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Dictionary of the History of Ideas

Studies of Selected Pivotal Ideas
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In book I, Part III, Chapter XIV, of A Treatise of
Human Nature
(1739), David Hume, having proposed
his now famous definitions of “cause,” stated what he
took to be a corollary of his view. According to Hume,
it should have been clear from the foregoing discussion
that “all causes are of the same kind....” Part of his
intention in making this statement was to make explicit
his opposition to the Aristotelian and scholastic doc-
trine of four kinds or genera of causes. “There is no
foundation,” he went on to say, “for that distinction
... betwixt efficient causes, and formal, and material,
... and final causes”; and he indicated clearly in this
passage that, on his view, all bona fide causal state-
ments were about efficient causes. Although the origi-
nality of Hume's discussion of causation has been ac-
knowledged, this contention has not usually been
singled out for attention. Commentators seem to have
assumed that, in declaring that all causes were of the
same kind, Hume was simply generalizing a maxim that
antischolastic advocates of the mechanical or corpus-
cular philosophy had proposed and followed in their
investigations of nature and that he displayed his origi-
nality in his analysis of the meaning of the causal terms
used in science and in daily life. Both parts of this
assumption would be difficult to defend. Among anti-
scholastic and (in Robert Boyle's inclusive sense of the
term) “corpuscular” philosophers in the seventeenth
century, there was a wide variety of reactions to the
traditional doctrine of fourfold causes; and there was
no agreement, in theory or in practice, that the dis-
covery of efficient causes was the exclusive aim, or
indeed the principal aim, of investigations of nature.
A survey of views about causal explanation in the
seventeenth century also shows that Hume's questions
about force and necessary connection had been raised
and that his own analysis of the meaning of certain
causal expressions had been proposed. The following
survey, by no means exhaustive, includes some pre-
Newtonian philosophers in England; Descartes and
some of his followers on the Continent; and the giants
of the end of the century, Newton and Leibniz.


The methodological discussions of Francis Bacon,
Thomas Hobbes, and Robert Boyle are of special inter-
est because they exhibit a variety of reactions among
advocates of the new science to the traditional distinc-
tion of four kinds of causation. Professedly and more
or less heatedly antischolastic, they shared the corpus-
cular view that the phenomena of nature were to be
explained by the motion of small particles or corpus-
cles. Yet each of them made use of scholastic terms
in distinguishing kinds of causal explanations.

In the classification of sciences in Book III, Ch. IV,
of De augmentis scientiarum (1623), Bacon distin-
guished four kinds of causes. The investigation of na-
ture was divided in two parts: physics was to be con-
cerned with efficient and material causes, while
metaphysics was to deal with final and formal causes.
Explaining this classification, Bacon cautioned his
reader that, although he was continuing to use tradi-
tional terms, he felt free to alter their senses; and it
is clear that his view differed from that of his scholastic
contemporaries in at least three important respects.
First, metaphysics, which was distinguished from first
philosophy and natural theology, was a part of natural
philosophy; and to metaphysics he assigned what he
took to be the most important and productive part of
his new science—the investigation of forms or formal
causes. Second, although the investigation of final
causes was also within the province of metaphysics,
it, unlike the investigation of forms, could provide no
knowledge of physical causes. Although it made sense
to assert “that the firmness of hides in animals is for
the armour of the body against extremities of heat or
cold,” such an explanation did not specify the actual
physical cause of the phenomenon; and it was, accord-
ing to Bacon's frequently cited condemnation, “barren
and like a virgin consecrated to God produces nothing”
(Book III, Ch. V). Third, the term forma underwent
a sea change in Bacon's philosophy. Aware of Platonic
and Aristotelian connotations, he explained in Novum
(1620) that, when he used this term to refer
to what was to be discovered in the productive part
of metaphysics, he did not mean “abstract forms and
ideas, either not determined in matter at all, or ill
determined” (Book II, Aphorism xvii). His forms could
be discovered, and could be precisely determined, by
“true induction,” i.e., by the method of “rejection or
exclusion.” An investigation of the form of heat, for
example, showed that it was a species of motion: spe-
cifically, a motion that was “expansive, restrained, and


acting in its strife upon the smaller particles of bodies”
(Book II, Aph. xx).

