## 1. Life and Works



La Forge was born on 24 or 26 November 1632 in La Fleche, in
the Loire valley in central France, the same town in which Descartes
had attended college between 1607 and 1615. He became a medical doctor,
and then moved to Saumur, where he married Renee Bizard in 1653.
He practised medicine at Saumur until his premature death in 1666.
There had been a Huguenot college at Saumur since 1599, when it was
founded by Philippe Duplessis-Mornay (1549-1623). Moise Amyraut (1596-1664) and
Robert Chouet (1642-1731) were among the notable contemporary
scholars who taught there. There was also an Oratorian school (the
*College royal des Catholiques*) and an adjoining seminary
in the same town, at *Notre Dame des Ardilliers*. A number of
Catholic philosophers had studied in the latter, including Bernard Lamy
(1640-1715) and, for a brief period, Nicolas Malebranche. Both
colleges were receptive to the 'new' philosophy of
Cartesianism and, apparently, their staff members enjoyed more amicable
relations than might have been expected from the history of the
religious traditions that they represented. Following revocation of the
Edict of Nantes (1685), the Calvinist college was razed, while
*Notre Dame des Ardilliers* survives as a school to this day.



La Forge became acquainted with Cartesianism when he studied at La
Fleche, and he continued his interest while practicing medicine
at Saumur, where he had opportunities to discuss philosophy with other
sympathetic readers of Descartes at both the Oratorian school and at
the Reformed Academy, especially with Chouet. Although he lived in the
provinces, he corresponded with some leading Cartesians of the period,
including Geraud de Cordemoy (1626-84), who published his
own contribution to Cartesianism in the same year as La Forge (Cordemoy
1666). When Claude Clerselier (1614-84) began to edit
Descartes' works and prepare them for publication, he acquired
manuscript copies of two of his unpublished essays entitled
*Traite de l'Homme* and *Description du Corps
Humain*, both of which have since been lost. The
*Traite* was the second part of a book that Descartes had
planned to publish as *Traite de la lumiere*.
However, those plans were deferred indefinitely when news of
Galileo's condemnation reached Holland in 1633 and, as a result,
the *Traite de l'Homme* remained unpublished during
its author's lifetime. Nonetheless, Descartes retained the
manuscript throughout his peripatetic life; he also appears to have
made at least two copies for friends (Otegem, 2002: II, 485-536),
through whom in turn his physiological studies acquired a limited
dissemination. In 1648, Descartes revisited his early work in
physiology; he reported that it was almost illegible, due to the
condition of the manuscript, and he began to draft a supplementary
sketch of the conception and birth of animals in a manuscript entitled
*Description du Corps Humain*.



Both unpublished texts were still in poor condition when Descartes
died in 1650. Among other deficiencies, they lacked most of the
diagrams that were required to make his theory intelligible to readers, which Descartes had been unable to draw. Since
Clerselier was equally incapable of providing adequate illustrations,
he invited various people to prepare them. A number of those who
understood Cartesian physiology (including Henricus Regius) refused to
cooperate. Clerselier eventually identified two willing collaborators;
one was Louis de la Forge, in Saumur, and the other was Gerard van
Gutschoven (1615-68), a professor of anatomy in Louvain.
Clerselier accepted both offers of assistance and published their
illustrations in the first edition. When the results of their artistic
efforts coincided, he usually preferred those of Gutschoven because
they were better drawn; however, when they differed, he published both
and used the letters 'F' and 'G' to identify
their respective authors. La Forge was thus credited with seven
of the published illustrations. Descartes' *Traite de
l'Homme*, with these illustrations and extensive notes by La
Forge, was published in Paris in April 1664. Thus La Forge's first publication was the lengthy set of notes that explain various
features of Descartes' *Traite*, which appeared as
*Remarques* on pp. 171-408 of the first French edition of
that work. Meantime, Florentius Schuyl (1619-69) had already
published independently a Latin translation of the manuscript of the
*Traite* in 1662, under the title *De Homine*
(Descartes 1662).



