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P H I L O S O P H Y   P A T H W A Y S                   ISSN 2043-0728

Issue number 187
9th September 2014


I. 'Molina's Solution to the Problem of Divine Foreknowledge' by
Kevin Kimble

II. 'Is Intentionality the Argument for Substance Dualism?' by Jani

III. 'Leibniz on the Relation between Force and Motion' by Sim-Hui Tee



The articles in this issue discuss the work of three thinkers who
tried, in rather different ways, to accommodate their religious
beliefs within a philosophical world view -- or conversely, in the
case of our first paper, to employ philosophical argument in
attempting to deal with difficulties arising for an avowedly
theological world view. Though their careers were separated by a
relatively short space of time -- the late sixteenth century to the
early eighteenth -- that period includes the beginning of the
Enlightenment, and the position of God in the work of these three men
is very different.

Kevin Kimble discusses the work of Spanish sixteenth-century
theologian Luis de Molina, who developed the notion of 'scientia
media' -- 'middle knowledge' -- as a way of solving two closely
related problems: how God can have infallible knowledge of causally
indeterminate future events; and how divine foreknowledge, which is
fixed and infallible, can be reconciled with the contingency of such
future events. Kimble concludes that, ingenious though it is, the
idea of middle knowledge, intermediate between God's 'natural
knowledge' of essential truths and his 'free knowledge' of contingent
facts about the world raises problems of its own, and thus does not
offer a distinctive contribution to solving the problems it was
devised to address.

Rene Descartes famously developed the idea of substance dualism
('Cartesian dualism'), the view that there are two fundamental kinds
of substance, mental and material -- thus making room in his
philosophical world view for the immortal soul insisted upon by
Christianity. Jani Kukkola's paper considers the implications of the
intentionality, or 'aboutness', characteristic of mental states,
which is sometimes regarded as the strongest argument in favour of
substance dualism. He concludes that it supports, instead, an
epistemological dualism: different kinds of knowledge, rather than
different kinds of substance.

Sim-Hui Tee's paper examines Leibniz's account of the relation
between force and motion. Leibniz's philosophy of physics
incorporates his notion of 'primitive active force', which underlies
other forces and must first be created by God before any motion can
take place in the mechanical universe. The paper discusses a
fundamental problem for Leibniz's account: how can primitive active
force, which in his metaphysical scheme corresponds to immaterial
'substantial form', lead to the production or alteration of motion in
material bodies? Leibniz offers two solutions to this difficulty, both
of which the paper finds to be inadequate.

Do the points made in these three papers entitle us to draw any more
general conclusions about the relationship between religious belief
and philosophy? Probably not: they deal with very specific issues,
and we should be cautious about extrapolating too far beyond them.
Nevertheless, they do serve to illustrate some of the problems and
complications that can arise when theses that incorporate, or seek to
defend, premises derived from religious faith are exposed to the
rigour of philosophical argument.

(c) Tim Taylor 2014

E-mail: phltet@leeds.ac.uk

About the editor:



1. Introduction

The Medieval period witnessed a rigorous debate between various
thinkers over the problem of the compatibility of divine
foreknowledge, on the one hand, and contingent truths about the
future (future contingents), on the other. This problem is a
two-sided coin that can be stated more clearly by posing two distinct
but closely intertwined questions: (1) how can God infallibly know
causally indeterminate future events? and (2) how is divine
foreknowledge, which is fixed and infallible, to be reconciled with
the contingency of such future events? The Spanish Jesuit theologian
Luis de Molina (1535-1600) espoused an intriguing and very
controversial theory, called the doctrine of scientia media or middle
knowledge, in an attempt to come to grips with these and other
questions. In Part IV of the Concordia Molina lays out in detail the
major tenets of his doctrine of middle knowledge and the way in which
the theory allegedly solves the traditional riddle concerning divine
foreknowledge and the contingency of future human actions.[1] After
sketching Molina's theory of the Scientia Media, I go on to assess
his claim that the theory satisfactorily answers the two questions
about divine foreknowledge.[2] I shall argue that Molina fails to
give a plausible solution to (1), and that his answer to (2), even if
it succeeds, is not a unique contribution of the doctrine of middle

2. Molina's theory of divine knowledge: the scientia media

The fullest explication of Molina's positive account of divine
knowledge is found in Disputation 52 of the Concordia. Central to his
theory is the curious doctrine of 'middle knowledge'. Molina's main
motivation for espousing the doctrine is that it is required in order
to explain the manner in which God acts providentially in the world
and predestines his creatures for certain ends. Without middle
knowledge of contingent events, God could not know how to order the
means to achieve His ends, and thus could not predestine certain ends
through (free) secondary causes. Molina describes three consecutive
'moments' in God's knowledge of the actual world. The first of these
he calls 'natural knowledge'. Such knowledge is logically or
conceptually prior to God's decision to create, and comprises all
metaphysically necessary truths along with all possible states of
affairs and complexes of states of affairs that could hypothetically
obtain. In Molina's own words,

