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Louis de La Forge

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Louis de La ForgeFirst published Tue Nov 15, 2011

Louis de la Forge was among the first group of self-styled disciples toedit and disseminate the writings of Descartes in the years immediatelyfollowing his death in Sweden (1650). La Forge initially used his medicaltraining to comment on Cartesian physiology. He also wrote the firstmonograph on Descartes' theory of the human mind, in which hedefended substance dualism and proposed a theory of occasionalcausation that was adopted and developed by other Cartesians, includingMalebranche.

1. Life and Works2. Explanation3. Substance Dualism4. OccasionalismBibliography

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1. Life and WorksLa Forge was born on 24 or 26 November 1632 in La Flche, in the Loirevalley in central France, the same town in which Descartes had attendedcollege between 1607 and 1615. He became a medical doctor, and thenmoved to Saumur, where he married Rene Bizard in 1653. He practised

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medicine at Saumur until his premature death in 1666. There had been aHuguenot college at Saumur since 1599, when it was founded byDuplessis-Mornay. Mose Amyraut (15961664) and Robert Chouet(16421731) were among the notable contemporary scholars who taughtthere. There was also an Oratorian school (the Collge royal desCatholiques)and an adjoining seminary in the same town, at Notre Damedes Ardilliers. A number of Catholic philosophers had studied in thelatter, including Bernard Lamy (16401715) and, for a brief period,Nicolas Malebranche. Both colleges were receptive to the newphilosophy of Cartesianism and, apparently, their staff members enjoyedmore amicable relations than might have been expected from the historyof the religious traditions that they represented. Following revocation ofthe Edict of Nantes (1685), the Calvinist college was razed, while NotreDame des Ardilliers remains to this day.

La Forge became acquainted with Cartesianism when he studied at LaFlche, and he continued his interest while practicing medicine atSaumur, where he had opportunities to discuss philosophy with othersympathetic readers of Descartes at both the Oratorian school and at theReformed Academy, especially with Chouet. Although he lived in theprovinces, he corresponded with some leading Cartesians of the period,including Graud de Cordemoy (162684), who published his owncontribution to Cartesianism in the same year as La Forge (Cordemoy1666). When Claude Clerselier (161484) began to edit Descartes' worksand prepare them for publication, he acquired manuscript copies of two ofhis unpublished essays entitled Trait de l'Homme and Description duCorps Humain, both of which have since been lost. The Trait was thesecond part of a book that Descartes had planned to publish as Trait dela lumire. However, those plans were deferred indefinitely when news ofGalileo's condemnation reached Holland in 1633 and, as a result, theTrait de l'Homme remained unpublished during its author's lifetime.Nonetheless, Descartes retained the manuscript throughout his peripatetic

Louis de La Forge

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life; he also appears to have made at least two copies for friends (Otegem,2002: II, 485536), through whom in turn his physiological studiesacquired a limited dissemination. In 1648, Descartes revisited his earlywork in physiology; he reported that it was almost illegible, due to thecondition of the manuscript, and he began to draft a supplementary sketchof the conception and birth of animals in a manuscript entitledDescription du Corps Humain.

Both unpublished texts were still in poor condition when Descartes diedin 1650. Among other deficiencies, they lacked most of the diagramswhich Descartes acknowledged he was unable to draw and which wererequired to make his theory intelligible to readers. Since Clerselier wasequally incapable of providing adequate illustrations, he invited variouspeople to prepare them. A number of those who understood Cartesianphysiology (including Henricus Regius) refused to cooperate. Clerseliereventually identified two willing collaborators; one was Louis de laForge, in Saumur, and the other was Gerard van Gutschoven (161568), aprofessor of anatomy in Louvain. Clerselier accepted both offers ofassistance and published their illustrations in the first edition. When theresults of their artistic efforts coincided, he usually preferred those ofGutschoven because they were better drawn; however, when theydiffered, he published both and used the letters F and G to identifytheir respective authors. La Forge was accordingly credited with seven ofthe published illustrations. Descartes' Trait de l'Homme, with theseillustrations and extensive notes by La Forge, was published in Paris inApril 1664. Hence the first published work of La Forge was the lengthyset of notes that explain various features of Descartes' Trait, whichappeared as Remarques on pp. 171408 of the first French edition of thatwork. Meantime, Florentius Schuyl (161969) had already publishedindependently a Latin translation of the manuscript of the Trait in 1662,under the title De Homine (Descartes 1662).