Although motion of this kind was said to be the cause
of heat, Bacon carefully distinguished this cause from
what he called the “efficient cause” of heat. The term
“efficient cause” was reserved for the results of investi-
gations of a quite different and less fundamental nature
that were to be a part of physics, namely, investigations
of the ways in which bodies could be heated. Holding
that heat could be produced in a body in various ways,
he maintained that the efficient cause was variable or,
in J. S. Mill's terms, that there was a plurality of
efficient causes of heat. By contrast, what was discov-
ered by “rejection or exclusion” was universally present
in all hot bodies; and Bacon seems to have called this
species of motion the “form” or “formal cause” of heat
because he thought that, in making this discovery, he
had discovered what heat really was—its nature or
essence—and not something that was distinct from heat
and, in Hume's terms, was “constantly conjoined” with
it. In a passage in which he was concerned to explain
precisely what he meant, and what he did not mean,
when he asserted that heat was a species of motion,
he expressed this thought quite clearly. He did not
mean, he explained, that “motion generates heat”;
rather, his conclusion was that “Heat itself, its quid
is Motion and nothing else...” (Book II, Aph.
xx). Although Bacon was not always as clear as he was
in this passage about the nature of conclusions reached
by “rejection or exclusion,” the view that he was at-
tempting to formulate in this passage was, in more
recent terminology, that the most basic laws of science
were contingent statements of identity; and he care-
fully distinguished these laws from conclusions of lesser
consequence about efficient causes and also material

Examining the metaphysicians' view of causation in
De corpore (1655), Hobbes claimed that the only tenable
distinction within the fourfold classification was that
of efficient cause and material cause (Part II, Chs. IX
and X). What the metaphysicians classified as final
causes and formal causes—ends and essences, respec-
tively—were, according to Hobbes, really efficient
causes. Ends, he maintained, could be ascribed only
to what had sense and will; and the end of a desire
was the object desired. On his view, however, the
object desired was the efficient cause of the motion
that constituted the desire; and, whereas it seemed “as
if we draw the object to us,” what was really the case
was that “the object draws us to it by local motion”
(“Short Tract on First Principles,” Appendix I in The
Elements of Law,
ed. F. Tönnies, Cambridge, 1928).
Taking the scholastics' view about formal causes to be
that “the essence of a thing is the cause thereof, as
to be rational is the cause of man
...,” there is little
wonder that Hobbes deemed the view unintelligible.
Yet he was not prepared to deny that essences func-
tioned as causes: “knowledge of the essence of any-
thing,” he maintained, “is the cause of the knowledge
of the thing itself; for, if I first know that a thing
is rational, I know from thence, that the same is
man...” (De corpore, Part II, Ch. X). Essences were
causae cognoscendi, but Hobbes insisted that, as such,
they were efficient causes, or rather parts of the ef-
ficient causes, of the knowledge that resulted from
knowledge of them.

Hobbes retained the terms “efficient cause” and
“material cause” to mark a distinction within what he
called the “entire cause” or “cause simply.” Antici-
pating Mill's view about a philosophical sense of
“cause,” the entire cause was for him “the aggregate
of all the accidents both of the agents how many soever
they be, and of the patient put together; which when
they are all supposed to be present, it cannot be under-
stood but that the effect is produced...; and if any
one of them be wanting, it cannot be understood but
that the effect is not produced” (Part II, Ch. IX). Since,
on his view of bodies, there was no substantial change,
every change was a change of an attribute or accident
of a body; and the cause, or “entire cause,” included
all of the many attributes of the agent and patient
bodies that were necessary and jointly sufficient for the
occurrence of the change. Realizing that not just one
condition but many were necessary and that the term
“cause” was usually used to refer to only one of these
conditions, he distinguished the “entire cause” and the
cause sine qua non and tried to state the criterion used
in the selection of one of the many conditions as the
“cause,” in the ordinary sense of the term, or cause
sine qua non. In this attempt, he seems not to have
been successful, but he did make clear what he (if not
others) meant by “material cause” and “efficient
cause.” The totality of conditions necessary for the
occurrence of a change included attributes of the body
acted upon, for instance, dryness of wood that was
ignited, as well as attributes of the agent body or
bodies. The former were the material cause, and the
latter the efficient cause.

When Hume claimed that all causes were of the
same kind, he seems to have been aware of one of the
distinctions that Hobbes made. In the passage quoted,
he claimed to find no basis for a distinction “betwixt
efficient causes, and causes sine qua non....” Holding
himself that “the same cause always produces the same
effect, and the same effect never arises but from the
same cause” (A Treatise..., Book I, Part III, Ch. XV),
he seems not to have been aware of the problem that
Hobbes discovered in the discrepancy between a defi-


nition of “cause” in terms of necessary and sufficient
conditions and the ordinary use (Hume's included) of
this term.

