gassendi on human knowledge

Gassendi on Human Knowledge of the Mind 1

Gassendi on Human Knowledge of the Mind

by Antonia LoLordo (Charlottesville)

Abstract: Gassendi holds both that we only have ideas of material things and that weknow – by faith and, at least in later works, by reason as well – that the mind is im-material. I examine the account of the mind provided in Gassendi’s Objections to theMeditations and show how Gassendi’s two theses can be rendered compatible. In-deed, the two theses, taken together, exemplify Gassendi’s account of the scope andlimits of human understanding.

Gassendi and Descartes had reason to feel sympathetic toward oneanother when Gassendi first read the Meditations and composed hisObjections.1 Both were friends and correspondents of Mersenne; bothwanted to replace scholastic orthodoxy with a new system, albeit rad-ically different new systems in the two cases; Gassendi admired Des-cartes’ mathematics while Descartes admired Gassendi’s astronomy.However, the tone of the Objections and Replies is rather less thanfriendly, on both sides. And in his Counter-Objections, Gassendi ex-presses his disappointment that a skilled mathematician like Descar-tes, someone of whom he had had such high expectations, paradedsuch spurious arguments as demonstrations (3.275b). One exemplarycase of this is the 6th Meditation argument that mind and body arereally distinct.2 Gassendi diagnoses the failure of the argument to liechiefly, though not exclusively, in Descartes’ mistaken identification ofthe natures of mind and body as thought and extension.

1 The 5th Objections and the Counter-Objections together constitute the DisquisitioMetaphysica. References to the 5th Objections are to the volume and page numberin Descartes 1973–78 (AT = Adam and Tannery), as are references to Descartes’Meditations and Replies. References to other of Gassendi’s works are either to theDisquisitio (volume 3 of Gassendi’s Opera Omnia) or the Syntagma (volumes 1and 2), cited by volume, page and column number in the Opera.

2 Gassendi tells us that he is disappointed that the promises made in the Prefaceare not fulfilled (3.275b). Now, the Preface and the title of the Meditations itselfallege to demonstrate three things: God’s existence; the immortality of the soul;and the real distinction between mind and body. Gassendi takes all three argu-ments to fail but concentrates on the last, since the other two claims, he thinks,are true and wholly non-controversial.

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I begin with Gassendi’s objections to Descartes’ argument for the na-ture of body and then move on to worries about knowledge of themind’s nature. With this in place, we will be in a position to examineGassendi’s own account of our knowledge of the mind, an accountwhich lies beneath the surface of the Objections and Counter-Objectionsand which is put forward in somewhat different form in his SyntagmaPhilosophicum, the roughly Epicurean replacement for the scholastictextbooks he found methodologically and ontologically unacceptable.For this account is best seen as emerging by contrast with the Cartesianaccount on one hand, and Gassendi’s own account of knowledge ofbody on the other.

It seems, from a quick look at the Objections, that for Gassendiknowledge of the mind would simply be knowledge of body. For hemakes quite clear there that we only have ideas of the material, so thatwhatever cognition of the mind is possible for us would seem to have tobe knowledge of the mind as a material thing. But Gassendi is no ma-terialist. He holds that we know by faith – and in later works by reasontoo – that the mind is immaterial. It is sometimes thought that there isan irreconcilable conflict between reason and faith within Gassendi’sthought, or that the nod to faith is less than sincere or consistent.3

However, this is not the case, as my examination of Gassendi’s focus onknowledge of the mind attempts to show. There is no inconsistency inholding both that the mind is immaterial and that we must cognize itas material for someone like Gassendi who holds that there are strictlimits to human understanding.

The Meditations, Objections, Replies and Counter-Objections

Let me begin with a brief overview of the debate over the mind and its relationship tobody. Gassendi objects to a number of theses he finds in the 2nd Meditation, but threeare particularly important for the current discussion. First, Gassendi objects thatDescartes has not established that the mind is an immaterial thing rather than, say, aparticularly subtle body, interspersed throughout the coarser matter of the humanbody (AT 7.260–261). In particular, Descartes has not proven that the power ofthought cannot belong to any material body, although he appears to be relying onthat assumption (AT 7.262). Second, Descartes has not established that the nature of

3 This is the position of Bloch 1970, who argues that Gassendi’s philosophy in-evitably points in the direction of materialism and atheism, and that Gassendihimself manages to avoid acknowledging this tendency only by refusing tosystematize his philosophy and make it consistent.


the mind is thought, for reasons we will look at more fully later on. And third, Des-cartes has not shown that the nature of the mind is better known than the nature ofbody, even if we grant that the cogito establishes that the existence of the mind isbetter known than the existence of body (AT 7.275). For knowledge of the existenceof something does not, on Gassendi’s view, imply knowledge of its essence. If wewant to know the essence of the mind, we cannot simply think about our idea of themind but should rather carry out something “like a chemical investigation of themind” (AT 7.277).

Descartes responds as follows. He denies that he has tried to prove, in the 2nd Medi-tation, that the mind is simply a thinking thing; rather, all he has argued is that he is,“insofar as [he] knows [himself …] nothing other than a thinking thing.” Similarly,he denies having tried to establish in the 2nd Meditation that the mind is distinct frombody. The demonstration of this does not occur, he tells us, until the 6th Meditation(AT 7.354–355). However, he does at the same time allow that he knows his nature tobe thought, as indeed the title of the 2nd Meditation suggests.4 Finally, Descartesreplies to the worry about existence and essence that “one thing cannot be demon-strated without the other” (AT 7.359).

Mocking the call for a chemical investigation of the mind, Descartes writes thathe has

never thought that anything more is required to reveal a substance than its variousattributes; thus the more attributes of a given substance we know, the more per-fectly we understand its nature (AT 7.360; cf. Principles 1.11 AT 8a.8).

