# “Diderot and materialist theories of the self”

Charles T. Wolfe

► To cite this version:

Charles T. Wolfe. “Diderot and materialist theories of the self”. Gábor Boros, Judit Szalai and Oliver Istvan Toth (eds.). The Self and Self-Knowledge in Early Modern Philosophy, Eötvös Loránd University Press, pp.37-52, 2020, 978-963-489-228-1. halshs-04242985

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Distributed under a Creative Commons Attribution 4.0 International License
Gábor Boros – Judit Szalai
– Olivér István Tóth (eds)

Personal Identity
and Self-Interpretation
& Natural Right
and Natural Emotions

Budapest Seminars in Early Modern Philosophy 2 & 3
© Authors, 2020

© Editors, 2020

ISBN 978-963-489-228-1

ISBN 978-963-489-229-8 (pdf)

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www.eotvoskiado.hu

Executive Publisher: the Dean of the Faculty
of Humanities of Eötvös Loránd University

Layout: Ádám Bornemissza

Cover: Ildikó Csele Kmotrik

Print: CC Printing Ltd

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# Table of Contents

Introduction .................................................................................. 7

## PERSONAL IDENTITY

Judit Szalai: States of the “Person” in Descartes .................................... 13

Przemysław Gut: Leibniz on Personal Identity ............................................ 22

Charles T. Wolfe: Diderot and Materialist Theories of Self ............................ 37

Ákos Forczek: Apperception and Affinity: Kant on the Material Condition of the Identity of the “Psychological Person” ............................................ 53

## SELF-KNOWLEDGE

Bartosz Żukowski: Richard Burthogge's Epistemology and the Problem of Self-Knowledge .................................................... 69

Peter West: Knowing Me, Knowing You: Berkeley on Self-Knowledge and Other Spirits ................................................................................ 84

## NATURAL LAW

Wilhelm Schmidt-Biggemann: The Space for Emotions in Natural Law ...... 107

Szilárd Tattay: Francisco Suárez and Modern Rationalist Natural Law Theories ................................................................................ 121

Gábor Boros: Natural Right and Worldly Emotions of Love: Descartes, Molière, Spinoza ................................................................................ 139

Heikki Haara: The Concept of Simple Esteem in *De jure naturae et gentium* ... 153

József Simon: Shame, Common Wealth and Religion in the Thought of Miklós Bethlen (1642–1714) ................................................................. 167
<table>
  <tbody>
    <tr>
      <td>Mariangela Priarolo: Love and Order: Malebranche and the Feeling of Natural Law</td>
      <td>188</td>
    </tr>
    <tr>
      <td>Paolo Santangelo: Chinese Cultures of Love: The “Cult of Qing” and Qing’s “Naturalness”</td>
      <td>198</td>
    </tr>
    <tr>
      <td>LIST OF CONTRIBUTORS</td>
      <td>221</td>
    </tr>
  </tbody>
</table>
Diderot and Materialist Theories of Self

"I am me because my little dog knows me but perhaps he does not and if he did I would not be me."

(Gertrude Stein, "Basket a story interlude," in Stein 1936/1995, 198)

Introduction

A materialist theory of self must be able to respond to certain objections, explain certain phenomena and reach a certain degree of articulation. The same applies for specifically early modern versions thereof, which shall be my concern in what follows. Our familiarity with the diverse forms of early modern materialism has grown a great deal in recent decades, marking a considerable advance over older (if still regrettably common at times) views of materialism as inherently mechanistic, fixated on the idea of the body as machine, or denying basic features of embodiment. But what of the self? I shall discuss the materialist treatment of the self, and overall the cluster of problems concerning selfhood, individuality and personal identity in various authors, but most centrally in Diderot. My analysis is neither a standard internalist reconstruction of a problem in Diderot, with passing mention of other period authors, nor an intellectual history-type survey of a problem in the period, with discussion of as many authors as possible. It is, as the title indicates, a reflection on Diderot *and* materialist theories of the self. That is, I aim to reconstruct a problem, and will suggest that Diderot puts forth one of the more significant and original versions of a materialist theory of the self – but one which, of course, appropriates elements from other authors.