Boyle was more hospitably disposed toward expla-
nations in terms of final causes than Hobbes or Bacon.
Concluding his discussion of final causes in The Use-
fulness of Experimental Natural Philosophy
(1688), he
maintained that “as to animals, and the more perfect
sorts of vegetables, it is warrantable, not presumptuous,
to say, that such and such parts were preordained to
such and such uses, relating to the welfare of the animal
(or plant) itself, or to the species it belongs to....”
Yet he exhorted the true “naturalist” not to “let the
search or knowledge of final causes make him neglect
the industrious indagation [i.e., investigation] of effi-
cients,” and he implied that the naturalist's principal
aim was the discovery of efficient causes. This supposi-
tion in Boyle's discussion of methodology does not seem
to accord with the Baconian way in which he stated
the conclusions of his investigations of the “origin” of
certain qualities. His investigation of heat, for instance,
revealed its “nature”; and this way of stating his con-
clusion suggests that, like Bacon, he thought that he
was discovering what heat really was—its nature or
essence. The apparent inconsistency can be explained
if we attribute to Boyle a view like John Locke's in
An Essay Concerning Human Understanding (1690),
in which the term “heat” was used equivocally to refer
both to heat as it existed in bodies and to heat as it
existed in us. (Cf. Book II, Sec. viii, of the Essay.) Using
“heat” in the first sense, Boyle could represent the
conclusion of his investigation as the discovery of the
nature of heat. Since what was discovered was also
thought to be the efficient cause of heat in the second
sense, he could also represent the conclusion of his
investigation as the discovery of the efficient cause of
heat. That Boyle used terms like “heat” in two senses
is evident from his seemingly contradictory statements
about color: color was not “an inherent quality of the
object,” yet whiteness—for Boyle, a color—could be
“considered as a quality in the object” and, as such,
“depended on the asperity of the superficies of the
body” (Robert Boyle on Natural Philosophy, ed. M. B.
Hall, pp. 255-56). Like Locke and unlike Bacon, Boyle
did not think it important to distinguish two kinds of
investigations of the phenomenon of heat; and the
conclusion of any investigation was alternatively about
the nature of heat as it existed in bodies or about the
efficient cause of heat, i.e., about a power in bodies
to produce heat in us, and also in other bodies. For
this reason, and because he did not think that the
nature or cause of heat was directly observable, there
was no temptation to characterize the aim of causal
inquiry in Humean terms as the discovery of constant
conjunctions between kinds of objects or events. In the
case of “forms and qualities,” it was the discovery of
their “origin.”


Though it is customary to contrast Hume's empiri-
cism with the rationalism of Descartes and the Conti-
nental philosophers whom he influenced, their discus-
sions of causal explanation had certain important
features in common. One was concern about the notion
of force. Descartes and the occasionalists, attacking
what they took to be animistic conceptions of forces
in nature, raised questions about the origin of the idea
of force; and Nicolas Malebranche, employing argu-
ments like Hume's, reached essentially the same con-
clusions as Hume did—much later in a nontheological
manner—about causal statements in science and in
daily life. A second common feature was the view that
physics was concerned with efficient causes and not
with final causes. While Descartes was prepared to
admit that there were causes other than efficient
causes—for instance, that created things could be
viewed as serving God's purposes, and also that God
as causa sui was not, strictly speaking, the efficient
cause but rather the formal cause of His existence—he
insisted that in physics only efficient causes were to
be investigated. Spinoza, also imposing this restriction,
rejected outright the doctrine of final causation and
also rejected Descartes' distinction of God's formal
causation of Himself and efficient causation of the

In Principia philosophiae (1644), Descartes, laying
down the rule that efficient and not final causes were
to be investigated (Part I, Princ. xxviii), was concerned
to banish several kinds of explanations in physics.
Although he thought that ends or purposes could be
attributed to creatures having a soul or mind and also
to God, “God's purposes... seem to be hidden in the
abyss of His inscrutable wisdom”; and, while some
parts of nature served our purposes, to say that they
were created for this reason would have been con-
jecture and not an expression of genuine knowledge.
Proposing this rule, Descartes also had in mind certain
kinds of statements and explanations that he found in
scholastic manuals, for example, that heavy bodies
sought the center of the earth. To say that heavy bodies
sought the center of the earth was to impute to these
bodies characteristics that, according to Descartes,
could only be ascribed to beings having a soul or mind.