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

Since Descartes died before he had completed even the first of these threestages, La Forge decided to fill the lacuna by developing what Descarteswould have written about the human mind and its union with the bodyhad he had time to complete his work, and he did so by borrowingextensively from Descartes' work. The result was the Trait de l'Esprit del'Homme, which was composed in parallel with La Forge's commentaryon Descartes' Trait de l'Homme, and in which he referred on numerousoccasions to a work in progress on the human mind (H 172, 262, 299,315, 334, 335). This treatise was eventually printed in Paris in November1665, although the publication date on the title page was 1666.

There is no official record of La Forge's death. However, Clerselierconfirmed in the preface to the third volume of Descartes' correspondence(which was printed in September 1666) that La Forge had died soon afterpublishing his Trait de l'Esprit de l'Homme (Clerselier 1667: Preface 2).It seems likely that he died sometime in early 1666, at the age of thirty-three.

2. ExplanationLa Forge endorsed fully Descartes' critique of the use of faculties orpowers in scholastic explanations. He reported that, for example, manyphysicians attributed the beating of the heart to a pulsific faculty of the

These men will be composed, as we are, of a soul and body. First Imust 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 bejoined and united in order to constitute men who resemble us.(CSM I, 98)

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soul, and added:

Likewise he asked:

He argued that all appeals to faculties and powers were nothing more thanre-descriptions, in general terms, of what needs to be explained.

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

This concept of a machine applies

Accordingly, the disciples of Descartes

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

does one really explain the cause of diarrhoea, for example, bysaying that it results either from the fact that the expulsive facultyof the intestines is irritated or that their retentive faculty is weak?Is that not the same as saying, in good French, that I know nothingabout it? (H 217)

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

not only to watches or other automata but to the human bodyand that of all animals, and even the whole universe could beconsidered a machine. (H 173)

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

Assuming that the motions and interactions of parts of matter aresufficient to explain the human body, La Forge acknowledges that theenterprise must be hypothetical, and that hypotheses cannot be restrictedto what is visible to the naked eye.

For similar reasons, one should not reject Descartes' assumptions aboutparts of matter in motion in the human body (such as animal spirits or thenerves) simply because, given their size, they are unobservable. AlthoughDescartes and La Forge were attempting to describe parts of the humanbody and their motions before the invention of the microscope, themethodological issue involved would not have changed even if thethreshold of observability had been reduced by optical instruments: theCartesian theory of explanation supported the postulation of unobservableparticles of matter to explain visible effects whenever they were thoughtnecessary. Their explanatory role justified their hypothetical postulation.

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

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

We would be very ignorant if we had to doubt everything that wedo not see . one surely sees that the Sun and the Moon aresometimes in the East and sometimes in the West, but one hasnever seen them move there; nevertheless almost no one doubtstheir movement. (H 217)

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

3. Substance DualismLa Forge was among the first commentators to attribute to Descartes anunambiguous dualism of mind and body. He defined a substance as athing in which some property, quality or attribute (of which we have areal idea in ourselves) resides immediately as in a subject and by which itexists (H preface 3). His Remarks were designed to extend theexplanatory scope of the machine model of the body to include all theactions of non-human animals and, in the case of the human body, toexplain how ideas arise in the brain, how they are stored in memory, andhow they are re-activated in the imagination. Accordingly, he initially

However, hypotheses are not only probable but also indubitablewhen they explain something very clearly and easily, when oursenses do not contradict them, when reason shows that thephenomenon in question could not occur otherwise and it isdeduced from principles that are certain, and when the hypothesesserve not only to explain one single effect but many different andeven distinct effects; for it would be impossible for hypotheses notto be found defective in some situation if they were not true. (H218)

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used the word idea, as Descartes had also done, to refer to the brain-states that are associated with the occurrence of thoughts in the mind (H262), and he defined memory as the physical capacity of the brain tofacilitate the repeated occurrence of such traces. Since the relevant brain-events were understood as patterns in the flow of animal spirits, memorywas explained as an acquired disposition of the paths through whichanimal spirits flowed to re-open on subsequent occasions whenappropriately stimulated (Sutton 1998).