While preparing his explanatory notes for the French edition of
Descartes' *Traite de l'Homme*, La Forge
adverted to the opening sentences of that book, which referred to the
hypothetical men described in it:



> 
> 
>  These men will be composed, as
> we are, of a soul and body. First I must describe the body on its own;
> then the soul, again on its own; and finally I must show how these two
> natures would have to be joined and united in order to constitute men
> who resemble us. (*CSM* I, 98)
> 
> 
> 



 Since Descartes died
before he had completed even the first of these three stages, La Forge
decided to fill the lacuna by developing what he believed Descartes would have
written about the human mind and its union with the body had he had
time to complete his theory, and he did so by borrowing extensively from
Descartes' published and unpublished work. The result was the *Traite de
l'Esprit de l'Homme*, which was composed contemporaneously with La Forge's commentary on Descartes' *Traite
de l'Homme*, and in which he referred on numerous occasions
to a work in progress on the human mind (*H* 172, 262, 299, 315,
334, 335). This treatise was printed in Paris in November
1665, although the publication date on the title page was 1666.



There is no official record of La Forge's death. However,
Clerselier confirmed in the preface to the third volume of
Descartes' correspondence (which was printed in September 1666)
that La Forge had died soon after publishing his *Traite de
l'Esprit de l'Homme* (Clerselier 1667: Preface
a2). It seems likely that he died sometime in early 1666, at the
age of thirty-three.


## 2. Explanation



La Forge endorsed fully Descartes' critique of the use of
faculties or powers in scholastic explanations. He reported that, for
example, many physicians attributed the beating of the heart to a
pulsific faculty of the soul, and added: 



> 
> 
> one cannot deny that
> the heart has a faculty of beating since it does indeed beat ...
> however, here and in many other places this word [faculty] is useless
> and does nothing to explain how the thing occurs. (*H*
> 183) 
> 
> 
> 



Likewise he asked: 



> 
> 
> does one really explain the cause of
> diarrhoea, for example, by saying that it results either from the fact
> that the expulsive faculty of the intestines is irritated or that their
> retentive faculty is weak? Is that not the same as saying, in good
> French, that I know nothing about it? (*H* 217) 
> 
> 
> 



He
argued that all appeals to faculties and powers were nothing more than
re-descriptions of the phenomena that need to be explained.



In physiology, La Forge supported an alternative Cartesian model of
explanation in terms of parts of matter in motion which, when linked
together by contact action, form a machine.



> 
>  By the word
> "machine" one cannot understand anything other than a body
> composed of many organic parts, which, united together, combine to
> produce some movements that they would be incapable of producing if
> they were separated. (*H* 173)
> 
> 
> 


 This concept of a machine
applies



> 
>  not only to watches or other automata ... but to
> the human body and that of all animals, and even the whole universe
> could be considered a machine. (*H* 173)
> 
> 
> 


 Accordingly, the
disciples of Descartes



> 
>  try to explain everything that occurs in
> an animal in the same way as the movements of an automaton occur.
> (*H* 335)
> 
> 
> 


 The same principle had been identified by critics of
Cartesianism as one of its major defects rather than one of its
strengths.



Assuming that the motions and interactions of parts of matter are
sufficient to explain the human body, La Forge acknowledges that the explanatory 
enterprise must be hypothetical, and that hypotheses cannot be
restricted to what is visible to the naked eye.



> 
>  We would be very
> ignorant if we had to doubt everything that we do not see ... one
> surely sees that the Sun and the Moon are sometimes in the East
> ... and sometimes in the West, but one has never seen them move
> there; nevertheless almost no one doubts their movement.
> (*H* 217)
> 
> 
> 


 For similar reasons, one should not reject
Descartes' assumptions about parts of matter in motion in the
human body (such as animal spirits or the nerves) simply because, given
their size, they are unobservable. Although Descartes and La Forge were
attempting to describe parts of the human body and their motions before
the invention of the microscope, the methodological issue involved
would not have changed even if the threshold of observability had been
modified by optical instruments: the Cartesian theory of explanation
supported the postulation of unobservable particles of matter to
explain visible effects whenever they were thought necessary. Their
explanatory role justified their hypothetical postulation.