In letters to the Princess Elizabeth (May 21 and June
28, 1643, in Correspondance, ed. Adam and Milhaud,
V, 289-92, 322-25), he distinguished four primitive
notions under which all of our ideas could be subsumed
and pointed out what he took to be misapplications


of certain ideas, or category mistakes, in scholastic
physics. In addition to (1) ideas that were applicable
to any conceivable entity—e.g., being, number, and
duration—there were (2) ideas that could be applied
only to bodies, namely, ideas of their extension, shape,
and motion; (3) ideas under the category of thought
that pertained only to souls or minds; and (4) ideas
applicable to the union of soul and body in a human
being, including an idea of the “force that the soul
has of moving the body.” When, according to Des-
cartes, the scholastics explained the behavior of heavy
bodies by asserting that their weight made them seek
the center of the earth, they misapplied ideas of the
third and fourth categories. They conceived of weight
as an unextended entity that was supposed to be in
some way attached to an extended body yet could also
be removed if the body ceased to be heavy. This
quasi-substantial unextended entity, or “real property,”
was, as it were, a small soul; and the animism of the
scholastics consisted in part in their imputing to in-
animate objects entities with characteristics of the third
category that could only be applied to beings having
a soul or mind. They also thought of the weight of
a body as exerting force and acting on the body; and,
so doing, they misapplied an idea of the fourth cate-
gory—namely, of the force that the soul has of moving
the body—to entities that were to be described exclu-
sively in terms of their geometrical properties and
motion and rest.

Although Descartes took exception to what he
thought was an animistic or anthropomorphic concep-
tion of force in scholastic physics, he made use of terms
like “force” in his own physics. Stating his principle
of inertia, for instance, he maintained that “once a
body has begun to move, it has in itself a force to
continue its motion...” (letter to Mersenne, October
28, 1640). In attributing an inertial force to moving
bodies, he did not think that he was imputing to them
the kind of force experienced in voluntary action; for,
as he carefully explained, the force that he attributed
to a moving body—its “quantity of motion”—could
be defined in terms of the clearly and distinctly per-
ceived properties of motion and (ultimately) volume.

Commentators have raised questions about Des-
cartes' attempt to explain what he meant by terms like
“force” and “tendency to move” by reference to mo-
tion and rest and the geometrical properties of bodies.
In his physics, he distinguished the motion that a body
tended to have from its actual motion; and, making
this distinction, it seems that he could not consistently
identify force, or quantity of motion, with the product
of mass or volume and actual motion. In the last year
of Descartes' life, Henry More raised an objection of
this kind: he was unable to reconcile Descartes' con
tention that motion, like shape, was a mode or state
of a body and his assertion that motion could be trans-
ferred or communicated from one body to another. In
his reply, Descartes found it necessary to make a dis-
tinction. Motion, in the sense of translation from place
to place, was, like shape, a mode or state of a body.
But this was to be distinguished from a body's moving
force (vis movens), which he explained “can be God's,
conserving the same amount of motion in matter as
he placed in it from the first moment of creation; or
also that of a created substance, such as our mind; or
that of any other thing to which God gave the force
of moving a body” (August, 1649, Correspondance,
VIII, 264). This explanation left the question open as
to whether God had bestowed this force on bodies
themselves. But Descartes added that he had not dis-
cussed the matter in his published writings for fear of
giving the impression that, on his view, God was the
soul of the world; and he implied, though he did not
clearly assert, that the moving force of bodies was not
to be attributed to bodies but to God. It seems that,
when More pointed out an ambiguity and Descartes
found it necessary to make a distinction, it was difficult
for him to say unequivocally where the force that he
had distinguished from motion was located. If he at-
tributed it to bodies, he would have been imputing
to them a property admittedly other than motion and
extension, and his own view would have been subject
to the kind of objection that he had raised regarding
the forms and qualities of the scholastics. Yet he needed
the notion of a body's force, or quantity of motion,
to explain its behavior. His last words on the subject
expressed an inclination to consign this putative prop-
erty of bodies of God.