     One type is purely natural knowledge, and accordingly could
     not have been any different in God. Through this type of
     knowledge He knew all the things to which the divine power
     extended either immediately or by the mediation of
     secondary causes, including not only the natures of
     individuals and the necessary states of affairs composed of
     them but also the contingent states of affairs -- through
     this knowledge He knew, to be sure, not that the latter
     were or were not going to obtain determinately, but rather
     that they were indifferently able to obtain and able not to
     obtain, a feature that belongs to them necessarily and thus
     also falls under God's natural knowledge.[3]     

For on the hypothesis and under the condition that God should will to
create this or that  order of things, the divine ideas represent to
God naturally, before any free determination of  His will, every
future contingent state of affairs under that hypothesis and

According to Molina, then, God's natural knowledge has two crucial
features: (a) it is prevolitional, in the sense that God possesses
this knowledge (logically) prior to His decision and will to create,
and (b) the content of this knowledge is essential to God, in that
God not only comprehends all metaphysically necessary truths
essentially, but He also knows all possibilities essentially,
including what each indeterministic secondary cause is able to do in
any possible situation in which it is in a position to act.

Molina goes on to describe a second type of knowledge, which he dubs
God's free knowledge. God's free knowledge is His knowledge of this
existent, actual world. It differs from natural knowledge in two
crucial respects. First, such knowledge is conceptually posterior to
His will and free decision to create, and hence is post-volitional.
In addition, its particular content is not possessed essentially by
the divine nature, but rather is contingent upon which world (out of
all the possible orders) God in fact decides to create. But these two
divisions of knowledge are not enough together to ground God's
knowledge of absolute future contingents. God's natural knowledge
tells Him only what each free secondary cause is able to do, but not
in fact what it would do, in each possible situation. And although
His free knowledge informs Him of the total causal contribution He
Himself makes to the world He decides to create, the fact that His
general concurrence with secondary causes is intrinsically neutral
prevents His causal contribution to the contingent effects of
secondary causes from uniquely determining what those effects will
be. Thus Molina needs to introduce yet a third division into the
structure of divine knowledge:

     The third type is middle knowledge, by which, in virtue of
     the most profound and inscrutable comprehension of each
     faculty of free choice, He saw in His own essence what each
     such faculty would do with its innate freedom were it to be
     placed in this or that or, indeed, in infinitely many
     orders of things -- even though it would really be able, if
     it so willed, to do the opposite... [5]     

Middle knowledge combines the prevolitional aspect of God's natural
knowledge with the contingent feature of His free knowledge. Middle
knowledge is that aspect of divine knowledge, prior to any
determination of the divine will, which encompasses the particular
decisions and actions finite wills would freely make under any
hypothetical set of circumstances, along with the total set of their
effects. To illustrate, let's take one of Molina's favorite examples,
Peter's denial of Christ. With respect to God's complete knowledge of
Peter, God knows prevolitionally by His natural knowledge everything
that is metaphysically possible for Peter to do, that is, every
action that Peter could perform or might perform, in any possible set
of circumstances in which Peter might be placed. God knows, for
instance, any other possible decisions or courses of action that
Peter might have taken on the night that he betrayed Christ. He also
knows all the different choices Peter might have made and the ways
his life might have turned out had he been placed in various
different sets of circumstances (e.g., if he had not been a fisherman
and had never met Jesus). Moreover, God knows prevolitionally
according to His middle knowledge, out of the vast sea of
possibilities, what Peter would in fact do (or would have done) if
placed in any particular set of circumstances. Perhaps if Peter had
been a merchant instead of a fisherman, he would have (freely) moved
his family to Rome. Then God knows by His middle knowledge that if
those circumstances had obtained, then Peter would have moved his
family to Rome. Finally, God knows post-volitionally, following His
decision to create the world that is actual, what Peter will do in
the circumstances which actually obtain. So God always knew (post
creation decision) that Peter will in fact deny Christ.

According to Molina, middle knowledge cannot be reduced to either
natural knowledge or free knowledge, but shares features of each. On
the one hand, middle knowledge is not part of God's free knowledge
because (i) it is logically prior to any free act of the divine will,
and (ii) the content of God's middle knowledge lies outside the scope
of His control. Divine knowledge of the particular contingent events
that would occur under any set of circumstances is independent of
God's actual decision to create a given set of circumstances, and is
in fact a prerequisite for God's knowledge of the future unfolding of
events. And since middle knowledge is (logically) prior to the divine
will, His knowledge of each conditional future contingent that
comprises the particular content of His middle knowledge is simply
given and not within the scope of His control.[6]

On the other hand, neither can God's middle knowledge be assimilated
to His natural knowledge. For whereas the specific content of God's
natural knowledge consists of necessary truths and hence is essential
to Him, the content of His middle knowledge is not, for it is
metaphysically possible for free creatures to act differently in the
exact same set of circumstances. Middle knowledge is similar to
natural knowledge in that the content of each is not dependent on any
divine decree to create, while it is similar to free knowledge in that
the content of each is contingent and dependent on free acts of will
(in the former case decisions of free creatures, in the latter case
the free activity of God).