This required La Forge to address the topical question about how, and
the extent to which, explanatory hypotheses may be confirmed. He
offered the same solution that was supported by other natural
philosophers in the seventeenth century, such as Robert Boyle or
Christiaan Huygens:



> 
> 
> However, hypotheses are not only probable but also indubitable when
> they explain something very clearly and easily, when our senses do not
> contradict them, when reason shows that the phenomenon in question
> could not occur otherwise and it is deduced from principles that are
> certain, and when the hypotheses serve not only to explain one single
> effect but many different and even distinct effects; for it would be
> impossible for hypotheses not to be found defective in some situation
> if they were not true. (*H* 218)
> 
> 
> 



Although he exaggerated the degree of certainty that could be
legitimately claimed for his hypotheses, La Forge did not claim
explicitly that all explanations must be mechanical. He is best
understood as contrasting the emptiness of scholastic explanations,
which were certain but non-explanatory, with the epistemic risks
involved in postulating hypotheses that were at least intelligible
(since they involved only pieces of matter in motion) and were
confirmed indirectly by their explanatory success. The limited choices
available among physiological explanations at that time
(either scholastic faculties, or matter in motion) did not imply any
conclusion about how the discipline could develop at a later time.


## 3. Substance Dualism



La Forge was among the first commentators to attribute to Descartes
an unambiguous dualism of mind and body. He defined a substance as
'a thing in which some property, quality or attribute (of which
we have a real idea in ourselves) resides immediately as in a subject
and by which it exists' (*H* preface u3). His
*Remarks* were designed to extend the explanatory scope of the
machine model of the body to include all the actions of non-human
animals and, in the case of the human body, to explain how ideas arise
in the brain, how they are stored in memory, and how they are
re-activated in the imagination. Accordingly, he initially used the
word 'idea', as Descartes had done, to refer to the
brain-states that are associated with the occurrence of thoughts in the
mind (*H* 262), and he defined memory as the physical capacity
of the brain to facilitate the repeated occurrence of such traces.
Since the relevant brain-events were understood as patterns in the flow
of animal spirits, memory was explained as an acquired disposition of
the paths through which animal spirits flowed to re-open on subsequent
occasions when appropriately stimulated (Sutton 1998).



> 
>  Memory,
> which consists in nothing else, when considered from the perspective of
> the body, than the facility which remains in the pores [of the brain]
> which had been opened previously to re-open subsequently.
> (*H* 304; cf. *T* 280-81: *THM* 178)
> 
> 
> 



This Cartesian use of the term 'idea' was ambiguous,
since it referred to thoughts in the mind and the brain-states that
accompany them. For that reason, La Forge decided in the
*Treatise* to restrict the use of the term to thoughts, and to
rename physical ideas in the brain as 'corporeal species'
(*T* 158, 256; *THM* 77, 159).



According to this theory, the delicate fluid material called
'animal spirits' functions in a quasi-hydraulic machine
(*T* 279; *THM* 177). Impressions on the external senses
are transmitted to the 'common sense' in the brain, and the
patterns in which animal spirits emerge from the brain in response to
external stimuli are corporeal species. All voluntary or involuntary
bodily actions, such as walking or blinking, are explained by the
motion of animal spirits from the brain to the muscles, while internal
sensations (such as hunger or thirst) are likewise experienced by the
subject as a result of associated motions of animal spirits in the
opposite direction, from other parts of the body to the brain. Even the
passions or emotions are triggered by similar mechanisms. Thus
everything that occurs in a human body may be explained by the motion
of various kinds of matter in its various parts (e.g., the brain,
nervous system, or the veins and arteries). The only exception in human
nature to this type of physiological explanation, i.e., thought, was
reserved exclusively to the mind.



La Forge began the *Traite* (1666) with a lengthy
preface in which he compared Descartes' theory of the human mind with
that of Augustine, from whom he quoted extensively to show
that the mind is a distinct substance that is immaterial and survives
the death of the body. This immaterial substance has two characteristic
properties, by which alone it is known: understanding and willing. The
understanding can generate ideas or conceptions of realities that have
never been observed or imagined, and to that extent it is independent
of the human body. Pure understanding 'is a faculty which is
independent of the body in the same way as the will is'
(*T* 292; *THM* 188).