In his published writings, Descartes had claimed that
God was the primary and universal cause of motion
(Principia, Part II, Princ. xxxvi), and he had explained
that, but for God's imparting motion to matter in the
beginning and continuing to impart motion by his
“ordinary concourse,” matter would have been a
homogeneous substance undifferentiated by the motion
of its parts. He was clearly on record that the divine
concourse, or God as causa secundum esse, was a
necessary condition of the motion of bodies. Accepting
this view, the occasionalists employed a variety of
arguments to show that God was also the sufficient
condition of a body's moving, and that a body of itself
lacked the power to continue its motion or to commu-
nicate it to other bodies. In Méditations chrétiennes
et métaphysiques
(1683), Malebranche argued that, in
conserving a body from moment to moment, God must
continue to will either that it exist in the same place
or that it exist in different places. If He willed that
it exist in the same place, the body was necessarily


at rest. God's will was inviolable, and nothing could
make a body move that He had willed to be at rest.
In similar fashion, if God willed that a body exist
successively in different places, nothing could keep it
from moving to those places. Since the motion or rest
of bodies was determined necessarily by the will of
God, Malebranche concluded that bodies could not
move themselves or other bodies and that the moving
force of bodies was the will of God.

To Malebranche, the inefficacy of bodies—and in-
deed of any “second cause”—seemed to be a direct
consequence of Descartes' doctrine of divine con-
servation. But he also supported his conclusion in other
ways. In Éclaircissement XV, appended to his De la
recherche de la vérité
... (1674-75), he maintained that
we could not form a clear idea of the putative force
in bodies nor indeed of the force allegedly exercised
in human volitions. He held that, when we consulted
our clear and distinct idea of the essence of a body,
we discovered that it was necessarily extended, divisi-
ble, and movable; but, in consulting this idea, we could
not discover the force that it was supposed to have
to move itself or other bodies. If such a force could
be discovered from an investigation of an idea of a
body, it would have been possible to determine a priori
and without recourse to experience how it would move.
It would have been possible, for example, to determine
a priori and without recourse to experience that, when
a billiard ball in motion came in contact with another
ball that was at rest, the second ball would move off
in a certain direction. There was, however, no neces-
sary connection between the motion of the first ball
and that of the second, and the behavior of the second
ball could not be determined a priori. It was only from
experience that we learned that the second ball would
move in a certain way. Since our experience of regu-
larities in the behavior of moving bodies was abundant,
the mind moved with great facility from the thought
of the first ball coming in contact with the second to
the thought of the second ball moving; and, as a result,
we tended to think that there was a necessary connec-
tion and that one event was the true cause of the other.
This, however, was a mistake. The two events were
distinct and not necessarily connected; and, for Male-
branche, the only necessary connection to be discov-
ered between distinct events was between the volition
of an omnipotent being and its execution.

In similar fashion, Malebranche argued against the
efficacy of human volitions. To show that we lacked
a clear idea of the mind's alleged power to move the
body, he maintained that there was only a contingent
connection between a volition and movement of the
part of the body that was willed. Moreover, the effort
that we sometimes experienced in attempting to move
a part of our bodies did not provide us with an idea
of efficacy or necessary connection, for effort of this
sort was not always successful. Like Hume, he also
appealed to our ignorance of the cerebral mechanics
required to move parts of the body and to our failure
to understand how a volition could bring about motion
of physical particles in the brain.

Although Melebranche proclaimed that God does
everything (Dieu fait tout), he did not deny outright
or unqualifiedly that bodies or minds were causes.
Following the precedent of Géraud de Cordemoy in
Le Discernement du corps et de l'âme (1666), he distin-
guished the real or true cause, on the one hand, and
the occasional or particular or natural cause, on the
other. When one billiard ball came in contact with
a second and the second moved, the impact of the first
ball could be called the occasional cause of the second
ball's moving. To say that it was the cause in this sense
was simply to say that the second ball moved on the
occasion of contact with the first ball and that events
of the one kind regularly followed events of the other
kind. About the analysis of causal statements of this
sort, Malebranche and Hume were of the same mind.
Hume was aware of this similarity, but he chose to
stress the difference between his view and that of the
occasionalists. The occasionalists distinguished two
kinds of causes; whereas, according to Hume, “all
causes are of the same kind...,” and there was “no
foundation for that distinction... betwixt cause and
occasion.” It is fair to say that, in rejecting this distinc-
tion and claiming that all causes were of the same kind,
Hume expressed what was truly original in his view
about causation.