The self was often seen as simply a part of the classic 'matter and mind' problem. Thus the salonist Suzanne Necker (later mother of Mme de Staël) reprises classic Cartesian points but to speak of the self: "half of a *self* is a contradictory absurdity, while a portion of matter that cannot be divided is also a contradiction: how can mind and matter not be different substances?" (Necker 1798, III, 88). One should note that this shift to the problem of the self presents a particular kind of conceptual challenge. Why should the materialist approach to the self be particularly challenging? Because the latter belongs to a time-honoured family of philosophical intuitions which are perennially presented as light years removed from the world of materialism. From Augustine (*Confessions*, X, 16, 25) to
Descartes and on to Paul Ricoeur (1992), or from Kant and Schelling onto Husserl and Heidegger (but also Wittgenstein, Anscombe, Chisholm, Nagel, etc.), we are told in endlessly varied ways that the self is not, to borrow Wallace Stevens' elegant line, "composed of the external world":<fnref n="1" /> that the self is not of the material world, whether this has to do with its lack of divisibility, its temporal essence, the inner sense, grammatical properties of the first person, or other "facts".

Contrasting with such views (or intuitions, which is often what they are), I point to the existence of an early modern materialist discussion of self – an intellectual “tradition”, even if it lacks direct transmission or continuity. It is early modern inasmuch as it extends, in the authors I focus on here, from Spinoza and Locke to Diderot. Indeed, I do not believe that the attempt to combine thoroughgoing materialism and a concept of self is somehow a “timeless” feature of materialist thought, and it may well be the case (although I make no such metahistorical claims on my own account) that concern with the self is a post-Cartesian development, in the sense of the Augustinian elements in Descartes, or even Luther on some readings (see Menn 1998 on the former and Schürmann 2003 on the latter).

This materialist approach to the self can take (at least) three forms, which occur independently of one another (e.g. in Spinoza or La Mettrie) but which can also be combined, as they are in admittedly programmatic form in Diderot. These are: externalism as a meta-physical position (§ 2), the biologization of individuality, i.e. a justification of individuality in biological terms (§ 3), and the equation of brain and self, in a reductionist approach to the problem of personal identity (§ 4), although ultimately 2 and 3 are the basic “planks” of the theory. In conclusion (§ 5) I suggest that rather than being “blind to the world of internal life” as was often claimed of materialism, there can be something like a materialist theory of self, notably but not exclusively as sketched in Diderot. Differently put, rather than a whole-scale elimination of the mental, the early modern materialist approach could also be a “naturalization” of the mental – an inscription of mental life in the broader natural world, which does not make it disappear as if by waving a wand (a separate issue is how early modern materialism might relate, or not relate to the emergence of psychology as a science).

## Externalism

Discussions of “person”, “self”, “experience”, even when they bring in an embodied, material dimension, frequently appeal to a *first-person* concept of experience. This is usually opposed to a *third-person* view, typically presented as the point of view of the natural scientist with her measuring instruments. Many philosophers hold that we will *never know what it is like* to have someone else’s first-person experience. There is something here like an opposi-

<footnote n="1">1 To be clear, Stevens's line goes the other way: "the soul, he said, is composed of the external world." (Stevens, "Anecdote of men by the thousand", in Stevens 1997, 41).</footnote>
tion between the internal and external; between internalists and externalists, in the sense
I will elaborate on below (namely, about epistemic content and indeed about the status of
minds in the physical world, not as semantic theories). I will defend a version of external-
ism in the following section.