Thus ideas originate in the mind in two distinct ways: in one case,
they are triggered by sensations, and in the other they arise without
any corresponding bodily stimulus. However, La Forge also repeated
Descartes' theory of the origin of ideas, according to which all
ideas are innate (in some sense) in the mind. He identified the 'principal and effective' cause of ideas as the mind, while bodily
sensations were described as the 'remote and occasional' causes of some ideas. The
argument here seemed to depend on the dissimilarity between the body and
the mind:



> 
> 
> Although one could say that the bodies that surround our bodies
> ... are in some sense the cause of the ideas we then have ...
> because these are material substances, the action of which does not
> extend to the soul insofar as it is simply a thing which thinks
> ... they cannot be more than their remote and occasional causes
> which, by the union of mind and body, cause our faculty to think and
> determines it to produce ideas of which the faculty of thinking itself
> is the principal and effective cause. (*T* 176; *THM*
> 92)
> 
> 
> 



The mind is thus an active cause of all its own ideas, including
those that it generates on the occasion of being stimulated by the
senses. In that sense, all ideas are innate because the mind is their
principal and effective cause.



The will is equally active; it is an



> 
>  active power ... of
> choosing or determining ourselves from within ourselves to everything
> to which we determine ourselves. (*T* 182; *THM*
> 97)
> 
> 
> 


 La Forge argued that, in addition to understanding and willing,
the human mind must have an intellectual memory; since it can reason
about purely spiritual realities, and since reasoning involves moving
from one step to another and remembering those on which one relies for
progress, the human mind must be capable of remembering purely
spiritual concepts of which it has had no corresponding corporeal
species (*T* 291; *THM* 187). La Forge concludes in
Chapter xxv that the human mind is immortal; since its essence is to
think, the mind continues to think constantly for eternity and may also
remember things that do not presuppose the presence of a body.



The stark definition of the human mind and body as distinct, simple
substances did not prevent La Forge from describing their union in
human nature as a 'composite subject' (*T* 112;
*THM* 39) and as 'a unity of composition and
association' (*T* 98; *THM* 28). It is known from
experience that there is some kind of union involved here, which
Descartes had struggled to describe in terms of an intermingling of two
substances. La Forge describes it more analytically in causal terms; it
consists in



> 
>  a mutual and reciprocal dependence of thoughts of
> one of them on the movements of the other, and in the mutual
> interaction of their actions and passions. (*T* 210;
> *THM* 122)
> 
> 
> 



La Forge frequently describes this interaction in causal terms,
apparently without qualification or reservation. Accordingly, external
bodies that interact with our sensory organs 'cause'
sensations in us; the motions of external stimuli are the 'true
causes' of our sensory perceptions (*T* 165, 326;
*THM* 83, 215). The interaction of mind and body is reciprocal,




> 
> for not only can the body stimulate (*exciter*) various
> thoughts in the mind, but the mind can also cause (*causer)*
> various movements in the body. (*T* 215; *THM*
> 126)
> 
> 
> 


 In general, the link between the human mind and body



> 
>  must
> consist in the relation or concurrence of the actions and passions of
> the mind and body. (*T* 212; *THM* 124)
> 
> 
> 



Critics of substance dualism claimed, or assumed without argument,
that it concealed an explanatory gap, since it failed to explain how
two substances that were so dissimilar could interact causally with
each other. La Forge addressed that issue in Chapter XVI of the
*Traite*.


## 4. Occasionalism




La Forge is one of the first Cartesians (together with Cordemoy and
Geulincx) who openly defends occasionalism. La Forge's
occasionalism, however, is distinctive for both its scope and the
arguments it uses. La Forge's occasionalism is restricted to the
domain of physical interactions among bodies and allows for the causal
activity of finite minds. In this sense, La Forge (unlike Cordemoy,
Geunlincx and Malebranche) is an advocate of "partial
occasionalism" (Radner 1993, Sangiacomo 2014). In order to
establish this form of partial occasionalism, La Forge builds his case
around a specific issue in Cartesian physics, namely, the
(im)possibility of any transfer of motion between interacting bodies.
His 'non-transfer' argument aims, in turn, to solve some
ambiguities in Descartes's own treatment and provide enough
support for body-body occasionalism without undermining the causal
efficacy of immaterial substances.