Benedict Spinoza, rejecting the Cartesian distinction
of God and nature, also took exception to certain
Cartesian views about causation. While Descartes ban-
ished final causes from physics on the ground that they
were unknowable, Spinoza, in the famous Appendix
to Part I of his Ethica (published posthumously, 1678),
maintained that the notion of final causation in nature
or in God was rationally indefensible. To suppose, he
argued, that God acted for certain ends entailed that
He sought something of which He was in need, and
this consequence was incompatible with the divine
perfection. Earlier, in Part I of the Ethica, he had also
argued that the supposition of God acting for an end
could not be reconciled with divine omnipotence or,
properly interpreted, divine freedom. Rejecting the
view that things in nature were created to serve our
ends, he maintained that everything followed of neces-
sity from the divine nature; and, contrary to Descartes,
he claimed that God was cause of Himself in the same
sense in which He was cause of all other things, namely,
as efficient cause. It has been noted, however, that


Spinoza's conception of an efficient cause was unlike
Descartes' and also Hume's. While agreeing with
Descartes that an efficient cause need not be tempo-
rally prior to its effect, he conceived of God as causa
that is, as not producing anything outside
of, or distinct from, Himself; and, though he antici-
pated Hume's view that all causes were of the same
kind, Spinoza's God and also the fixed and eternal
things causing individual mutable things were not
temporally prior to, nor in reality distinct from, their


“Mechanism” is sometimes defined as the view that
the phenomena of nature are to be explained by the
motion of bodies having only geometrical properties.
In this sense of the term, neither Isaac Newton nor
G. W. Leibniz can be said to have advocated mecha-
nism or subscribed to the mechanical philosophy. Both
distinguished motion and change of motion from the
forces required to bring them about; and, though they
thought that these forces were measurable, they did
not attempt to identify them with the properties by
which they were measured. Nor, in their accounts of
the nature and properties of bodies, were they pre-
pared to reject in its entirety the scholastic doctrine
of fourfold causation, though both excoriated attempts
to explain particular phenomena by invoking occult
qualities and forms.

Defining “force” as the “causal principle of motion
and rest,” Newton attributed to bodies an internal
force—vis insita or vis inertiae—“by which existing
motion or rest is conserved in a body, and by which
any being endeavors to continue in its state and op-
poses resistance” (“De gravitatione et aequipondio
fluidorum,” Unpublished Scientific Papers of Isaac
ed. Hall and Hall, p. 148). This force was listed
as one of the essential properties of bodies and was
distinguished from external forces and active princi-
ples, such as the force of attraction or gravity. Although
Newton did not include gravity, along with vis inertiae,
among the essential properties of bodies, he thought
that it was a universal property; and, when the charge
was raised that gravity was an occult quality, enjoying
the same dubious status as the forms and qualities of
the scholastics, Newton insisted that it was a “mathe-
matical force,” the existence of which was attested by
experience. He also denied that, in positing this force,
he had attempted to explain, or give the cause of,
gravity. On this point, Leibniz, seems to have misun-
derstood him; for, like Leibniz, he thought that the
notion of bodies acting on one another at a distance was
unintelligible, and he professed ignorance of the means,
physical or spiritual, by which gravitation was effected.

Attacking the Cartesian view that the essence of
bodies was simply extension, Newton adapted scholas-
tic terminology in presenting his own view. Space or
extension, of which God was causa emanativa and
which was coeternal with God, was the materia prima
on which God, in creating bodies, imposed impene-
trability and form; and “that product of the divine will
is the form or formal reason of body denoting every
dimension of space in which body is to be produced”
(“De gravitatione...,” p. 140). Newton hastened to
add, however, that his notions of materia prima and
substantial form differed from the nebulous notions of
his predecessors.

Leibniz, also rejecting the Cartesian conception of
matter, contended that the simple substances or
monads of which bodies were constituted were un-
extended centers of force. By “force,” he explained,
he meant “something between the capacity and action,
something which includes an effort, an act, an en-
telechy... [and] passes of itself into action, in so far
as nothing hinders it” (Leibniz, Philosophischen Schrif-
ed. C. I. Gerhardt, IV, 472). Motion and geometri-
cal properties, like the sensible properties—heat, color,
etc.—were appearances or well-grounded phenomena
(phaenomena bene fundata). According to Leibniz,
each monad mirrored the universe from a particular
point of view, and there was harmony or corre-
spondence in the states of the various monads. But
these correspondences did not result from, nor consti-
tute, efficient causation among monads. Each state or
property of a monad followed from its given nature;
and, though it was not incorrect to speak of causation
among monads, this was “final” or “ideal” causation
based on God's having formed monads in advance in
such a way that they accommodated themselves to one
another. In his metaphysical system, Leibniz found a
place for each of the traditional four genera of causes,
distinguishing materia prima and substantial form and
arguing for the compatibility of explanations by effi-
cient and final causes. He was more charitably disposed
toward the scholastics than other corpuscular philoso-
phers: they were not, he observed, entirely to be de-
spised, though they erred in attempting to explain
particular phenomena by forms and qualities.