By externalism I do not mean a semantic theory or a social theory of mind (at least two
of the other senses of the term)<fnref n="2" /> but rather the position according to which mental states
lack any inaccessible, “first-person” dimension; any such dimension would be either ex-
plainable in external terms or traceable to processes in the agent (the nature of which need
not be specified, as indeed the Identity Theorists of the 1960s–1970s did not, but we could
think of them as brain processes), which produce a “feeling” of interiority. The externalist
does not need to deny that a person has experiences, but she does not hold that experience
is thereby inaccessible, radically private, incommensurate with the rest of the physical uni-
verse. If the internalist holds that “States, or experiences [...] owe their identity as particu-
lars to the identity of the person whose states or experiences they are”, as in Cudworth’s
conception of the self as *to hegemonikon* or as defined by *sui potestas*, endlessly echoing itself
(Cudworth 1996, X, 178), the externalist holds that “no fact is only accessible to a single
person”<fnref n="3" /> and deplores, as Diderot does in § X of his 1753 *Pensées sur l’interprétation de la
nature*, that it is easier to consult oneself than to consult Nature.

The externalist will hold that any sense of unity, any foundational dimension of self-
hood, in fact comes from *outside*. Materialism implies externalism but externalism does
not imply or entail materialism (a vision of the mind as social, including as behaviourally
constituted in a world of activity, is not committed to a materialist metaphysics).<fnref n="4" />

One can also see the distinction between internalism and externalism in the difference,
familiar to scholars, between the Cartesian *cogito* and the Spinozist *homo cogitat* (*Ethics
IIa2*). That “homo cogitat” is not a foundational property of a first person; the self, and its
key property, thinking, is not *foundational*. To be a thinking subject is simply to belong
to the universe of causal relations, to be a particular intersection within it (compare Renz

<footnote n="2">2 Notably in Putnam’s sense. Tyler Burge’s “social externalism” (e.g. Burge 1979) takes an ontological step further but is still about “mental contents”, whereas the “Spinozist” externalism I am suggesting here is straightforwardly ontological (if any such thing is straightforward), although it shares the suspicion (or deflationary attitude) towards any a priori, privileged self-access. Thanks to Ville Paukkonen for making me clarify this point.</footnote>

<footnote n="3">3 Strawson 1959, 97 and Dretske 1995, 65 (although of course some would accept this claim and nevertheless argue that some objects of knowledge are not facts – thanks to an anonymous reviewer for this point).</footnote>

<footnote n="4">4 It is possible for there to be a materialist who is not also an externalist, in a rather forced thought experiment in which there only exists one atom. But from Lucretius to Hobbes, the anonymous *Theophrastus redivivus* of 1659, Collins, La Mettrie, d’Holbach, Priestley, Cabanis, Büchner and Vogt, Dewey, the Spinozist social psychologist Lev Vygotsky, Quine in some moods, D.M. Armstrong, David Lewis and present-day physicalism, materialists are externalists (names missing from this list are not non-externalist materialists, but rather materialists like Toland or J. J. C. Smart who do not offer a position on the matter). On externalism in a non-materialist context as a social theory of mind in Locke, see Lenz 2013, and for a different, but complementary perspective, Wolfe 2010.</footnote>
2017). In Spinoza's memorable phrase, "The order and the connection of ideas is the same as the order and the connection of things."<fnref n="5" /> For the externalist, no fact, datum or *vécu* belongs to a private, off-limits zone, for what is first is not the thinker but the web of relations to which thought belongs. Of course, Spinoza doesn't content himself with this static vision of a grid of relations; he emphasizes that any such particular "individuated" entity strives to persevere in existence, as the finite mode it is. I cannot improve on Morfino's summary:

> [F]or Spinoza the individual is neither substance nor subject [but...] is a relation between an outside and an inside constituted by this very relation (there is no absolute interiority of the *cogito* opposed to the absolute exteriority of a world). This relation constitutes the essence of the individual, comprised of its own existence-power. [...] It is a variable power, precisely because the constitutive relation between inner and outer is unstable, not established. The passions are not, therefore, the property of an already given human nature, but they are relations constituting the human individual; *their locus is not interiority, but the space between individuals*. (Morfino 2006, 118; trans. modified, emphasis mine)