3. Molina's application of the scientia media to the problem of
divine foreknowledge

Having briefly explored Molina's doctrine of middle knowledge, I now
consider Molina's attempt to utilize the theory in resolving the
problem of divine foreknowledge. Recall how the traditional problem
of divine foreknowledge can be formulated by asking two questions:
(1) how can God know certainly and infallibly the occurrence of
causally indeterminate future events? and (2) how is such fixed and
infallible foreknowledge to be reconciled with the contingency of
future (free) actions and events? The answer Molina gives to the
first of these questions involves two distinct stages. The first
stage is Molina's unequivocal claim that it is God's middle knowledge
coupled with knowledge of His will and decision to create that form
the basis of His foreknowledge of future contingent events in the
actual world. There is first God's pre-volitional middle knowledge of
conditional truths about possible futures, by which He knows which
contingent effects would emanate from any arrangement of
circumstances and secondary causes. In addition to that, God has
post-volitional knowledge of the total causal contribution He wills
to make to the created world, including which secondary causes He
will create and the particular arrangement of circumstances in which
He will place them. This provides God with complete free knowledge of
all absolute future contingents. By choosing to actualize a certain
order of hypothetical states of affairs, God knows what further
states and events will be actual as a consequence.

Molina also appeals to this first stage of his answer to (1) in
trying to meet the often noted objection that external events cause
God's knowledge, and hence that knowledge is causally dependent on
something outside of God. Molina insists that God does not acquire
His knowledge from external sources, but knows all future contingents
in Himself. God's knowledge that a certain state of affairs will
obtain is grounded in His decreeing that the state of affairs obtain.
And this divine decree is guided by God's pre-volitional middle
knowledge of how certain possible secondary causes would act in
various possible sets of circumstances. In other words, God's
(post-volitional) foreknowledge of any future event or state of
affairs is grounded in His creative decree to order the world in such
a way that the states of affairs in question will be produced with
God's concurrence through the relevant secondary causes. Hence there
is no appropriate sense in which it can be claimed that entities and
events external to and independent of the divine being and will are
the bona fide cause of His foreknowledge.

One might well wonder whether invoking middle knowledge to explain
simple foreknowledge simply pushes the problem one step back to the
question of how God possesses middle knowledge of conditional future
contingents. Along similar lines, one might wonder (in response to
the above objection) whether it is the case that God's middle
knowledge is caused by states of affairs external to and independent
of Him. This is precisely where the second stage of Molina's answer
to (1) comes in. In answering the question of how God has
pre-volitional knowledge of the contingent effects secondary causes
would produce given the obtaining of various hypotheses or
circumstances, Molina invokes the notion of divine comprehension or
super-comprehension. Because of God's 'infinite and unlimited
perfection, by which He comprehends each created faculty of choice in
a certain absolutely profound and eminent way',[7] God's intellect
infinitely surpasses the capabilities of finite free wills so that He
understands them so thoroughly that He knows not only what they could
choose to do under any set of circumstances, but also what they would
choose. Molina elaborates:

     Before (in our way of conceiving it, but with a basis in
     reality) He creates anything at all, He comprehends in
     Himself -- because of the depth of His knowledge -- all the
     things which, as a result of all the secondary causes
     possible by virtue of His omnipotence, would contingently
     or simply freely come to be on the hypothesis that He
     should will to establish these or those orders of things
     with these or those circumstances; and by the very fact
     that through His free will He established in being that
     order of things and causes which he in fact established, He
     comprehended in His very self and in that decree of His all
     the things that were in fact freely or contingently going
     to be or not going to be as a result of secondary causes.[8]     

In explaining the basis of God's middle knowledge of conditional
future contingents, Molina appeals ultimately to God's cognitive
perfection. Middle knowledge demands a kind of cognitive power
ascribable to the supreme deity alone, a super-comprehension by which
the deity must surpass in perfection by an infinite distance the
creature known, and must have epistemic certitude regarding states of
affairs and events that do not (before they occur) have metaphysical
certitude. Thus Molina's answer to the question of how God knows
absolute future contingents involves a two part solution. His
explanation appeals to a free determination of the divine will to
create free creatures in certain circumstances along with the divine
comprehension in His essence of each created free will through His
middle knowledge.

4. The failure of middle knowledge as an adequate solution

Does Molina provide a satisfying answer to question (1)? If the
doctrine of the scientia media is to shed any real light on the
problem as part of a helpful explanation of how God has divine
foreknowledge of certain kinds of events, then the doctrine must do
more than merely explain God's knowledge of one kind of contingent
truth in terms of another that is just as mysterious. But this is
precisely what Molina himself appears to do.[9] Moreover, if the
source and basis of divine foreknowledge of simple future contingents
is thought to be (as it was for many medieval thinkers) the common
notion of God's profound and preeminent comprehension of His
creatures and their actions, and if such a notion has yet to be
explained, then it is difficult to see how Molina's own appeal to a
kind of super-comprehension of conditional future contingents amounts
to any real progress in satisfactorily explaining God's foreknowledge.
For the notion of super-comprehension is itself rather mysterious and
unexplained, and Molina's discussion leaves it at a somewhat vague
and abstract level.