To fully understand La Forge's discussion, it is helpful to keep
in mind the overall argumentative strategy that he tries to push. In
the *THM*, La Forge's main task is to show that *there
is* mind-body interaction and that this is not so difficult to
understand--as many of Descartes's opponents have claimed.
The Cartesian account of mind-body interaction has been widely
criticized because of the radical heterogeneity of thinking and
extended substances in Descartes's ontology. Elisabeth of
Bohemia, for instance, provides a paradigmatic expression of this
concern:



> 
> 
> I ask you please to tell me how the soul of a human being (it being
> only a thinking substance) can determine the bodily spirits, in order
> to bring about voluntary actions. For it seems that all determination
> of movement happens through the impulsion of the thing moved, by the
> manner in which it is pushed by that which moves it, or else by the
> particular qualities and shape of the surface of the latter. Physical
> contact is required for the fi rst two conditions, extension for the
> third. You entirely exclude the one [extension] from the notion you
> have of the soul, and the other [physical contact] appears to me
> incompatible with an immaterial thing. (AT iii.661; Shapiro 62)




Elisabeth's critique is truly Cartesian since it builds on the
criterion of clear and distinct intelligibility advocated by Descartes
himself. La Forge addresses this concern by denying that even
*homogeneous* or univocal causation (like body-body causation)
is as intelligible as it looks. By showing that univocal causation
among bodies is in fact impossible, La Forge aims to show that
*every* form of causation entails an interaction between
something corporeal and something spiritual. Hence, the case of
mind-body interaction ceases to be a puzzling scenario and becomes an
instance of a broader and more general account of causation.




This point is clearly stated at the beginning of Chapter 16 of La
Forge's *THM*:



> 
> I think most people would not believe me if I said that it is no
> more difficult to conceive how the human mind, without being extended,
> can move the body and how the body without being a spiritual thing can
> act on the mind, than to conceive how a body has the power to move
> itself and to communicate its motion to another body. Yet there is
> nothing more true, and that is what I propose to show in this chapter.
> (THM 143)




Critics think that body-body causation is easy to conceive while
mind-body causation is hardly intelligible (especially in a Cartesian
dualistic ontology). La Forge aims to reverse this impression by
showing that body-body causation is very hard to clearly and distinctly
conceive and that, actually, it works in the same way as mind-body
causation.




To fully accomplish this task, La Forge has to disqualify the
possibility of a purely body-body interaction and he has to prove that
bodies are always moved by a non-bodily cause. To reach this
conclusion, La Forge uses an argument by elimination which reviews
different potential sources of causal activity and shows that they do
not offer a satisfying account of causation. The argument identifies
three potential candidates as sources of causal activity in bodies: (i)
other bodies; (ii) finite minds (e.g. human minds); and (iii) an
infinite mind (i.e. God). La Forge discusses all three options in turn
in order to prove that neither (i) other bodies nor (ii) finite minds
can be the real causes of bodily movement in nature, and thus only God
can be their genuine cause.




In order to prove that a body can move neither another body nor
itself, La Forge uses the 'non-transfer' argument.



> 
> motion is only a mode which is not distinct from the body to which
> it belongs and which can no more pass from one subject to another than
> the other modes of matter, nor can it belong to a spiritual substance.
> But the motive force, i.e. the force which transports a body from one
> vicinity to another and which applies it successively to different
> parts of the bodies which is leaves behind [...], is not only
> distinct from this application but also from the body which it applies
> and moves [...]. *Now if the force which moves is distinct from
> the thing which is moved and if bodies alone can be moved, it follows
> clearly that no body can have the power of self-movement in
> itself*. *For if that were the case this force would not be
> distinct from the body, because no attribute or property is distinct
> from the thing to which it belongs*. If a body cannot move itself,
> it is obvious in my opinion that it cannot move another body. Therefore
> every body which is motion must be pushed by something which is not
> itself a body and which is completely distinct from it. (*THM*
> 145, emphasis added)



Because movement is only modally distinguished from the body, it
cannot be separated from the moved body and it cannot be transferred
from one body to another. However, because the force of movement can be
separated from a body, it should be really distinguished from the body.
Now, because the force of movement is really distinguished from the
moved body, this force is not corporeal and does not pertain to such a
body. In the same way in which Descartes used the real distinction
between thought and extension to prove that the nature of thought has
nothing to do with extension, La Forge argues that the real distinction
between movement and force of movement entails that the force of
movement cannot have anything extended in its own nature. Therefore, a
body cannot have the force to move itself and, thus, it cannot have the
force to move another body (because the force of motion is not in
itself something bodily at all). 