The externalist has a *relational* definition of what it is to be an individual, as a particular portion of a given, causally closed space-time, of a state of relations which constitutes a given individual – an oak tree, a stag beetle, Mutlu the cat – *qua* that which resists decomposition (a “conatus ad existendum”). Of course, to claim that Spinoza defines the individual as a relation, or gives ontological primacy to relation, may seem to run counter to the obvious fact that Spinoza thinks the individual is defined by its own conatus, its own essence (EIIIp9s: the conatus is our essence). Yet the relational view has in favour of it equally core Spinozist definitions: our body needs a great number of other bodies to survive (EIIp13, 4th postulate), just as our mind would be imperfect if it only took itself as an object (EIVp18s). In addition, bodies form a single body or individual when their movements are related to one another (or when they “communicate” according to a precise ratio or relation: EIIp13d). In sum, we are defined by a certain ratio, proportion or relation of motion and rest (*ratio motus et quietis*).<fnref n="6" />

For the externalist, an experience, a desire, or a belief do not belong *de jure* to a constitutive subject, but rather *de facto*, to a subject which *they* constitute. As Dewey put it,

<footnote n="5">5 *E* IIp7; see also IIIp2s. This is an ontological assertion of the primacy of relations; some readers, including Vygotsky, also viewed it as expressing the non-independence of mind and brain with regard to this world. (Vygotsky 1972, 362–82).</footnote>

<footnote n="6">6 Beyond the comment to Jarig Jelles, Spinoza can handle individuality structurally, as a particular ratio of motion and rest: *E* IIp13s (the physics), esp. lemmas 1 and 7s.; *Short Treatise*, appendix, II.14 – leading, however, to troubles such as the case of the Spanish poet (*E* IVp39s). At the structural level of ratios, he is the same person, *certa quadam ratione*; at the level of his mind, he is not. See also Toto 2015, 65.</footnote>
We live from birth to death in a world of persons and things which is in large measure what it is because of what has been done and transmitted from previous human activities. When this fact is ignored, experience is treated as if it were something which goes on exclusively inside an individual's body and mind. It ought not to be necessary to say that experience does not occur in a vacuum. There are sources outside an individual which give rise to experience. (Dewey 1938/1963, 39)

Indeed, the subject is constituted by her progressive filtering (and filtering out) of the world, which also serves as an argument against scepticism, according to the idea that the senses are made for x. This sensory filtering is described in Diderot's important, but at the time unpublished *Rêve de D'Alembert* (1769) as constitutive of our individuality: no one's sensory make-up is identical to anyone else's sensory make-up. “The animal is a unified whole” for Diderot, both because of its specific physiological constitution (*organisation*) and specifically because of what he calls its organic *continuity*, as distinct from the mere *contiguity* of parts.<fnref n="7" />

The limits of my sensory system are also my limits as an individual, in the sense that however much all of matter may be living matter, I cannot sense what is happening on Saturn, for between me and this planet “there are only contiguous bodies, instead of continuity” (*Rêve de D'Alembert*, in Diderot 1975–, XVII, 142). Elsewhere, in the *Éléments de physiologie* (hereafter EP), Diderot puts it this way: “if external sensations [...] and inner sensations were equally intimate to me, *everything* would be me, and I would be *everything*” (Diderot 1975–, XVII, 460). I don’t perceive the cosmos directly (my perceptual apparatus acts as a filter); if I did, the barriers of my self would somehow be the barriers of the world. For sensation (perception, experience) are both real and constitutive of self here.

The self is constituted from without, and the sensory part of this process entails that no two subjects will perceive the same object in the same fashion. This is the properly materialist way of accepting that someone's life history, including the larger-scale evolutionary history, is constitutive of their being. Notice that we have a criterion of personal identity here: “For any organism x and any y, if x = y if and only if x's life is y's life” (Olson 1997, 138). And since externalism does not mean that my self is equal to the universe as a whole, we can see something of a biological emphasis being smuggled in here. If I am not defined by a free, unconditioned inner space of interiority, but by a multitude of “petites perceptions” (often interpreted in determinist and materialist terms in the early eighteenth century, e.g. by Anthony Collins in his *Inquiry Concerning Human Liberty* of 1717; see Wolfe 2007) crisscrossing in my mental life, by my physiological constitution, by “the blood which flows

<footnote n="7">7 Diderot, *Eléments de physiologie* (hereafter ÉP), in Diderot 1975–, XVII, 335; *Rêve de D'Alembert*, in Diderot 1975–, XVII, 140, 142. Diderot always insists on the specificity of each individual's *organisation*.</footnote>
in my veins”, as La Mettrie would have it,<fnref n="8" /> then we have gradually shifted from externalism per se to a *biologization of individuality*.