This Cartesian use of the term idea was ambiguous, since it referred tothoughts in the mind and the brain-states that accompany them. For thatreason, La Forge decided in the Treatise to restrict the use of the term tothoughts, 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 spiritsfunctions in a quasi-hydraulic machine (T 279; THM 177). Impressionson the external senses are transmitted to the common sense in the brain,and the patterns in which animal spirits emerge from the brain in responseto external stimuli are corporeal species. All voluntary or involuntarybodily actions, such as walking or blinking, are explained by the motionof animal spirits from the brain to the muscles, while internal sensations(such as hunger or thirst) are likewise experienced by the subject as aresult of associated motions of animal spirits in the opposite direction,from other parts of the body to the brain. Even the passions or emotionsare triggered by similar mechanisms. Thus everything that occurs in ahuman body may be explained by the motion of various kinds of matter in

Memory, which consists in nothing else, when considered fromthe perspective of the body, than the facility which remains in thepores [of the brain] which had been opened previously to re-opensubsequently. (H 304; cf. T 28081: THM 178)

Louis de La Forge


its various parts (e.g., the brain, nervous system, or the veins and arteries).The only exception in human nature to this type of physiologicalexplanation, i.e., thought, was reserved exclusively to the mind.

La Forge began the Trait (1666) with a lengthy preface in which hecompared Descartes' theory of the mind with that of Augustine, fromwhom he quoted frequently and at length to show that the mind is adistinct substance which is immaterial and survives the death of the body.This immaterial substance has two characteristic properties, by whichalone it is known: understanding, and willing. The understanding cangenerate ideas or conceptions of realities that have never been observed orimagined, and to that extent it is independent of the human body. Pureunderstanding is a faculty which is independent of the body in the sameway as the will is (T 292; THM 188).

Thus ideas originate in the mind in two distinct ways: in one case, theyare triggered by sensations, and in the other they arise without anycorresponding bodily stimulus. However, La Forge also repeatedDescartes' theory of the origin of ideas, according to which all ideas areinnate (in some sense) in the mind. He distinguished the mind as theprincipal and effective cause of ideas from bodily sensations as theirremote and occasional causes. The argument here seems to depend onthe 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 doesnot extend to the soul insofar as it is simply a thing which thinks they cannot be more than their remote and occasional causeswhich, by the union of mind and body, cause our faculty to thinkand determines it to produce ideas of which the faculty of thinkingitself is the principal and effective cause. (T 176; THM 92)

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

The will is equally active; it is an

La Forge argued that, in addition to understanding and willing, the humanmind must have an intellectual memory; since it can reason about purelyspiritual realities, and since reasoning involves moving from one step toanother and remembering those on which one relies for progress, thehuman mind must be capable of remembering purely spiritual concepts ofwhich 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 foreternity and may also remember things that do not presuppose thepresence of a body.

The stark definition of the human mind and body as distinct, simplesubstances did not prevent La Forge from describing their union in humannature as a composite subject (T 112; THM 39), and as a unity ofcomposition and association (T 98; THM 28). It is known fromexperience that there is some kind of union involved here, whichDescartes had struggled to describe in terms of an intermingling of twosubstances. La Forge describes it more analytically in causal terms; itconsists in

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

a mutual and reciprocal dependence of thoughts of one of them onthe movements of the other, and in the mutual interaction of their

Louis de La Forge


La Forge frequently describes this interaction in causal terms, apparentlywithout qualification or reservation. Accordingly, external bodies thatinteract with our sensory organs cause sensations in us; the motions ofexternal stimuli are the true causes of our sensory perceptions (T 165,326; THM 83, 215). The interaction of mind and body is reciprocal,