Hence we understand the mind’s nature better than the body’s nature because when-ever we come to know an attribute of body, we thereby also – in addition to theknowledge derived from the cogito – know that the mind has the power to know thatattribute of body. Margaret Wilson has famously suggested that Descartes is notreally entitled to make this reply: knowing more attributes of particular extendedbodies does not, for Descartes, automatically give us more knowledge of their nature.She suggests instead that a good Cartesian answer would involve developing the twothemes of the transparency of mental processes and the distinction between humanand animal or ‘mechanical’ thought processes – although there is in the end, sheadds, a tension between these two themes given the assumption that “our expla-nations, and hence in an important sense our understanding, are limited to what canbe explained on mechanical models”5. We shall see that this is a Gassendian assump-tion – one which, I have argued elsewhere, Descartes rejects. But Descartes’ rejectionof this assumption, like Gassendi’s acceptance of it, is closely tied to his account ofhuman cognition.

The major theme of Descartes’ reply is that Gassendi has illegitimately taken himto task for not proving, in the 2nd Meditation, conclusions which he did not try toprove until the 6th Meditation. However, it is clear from Gassendi’s objections to the

4 See Wilson 1978, 73f. on this point.5 Wilson 1978, 99.

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6th Meditation that this reply would not satisfy him. For instance, Gassendi objectsthat the 6th Meditation claim that the nature of the mind is thought has received nosupport beyond that given in the 2nd Meditation (AT 7.335). Similarly, he points outthat Descartes has not added anything to rule out the mind’s being a particular sortof subtle body (AT 7.336–337). Thus he takes the real distinction argument to relyentirely on the claims about the natures of mind and body he sees as developed in the2nd Meditation. Gassendi adds to his worries about our knowledge of those naturessome difficulties he finds in the hypothesis that the mind is an immaterial substanceinteracting with the body, objections which concern the nature of body as well as thenature of mind. Thus before we can deal with the alleged unintelligibility of Descar-tes’ conception of the mind, we need to see what Gassendi thinks is wrong with theCartesian accounts of the nature of body and mind, and what he would like to put intheir place.

The Nature of Body

Let us start with what Descartes’ and Gassendi’s accounts of the natureof body have in common. For, although Descartes and Gassendi haverather different conceptions of natures or essences, they still haveenough in common to engage with each other. First, for both of themessences are only conceptually distinct from the substances whose es-sences they are, so that an essence individuates a substance. Second, forboth of them modes or accidents of substances are understood as waysof being of those substances, in contrast with more traditional Aristote-lian ways of understanding accidents which were sometimes thought toraise the specter of ‘real accidents’. From these two points follows acommon way of understanding what is involved in giving an account ofthe essence of body: identifying that which is the same in all bodies suchthat they can have the modes or accidents they do in fact have.

Now Gassendi argues that Descartes’ identification of the essence ofbody as extension fails to do this successfully. For although Descartesnames a feature which all bodies have in common, this feature does notby itself show how it is possible for bodies to have the modes or acci-dents they have.6 The chief locus for this argument is the example of the

6 This may strike some contemporary readers as an odd objection. It is sometimesthought that the kind of explanations of particular bodily phenomena given inthe later books of the Principles is somehow derived from the claim that theessence of body is extension (although it is disputed exactly how such a deri-vation could go, especially given the notorious role of extension in Descartes’system). Gassendi does not seem to think of Descartes’ essence-claim as issuingin particular explanations for particular bodies. Although I think this is a plau-


piece of wax from the 2nd Meditation. In response to this example andthe intellectualist conclusions Descartes draws from it, Gassendi saysthat he agrees with the claim that we have intellectual perception of thesubstance of the wax – so long as that claim just amounts to “whateveryone commonly asserts, viz. that the concept of the wax or its sub-stance can be abstracted from the concept of its accidents”. However,he goes on to ask,

does this really imply that the substance or nature of the wax is itself distinctlyconceived? Besides the color, the shape, the fact that it can melt, etc., we conceivethat there is something which is the subject of the accidents and changes we ob-serve; but what this subject is, or what its nature is, we do not know. This alwayseludes us; and it is only a kind of conjecture that leads us to think that there mustbe something underneath the accidents. So I am amazed at how you can say thatonce the forms have been stripped off like clothes, you perceive more perfectly andevidently what the wax is. Admittedly, you perceive that the wax or its substancemust be something over and above such forms; but what this something is you donot perceive (3.311a).

Rather than showing us what the substance of the wax is, Gassendi sug-gests, Descartes’ mentis inspectio shows instead merely that it is part ofour concept of wax that it can melt, change colors in certain ways, andso on. Instead of showing how it is possible for the wax to have thepower to undergo such changes – as natural philosophy should do –Descartes has merely told us that the wax has such powers. And this,Gassendi goes on, is something which we all already know:

I took exception on the grounds that this inspection of the wax – more imperfector more perfect, more confused or more distinct – pertained only to accidents andchanges of accidents but did not apply to the substance itself. Thus from these in-spections we can conceive of and explain what is understood by the name wax.However, we cannot conceive of and explain that nude substance, or rather, thatsubstance which always remains hidden, with the result that we never know whatthe thing lying hidden under the accidents and subject to changes is (3.310a).

In exactly the same way, Gassendi will argue, the introspection of thethinking I will tell us only what is involved in the concept of the mind,without revealing anything about the underlying nature or substance ofthe mind.

At this point, we must note a difference between the levels at whichGassendi’s and Descartes’ respective explanations of the nature of body

sible reading, I shall not defend it here. For in any case, Descartes’ replies toGassendi never suggest that particular explanations of bodily phenomena shouldfollow from the claim that the essence of body is extension.