## The Organic Self

There is nothing novel or particularly radical about philosophy turning to the biological world to obtain its “best definition” of what an individual substance is; think of Aristotle, who tended to use actual organisms as paradigm cases of individual substances, or in contemporary parlance, “paradigmatic individuals”.<fnref n="9" /> But it is a further step to say that the traits associated with our interiority are themselves biological in nature – whether it be the “inner sense”, intentionality, the synthetic unity of apperception, consciousness, and so on. Indeed, one author, Nietzsche, warned in the late nineteenth century against committing a sort of category mistake and confusing the self with the “feeling of organic unity” (“Das Ich – nicht zu verwechseln mit dem organischen Einheitsgefühle”: fragment from Spring–Fall 1881 = M III, 11(14), in Nietzsche 1973). I am interested in the narrower class of thinkers who explicitly disobey the Nietzschean warning not to confuse the self with the feeling of organic unity, or in more general terms, who think that *facts about selves*, including experiential ones, *might turn out to be biological facts*, i.e. that “personal” facts are actually “organismic” facts, and as such (unless biology should be restricted to genetics or molecular biology), biological facts. Of course, even in this narrower class we can find the argument running in two contrasting directions: either

— a *reductionist* direction, in which the thinker will retain whichever experiential, existential or phenomenal properties can be successfully preserved after a reduction to the biological facts

or

— a *holist* direction, in which there is a “transfer” of subjective properties onto biological entities, usually the “organism” (which is one major reason for the bad

<footnote n="8">8 For La Mettrie, as he details in his *Discours sur le Bonheur*, each of us, the criminal and the honest man, are in pursuit of our own good – happiness, particularly understood as pleasure; whether I am virtuous or vicious depends “on my blood”: surely something individual, but equally surely, not the sort of individuality most philosophers of personhood would be happy with.</footnote>

<footnote n="9">9 Aristotle often insists that animals (not artefacts) are the paramount case of individual substances (*Metaph.* Z.7 1032319); Aristotelian scholarship since at least Montgomery Furth’s tour de force work (ultimately presented in Furth 1988) has spoken of animals as “paradigmatic substances”: “Animals, in Aristotle’s view, are paradigm instances of substance-being” (Kosman 1987, 360). For the notion of individual substance in contemporary philosophy of biology, see Hull 1992, 182 and Richards 2010, 164–5 for discussion.</footnote>
reputation of the concept of organism in some circles, as it is taken to be a kind
of “last gasp” of Romantic subjectivism within biological theory).

Both of these are naturalistic, but the former squares more easily with most understand-
ings of naturalism (admittedly a rather loose term), while the latter, because it will insist
on retaining a modicum of subjective language (from self and selfhood to “inner states”,
“experience” and the like), can be deemed unnaturalistic on some accounts. Now, the
more reductionist version of a biological theory of self will equate “self” with a set of bodily
or even cognitive processes or states, to be specified (and this place-holder quality raises
further questions I do not address here, such as: is it an evolutionary account? cerebral?
neurobiological? etc.), which is not the same as the eliminativist view according to which
no such thing as the self exists.