The distinction of kinds of causation, along with the
Leibnizian conception of force, was rejected by Hume
in the Treatise. Correspondences, in the sense of con-
stant conjunctions of temporally successive and spa-
tially contiguous objects or events, were ipso facto
causal relations; and all explanations and inferences
concerning matters of fact were based on relations of
this kind. To many philosophers of an empiricist or
positivist persuasion, Hume's criticisms of traditional
views and formulation of a regularity theory of causa-


tion have seemed an impressive and lasting achieve-
ment. Some recent opinion has been more critical.
Concerning the explanation of human behavior, it has
seemed important to distinguish reasons and causes;
and it has been suggested that, as there are different
types of causal inquiry, there “may not be a single
conception of causation but rather a cluster of related
concepts” (H. L. A. Hart and A. M. Honoré, Causation
in the Law,
p. 17).


Francisco Suárez's influential Disputationes metaphysicae
(1597) contains an extended presentation and discussion of
the scholastic doctrine of fourfold causation. See Disputa-
tions XII-XXXIII, in Vol. II, 323ff., and Vol. III of the recent
Latin and Spanish edition (Madrid, 1960-64). The interest-
ing and revealing controversy between Descartes and More
is to be found in Vol. VIII, 90-107, 121-39, 154-85, 204-17,
240-52, and 261-67 of Descartes: Correspondance, edited
by Charles Adam and Gérard Milhaud (Paris, 1963). New-
ton's anti-Cartesian tract “De gravitatione et aequipondio
fluidorum” was published by A. Rupert Hall and Marie Boas
Hall in Unpublished Scientific Papers of Isaac Newton (Cam-
bridge, 1962), pp. 89ff. The following books and articles,
representing a very small part of the literature, have been
particularly useful: Yvon Belaval, Leibniz, critique de Des-
(Paris, 1960); M. H. Carteron, “L'Idée de force
mécanique dans le système de Descartes,” Revue philos-
ophique de la France et de l'étranger,
94 (1922), 243-77,
483-511; R. W. Church, “Malebranche and Hume,” Revue
internationale de philosophie,
1 (1938), 143-61; Étienne
Gilson, “De la Critique des formes substantielles au doute
méthodique,” Études sur le rôle de la pensée médiévale dans
la formation du système cartésien
(Paris, 1951), pp. 141-90;
Marie Boas Hall, Robert Boyle on Natural Philosophy
(Bloomington, 1965); Peter Hoenen, Cosmologia (Rome,
1949); Max Jammer, Concepts of Force (Cambridge, Mass.,
1957); Alexandre Koyré, “Galilée et la loi d'inertie,” Études
Vol. III (Paris, 1939); idem, “Newton and Des-
cartes,” Newtonian Studies (London, 1965), pp. 53-200;
David Kubrin, “Newton and the Cyclical Universe, Provi-
dence and the Mechanical Philosophy,” Journal of the His-
tory of Ideas,
28 (1967), 325-46; Maurice Mandelbaum,
Philosophy, Science, and Sense Perception (Baltimore, 1964);
Richard McKeon, “Causation and the Geometric Method
in the Philosophy of Spinoza,” The Philosophical Review,
39 (1930), 178-89 and 275-96; Paul Mouy, Le Développe-
ment de la physique cartésienne, 1646-1712
(Paris, 1934);
idem, Les lois du choc des corps d'après Malebranche (Paris,
1927); Joseph Prost, Essai sur l'atomisme et l'occasionalisme
dans la philosophie cartésienne
(Paris, 1907); P. P. Wiener,
“The Experimental Philosophy of Robert Boyle,” The Philo-
sophical Review,
41 (1932), 594-609.


[See also Atomism; Baconianism; Causation, Final Causes;
God; Man-Machine; Nature.]