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primarily operate. For both men there is a legitimate question at thelevel of bodies in general – the question which Descartes answers withthe claim that bodies are extended and Gassendi with the claim thatthey are structures of atoms in the void. However, for Gassendi, thegeneral question is not the important one: what is more useful, hethinks, is to explain the nature of bodies of a specific type. Thus hisphysical explanations typically involve attempts to discern the particu-lar corpuscular structure or contexture of a certain type of body – mag-nets, gold, wine – and to see how these structures explain the manifestfeatures. Gassendi typically uses the terms ‘nature’ or ‘essence’ to referto such structures, although he sometimes uses those terms to refer tothe ideas produced in the mind instead.7

Unfortunately, Gassendi does not think we have as yet succeeded ingiving explanations which reach all the way down to structures ofatoms in the void: rather, as he tends to put it, the “secret or hidden es-sences” lying behind the appearances remain obscure to us (3.352b).However, we have met with some success in explaining manifest beha-vior in terms of the behavior of insensible parts, and an example of suchsuccess may be helpful:

We used to marvel when people pointed out that a small piece of rotten cheese,strewn on a garment and brought near the skin, caused so much stinging tothe senses. The Microscope has demonstrated the reason, namely, that all thosegrains [of cheese] are little animals who, among other things, push their littlebeaks into the skin and bore through and damage it, just as they might borethrough and damage the surface of the earth, in order to seek their food(3.463a–b).

Here we have explained a manifest operation of a thing in terms of thebehavior of its smaller parts, and this sort of explanation is the first stepon the way to a complete natural-philosophical account. In order tocomplete the account, we should then go on to investigate the “littleanimals” themselves, and so on. Thus – to use another of Gassendi’sfavorite examples – we would be giving a useful statement of an essenceif we could say that a magnet is a structure of atoms arranged in ways x,y and z such that x, y and z together make possible the range of mani-fest properties and powers of the magnet.

7 See e.g. 2.463a for a clear case of the first usage. The second usage generally comesup when Gassendi is criticizing the views of those who, like Descartes and theAristotelians, understand essences as real, immaterial, mind-independent things;it is in that context that Gassendi argues that such “essences” are simply ideas(if indeed they are anything at all). See 3.373aff.


Now it is a little harder to give a programmatic explanation of what isgoing on for Descartes when we explain the possible range of modes oraccidents of particular types of bodies. Descartes obviously does takebodies as falling into different types (rainbows, eyes, fetuses) which areexplained in different ways – but the connection between this and thegeneral claim that the essence of body is extension is not direct. This isvery different from Gassendi’s case, where an account of the essences ofparticular types of bodies is simply a specification of the account of theessence of bodies in general.

We are now in a position to see why Gassendi takes the claim that theessence of body is extension to be unhelpful. For it gives a general ac-count of what bodies are without giving us any real help in figuring outwhat individuates particular bodies and makes it possible for them tohave the modes or accidents they do. But Gassendi takes Descartes’claim to have pernicious consequences as well, if taken seriously as astarting-point for natural philosophy. Gassendi argues elsewhere thatthe experienced fact of motion requires a void, so that Descartes’ es-sence-claim cannot be right. While he grants that our concept of bodyincludes being extended, this does not on his view exhaust the nature ofbody even as we know it: an adequate concept of body must also in-clude impenetrability or resistance (1.55a).

As well as disagreeing with the Cartesian claim that the nature ofbody is extension, Gassendi has worries about the methodology bywhich it was arrived at. This worry begins with a point about knowl-edge of existence and knowledge of essence:

the knowledge of the existence of a thing has no necessary connection with theknowledge of its essence or inner nature, for otherwise we would know the nature,essence and inner depths of anything that was obvious to the senses or whoseexistence we knew of in any way at all (3.290a–b).

Knowledge of existence is easy, on Gassendi’s view, since simply by per-ceiving a collection of accidents we naturally “conceive that there issomething that is the subject of the accidents” and thus come to knowthat a certain thing exists, without acquiring a good idea of the thingitself, i.e. its substance or nature. Knowledge of substance or nature israther more difficult to get and “requires a certain complete internalexamination”: “essence does not become known except by bringing tolight every inner depth” (3.311b–312a). Knowledge of existence doesnot amount to knowledge of essence, then, because essence is not per-ceived directly but rather is inferred from the perception of an existingthing.

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Descartes, of course, would not agree with the account of the acquisi-tion of knowledge of essence which bases Gassendi’s distinction be-tween knowledge of essence and knowledge of existence. Here Gassendisimply objects that if Descartes’ equation of knowledge of essence andknowledge of existence were sound, there would be no substantivenatural-philosophical questions left for us to answer:

If this method of philosophizing of yours were sound, what property and what na-ture in the world would then remain hidden? And if anyone struggled to exploreand investigate the nature of the magnet, wouldn’t he be very silly since he shouldconsider himself satisfied by this little formula of yours, that the entire nature ofthe magnet consists in the fact that it attracts iron and points toward the poles?(3.306a–b).

This quite clearly relies on the previous point, that for Gassendi inter-esting natural-philosophical questions are questions about the natureof particular types of bodies.8 Gassendi will go on to argue that the caseof the mind parallels the magnet case closely.

Gassendi’s objection is not merely skeptical. Rather, it derives from analternative theory of cognition of essences – indeed, of imperceptible en-tities in general. Since it is this account which in the end leads Gassendito the view that we only have an idea of the mind as a corporeal thing, letus now turn to that alternative theory. It begins with the recognition thatwhat is evident to sense-perception is insufficient for constructing anynatural philosophy which appeals to insensible entities like atoms orvoid. However, Gassendi holds that cognition of the insensible is para-sitic on what is evident: it proceeds by analogy with the sensible, usingsigns – in particular, indicative signs.9 Thus the theory of signs is in-tended to explain the source and limits of knowledge of the insensible, aswell as the proper criteria for judging cognition of the insensible.