The reason to distinguish between movement and force of movement
lies in the fact that movement is just a modification of the body and
no modification can be transferred from a subject to another. On the
contrary, it is necessary to think that the same force of movement,
which causes the motion of a body, applies differently to different
bodies, and thus it must be really distinguished from them. It is
important to note that if the force of movement is really distinct from
anything extended, then it should not be conceived as properly
'divided'. Divisibility is a property of extended things,
and if the force of movement is not extended, then it cannot be
divisible in the way in which distances or bodies are. The
(re)distribution of the force of movement across different bodies has
thus to be understood more figuratively, perhaps analogously to the
Cartesian claim that the mind itself is equally present in the whole
body and in each of its parts.



The fact that the force of movement can be applied to different
bodies appears as the crucial point in La Forge's argument.
However, it might be asked why we should grant that the force is
separable from the body and can be transferred. In the end, what
prevents us from claiming that even the force is a modification of the
body and thus cannot be separated from it? La Forge seems well aware of
this problem and proposes a *reductio ad absurdum* to support
this point:



> 
> I may be told that I assume without argument that the force which
> moves must be distinct from the thing which is moved. [...] But
> let us assume, if you wish, that this force is a mode of a body; *it
> could not then be distinguished from it and consequently it could not
> pass from one body to another*. If you conceive it in the same way
> as real qualities are conceived in the Schools and if you think it is
> definitely an accident of a body, even if it is distinct from it, then
> you would have to conceive that it subdivides itself when one body
> moves another and that it gives part of its movement to the other body
> and is therefore itself a body, at the same time as you assume that it
> is distinct from corporeal nature; for anything which is divisible and
> which has parts which can exist independently is a body; or you would
> have to say that it does not subdivide but that the body in which it is
> present produces a similar property in the body it touches when it
> pushes it. You thereby give to bodies the power of creation.
> (*THM* 145-146 emphasis added)




Under the hypothesis that the force of movement is a modification of
the body, the non-transfer argument prevents any transfer of such a
force from one body to another. However, La Forge assumes as factual
that impact implies a redistribution of quantity of motion. Provided
that the total amount of motion is conserved, this redistribution can
be explained by redistribution either of the movement itself or of the
force of movement. But if movement is a modification of the bodies, the
non-transfer argument prevents its transfer. Thus, it must be the force
of movement that is redistributed among the colliding bodies. This
implies that the force of movement would be simultaneously
*non*-distinguished from bodies (which was the hypothesis) and
actually distinguished from them (because of the fact that it is
redistributed). Unfortunately, this conclusion leads to absurdities.
Indeed, either the force of movement is something like a real quality,
which La Forge considers a contradictory entity, or we should accept
that bodies have the power to create accidents in other bodies, which
is taken as another absurdity. Thus, the force of movement cannot be a
modification of a body, and the hypothesis must be
rejected*.*




La Forge presents his use of the non-transfer argument as nothing
but a faithful reading of Descartes. La Forge's discussion,
however, is better seen as an emendation of Descartes's own
position, which was more ambiguous on this subject. In the discussion
of the third law of nature in his *Principles of Philosophy*,
Descartes licenses a language that seems to accept transfer of motion
between bodies (Sangiacomo 2014). Henry More was puzzled by this and
pressed Descartes to clarify this point during their correspondence. In
his reply to More, Descartes denies that he ever allowed for any
transfer of motion.




From a historical point of view, it is interesting to note that more
or less during the same years in which La Forge works at his
*THM*, Margaret Cavendish (1623-1673) also discusses the
possibility of deriving occasionalism from the
'non-transfer' argument (Cavendish 1664, letter 30: 97-98).
Cavendish may have been inspired by More's exchange with
Descartes on this topic. However, she seems to ultimately reject
occasionalism itself as understood and developed by La Forge and other
Cartesian occasionalists. La Forge, anyhow, quotes at length
Descartes' answer to More, suggesting it as the true
interpretation of Descartes' physics.




Nonetheless, up to this point, La Forge has only proved that force
of movement is not something corporeal. This implies that all physical
movements are always brought about by immaterial causes, which allows
that in some cases, immaterial substances like human minds can cause
some physical movements, i.e. voluntary motions, through the law of
their union with the body. However, La Forge clearly would not assert
that finite immaterial substances, such as angels or intermediate kinds
of beings, produce every physical movement. Therefore, La Forge still
needs a further argument to refute this kind of inference and show
that, generally speaking, God himself directly moves physical
bodies.