Why is the above reductionist option not the same as eliminativism? To take a clas-
sic example from a self-proclaimed early modern materialist, La Mettrie: when he writes
that “The soul is just a pointless term of which we have no idea and which a good mind
should only use to refer to that part of us which thinks” (La Mettrie 1987, I, 98), is this
reductionist or eliminativist? Contemporary terminology relies on the distinction between
reductionism and eliminativism, both of which have a respectable materialist pedigree. In
the above case (the existence of the soul), eliminativism holds that the soul and all of its
properties that have been described and argued over from, say, antiquity and Scholasticism
through Swedenborg does not exist and indeed none of these properties are real; thus, what
is real would be the brain, or the heart, or the stomach, and so on. Reductionism holds
that the soul (to stay with the same example) is indeed not something that exists in any
traditional sense; but notice that when La Mettrie says above that we really should only use
the word to refer to “that part of us which thinks”, he is not saying mental faculties do not
exist but that we need to rethink what their “seat” is, where they come from, and the extent
to which they are independent from the rest of bodily processes, or not. However, he is not
suggesting a weaker thesis, which would be that soul/mind might be autonomous in some
sense but could be “defined in terms of” bodily processes. The materialist theories of self
discussed here share a commitment to reductionism, but not to eliminativism (although
the extent to which this distinction is clearly applicable to the texts at hand is unclear).<fnref n="10" />

I shall take Diderot as my major example of the biologization of individuality. For Diderot, materialism definitely implies a degree of reduction – a deflationary or destructive impulse to trace back, as he writes to Damilaville, “our most sublime feelings and our purest tenderness” to “a bit of testicle” (Nov. 1760 letter, in Diderot 1955–1970, III, 216). But this is not a reduction of human or animal action or personhood to the action and necessitation

<footnote n="10">10 Not just in the early modern context, but also in contemporary philosophy of mind, some authors are not clearly reductionist or eliminativist despite being naturalists, such as Dennett who views the self as a fictional entity, but one which is useful in evolutionary terms (Sturm 2007, 173). A significant precursor of Dennett’s here is, of course, Dewey.</footnote>
of falling stones or clockwork. It is a reduction to the animal, so to speak – as when Diderot commented critically on Hemsterhuis’ 1772 *Lettres sur l’homme*, “wherever I read *soul* I replace it with *man* or *animal*” (Diderot 1975–, XXIV, 340). It retains an embodied focus, so that, e.g. properties of the soul are explained in terms of properties of the body (ÉP, Diderot 1975–, XVII, 334–335), not of fundamental physics. In the language of theory reduction, we could say that for Diderot, the reducing theory is biology, not physics (there was no physics to speak of, and more importantly, he felt that the cluster of theories later to be termed biology, and then referred to as “natural history” as a catch-all term, which indeed could mean the science of life in general, was the richest).

In the *Rêve de D'Alembert*, the character D'Alembert challenges the character Diderot to account for the self. Diderot has more or less successfully defended the concept of a living, sensing and thinking matter, but D'Alembert queries: “Could you tell me about the existence of a sentient being in relation to itself?”, that is, about the self-awareness of a sentient being. Diderot speaks in Lockean terms of memory as the basis for our self, with the materialist twist that memory itself is the product of our physiology (*organisation*). But later in this work the character Mlle de Lespinasse states how obvious it is to her that she is herself: “it seems to me that there is no need of such verbiage to know that I am me, I have always been me, and I will never be any other” (Diderot 1975–, XVII, 134).

Diderot’s materialist reply is that the self is itself the result of a construction of smaller elements – parcels of living matter. An organism is formed by adjunction of living points or animalcules, by purely material processes: “A hundred, a thousand times, I have seen the shift from inert matter to active sensitivity, to the soul, to thought, to reasoning – without any other agent or intermediary than material agents or intermediaries.” (*Observations sur Hemsterhuis*, in Diderot 1975–, 277). In this shift from inert matter to sensing, living matter, how do I *feel* that I am myself? For Diderot, the answer is: in and through my central nervous system – which is both *myself* and a guarantor of my relation to the rest of the material world in a constant process of exchange.