8 The criticism of Descartes thus seems unfair: Descartes does not hold that fullunderstanding of the magnet is reached through its concept, but rather throughpostulating a certain inner structure. Descartes would not, that is, say that wehave explained the modes of the magnet by saying that its nature is extension.Gassendi generally tends to over-emphasize both the aprioricity of Descartes’programme and the extent to which the Meditations is supposed to issue in sub-stantive conclusions about bodies. Neither of these tendencies, however, are par-ticularly worrying for the topic at hand, since Cartesian investigation of themind – unlike the magnet – is a priori and is supposed to issue in substantive con-clusions about particular minds.

9 Gassendi distinguishes indicative from admonitory signs, where admonitorysigns signify things “hidden by circumstance” such as smoke signifying fire, lac-tation pregnancy, and so on (1.79b).


Indicative signs signify things “hidden by nature”, i.e. never percep-tible, such as God, the void, atoms, or unmodified substances. An in-dicative sign signifies its object “because it is the sort of thing which, ifthe object did not exist, could not itself exist, and therefore when itexists, the object also exists necessarily” (1.81b). Thus, sweat is – or atleast was, before the invention of the microscope – an indicative sign ofpores in the skin, and the ‘wholly admirable works of nature’ indicateGod’s existence. And since that which is signified explains or makes in-telligible the existence of the thing construed as a sign, the range ofmanifest qualities and operations of a thing together indicate its sub-stance or nature. When we think of the underlying substance or natureof things whose manifest properties we perceive, we form a notion ofsomething which underlies the manifest properties (i.e. somethingwhich fills a certain specified role) and then imagine it by analogy withsensible things. Thus our cognition of objects cognized through signsmust in principle be like cognition of sensible objects. When we form anidea of something by the use of signs, we must, on Gassendi’s account,do so by analogy with things we already have ideas of, namely, thingsevident to sense. Thus all our ideas must in the end represent things asmaterial. Even though we know that God is immaterial, for instance,we do not have an idea which represents him as immaterial but merelyan idea formed by analogy with powerful men we have encountered inthe past.

The Nature of the Mind

Let us again start with what Gassendi and Descartes agree about. First,they agree that we have knowledge of the modes or accidents of themind; this is given to us in experience. Second, they agree that thesemodes or accidents should not be explained by recourse to scholasticfaculties or souls any more than the modes or accidents of bodiesshould be explained by recourse to forms and qualities. And third, theyagree that some explanation of the possibility of the modes or accidentsof the mind is required. It would be insufficient for the natural philos-opher to simply say that fire exists and can burn things, without givingan explanation for how there can be something with those powers. Inthe same way, it would be insufficient for the natural philosopher to saysimply that the mind exists and can take on a variety of modes or acci-dents and perform a variety of operations, without explaining whatkind of thing the mind is such that it can have such modes or accidents.

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Now Gassendi reads the Meditations expecting Descartes to show uswhat kind of thing the mind is such that it can have the variousthoughts, sensations and operations we experience. Gassendi’s disap-pointment stems here, just as it did in the case of body, from his judg-ment that Descartes has not given any such explanation but merely toldus that there is some thing called the mind underlying that collection ofmodes and accidents:

when you say that you are simply a thing that thinks you mention an operationwhich everyone was already aware of – but you say nothing about the substancecarrying out this operation: what sort of substance it is, what it consists in, how itorganizes itself in order to carry out its various different functions in differentways, and other issues of this sort, which we have not known about up till now(3.300b).

Gassendi thus takes Descartes’ claim that the mind is a thinking thingto simply pick out a certain entity – the unitary subject of the variouscognitive powers – without telling us what the underlying substance oressence of that entity is, let alone demonstrating that it is distinct fromany body. For, he argues, if Descartes had really uncovered the nature ofthe mind then a number of questions that are currently unansweredwould have clear answers, questions such as the following:

What sort of thing [the underlying principium of thought] is, how it exists, how itholds together, how it acts, whether it has certain faculties and functions, whetheror not it has parts, and if it has any, what kind they are: if it does not have any andis indivisible, how it arranges itself in so many different forms; how it performs somany functions; by what means it deals with the body; by what means it goesbeyond it; how it lives without it; how it is affected by it (3.306b).

Since Descartes has failed to answer these questions, Gassendi takesit that the claim that the mind is a thinking thing is merely a nominalor, perhaps, accidental definition – one which describes the operationor quality proprietary to the mind without making clear the essenceor substance from which that operation flows. And again, Gassendidiagnoses the underlying problem with Descartes’ account as metho-dological:

given that you are looking for knowledge of yourself which is superior to com-mon knowledge […] it is certainly not enough for you to announce that you are athing that thinks and doubts and understands, etc. You should carefully scruti-nize yourself and conduct something like a chemical investigation of yourself, ifyou are to succeed in uncovering and explaining to us your internal substance(3.311a).


To this, Descartes responds that he does not see “what more [Gassendi]expect[s] here, unless it is to be told what color or smell or taste thehuman mind has, or the proportions of salt, sulphur and mercury fromwhich it is compounded” (AT 7.360–361). I shall return to this responsein a moment, but first let us see the particular explanatory problemsGassendi sees for the conception of the mind as a thinking substance.