In general, the link between the human mind and body

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

4. OccasionalismLa Forge borrowed a distinction from Suarez and other earlier scholasticphilosophers between univocal and equivocal causes. The former werecauses that resembled their effects (as when one fire causes another),whereas the latter were causes that were dissimilar to their effects. Thedegree of dissimilarity that was required for this distinction wasunspecified; for example, could a living creature give rise to a dead one ifliving and dead are exact opposites? Thus a metaphysical distinctionoriginated from an inadequately analysed description of observableproperties. Without addressing that issue, La Forge argued that even

actions and passions. (T 210; THM 122)

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

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

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radical dissimilarity could not constitute a valid objection in principle tothe efficacy of a putative cause; otherwise God, the supreme cause ofeverything, could not cause creatures that are so dissimilar to his nature(T 213; THM 124). The assumption that the term cause could be appliedunivocally to God and to natural events concealed a major assumption,which facilitated the transition to occasionalism for which La Forge thenargued.

Assuming that God is a cause of creation, then a fortiori the meredissimilarity between minds and bodies could not be an objection to theirreciprocal causal interaction. In fact, La Forge claims that

What is needed, initially, is a general explanation of how anything can bea cause of something else, and La Forge begins to address that issue byinquiring how one body moves another on impact.

One can observe that heavy bodies fall towards the earth, and that themotions of bodies change in systematic patterns as a result of impact.However, one cannot observe why bodies fall or how movement istransferred from one body to another on impact. To understand the causeof such motions, La Forge proposed a distinction between the observableor local motion of a body and the force that causes its motion. He definedlocal motion, as Descartes had done in the Principles of Philosophy (CSMI, 233), as the transfer of a body from the vicinity of those with which itis immediately in contact and which are regarded as at rest to the vicinityof others. In that sense, motion is a mode of a body that cannot beseparated from that body and, therefore, cannot be transferred to others. Incontrast, the motive force (force de mouvoir) that moves a body is distinct

it is no more difficult to conceive how the human mind canmove the body and how the body can act on the mind, than toconceive how a body has the power to move itself and tocommunicate its motion to another body. (T 235; THM 143)

Louis de La Forge


from the moved body. La Forge argued as follows:

It is difficult to understand how this argument is supposed to work.

There is at least a conceptual distinction between the change of locationof a body and whatever causes that change; the latter is the cause of theformer, which is its effect. The link between that premise and La Forge'sconclusion depends on adopting the definition of a real distinction thathe had borrowed from Descartes. According to that definition, a realdistinction obtains only between one substance and another (or betweenone substance and the modes or properties of another). Thus there cannotbe a real distinction, in this sense, between any body and its ownproperties, such as its motion or shape. Descartes had concluded that themodes of one substance cannot be transferred to another; for example, theshape of one body cannot be transferred to another. This way of talkingseems to assume an understanding of the identity of modes that ties them,by definition, with the thing or substance to which they are attributed.Thus, if one body loses its cubic shape and another one gains a similarshape, the shape of the latter could not be the same shape as that of theformer body even if they had exactly similar dimensions.

Although La Forge does not use the phrase real distinction in the

Now if the force which moves is distinct from the thing which ismoved and if bodies alone can be moved, it follows clearly that nobody can have the power of self-movement in itself. For if thatwere the case this force would not be distinct from the body,because no attribute or property is distinct from the thing to whichit belongs. If a body cannot move itself, it is obvious in myopinion that it cannot move another body. Therefore every bodywhich is in motion must be pushed by something which is notitself a body and which is completely distinct (entirementdistingue) from it. (T 238; THM 145)

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passage quoted above (he uses the verb distinguer throughout), theargument works only if that is assumed. It could be restated as follows:

1. There is a real distinction (in Descartes' sense) between local motionand the motive force that causes it.

2. There is no real distinction between a body and its modes.3. Therefore, the motive force that causes motion is not a mode of any

body and is completely distinct from it.

This implies that the motive force that explains why bodies move must beeither a substance or a property of some other reality apart from bodies; ifit is a property, the only other kind of entity to which it can be attributedin a Cartesian universe is a spiritual substance of some kind.

La Forge acknowledges later in the same text that he had assumed a realdistinction between motion and force. He provides a supplementarysupporting argument for that premise and, in doing so, he uses the phrasereally distinct.