Just after the previous quote, La Forge introduces a further part of
his discussion in order to rule out the direct involvement of finite
minds in natural phenomena. La Forge reminds us that movement produces
every difference we observe in the physical world. Thus, if God would
eliminate movement, the world would remain an inert mass of matter
whose parts would be indistinguishable. Accordingly, La Forge focuses
on the conditions in which God must introduce movement in such a mass
to make a single body move.



> 
> 
> [1] I also claim that there is no creature, spiritual or corporeal,
> which can cause change in [matter] or in any of its parts, in the
> second moment of their creation, if the Creator does not do so himself.
> Since it was He who produced this part of matter in place *A*,
> for example, not only must he continue to produce it if he wishes it to
> continue to exist but also, since he cannot create it everywhere or
> nowhere, he must put it in place *B* himself if he wishes it to
> be there. *For if he put it anywhere else there is no force capable
> of removing it from that location*.
> 
> 
> 
> [2] Let us even consider that if God gave this particular body
> *A* all the motive force which he uses at present to move the
> whole of nature, it would not be enough even with all that to change
> its location, both because it would not be able to overcome the
> resistance of the rest of matter which we assume is at rest, and
> because in order to make body *A* capable of leaving its place
> to enter that of another body, the other body which it replaces would
> also have to move at the same moment that body *A* begins to
> move, since it is impossible for the first body to take the place of
> the second unless, at the same time as it tries to do so, the second
> body leaves that place and enters that of a third body and the third
> enters that of a fourth, and so on. That is how it could happen when
> everything is at rest. *Therefore no matter what force God gives to
> body A to move itself, it would be ineffective*. That is why when
> God decided to move matter in various ways he had to apply the force
> that he chose to put into matter to many of its parts at the same time,
> so that they could give up their places to each other at the same
> instant without which no motion could have been produced. (*THM*
> 147, emphasis added. Numbers in brackets added to help discussion)
> 
> 
> 



Scholars used to consider the appeal to continuous creation (point
1) as an independent argument (Garber 1987, Nadler 2010: 123-41).
However, this reading is difficult to maintain. Indeed, without the
further development provided by the discussion at point 2, what is
stated at point 1 remains unproved. *Why* should it be God
himself that has to recreate a moving body in a certain place?
*Why* is there no creature, spiritual or corporeal, which can
cause change in the position of a body? As La Forge says, "for if
he put it anywhere else there is no force capable of removing it from
that location". But this is a mere assertion, which is proved
only at point 2. Evidently, *if* God has to recreate a body in
each of its positions, then nothing can work against God's force.
However, without establishing *why* God has to do so, the mere
appeal to his continuous creation begs the question.




Rather, La Forge's argument suggests that he aims at proving
*why* the nature of force is such that God has not only to
continuously recreate a moving body but also must place that body in
each of the different positions that the body undergoes throughout its
movement. The reason for this derives from the conditions of motion in
a plenum*.* La Forge's argument has two premises. First,
the force of rest of an indefinite mass of bodies at rest is even
greater than the infinite force of movement of just one single body.
Second, to allow just one single body to move, it is necessary that all
other bodies move too. It follows that, in such a condition, even if a
single body had an infinite force of movement, it would not move unless
other bodies also moved. Hence, because in order to move a body from
one place to another it is necessary that all other bodies move, it
follows that the force that moves the body is the same that moves all
the other bodies, namely, the same force that introduces motion in
matter, i.e. God's force. Accordingly, the only force able to
move a body away from a certain position is the same force that
simultaneously moves all the other bodies, i.e. God's force.
Because motion is nothing but the passage from one position to another,
God himself not only recreates the moving body but recreates it in each
of its positions.




La Forge introduces his reinterpretation of continuous creation to
complement the non-transfer argument. La Forge's treatment of
this argument does not suggest any kind of generalization concerning
the way in which God's continuous creation should be conceived
concerning thinking substances. The reason why God has to recreate not
only bodies but also bodies in specific places, that is, bodies and
their modifications, is grounded in the nature of bodies and in the
conditions for a movement in a plenum. But a thinking substance neither
moves nor exists in a plenum. Therefore, God's *modus
operandi* ought not be the same. This is the reason why La Forge
presents these arguments exposed in Chapter 16 of his
*Traite* as strong support for his interactionist account
of mind-body union.