As a preliminary, Gassendi argues simply that Descartes has shed nolight on the traditional problems of explaining what sort of substancecan be capable of having sensations, performing abstract thought, andthe like. Whereas scholastic explanations failed because the forms andfaculties they appealed to were unacceptable, Descartes simply gives noexplanation apart from the bare claim that it is in the nature of the mindto do these things. More importantly, however, Gassendi argues thatDescartes’ account has raised new explanatory problems, ones whichprevious accounts of the mind did not need to deal with – namely, theproblem of body-mind causation and the problem of representation.

The problem of body-mind interaction is a familiar one. Descartessometimes explains interaction by positing the pineal gland as its locus,but this, Gassendi says, is unsatisfactory. There is no place – whether apart of extension or a mere point – at which material and immaterialsubstances could be joined with the desired result (3.405a). As a resultof this, Gassendi says, we cannot make sense of the possibility of bodiesaffecting an immaterial mind, for bodies act by contact and contactwith the immaterial is impossible. The mechanist powers of body can-not explain bodies having actions which do not occur in any place;indeed, mechanism, in either its Cartesian or Gassendian form, seemsto rule out this possibility.10

The problem of representation is less familiar and may strike thereader as less worrying. It hinges on the claim that the immaterial mindis simple and indivisible, that is, lacks parts. Gassendi asks:

10 Body-mind interaction is often described as a two-way problem. However, Gas-sendi only seems worried about bodily causes having mental effects and not viceversa. For Gassendi does not claim to grasp what a Cartesian mind would be likewell enough to say that such a mind could not have bodily effects; he can makeonly the weaker objection that Descartes does not make clear how an immaterialmind affects the body. Since Gassendi takes himself to lack any clear idea of animmaterial mind, he cannot insist that its causal mechanisms preclude action inthe material world; and since he holds that God is immaterial and acts in the ma-terial world, he would not want to suggest that our inability to understand howthe immaterial can affect the material is grounds for thinking that the immaterialcannot affect the material.

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how […] do you think that […] an unextended thing could receive the semblanceor idea of a body that is extended? […] if it lacks parts, how will it manage to rep-resent parts? If it lacks extension, how will it represent an extended thing? […] If itlacks all variation, how will it represent various colors and so on? (3.400b)

It is tempting to read this as a commitment to a naïve picture theory ofrepresentation.11 But this is not Gassendi’s settled view: his account ofvision, for instance, holds that while the image imprinted on the retinaresembles the apparent object, the impression formed in the brain as aresult of the reception of the retinal image does not. Instead, I think,Gassendi has in mind the deeper point that in order to represent struc-ture and variation, the representing mind must itself possess structureand variation.

Indeed, this is part of a larger problem about how any sort of expla-nation can be given of the workings of a simple thing like a Cartesianmind. The explanations we are familiar with – explaining pictorial rep-resentation in terms of isomorphism; explaining the properties of thewine in terms of its composition; etc – explain the operations or prop-erties of a whole in terms of the interaction of smaller parts arranged insome sort of structure. Descartes’ account of the mind precludes anysuch explanation because he holds that the mind has no parts, physicalor otherwise, a claim which Gassendi seems to take as amounting to theclaim that Cartesian minds have no internal structure at all.12

Let me now return to Descartes’ reply to Gassendi’s call for “some-thing like a chemical investigation of the mind”. Descartes respondsthat he does not see “what more [Gassendi] expect[s] here, unless it is tobe told what color or smell or taste the human mind has” (AT 7.359).To say this is in effect to claim that one should not expect an expla-

11 For instance, Arnauld 1990, 61, quotes from this or a very similar passage in anattempt to show how “damnable” are the conclusions one is led to if one modelscognition on physical vision.

12 It is not entirely clear to me whether Descartes would grant that the simplicity ofthe mind precludes its having structure. Although Descartes does not talk aboutmental structure, it seems, as Wilson points out, that the doctrine of innate ideasrequires some underlying structure in the mind. Nor am I sure whether we oughtin general grant that a simple immaterial thing lacks structure: perhaps simplicitycould be preserved so long as the structure is not divisible into parts. But Gas-sendi himself must think of the lack of structure of the immaterial mind as fol-lowing from Descartes’ claim that it is simple, for – given his claim that we haveno real idea of an immaterial mind – he has no independent grounds for insistingthat the mind’s immateriality precludes its having structure. He could only makethe weaker claim that we cannot conceive of the immaterial mind as having struc-ture.


nation of the mind parallel with physical explanations in terms of struc-ture. The Gassendist response is simply to point out that Descartesdoes not offer us any other sort of explanation, so that the Cartesiantheory of the mind not only fails to provide us with a science of themind but also seems to preclude the possibility of our developing one.

We have now seen why Gassendi rejects both the claim that theessence of body is extension and the claim that the essence of mind isthought. Because of this, together with the new explanatory problemsraised by the hypothesis of an immaterial thinking substance, Gassendidismisses Descartes’ claim that mind and body are two distinct sub-stances. It is now time to turn to the account of the mind Gassendi cansuggest in its place.13

Human Knowledge of the Mind

On Gassendi’s account, it will turn out, our knowledge of the mind isquite strictly limited. We know various modes or accidents of the mindby reflective experience, but the mind itself – the inner substance ornature which grounds and makes possible these modes or accidents – ishidden from sensation and reflection. Thus acquiring an idea of thesubstance of the mind can only be done through signs, by means of thefollowing process. First, I perceive my various thoughts and feelings byreflection, and then construe those thoughts as signs of a hidden some-thing which must exist in order for the existence of the thoughts to bepossible. I thereby form a notion of a role: being that whose existencemakes thoughts possible. Finally, I form an idea of the thing which fillsthat role, by analogy with something I already know. But since every-thing I know I originally knew through the senses, the basis of my anal-ogy will always be a sensible, corporeal thing, so that my idea of themind will always be the idea of a thing analogous to some corporealthing. Here Gassendi favors the use of a ‘subtle body’ like wind or etheras the basis of analogy:

13 Until this point, Gassendi’s objections to the Cartesian account of knowledge ofthe mind or its nature may strike the reader as very similar to those later made byMalebranche (save for Gassendi’s allowing that we could have a clear idea of athing without thereby knowing its nature). The chief difference, that for Gassendiour idea of the mind must be the idea of a material thing even though we knowthrough other means that the mind is immaterial, will become clear in the nextsection.