Familiar 'Thomistic' solutions to (1) tend to ground divine knowledge
of future contingents strictly in the determination of the divine will
whereby God decrees and determines even the effects of secondary
causes; and in this way divine foreknowledge can be seen as a species
of causal knowledge, albeit of a special sort (about the future). But
defenders of divine foreknowledge who, like Molina, affirm an
indeterministic or 'libertarian' notion of free will and contingency
cannot employ this same strategy. There are simply no analogous
metaphysical underpinnings available to explain how it is that God
certainly and infallibly knows, for example, that Peter would deny
Christ if placed in circumstances C, when in fact it is fully
consistent with the obtaining of those exact same circumstances that
Peter not deny Christ in C. To that extent Molina's answer to (1)
seems severely impoverished in comparison with other suggestions
offered from within the Thomistic camp, and his answer fares no
better than certain other solutions which are sympathetic to
libertarian conceptions of free will. I conclude, then, that with
regard to question (1), Molina's appeal to middle knowledge does not
improve upon other explanations found within the Medieval tradition.

What about the second half of the foreknowledge problem, as expressed
in our question (2)? How is the theory of middle knowledge supposed to
reconcile the tension between the certainty and infallibility of God's
foreknowledge and the contingency of the actions and effects of
secondary causes? I think the best way to understand Molina's
position here is by turning to the argument he discusses for
theological fatalism:

1) (Assumption) Suppose that it is true at time t that p, i.e. that
God foreknew 80 years ago that S will do A.

2) Closure of necessity under logical entailment (CL): If p is
absolutely necessary, and p entails q, then q is absolutely necessary.

3) Fixity of the past (FP): For any proposition p about the past that
is true at t, no agent (including God) has the power at or after t to
bring it about that p is false.

4) Absolute necessity (AN): Any proposition that is 'fixed by the
past' according to (FP) is absolutely necessary.

5) Conclusion: therefore, q is absolutely necessary (S will do A is
absolutely necessary).

Molina clearly accepts both FP and AN, contrary to the Ockhamist line
of response. He holds that were some future contingent, foreknown by
God, not to obtain, then God's infallible middle knowledge would have
been different, and God would thus not have foreknown that the event
would occur under those circumstances. Molina is careful to
distinguish the following two kinds of claims:

(A) God's knowledge that p is now such that, having known that p, God
is able not to have known that p.

(B) God's knowledge that p is such that He might have never known
that p at all.

Molina vehemently denies (A) but gives assent to (B).[10] In other
words, it does not follow from the contingency of future states of
affairs that God's knowledge of them is able to be different than it
in fact is; it follows only that were the future contingents not to
occur, then God's knowledge of them would have been different all
along, since He would have known from eternity other future
contingents instead. To illustrate with one of Molina's favorite
examples, there is an absolute necessity now involved in God's
knowing that Peter would sin. When God in actual fact possesses that
piece of knowledge at t, it cannot then or at a later time be negated
or erased in any way. But it is possible that God had never known that
Peter would sin under the circumstances, just in case Peter would not
have sinned in those circumstances. And in that case God's middle
knowledge -- His knowledge of certain conditional future contingent
states of affairs -- would have been different.[11]

We are now in a better position to see how Molina attempts to
circumvent the argument for theological fatalism, namely by rejecting
the only remaining principle in the argument -- the closure principle
CL. And that is precisely what Molina does:

     Even if (i) the conditional is necessary (because in the
     composed sense these two things cannot both obtain, namely,
     that God foreknows something to be future and that the thing
     does not turn out that way), and even if (ii) the antecedent
     is necessary in the sense in question (because it is
     past-tense and because no shadow of alteration can befall
     God), nonetheless the consequent can be purely
     contingent... if the truth of the antecedent is posited (as
     is in fact the case), then the consequent is necessary only
     with a necessity of the consequence, by which it is validly
     inferred from that antecedent, and not with a necessity of
     the consequent, since the condition in question does not
     render the consequent absolutely necessary in the way that
     it does render the antecedent absolutely necessary. The
     consequent is not affected by it in any way, but is instead
     unqualifiedly able to obtain and able not to obtain.[12]     

Molina claims that the antecedent of a conditional may be absolutely
necessary but the consequent contingent, in cases in which the
necessity involved is temporal necessity and the knowledge claim in
the antecedent depends on the contingent fact that the state of
affairs known was going to obtain.[13] The power of secondary causes
to act freely is not closed under entailment. Hence it is within
Peter's power not to sin, but it is not within his power to alter
God's foreknowledge; even if Peter were to refrain from sinning under
the given circumstances, then God would always have known the
complement of that particular conditional future contingent, and that
proposition would have been absolutely necessary instead. So Molina's
strategy is to attack CL, and if CL is false, then the entire
argument for theological fatalism is rendered untenable.