La Forge assumes that Cartesian bodies are defined by extension, and thatthe concept of a genuinely bodily mode (such as shape) must include theconcept of extension. How can he draw the negative conclusion, that theconcept of force contains no relation to the concept of extension? This

if the force which transfers and which thereby applies bodies toeach other could belong to them in such a way that the thingwhich is moved were itself the principle of its motion and thisforce were identical with it, then the notion of this force wouldhave to include in its concept the idea of extension, as the othermodes of body do. This is not the case. Therefore the forcewhich moves is no less really distinct (distingue rellement) frommatter than thought is and it belongs as much as thought to aspiritual substance. (T 238; THM 145)

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argument seems to parallel his objection to the scholastic concept ofweight; he describes that concept as inconceivable

However, that kind of conceptual empiricism is inconsistent with thewell-known Cartesian argument concerning the limitations of theimagination in the Sixth Meditation (CSM II, 5051), and with La Forge'sown discussion of the powers of the imagination, which includes thesummary statement:

Thus a failure to imagine force, in the same way that we imagine theshape or size of a body, does not imply that it is incapable of being aproperty of matter.

Despite this, La Forge concludes that force cannot be a mode of bodies.Since the human soul is linked to a body without being one of its modes,that suggests that motive force might be a substance, or it might bevaguely substantial like the real qualities of the Schools, which could bedistributed between bodies as divisible accidents. La Forge dismissedboth solutions; he concluded without further argument that the motiveforce that moves bodies is not a substance, and that it must thereforebelong to some spiritual substance.

This coincides with a suggestion that Clerselier had made in a letter to LaForge (4 December 1660) and which, though obviously not a letter to orfrom Descartes, was included in the third volume of Descartes'correspondence (Clerselier 1667: 64046). Clerselier had distinguished, as

because we could not imagine what it is and, in respect of bodies,we understand only what our imagination is capable ofconceiving. (T 239; THM 144)

we perceive many properties of bodies by the understanding which we could not imagine. (T 263; THM 165)

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had Descartes and La Forge, between the local motion of a body and thedetermination of that motion (which included its direction). He alsosuggested that since force belongs to a spiritual substance, it must beattributed to either an infinite or a finite spiritual substance. Clerseliercombined these suggestions to propose that the force that causes motioncomes from God, while finite spirits cause the determination of motionsthat already exist (Clerselier 1667: 6412). In other words, Godexclusively provided the total quantum of motion in the universe, andhuman minds act merely in the redirection of motions that are alreadypresent in bodies.

La Forge offered an alternative path to this conclusion in the followingthought experiment. Imagine that all motion was removed from the matterin the universe. How could it then acquire motion?

It is not clear whether the concept of an active body is taken to be anindependent and intuitively clear concept (are moving bodies not active?),or whether it merely repeats the claim already made that bodies as suchdo not contain any motive force. Assuming that matter is not active in thelatter sense, it could begin to move only if an external source of motiveforce were applied to it. Since God was assumed to be the creator ofmatter, it seemed as if God were also the only possible source of motive

among all the parts of this formless mass, [is] there one whichcould move itself or move its neighbour? It is easy to decide in thenegative because extension, in which the nature of body in generalconsists and which is the only quality which it retains in thiscondition, is not active not only can it not change its conditionby its own power; I also claim that there is no creature, spiritual orcorporeal, which can cause change in it or in any of its parts, inthe second moment of their creation, if the Creator does not do sohimself. (T 23940; THM 1467)

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force.

In the course of this argument, La Forge has introduced a divine creationaccount to explain how matter might acquire motion. If God were left outof the discussion, one could accept the claim that motionless matter isconceivable, and therefore that motion is an additional quality or attributethat requires an explanation. La Forge argues (as Descartes had done:CSM I, 2379) that it would be impossible to move only one part ofmatter without moving others in its vicinity, because matter isimpenetrable; therefore, any given part could move only if other partsmove to make room for its relocation. He concludes that other parts ofmatter in the vicinity of a moving body must also move to make possiblethe changes of location involved, although this conceivably could occur ina limited part of space. Then, if the language of God as cause is re-introduced, one may conclude that God could move one part of matteronly by moving some other parts simultaneously.