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As for the ideas of allegedly immaterial things, such as those of God and an angeland the human soul or mind, it is clear that even the ideas we have of these thingsare corporeal or quasi-corporeal, since (as previously mentioned) the ideas are de-rived from the human form and from other things which are very rarefied andsimple and very hard to perceive with the senses, such as air or ether (3.386a).

Now, it is notable that Gassendi does not claim that the idea of themind as some sort of subtle body is a terribly good idea. In fact, Gas-sendi’s account makes it clear that the human idea of the mind is quitea bad one. For one important criterion for ideas acquired through theuse of signs is this: they are good ideas to the extent that what the idearepresents really would make possible the manifest properties andoperations of the thing in question. That is, ideas acquired on the basisof signs are good ideas only if they have some significant explanatorypower, since they are acquired by a sort of inference to the best expla-nation – in fact, the only explanation – to begin with. Now, Gassendidoes not claim that his idea of the mind as a sort of subtle body actuallydoes any significant work in explaining the manifest properties and op-erations of the mind. In fact, as we have seen from the argument againstDescartes, Gassendi thinks that we have no understanding of how theseproperties and operations are possible.

Here, then, is the situation. Gassendi claims that we have some ideaof the mind, in that we can talk about it and we know some of its pos-sible accidents and operations, but denies that our idea of the mind issufficiently good to count as revealing to us the inner substance ornature of the mind. At the same time, Gassendi is quite harsh in criti-cizing Descartes for claiming to know the nature of the mind when allhe really has is the vague and entirely non-explanatory conception of itas some unknown thing that is not material. One might wonder at thispoint if Gassendi’s criticism is fair: isn’t he in more or less the sameposition as Descartes here?

I answer that he is not, for two reasons. First, Gassendi would saythat at least his account of the mind makes the idea of the mind an ideawe can have. We have no problem conceiving of a sort of subtle body in-terspersed throughout the coarser matter of the brain but, Gassendi ar-gues, Descartes’ “immaterial substance” is something we can conceiveof only to the extent of saying that it is like a material substance, only notmaterial. Gassendi has told us what the mind is, albeit not in any detail;Descartes has only told us what the mind is not. And telling us that themind is not material gives us no help in conceiving of what an imma-terial thing could be like (3.402b). Second, Gassendi himself neverclaims to know or have an idea of the nature of the mind. To say that the


mind is some sort of subtle body is no more to claim to know the natureof the mind than to say that a magnet is composed of atoms arranged inthe void in some way is to claim to know the nature of the magnet. Des-cartes requires an idea of the mind which is good enough to reveal themind’s nature, for the real distinction argument to work: we need toknow the nature of the mind in order to be certain that what underliesthe range of modes or accidents we know from reflection is not a speciesof body. This sets the bar for the idea of the mind pretty high – it has tobe such as to exhibit the nature of the mind to us, at least clearly enoughto distinguish it from body. But Gassendi does not attempt to deriveany dramatic ontological conclusions from his description of the mind,and hence his idea need not fulfill any such stringent criteria. Indeed, aswe are about to see, Gassendi argues that no ontological conclusions atall should be inferred from the idea of the mind.

Faith and the Human Soul

The reader might wonder, at this point, how a mid-seventeenth-centurypriest could have believed, let alone stated for publication, that we mustconceive of the mind as material. Isn’t this, one might ask, dangerouslyclose to a commitment to materialism? Isn’t Gassendi in danger of vi-olating the requirements set out in the condemnation of Pomponazzi,for instance? However, Gassendi takes pains to point out that his claimthat we conceive of the mind as material is a claim about human cogni-tion rather than an ontological claim. In matters of ontology, Gassendimakes clear, he follows the dictates of faith:

I hold by Faith that the Mind is incorporeal. I hold that this issue appears too ob-scure by the natural light for me to claim to know the nature of the Mind […] it isnot apparent how, while the Mind dwells in the body, it can represent or under-stand any substance except under some corporeal species [and thus it is not appar-ent] under what species the Mind might represent itself other than as some subtlebody (3.369a).

A number of conclusions are to be drawn from the claim that we knowby faith that the mind is material, even though the mind must representitself by means of a corporeal image and thus must represent itself ascorporeal. The first such conclusion is that our idea of the mind isdeeply misleading. But this seems to raise a problem of its own, in theguise of a possible conflict between the deliverances of faith and rea-son. Fortunately, however, Gassendi has the resources to avoid any suchconflict – resources which we have already seen. First, on Gassendi’s

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view, the idea of the mind as a corporeal entity is not a very good ideaeven by its own light. And second, we can see, again from the theory ofsigns, that we would think of the mind as material regardless of whetheror not it actually is material. For the explanation of why we must con-ceive of the mind as material makes no reference whatsoever to the ac-tual nature of the mind but only to the nature of things evident to usthrough sense. Thus reason itself makes us aware that our idea of themind as corporeal is unreliable.

But in what position are we left when we conclude that reason’sdictates about the mind are systematically unreliable? Does this, forinstance, leave us with complete skepticism about the mind, or is therestill a reason to continue natural philosophical investigations of themental? Gassendi can, I suggest, maintain the latter option. For heholds that empirical investigations like his investigations of theformation of ideas in the brain as a result of the physiological pro-cesses of vision give some further understanding of the mind. They donot penetrate into the nature or substance of the mind (any more thanmicroscopic investigation of the cheese revealed its atomic structure),but they do bring about some increase in understanding. That thenature or substance of the mind is in principle concealed from reasonneed not make us despair of getting further knowledge of the processesunderlying its manifest characteristics.