Is it a plausible move to deny the closure principle? One
consideration weighing in favor of the plausibility of rejecting CL
is that many philosophers have regarded as problematic other parallel
closure principles which play a role in philosophical argumentation.
For example, there is the famous epistemic closure principle which
has been attacked by Fred Dretske and others. In discussions of
ethical reasoning and the logic of ought, forms of the deontic
closure principle have come under fire. Finally, in the free will
debate, closure principles involving what actions are within an
agent's power to do (sometimes referred to as power necessity
principles) have also been sharply criticized as untenable.[14] All
this is just to say that there is some precedent from these other
cases for casting prima facie doubt on FP and for thinking that
Molina's strategy might be a viable one.

An alternative solution open to a Molinist to pursue goes as follows.
Molina claims the consequent of a conditional of the form 'If God
foreknows that p, then p' is contingent, such that the agent is able
to perform or refrain from performing the action described by p.
Moreover, we have seen that Molina clearly distinguishes assertions
of the form of (A) from those of type (B). Thus it seems that he
ought to endorse the following claims:

(i) God foreknew at an earlier time t the proposition p 'S performs A
at t*';

(ii) an agent S is free with respect to action A that he performs at
t*; and

(iii) S has it within his power to refrain from performing A at t*,
and if S were to do so, then God at t would have foreknown the
negation of p.

In other words, Molina can accept that agents have a kind of
counterfactual power over the past and claim that counterfactual
power is all that is required for genuine, libertarian free will.
Given this, Molina can then concede the entire line of reasoning in
support of fatalism, including the conclusion of the argument,
without undermining the contingency of future free effects of
secondary causes. The sense in which p is said to be absolutely
necessary in the argument is too weak to undermine free will and
genuine contingency, for no one thinks that such free will requires
agents to have causal -- or to put it more pointedly, retro-causal --
power over the past. Thus it appears that Molina can escape the
unwelcome consequences implied in the fatalistic argument even if he
concedes the truth of CL.

However, both of the above Molinist responses have a significant
shortcoming. Neither solution constitutes a unique explanatory
contribution of the doctrine of middle knowledge per se, for neither
solution need invoke the doctrine in order to preserve the
consistency between divine foreknowledge and indeterministic free
will. Molina's preferred solution involves denying CL in cases of
temporal necessity, but the rationale he gives appeals to God's free
knowledge, not his middle knowledge. The alternative reply suggested
circumvents the fatalistic argument by invoking an agent's
counterfactual power over the past and claiming that such power
suffices for the ability to do otherwise, but once again, the
reasoning is not tied to any doctrine of middle knowledge.

Molina's theory of middle knowledge is an ingenious attempt to come
to grips with the traditional problem of divine foreknowledge. He
offers what I take to be a tenable strategy for answering question
(2), but such a strategy leaves no room per se for middle knowledge
to make any special contribution. With regard to (1), I have tried to
show that in order for the doctrine to be helpful in explaining the
basis of God's foreknowledge of future contingents, Molina owes us a
more satisfying account of what constitutes the ground of divine
middle knowledge itself.


Craig, William Lane. The Problem of Divine Foreknowledge and Future
Contingents from Aristotle to Suarez. Leiden: E.J. Brill, 1988.

Flint, Thomas P. Divine Providence: The Molinist Account. Ithaca, NY:
Cornell University Press, 1998.

de Molina, Luis. On Divine Foreknowledge (Part IV of the Concordia).
Translated by Alfred J. Freddoso. Ithaca, NY: Cornell University
Press, 1988.

Normore, Calvin. 'Future Contingents', in Norman Kretzmann, Anthony
Kenny, and Jan Pinborg, eds., The Cambridge History of Later Medieval
Philosophy. Cambridge: Cambridge University Press, 1982, pp. 358-381.


1. Luis de Molina, On Divine Foreknowledge (Part IV of the
Concordia). Translated by Alfred J. Freddoso. Ithaca, NY: Cornell
University Press, 1988. Unless otherwise specified, all references to
Molina that follow in this paper are to this translation.

2. In order to restrict the scope of this paper to these points, I
will not weigh in on issues regarding the fruitfulness of applying
Molina's views to other doctrines such as divine providence,
prophecy, and petitionary prayer. Nor do I have the space to discuss
one important objection to Molina's doctrine that has been ably
articulated and defended by two contemporary anti-Molinists, Robert
Adams and William Hasker. For a thorough review of Adams and Hasker's
objection , see Flint.

