Even this account, Kosman argues, is prefigured in the physical treatises, in have an inner active source of their own motion. According to Hahm, the
their claims that the outermost sphere is a living thing. This characteriza- Stoic scala naturae comprised four levels-inanimate objects, plants, ani-
tion suggests that the Prime Mover is the soul of the outermost sphere, mals, and human beings-and to each level belongs a proper self-motion.
which is therefore the paradigmatic self-mover. Why, then, does Aristotle The pneuma that activates bodies at each level is the same material stuff but
never say this? The account of the soul in De an. 11-111 describes it as a "first in a different physical state. Although a particular type of self-motion is
actualitym-a capability-and thus fails to capture the nature of an eter- proper to each level, Hahm argues that bodies at each successive stage
nally active being. Nevertheless, in all of Aristotle's discussions of the Prime display not only their own self-motion but also those characteristic of
Mover, argues Kosman, it is the psychic aspect of the outermost sphere of bodies lower on the ontological scale. The types of self-motion are thus
the heaven that he is attempting to characterize. cumulative. Hahm further argues that human beings, who achieve at matu-
Lindsay Judson, in "Heavenly Motion and the Unmoved Mover," de- rity the highest type of self-motion, develop via the simpler levels. Such
fends the developmental hypothesis against Kosman's attack. Judson development involves the interaction of internal self-motions and external
points out that the De caelo's claim that the first sphere is alive need not stimuli, which results in a series of quantum shifts to a higher physical
entail that the sphere's Prime Mover be a soul. The material that constitutes state. Each state enables a corresponding self-motion.
the first sphere is said to move, precisely as the sublunary elements do, by In "Duns Scotus on the Reality of Self-Change," Peter King argues that
nature. If the motion of the superlunary element, unlike that of the other Duns Scotus, in defending self-motion, departs from most of his medieval
elements, is due to a psychic mover, it is odd that this difference goes predecessors, who had argued that self-motion is impossible in the physi-
unmentioned. Furthermore, although all the heavenly spheres are said to cal world. If they admitted self-motion at all, they allowed it only in con-
be alive, Aristotle denies that the inner spheres are self-movers. As for Phys. texts involving nonphysical causes, such as the will. All apparent cases of
VIII, the gravest difficulty for an account of the Prime Mover as an imma- physical self-motion were construed as instances of interaction between an
nent aspect of the heaven is Aristotle's denial that the unmoved mover is agent and patient that are really distinct. Breaking with this tradition,
moved even accidentally-for he claims that souls of animate things are so Scotus constructed an argument for the possibility of self-motion that built
moved. On Judson's view, Phys. v111 argues that the Prime Mover is not a into the traditional model of change a number of subtle distinctions. For
self-mover, but rather, on pain of vicious regress, an unmoved mover. example, on the simple Aristotelian model, an object can become hot, if it
Aristotle still needs to provide a positive characterization of its nature, and is potentially but not actually hot, and if something acts on it that is
according to Judson, he does so in Meta. A.6-8. Here he describes a Prime actually hot. This scheme seems to exclude self-motion, because the same
Mover that is eternally active but thoroughly transcends the world of thing would need to have (as agent) the same property that it lacks (as
change. Were such a mover immanent in the eternal, perceptible heaven, as patient). Scotus argues that self-motion is excluded only in cases of univo-
the soul of the first sphere, Judson argues that it would be subject to the cal causation-cases in which the active principle of the agent is the same
analysis of composite substance in Meta. A.1-5. The Prime Mover is not as that induced in the patient. In defending self-motion, he argues for what
the form of an eternal body; on the contrary, it is the fully actual, imma- he calls equivocal causation, in which the agent acts in virtue of a property
terial being that the living heaven strives to emulate. The Prime Mover is more "eminent" than that induced in the patient. King shows that Scotus
not a soul, because it is not the form of any body at all. does not restrict self-motion to living organisms. Like the Stoics, he re-
XX INTRODUCTION INTRODUCTION xxi
garded even the natural motions of inanimate objects as self-motions, and manuscripts of Newton in which he transcribes, translates, and comments
he argued that this was the correct interpretation of Aristotle as well. In on passages in Aristotle's De caelo and Physics that focus on the concept of
such cases, the agent and patient are really the same, but the active and nature as an inherent source of change. Newton's appeal to a vis insita
passive principles within the object, which enable the change, are distinct. raises a basic puzzle about his dynamics: In n world of inertial mass,
Calvin Normore, in "Ockham, Self-Motion and the Will," examines momentum, and external forces, where is thcre room for a N ~ Sim ita?
William of Ockham's theory of the will against the background of earlier McGuire argues that the Principia operates with both a st~rhcea nd an
medieval discussion. According to Normore, the early Middle Ages inher- inner ontology: on the surface, vis insita is virtually identified with inertia;
ited from Platonism a conception of the soul as a self-moving power, and but below the surface, the vis insita represents the Aristotelian notion of an
this conception was slowly transformed into a conception of the will as a inherent cause of a natural body's motion.
self-moving power. With the rise of Aristotelianism in the thirteenth cen- McGuire's essay is a most fitting conclusion to this volume, finding as it
tury, this conception was temporarily submerged by the thesis (discussed does that Newton was steeped in the traditions explored by the other
by Peter King) that everything moved is moved by another. But thanks essays, and exposing the extent to which those traditions shaped the
largely to Duns Scotus, whose defense of self-motion in physics was by thought of the most influential student of nature in the modern world.
Ockham's time widely taken for granted, the conception of the will as a
self-mover had reemerged. Ockham rejected Scotus's appeal to formal
distinctions, so he could not use such a distinction to explain the freedom
of the will. Instead he argued that the will is free in the strong sense that it is
able to move from potency to act without any "triggering" cause. Though
he defended the freedom of the will, Ockham broke with Scotus in denying
that bodies are able to move themselves locally. On Ockham's account,
local motion always involves an external mover at some point in the causal
series. According to Normore, Ockham's view, which treats the will as
totally free but the motion of bodies as always determined by external
causes, marks an important break with Aristotle and Scotus, and it paves
the way for the early modern division between a realm of free spirits and a
realm of corporeal objects that are themselves inert.
In his essay, "Natural Motion and Its Causes: Newton on the 'Vis Insita'
of Bodies," J. E. McGuire argues that, contrary to common opinion, Isaac
Newton's Mathematical Principles of Natural Philosophy did not break
decisively with the Aristotelian analysis of motion and its causes. Though
Newton's First Law of Motion treats motion and rest as primitive states,
whose changes are explained by reference only to external forces, his third
definition and corollary tell another story. According to this story, a natu-
ral body possesses a vis insita, an inherent source of its persistence in a
state-ideas already clearly present in Newton's Quaestiones and Degrav-
itatione, written in the 1660s. McGuire traces the concept of the vis insita
through the widely read Renaissance Aristotelian Zabarella back to the
works of Duns Scotus, Albert the Great, Averroes, Philoponus, and the
Stoic Chrysippus, all of whom held that even inanimate bodies are self-
movers. Zabarella's insistence that the forms of inanimate bodies are inter-
nal active sources of change that act upon their matter as subject in turn
finds its way into many texts on natural philosophy familiar to Newton.
Besides these indirect influences, McGuire cites passages in unpublished