Indeed, Gassendi suggests, it is difficult if not impossible for us to at-tain knowledge of the inner substance or nature of anything known byobservation. Given this, we need to recognize that the difficulty ofknowing natures or underlying substances provides insufficient reasonfor skeptical despair. Granting that inner substances or natures arehidden, we can still have full knowledge of the manifest characteristicsof things – and it is knowledge of those manifest characteristics that istruly necessary for us. Making use of a distinction between essence andappearance – a distinction that he tends to equate with the distinctionbetween hidden substance and manifest properties – Gassendi tells usthe following:

since the attribute or property is one thing and the substance or nature of which itis [an attribute] or from which it emanates is another, so to know the attribute orproperty or collection of properties is not thereby to know the substance ornature itself. What we can know is this or that property of this substance ornature when it lies open for the purpose of observation and is perspicuous by ex-perience, and we do not thereby penetrate into the inner substance or nature –just as when looking at bubbling spring water, we know that this water comesfrom this source, but do not thereby strike the edge of our gaze on the interior


and establish the subterranean source. So, it seems, the good, all-powerful Godestablished when he founded nature and left it to our use. For whatever is neces-sary for us to know about every thing, he made open for us by granting thingsproperties through which we might come to know them and by granting us vari-ous senses through which we might apprehend them and an interior facultythrough which we might make judgments about them. But he willed that theinternal nature and, as it were, source be hidden, since knowledge of it is notnecessary for us (3.312b).14

Since God has allowed us to know what we need to know, by creatingthings with manifest characteristics that correspond to our ability toacquire sensory information and the power to reason about those mani-fest characteristics, it would be unreasonable of us to complain that ourcognitive faculties were not terribly well fitted for the knowledge of thehidden, underlying substance of things. It is unfortunate here that Gas-sendi does not tell us what it is that our knowledge of the appearances isnecessary for, as Locke does in similar passages: but I take it that whatGassendi has in mind here is simply the successful continuation ofeveryday life.

The passage just quoted is importantly ambiguous: Gassendi maymean that it is in keeping with how God arranged things that we do notnow know the nature of things, or that it is in keeping with how Godarranged things that we cannot in principle know the nature of things. Itis clear in the case of the mind that Gassendi thinks inner substance isin principle ungraspable – but the mind is, as we have seen, a ratherspecial case. Considering the corporeal example Gassendi gives us –“when looking at bubbling spring water, we know that this water comesfrom this source, but do not thereby strike the edge of our gaze on theinterior” – may help us to figure out whether substance is unknowablein principle or just unknown. I read Gassendi as saying here that whenwe look at the spring water rising from the ground we take it as a sign ofa hidden spring. We do not know exactly what the hidden spring is like:in particular, we have no direct idea of it. Rather, when we think of

14 Compare the following passage, made in the context of a suggestion that just asthe microscope has allowed us to explain some phenomena in terms of smallerinternal parts, we might be able to explain all the manifest properties of things ifwe could see the smallest parts of things (that is, the atoms), a possibility whosenon-actuality Gassendi bemoans: “since we are destitute of vision of this sort(that is, microscopic vision), and since there is no great hope of ever obtainingsuch a splendid microscope […] should we, I ask, be content with those things forthe purpose of whose knowledge – as [that knowledge] alone is necessary for us –our author has instructed us?” (2.463b).

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the hidden spring we imagine something by analogy with springs wehave seen. Now, such an analogical idea can never be as certain or asinformative as a similar idea acquired through sense, on Gassendi’sview: what is known by the use of indicative signs does not transcendprobability, whereas our knowledge of the manifest is, in the best cases,entirely certain.

I take this to imply two things about knowledge of hidden, corporealsubstances, on Gassendi’s view. In practice, we do not know any ofthem as completely as we could. And even in principle, we cannot haveknowledge of them which is as evident and certain as our knowledge ofwhat is directly sensed. For the only way we could have such knowledgeis if, per impossibile, we could literally perceive the inner substanceitself. One might wonder whether Gassendi thinks we will ever get eventhis less certain kind of knowledge concerning the hidden substances ofcorporeal things. I cannot claim with any confidence to know whatGassendi really thinks here; he certainly does not commit himself oneway or another. Perhaps he does not want to venture a guess aboutwhether we will ever get far enough with the programme of corpuscu-larian natural philosophy to get down to the level of the atoms or not.Such a refusal to speculate would be entirely in keeping with his philo-sophical temperament.

I have argued that Gassendi’s conceptual materialism about the mindco-exists peacefully with his claim that we know, at least by faith, thatthe mind is immaterial. Given the limitations his theory of the cogni-tive faculties places on itself, we have no reason to see any principledtension between the two claims, and hence no reason to think that hissubmission to the dictates of faith is in any way philosophically prob-lematic. Thus the reading I have offered opposes that of Olivier Bloch,who takes the case of the nature of the mind as one of the strongestexamples for his overarching thesis that Gassendi fails to systematizeand make fully coherent his philosophy in order to avoid confrontingthe tension between orthodox religion and the materialist philosophyhe was in the process of developing. Bloch grants that Gassendi maywell have been personally sincere, but holds that his philosophy has astrongly materialist orientation15, an orientation that does not becomefully explicit because of the tension which would be created if it did.Now Bloch’s reading relies on his understanding of such episodes as theobjections to Descartes as themselves requiring materialism. He does

15 Bloch 1970, 156f.


not seem really to consider the possibility that these claims should beread as claims about our knowledge of the mind rather than about themind itself. And, so far as I can see, if he did not read the Disquisitio inthe way he does, he would not see any such tension between faith andphilosophy in Gassendi’s work. I have argued that a more nuancedreading of the Disquisitio and Gassendi’s account of knowledge of themind shows that he is not committed by what he says there to ontologi-cal materialism: quite the contrary. Hence I take myself to have dis-solved the chief motivating factor for Bloch’s diagnosis.16 And sincethere are strong, although not indefeasible, reasons to avoid ascribingrelatively blatant inconsistency to historical figures, I take that showingthat there is a coherent alternative to Bloch’s interpretation by itselfgives good reason to accept that alternative.