3. Disputation 52, sec. 9.

4. Disputation 50, sec. 17.

5. Disputation 52, sec. 9.

6. As is the case, presumably, with mathematical truths, logical
truths, and any other necessary truths that form part of His natural

7. Disputation 52, sec.15 (see also sec.17).

8. Disputation 49, sec. 8.

9. A similar point is made by Calvin Normore in his paper 'Future
Contingents,' p.380.

10. Disputation 51, sec.18. See also sec.24, and Disputation 52,

11. Disputation 52, sec.30.

12. Disputation 52, sec.34.

13. See Craig, p. 191.

14. See, for example, Ted Warfield and Keith DeRose, eds.,
Skepticism: A Contemporary Reader (NY: Oxford University Press,
1999), pp. 1-26; H. E. Mason, ed., Moral Dilemmas and Moral Theory
(Oxford: Oxford University Press, 1996), pp. 31-58; and John Martin
Fischer, The Metaphysics of Free Will (Cambridge, MA: Blackwell,
1994) pp. 23-45.

(c) Kevin Kimble 2014

National Chung-Cheng University, Taiwan

Email: kekimble@ccu.edu.tw



In this short article I will review Cartesian dualism and
intentionality. The latter has been considered by many as the most
convincing argument for Cartesian substance dualism. I will study the
relationship between dualism and intentionality, and evaluate whether
intentionality really supports such a view.

Cartesian Dualism

Rene Descartes' substance dualism argues that there are two
fundamentally different kinds of things: physical and mental things.
According to his method of doubt, Descartes claims that everything
physical can be doubted; they can be treated as if they were false.
In the case of the human mind, the doubting ends. Because I can doubt
and I can be fooled (by an evil demon) to believe false things, the
mind itself that doubts cannot be doubted. Thus, the physical body
can be doubted, but the mind cannot. The mental stuff of mind is
fundamentally different from the stuff of the body or the brain. Mind
is a thinking and body an extended thing. The body extends itself so
that the intellect can perceive things in the world.

Descartes argues that the mind and the body/ brain do not share all
the same properties. The brain is divisible into parts: brain cells
and functional areas. The mind on the other hand is a unity, which is
not divisible into smaller parts. As Descartes puts it: 'I am unable
to distinguish any parts within myself.'[1] Another property the mind
and the brain don't share is the capability for introspection. One can
think of one's own mind, but one cannot come to know about one's brain
by merely thinking about it. There is also difference in spatiality:
the body/ brain is spatially located, but the mind isn't as it is
impossible to point out where thoughts exactly occupy space.

Intentionality and Substance Dualism

Intentionality is often referred to as the 'aboutness' of mental
states. As Franz Brentano and later phenomenologist Edmund Husserl
put it, intentionality is directedness towards the world and its
objects. To have intentional mental states is to be directed towards
something in the world: the thought that the painting I see is
beautiful is about the painting, but this 'aboutness' is not
reducible to the painting nor to my nervous system. Thus,
intentionality, or 'aboutness', is not part of the physics of the
world or my brain chemistry. Intentionality has been considered as
perhaps the strongest argument favoring dualism.[2] Intentionality
poses a problem for physicalist positions: intentional states are
essentially holistic, but there appears to be no counterpart of this
feature in purely physical states of affairs. The mind is
qualitatively different from non-mental, purely mechanical things,
because of the fact that mind is intentional. It seems, that
intentionality is not physically constituted, as no physical thing
possesses the same properties as intentionality does. However, it
does not follow from this, that intentionality by necessity favors
substance dualism.

Is Intentionality Really the Argument for Cartesian Dualism?

Intentionality is an emergent property; it is not reducible to other,
more primary physical features of a biological organism. It is
impossible to explain how such reduction occurs, at least on the
basis of our current scientific knowledge. But even though we cannot
explain how such reduction occurs, it does not mean that it doesn't
happen: intentionality could emerge from those physical properties.
Intentionality is not, thus, necessarily an argument for
(ontological) substance dualism, but it functions as a
knowledge-argument, favoring epistemological dualism. We cannot know
how intentionality emerges from physical properties, but even though
we lack the knowledge, we ought not necessarily to conclude from this
that substance dualism is correct. Even though intentionality and the
immediate experience we have of it seems to fit well with Descartes'
thinking of the introspection and indubitability of our own minds,
this experience does not necessarily require two different kinds of
stuff, mental stuff and physical stuff, but only two different kinds
of knowledge of things. Those two kinds are (1) the subjective,
irreducible, intentional experience of things in the world, and (2)
the objective knowledge of things in the world. From the perspective
(2) we cannot get to know what it is like to have knowledge (1). As
Thomas Nagel[3] explains, we can observe bats and get to know their
behavior or have understanding of their sonar sense, but we can never
have the first person perspective knowledge of what it is like to be a
bat. Intentionality is a property of the knowledge (1), it is a
necessary part of the first person perspective. In knowledge (2) we
can observe things in the world and we can even expect them to be
true to others, regardless of them having any personal experiences of
those things. There is thus an unbridgeable gap between the two types
of knowledge, and this is what I think is in the heart of the
problems with Cartesian dualism and intentionality. Therefore, the
problem with mind and matter is not necessarily a problem of two
different substances, but of two different kinds of knowledge.