However, the conclusion for which La Forge argues is a more radicalone: that no body has the power to move itself and that the force whichmoves it must belong to some other substance (T 241; THM 147). Sincehe also assumed that God created the universe, and since motive forcewas an extra property that is really distinct from matter, he concluded thatGod is the first, universal and total cause of motion (ibid.). This still leftopen at least two alternative theological interpretations.

One is that God created the universe of matter in motion, as in theGenesis account, and also the laws by which nature is regulated, and thathe then left creation to operate in accordance with those laws. Descarteshad made a significant contribution to dynamics by showing that it is notnecessary to explain why bodies in motion continue to move, and that anexplanation is required only for a change in the condition of motion orrest of a given body. That implies that, once we assume the existence of

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bodies in motion (however that came about), no further explanation isrequired of why bodies in motion continue to move. However, theapparent transfer of motion from one body to another requires anexplanation, and this explanandum remains to be addressed even if Godcreated matter in motion.

The other alternative is to think of God as continuously involved in theconservation of the universe, so that his causal activity continuesthroughout time. La Forge adopts this second option.

He adds another unsupported premise: that it would be equivalent toinconstancy on God's part if he were to change the total quantity ofmotion in the universe.

The thesis about God's creative action (however it is understood inrelation to time) begins to implode when La Forge accepts the traditionalscholastic view that everything that is in God is God himself. Thatimplies that this force [which moves bodies] is nothing other than God(T 242; THM 148). Thus it is possible for something that is identical withGod (i.e., motive force) to be distributed in matter and to be transferredfrom one body to another when they collide. One might object that it iseven more difficult to explain how a property of Godor God Himself,since there is no distinction between God and His propertiesistransferred from one body to another on impact than to explain theobservable phenomena without any mention of God. Alternatively,

Just as He had to use his omnipotent word to draw the whole ofnature out of nothingness, it is also by means of this word that Hedrew this same nature out of chaos by producing motion in it. Andjust as nature would revert to nothingness if He ceased drawing itout from it at every moment in which He conserves it, it wouldlikewise return to its pristine confusion if He did not maintain themotion which He produced (T 241; THM 1478).

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something that is observable but not understood is explained bysomething else (i.e., God's powers and attributes) that, in principle, isboth unobservable and beyond our understanding. It seems as if La Forgehas breached the fundamental Cartesian prohibition, that one not pretendto explain something that is not understood by means of something elsethat is even less well understood.

When faced with this objection, God's omnipotence fills the explanatorygap, because God can do anything that is conceivable to us. A theologicalbelief has been substituted for a mechanical explanation.

Although La Forge concluded that God is the universal cause of all themotions which occur in the world, he also recognised bodies and mindsas particular causes of these same motions in determining andcompelling the first cause to apply his force and motive power to thebodies to which he would not otherwise have applied it in accordancewith laws of nature that God decreed (T 242: THM 148). He confirmedthis view when he wrote, in relation to the reciprocal interaction ofmotions in the human body and thoughts in the mind:

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

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

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Despite these explicit confirmations of the efficacy of dependent causes(i.e., those that are other than God), it is difficult to avoid the conclusionthat La Forge assumes a clear conception of how God's creative actionoperates, and that the sufficiency of God's causation makes the causationof natural events redundant. Nonetheless, La Forge failed to provide anyaccount of how God creates, what kind of activity is involved in creation,and how it can give rise to effects that are so dissimilar to the cause. Onemight expect him to have argued in the opposite direction, from anunderstanding of causation in nature to a conception that is acknowledgedto be less clear, and merely analogical, of causation in God.

Secondly, La Forge's conception of a continuous divine creation remainsopaque. He assumed a scholastic distinction between two kinds of cause,a causa secundum fieri and a causa secundum esse. The former applies tocases where one makes something that continues to exist (as a thing) evenwhen one's causal activity ceases. In that sense, an effective builder canstop building once a house has been completed, and the house continuesto exist. The second type of causation applies when an effect occurs onlyas long as the cause remains active, as when the Sun heats the earth. IfGod's creative action were understood by analogy with the work of anartisan, as in the opening chapter of Genesis, it is unclear why God mustcontinue to create if He wishes to prevent creation from lapsing back intonothingness.