Gassendi’s Later View

Gassendi’s later work contains what at first looks like a dramatic change of opinionfor him: a set of arguments alleged to show that the mind is immaterial.17 He providesthree examples of operations performed by the mind which in principle could not beperformed by a material thing. First, the mind or intellect can understand itself andits functions, while no material thing can act on itself directly.18 Second, the mind canapprehend certain notions lacking imagistic content (such as the notion of an imma-terial substance, formed by way of negation) (2.440b). Third, the intellect can havesome grasp of universals although genuine universals cannot be apprehended bysense or derived from sensory apprehension (2.441b). These are traditional argu-ments, and it is interesting to note that Gassendi often ran them in reverse in his ear-lier work, arguing, for instance, that we cannot entertain genuine universals becausewe lack the immaterial intellect needed to do so.

What matters for present purposes, however, is what these arguments for the im-materiality of the mind imply. They are supposed to be probable arguments, based onreason, to the effect that the human soul cannot be corporeal. Thus they are not in-tended to show, as Descartes’ argument is intended to show, that the human soul is asubstance individuated by something we grasp which rules out corporeality. Gas-sendi neither says anything that seems intended to establish that the incorporeal

16 More recent English secondary literature has not tended to endorse Bloch’s read-ing: see Michael and Michael 1988, Osler 1994 and Sarasohn 1996.

17 For a full account of this, see Michael and Michael 1988, 483f.18 2.441a. It is odd that Gassendi here runs together the mind’s capacity to reflect

on itself directly – which Gassendi explicitly denies in the Disquisitio – and itscapacity to notice its functions – which Gassendi allows in the Disquisitio butdoes not seem to think requires incorporeality.

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mind is a substance,19 nor anything suggesting that we have some positive grasp onthe nature of the incorporeal mind. Although the claim that the intellect can reflecton itself directly seems as if it should imply that we can form a positive conception ofour own minds, Gassendi does not offer any description of such a conception, butrather holds that our idea of the mind is formed by negation. Our idea of the incor-poreal mind is the idea representing some thing, different in kind from the corporealthings we experience because incorporeal, which can perform these three operations.

This idea is barely, if at all, more informative than the earlier idea of the mind as acorporeal subtle body. Certainly it gives us no more resources for further investi-gation of the mind. Indeed, it is remarkable that when Gassendi makes this shift tothe claim that we know by reason that the mind is immaterial, nothing else in hisaccount of the mind changes. The claim that the mind is incorporeal neither rules outthe physiology of impression-formation in the brain nor provides us with any new ex-planation of the states and operations of the mind. Gassendi’s switch in views bringstogether the ontologies suggested by faith and natural philosophy without makingany impact on natural-philosophical accounts of the mind.

We should have expected this. Recall Gassendi’s objection to Descartes that postu-lating a simple, indivisible, immaterial mind rules out any explanatory resources.Now, while Gassendi does not explicitly assert that the incorporeal mind is simpleand indivisible, he does not think that our idea of it depicts it as having any parts orstructure, and hence it is no more useful for explanatory purposes than an idea rep-resenting a simple, indivisible, incorporeal thing. Thus on Gassendi’s view, whetheror not we have an idea of reason of the mind which is in keeping with the dictate offaith that the mind is immaterial, the immaterial mind whose existence we accept hasnothing to do with the natural philosophy of the mind. I take this to be a straight-forward expression of Gassendi’s commitment to discovering the limits as well as theextent of human knowledge.20

19 It seems most natural to think that Gassendi’s incorporeal mind is a thing, but hedoes not really tell us so. For all he says, the incorporeal mind might as well be aform. Although he argues elsewhere that explanation in terms of forms is vacu-ous and unhelpful, this does not rule out the possibility of saying that there isa form in a case where he has already said that full explanation cannot be given.Indeed, he does not rule out the Lockean view that the mind may be an imma-terial power, although there is no evidence that he thinks this and, indeed, doesnot much trade in the language of powers.

20 Part of the research for and writing of this paper was supported by a fellowshipfrom the Huntington Library. I would like to thank the Huntington for its gen-erous support. I would also like to thank two anonymous referees for this journalfor helpful comments on a previous version of this paper.


Arnauld, A. 1990. On True and False Ideas. Transl. Stephen Gaukroger. Manchester.Bloch, O. 1970. La Philosophie de Gassendi. The Hague.Descartes, R. 1973–1978. Œuvres de Descartes. Ed. Charles Adam and Paul Tannery.

Paris.Gassendi, P. 1658. Opera Omnia in sex tomos divisa. Lyon (reprint: Stuttgart-Bad

Cannstatt 1964).Michael, E. and Michael, F. 1988. “Gassendi on Sensation and Reflection: A Non-

Cartesian Dualism”. History of European Ideas 9.5: 483–495.Osler, M. 1994. Divine Will and the Mechanical Philosophy. Cambridge.Sarasohn, L. 1996. Gassendi’s Ethics. Ithaca, NY.Wilson, M. 1978. Descartes. Boston.

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