As I have shown, the relationship between intentionality and
Cartesian dualism is not as symbiotic as many would argue.
Intentionality is a strong but not a definitive argument for
substance dualism. In fact, the relationship between intentionality
and dualism appears to be more problematic than it may first seem.
Intentionality does not only support substance dualism, but one could
also argue in favor of another kind of dualism from it. This other
dualism is epistemological dualism, which points out a certain
perspectiveness behind the constitution of different types of


1. Descartes, Rene. 'Meditations on First Philosophy,' in Chalmers,
David. (ed.) Philosophy of Mind. Classical and Contemporary Readings
(New York: Oxford University Press, 2002), p. 18.

2. Brentano, F. 1995. The Distinction between Mental and Physical
Phenomena. In: D. Terrell, A. Rancurello & L. McAlister (eds.)
Psychology from an Empirical Standpoint. New York: Routledge; Horgan,
T. & Tienson, J. 2002. The Intentionality of Phenomenology and the
Phenomenology of Intentionality. In: D. Chalmers (ed.) Philosophy of
Mind. Classical and Contemporary Readings. New York: Oxford
University Press, pp. 520-533; Chalmers, D. 1996. The Conscious Mind.
New York: Oxford University Press, p. 19; Robinson, D. 2008.
Consciousness and Mental Life. New York: Columbia University Press,
pp. 87-88; Frank, M. 2012. Ansichten der Subjectivitat. Berlin:
Suhrkamp, pp. 223-224; Foster, J. 1982. The Case for Idealism.
London: Routledge & Kegan Paul.

3. Nagel, Thomas. 'What Is it Like to Be a Bat?' (Philosophical
Review, 1974), pp. 435-50.

(c) Jani Kukkola 2014

Email: jani.koskela@helsinki.fi



Leibniz argued that motion is one of the properties of extension
which constitutes physical bodies. This interpretation of motion is
clearly geometrical and mechanical, which is characteristic of his
contemporaries. However, Leibniz's mechanical worldview incorporates
a new element which is not mechanical in essence, that is, the
induction of substantial forms. Substantial forms are needed in
metaphysics, according to Leibniz, for they are the necessary basis
for active force, which makes a substance genuine. However, Leibniz
denies that substantial forms have mechanical effects on the physical
phenomena, though the derived active force is substantial in
explaining the mechanical bodies.

     ... the whole nature of bodies is not exhausted in their
     extension, that is to say, in their size, figure and
     motion, but that we must recognize something which
     corresponds to soul, something which is commonly called
     substantial form... (Leibniz 1908, 18)     

The properties of extension, which is an intrinsic property of all
physical bodies (including living ones), presuppose the properties of
inertia and impenetrability. These latter inactive properties
constitute the passive force, which is the resistant force of
extension. Besides, motion presupposes the existence of active force
in physical bodies, without which the physical bodies would remain in
the state of rest. Active force, which is grounded in substantial
form, is the mirror of God's action. Active force that is imposed on
a physical body is a necessary characteristic by which motion can be
distinguished from rest. Leibniz holds that force (both active and
passive) is the property that makes possible motion of physical

Leibniz views the relation between force and motion in two ways.
First, he maintains that force is realized through motion, without
which the force cannot come into existence. In a letter to Burcher de
Volder dated 1699, Leibniz maintained that active force 'exercises
itself through motion.' (Leibniz 2006, 128). The nature of this
active force is governed by the perpetual law. According to Leibniz,
the primitive active force must be first created by God before any
motion can take place in the mechanical universe. According to
Duchesneau (2008), primitive force can be equated with fundamental
laws governing the changing nature of physical bodies at the
phenomenal level. However, this interpretation does not take into
account the primitive force as the God's initial creation that gives
rise to the derivative forces. Because Duchesneau's equating
primitive force with fundamental laws is taken to be effective at the
phenomenal level, it fails to explain the divine properties that
Leibniz was originally attributing to the primitive forces.

Apart from characterizing the force as a property realizable by
motion, Leibniz has taken the relation between force and motion as a
causal relationship. He states that force is the cause of the motion
by which the latter arises from it. However, this mechanical
interpretation of the relation between force and motion is not
without problems. First, as force is a substantial form, it cannot
possess mechanical properties. In other words, the mechanical effects
exhibited by motion are force-independent and must not lie in force,
for the mechanical movement cannot be realized without a physical
body yet it is conceivable in the absence of force. The notion of
force as a non-mechanical substantial form renders the causal account
untenable. Second, the problem persists even if we grant that the
mechanical property of motion, which lies in the physical bodies, is
induced by force. There remains a question of how an immaterial force
can cause (induce) a mechanical motion. It is unlikely for Leibniz to
have recourse to the first cause, for the force in the universe is
not directly imposed by God upon physical bodies. This difficulty is
exhibited by various names conferred to 'force' over years in
Leibniz's writing: 'motive force', 'moving force' (Loemker 1969,
297), 'living force' (Loemker 1969, 438), 'absolute force' (Loemker
1969, 639), 'force of elasticity' (Leibniz 2006, 126), and 'final
causes' (Leibniz 1908).