The use of tensed language to speak about God, as if He acted in time,was prohibited in principle by those who constructed the medievalconcept of a creative God. This may have provided a reason to speak ofGod, in a kind of atemporal present tense, as creating the universe, andthat in turn may have suggested that one should think of God as a causasecundum esse. According to this metaphor, God sustains every createdthing in existence, and nature would revert back into nothingness if God

Louis de La Forge


did not maintain it in existence from one moment to the next. However,that seems to be something that theists say about the effects of God'screation (i.e., that their existence depends on His creative action), ratherthan about some activity in God which creates (i.e., that it is continuous,and is subject to temporal qualifications).

Having adopted this language of continuous creation, La Forge uses it toextend God's causal activity into the details of each body's modes. Forexample, God could not create a body, such as a block of marble, in somegeneric way that abstracts from its precise location in space and time,because those modes are (according to Descartes's definition) inseparablefrom the body. He must create it either in motion or at rest, at a specificplace and time, and He must do likewise for all other bodies in itsvicinity.

However, by extending God's creative activity in this way to the modes ofbodies, La Forge seems to reduce the whole account to incoherence,because the same considerations would apply to human minds, as Nadlerpoints out (Nadler 2011: 12341). God could not create a human mindwithout its specific modes, which include all its thoughts and acts of thewill. However, acts of the will as modes of a human mind are assumed byLa Forge to be the basis on which human minds are genuinely active indetermining themselves. If God creates even the acts of will of individualagents, it seems to undermine the claim that they are self-determiningwhen, in fact, they are determined by God's creative activity.

Since it was He who produced this part of matter in place A, forexample, not only must he continue to produce it if He wishes it tocontinue to exist but also, since He cannot create it everywhere ornowhere, He must put it in place B himself if He wishes it to bethere. For if He put it anywhere else there is no force capable ofremoving it from that location. (T 240; THM 147)

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This conclusion is an exact parallel, in an occasionalist account of naturalcausation, to the theological controversy about God's grace that engulfedboth Catholicism and Calvinism in the same period. Those whoemphasized the sufficiency of grace to explain morally meritorioushuman action concluded that the human will was correspondinglyinefficacious in relation to the same actions. To avoid these conclusionsabout nature and grace, God's creative action should be described as sometranscendent and unintelligible event, and the causation of natural eventsand human decisions should be explained, if at all, without reference tothe dominant causation of God.

Thirdly, La Forge seems to have understood causation by analogy withhuman agency, in which a cause does somethingsuch as building ahouse, or injuring an enemyand an effect is sufficiently distinct to beobserved as such. The conceptual limitations of this framework wereexacerbated by conceiving of the causal activity in terms of somethingpassing from the cause to the effect. Once motion was defined inCartesian terms as a mode that, like shape, is inseparable from thesubstance of which it is a mode, it was conceptually impossible for themotion of one body to be shared with another or to pass from one toanother. The metaphor of something being transferred from cause toeffect was inconsistent with the definition of motion as a mode that isinseparable from its host body.

Nonetheless, a similar restriction was not applied to motive force when itwas attributed to God. Therefore it remains as obscure as ever how thisproperty of God (rather than of bodies), which is not distinguishable fromGod, could be maintained at a constant level in the effects of his creativeaction without identifying the natural world with God, and withoutleaving unresolved the original explanandum, namely, how motive forceis transferred between bodies on impact.

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Once this occasionalist account of causation had been adopted to explainwhat happens when bodies collide and, as a result, how they change theirspeed or direction, there was no new challenge in explaining how humanminds and bodies interact. The assumed dominance and efficacy of divinecausation made the human mind a mere occasion on which appropriatemotions are triggered in the body, and motions in the body (such as thoseassociated with sensations) became the occasions on which thoughts arecaused in the mind. As in the case of body-body causation, this accountprovides no genuine understanding of what occurs in mind-bodyinteractions; instead, it transfers the explanandum to God, for whom allsuch causal interactions are easy to achieve, even if they remainunexplained to us.