However, by extending God's creative activity to the modes of
bodies, La Forge seems to reduce the whole account to incoherence,
because the same considerations would apply to human minds. God could
not create a human mind without its specific modes, which include all
its thoughts and acts of the will. However, acts of the will as modes
of a human mind are assumed by La Forge to be the basis on which human
minds are genuinely active in determining themselves. If God creates
even the acts of will of individual agents, it seems to undermine the
claim that they are *self*-determining when, according to
La Forge, they are determined by God's creative activity.




To address this concern, two considerations are in order. First, from a
historical point of view, it is crucial to keep in mind that the
account of Divine concurrence was defended by Scholastic authors (from
Aquinas to Suarez) as an *antidote* to (medieval)
occasionalism and as a way of preserving the causal efficacy of
secondary causes without denying God's constant involvement in
nature (e.g. Sangiacomo 2016). Despite appearances, thus, the claim
that God is directly involved in the operations of his creatures does
not entail by itself a commitment to the (stronger) claim that God is
the *sole* cause responsible for those operations. Second, from
a more theoretical point of view, in order to reach this stronger
claim, one needs to rule out the possibility that creatures make any
genuine causal contribution to the causal process. La Forge argues that
this is in fact the case for bodies, which (given how the physical
world works) cannot have any causal powers. However, this is not the
case for human minds, which (given how minds work) do have a genuine
active role to play in their operations.




As La Forge himself expressly points out:



> 
> I would add to Mr. Descartes that although all things depend on God,
> as he says, *they do so in different ways*. For in the
> production of effects to which neither our own will nor that of any
> other free agent contributes, one could say that God consulted his own
> will alone, by which he unconditionally determined to produce them in a
> certain way and at a certain time; but in the case of effects to which
> our will contributes, God did not consider his own will alone but he
> also included the consent of our will in his decree, and it was only
> after having foreseen how our will would determine itself in such and
> such circumstances that he consequently willed absolutely that such
> effects would result. (*THM* 106-107, emphasis added)



Here, La Forge clearly aims at clarifying Descartes' account of
will rather than at contradicting it. Thus, he plainly acknowledges a
difference in God's *modus operandi*, due to the
difference between extended (inert) substances and spiritual (active)
substances.



Although La Forge concluded that 'God is the universal cause of
all the motions which occur in the world', he also recognised
'bodies and minds as particular causes of these same motions
... in determining and compelling the first cause to apply his
force and motive power to the bodies to which he would not otherwise
have applied it' in accordance with laws of nature that God
decreed (*T* 242: *THM* 148). He confirmed this view
when he wrote, in relation to the reciprocal interaction of motions in
the human body and thoughts in the mind:



> 
> One should not say that it is God who does everything and that the
> body and mind do not really act on each other. For if the body had not
> had such a movement, the mind would never have had such a thought, and
> if the mind had not had such a thought the body might also never have
> had such a movement.
> (*T* 245; *THM* 150)



God has arranged matters, in human nature, so that certain thoughts
in the mind are accompanied by changes in the brain, and certain
motions of animal spirits trigger specific thoughts in the mind. God's
creative arrangement by which these twinned realities interact provides
the ultimate explanation (if it is such) of a familiar fact of our
experience. In that sense, the role of God in relation to mind-body
interaction is exactly similar to God's role in relation to body-body
interactions.




From a historical point of view, La Forge's emphasis on the
non-transfer argument for occasionalism had some impact on later
debates, especially in the British arena. Antoine Le Grand (1629-1699),
originally from France, spent a large part of his life in England. He
was active in the second half of the seventeenth century as an author
of important Cartesian textbooks, in which he shows sympathy for
occasionalism and supports it by adopting La Forge's non-transfer
argument. Arguably reacting against the success that occasionalism was
enjoying, John Toland (1670-1722) would go on to call occasionalism
applied to the physical realm a "monstrous hypothesis" and
reject it in his *Letter to Serena* (1704, letter V; see
Sangiacomo 2013) discussing again the same argument.