Despite the difficulty faced by Leibniz in accounting for the
relation between force and motion, these properties lay the
foundation for the phenomena of matter, and should be accounted for
through recourse to metaphysical rather than physical consideration
if one aims to understand the principles. However, Leibniz does not
deny that the notion of force has its place in the laws of nature.

     This consideration of the force, distinguished from the
     quantity of motion, is of importance, not only in physics
     and mechanics for finding the real laws of nature and the
     principles of motion, and even for correcting many
     practical errors which have crept into the writings of
     certain able mathematicians, but also in metaphysics it is
     of importance for the better understanding of principles.
     (Leibniz 1908, 32)     

Notice that in the quoted paragraph above, Leibniz has restated the
problem of 'the distinction between force and motion' as the problem
of 'the distinction between force and quantity of motion'. To
understand the nature of force in physics and metaphysics, Leibniz
holds that one should view force as a property which is different
from the quantity of motion rather than from the motion. This is
evidenced in Machina animalis, where Leibniz has disconnected motion
from force by stating that the motion of animal bodies may be
described merely by 'animal economy' (the study of the relation
between organs and their functions) without taking force into
consideration (Smith 2011). Motion is taken to be a functional
property rather than a physical property. Quantity of motion, in
contrast, is the physical property of the moving object. It is
defined as the velocity multiplied by the mass of the moving object.
Leibniz further elaborates this point by claiming that motion is
unreal (non-physical).

     Because motion, if we regard only its exact and formal
     meaning, that is, change of place, is not something
     entirely real, and when several bodies change their places
     reciprocally, it is not possible to determine by
     considering the bodies alone to which among them movement
     or repose is to be attributed... (Leibniz 1908, 32)     

However, Leibniz has recognized that a fixed quantity of motion is
inadequate in explaining the activities of physical bodies,
especially the living ones. Therefore, the notion of motion serves as
a principle that accounts for the functional aspect of physical
bodies. Taking quantity of motion and motion together, the movement
of a physical object can be explained in terms of physical property
and functional property, respectively, without being able to explain
the cause of the movement. Still, a convincing account of the
relation between force and motion (or quantity of motion) is required.

Leibniz attempts to provide such an account by conferring on both
force and quantity of motion a mechanical status of realness. By so
doing Leibniz implies that force and quantity of motion are real
physically, in the sense that the change of place is brought about in

     But the force, or the proximate cause of these changes [of
     place] is something more real, and there are sufficient
     grounds for attributing it to one body rather than to
     another, and it is only through this latter investigation
     that we can determine to which one the movement must
     appertain. (Leibniz 1908, 32)     

Granting that force is mechanically real, it seems to solve the
problem of the causal relationship between force and motion. However,
this Pyrrhic victory has incurred an enormous difficulty in defending
Leibniz's position of the substantial forms. This is because the
mechanical nature of force cannot be explained in the non-mechanical
interpretation of substantial forms, for force is derived from the
latter. Besides, difficulty arises in the distinction between motion
and the quantity of motion. Because Leibniz has characterized motion
as unreal (non-physical) while the quantity of motion is real
(physical), it remains elusive how the latter can be derived from the

In conclusion, Leibniz's account of the relation between force and
motion is unsatisfactory. Leibniz has attempted to solve this problem
using two strategies. In the first strategy, force is taken to be
either: (1) an immaterial (which is consistent with substantial
forms) property which could be realized by motion; or (2) the cause
of motion. This account of the relation between force and motion
fails to explain how the immaterial force can (1) be realized by
physical motion; or (2) cause the movement of physical bodies.
Leibniz's second strategy in restating the relation between force and
motion as the relation between force and quantity of motion fares no
better. By conferring both force and quantity of motion a mechanical
status of realness, Leibnizian account of substantial form and force
is incoherent.


Duchesneau, F (2008). 'Rule of Continuity and Infinitesimals in
Leibniz's Physics,' In Infinitesimal Differences: Controversies
between Leibniz and his Contemporaries. Ursula Goldenbaum and Douglas
Jesseph (ed). Berlin: Walter de Gruyter. pp. 235-253.

Leibniz, G (1908). Discourse on Metaphysics, Correspondence with
Arnauld and Monadology. George Montgomery (Trans). Chicago: The Open
Court Publishing Company.

Leibniz, G (2006). The Shorter Leibniz Texts: A Collection of New
Translations. Lloyd Strickland (ed). London: Continuum.

Loemker, L.L. (trans. and ed.) (1969) Leibniz: Philosophical Papers
and Letters, Dordrecht-Holland: Reidel.

(c) Sim-Hui Tee 2014

Email: teesimhui@hotmail.com

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