In his discussion of How the Mind and Body Act on each other, and howone Body moves another (T 235;THM 143), La Forge took the firsttentative steps towards occasionalism, without realizing the revolutionaryimplications of what he believed was a restatement of the philosophy ofDescartes.

BibliographyLa Forge's Works

[H] Clerselier, Claude (ed.), 1664, L'Homme de Ren Descartes et unTraitt de la Formation du Foetus du mesme autheur, Avec lesRemarques de Louys de la Forge, Docteur en Medicine, demeurant La Fleche, sur le Trait de Ren Descartes; & sur les Figures parluy inventes, Paris: Charles Angot.

La Forge, Louis de, 1666, Traitt de l'Esprit de l'Homme, de ses facultezet fonctions, et de son union avec le corps. Suivant les Principes deRen Descartes, Paris: Theodore Girard. [Another printing the sameyear, in Paris, by Michel Bobin and Nicolas Le Gras.]

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La Forge, Louis, 1669, Tractatus de Mente Humana, Ejus Facultatibus &Functionibus, Nec non De ejusdem unione cum corpore; secundumPrincipia Renati Descartes, Amsterdam: Daniel Elzevier. [aposthumous Latin translation]

[T] La Forge, Louis de, 1974, Oeuvres philosophiques, avec une tudebio-bibliographique, Pierre Claire (ed.), Paris: Presses universitairesde France.

[THM] La Forge, Louis de, 1997, Treatise on the Human Mind, trans.Desmond M. Clarke, Dordrecht: Kluwer.

Related Early Works

Clerselier, Claude (ed.), 1657, 1659, 1667, Lettres de Mr Descartes, 3vols., Paris: Charles Angot.

Cordemoy, Graud de, 1666, Le Discernement du Corps et de l'Ame ensix Discours, pour servir l'claircissement de la Physique, Paris:Florentin Lambert.

Cordemoy, Graud de, 1968, Oeuvres philosophiques, P. Clair and F.Girbal (eds.), Paris: Presses universitaires de France.

Cottingham, J., R. Stoothoff, and D. Murdoch (eds.), 198485, ThePhilosophical Works of Descartes, 2 vols., Cambridge: CambridgeUniversity Press. [CSM]

Descartes, Ren, 1662, De homine; figuris et latinitate donatus a F.Schuyl, Leiden: Leffer & Moyardus.

Descartes, Ren, 1972, Treatise of Man, trans. Thomas S. Hall,Cambridge, MA: Harvard University Press.

Descartes, Ren, 1996, Le Monde, L'Homme, Annie Bitbol-Hespris(ed.), Paris: ditions du Seuil.

Descartes, Ren, 1998, The World and Other Writings, trans. S.Gaukroger, Cambridge: Cambridge University Press.

Secondary Literature

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Clarke, Desmond M., 1989, Occult Powers and Hypotheses: CartesianNatural Philosophy under Louis xiv, Oxford: Clarendon Press.

Nadler, Steven, 2011, Occasionalism: Causation Among the Cartesians,Oxford: Oxford University Press.

Ott, Walter, 2009, Causation and Laws of Nature in Early ModernPhilosophy, Oxford: Oxford University Press.

Sutton, John, 1998, Philosophy and Memory Traces: Descartes toConnectionism, Cambridge: Cambridge University Press.

Van Otegem, Matthijs, 2002, A Bibliography of the Works of Descartes(16371704), 2 vols., Utrecht: Zeno (The Leiden-Utrecht ResearchInstitute of Philosophy).

Academic Tools

Other Internet ResourcesOccasionalism, by Jason Jordan (U. Oregon), in the InternetEncyclopedia of Philosophy.

Related EntriesArnauld, Antoine | causation | Cordemoy, Geraud de | Descartes, Ren |Malebranche, Nicolas | modal metaphysics | occasionalism | Regius,

How to cite this entry.Preview the PDF version of this entry at the Friends of the SEPSociety.Look up this entry topic at the Indiana Philosophy OntologyProject (InPhO).Enhanced bibliography for this entry at PhilPapers, with linksto its database.

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