Diderot is one of the first materialists to explicitly take note of the “fact” that organisms are in part defined by their sense of unity, a unity he describes in the language of unified causality:

> without regard for the sum of elements of which I am composed, I am one, and a cause only has one effect; I have always been one single cause [une cause une], thus I have never had more than one effect to produce; my duration is thus nothing more than a succession of necessary effects. (*Jacques le fataliste*, in Diderot 1975–, XXIII, 190, 28)

In that sense, I cannot “do otherwise than myself” or “be anything other than myself” (ibid.). Diderot does not provide an extended philosophical commentary on this “single cause” or unified selfhood, but it is clearly a recurrent concern in his work, whether he is faced with its denial in other, more reductionist projects or its defence in “dualist” or otherwise implausible projects which neglect, for example, determinism.
Diderot’s articulation of an embodied materialism – not synonymous with “physicalism” – can help itself to some of the key features of selfhood, individuality and identity, which anti-materialists from More and Cudworth to Reid and Husserl insisted could not be present in a materialist analysis.<fnref n="11" /> Commentators often overlook Diderot’s critique of Helvétius’ *De L’Homme* (1773), which precisely focuses on the latter’s excessively “mechanistic” picture of behaviour as subject to standardized rules of social conditioning. Now, Diderot disagrees with Helvétius’ “social determinism” of operant conditioning, but unlike Cudworth, Clarke, Reid or Madame Necker, he does not do so in the name of an unconditioned, uncaused or otherwise “extra-territorial” self (Wolfe 2007). He finds Helvétius’ programme to be not only dangerous but condemned to fail, at the very least because of the irreducible “organic” or “psycho-physiological” specificities of each individual. But within that organic individuality, there is no homuncular self.

In that sense, the judgment, found in a study of Diderot, that “Materialism as a working philosophy, used as a tool in the scientific investigation of the material universe, is appropriate and highly effective. Intended for the objective analysis and description of the world of externals, it yields disastrous results when applied to the inner, subjective world of human nature, human thought, and human emotions,”<fnref n="12" /> is at best the wielding of a very blunt explanatory instrument, and at worst, a projection of a personal valuative decision onto seventeenth- and eighteenth-century texts. Both La Mettrie and Diderot, and most of their critics in the eighteenth century, would have been surprised to hear that materialism was an effective tool for science and for handling “the world of externals”, but not for the inner life. Perhaps Charles Bonnet would have been satisfied by this distinction, for he believed that his wholly naturalistic, causal, mechanistic analysis of the neurophysiological bases and correlates of psychological association was at the same time, non-materialist. And what is this inner, subjective world such that it should be left untouched by the materialist, who knows only “the world of externals”? As the French neuroscientist Marc Jeannerod wrote, it is dangerous to leave subjectivity to the philosophers…<fnref n="13" />

<footnote n="11">11 More 1653, XI; Cudworth 1996, as cited earlier; Reid 1788/2010, 4.4, and discussion in Yaffe 2004; Husserl 1989, § 32.</footnote>

<footnote n="12">12 Hill 1968, 90. I have developed my criticisms of this view of materialism a bit further (including with respect to ethics) in Wolfe 2016.</footnote>

<footnote n="13">13 Jeannerod 1983, 121. Jeannerod had in mind a kind of intellectual abandonment in which the life of the mind, the preserve of philosophers, is taken to be “subjective” and “qualitative”, while cerebral life per se would be “external” and “quantitative”. This is among other things, as he observes, an extremely impoverished vision of causality.</footnote>
Self and Personal Identity

If the biologization of individuality seems to enable the materialist to do justice to some core features of selfhood (on the condition that she is not a strict physicalist, in which case facts about the self would be declassified from any material standing, and relegated to qualia, folk psychology, etc.), the same cannot be said, or at least not as easily, of externalism. Thus a “qualitative” argument against externalism (which is, however, quite compatible with biological theories of individuality) will declare that there is something that it is like to be me, a special relation, which cannot be grasped from outside, and a for-tiori by the scientific, ‘third-person’ perspective. The world of relations seems to “drown” individuality: this seems to have been Montesquieu’s reaction to Spinoza, which I cite not least because of its vivid turn of phrase: he felt that Spinoza “deprived him of everything personal,” so he could no longer “find that self in which I was so interested”; “why glory? why shame? [...] in the universality of substance, both the lion and the insect have come and gone indistinguishably, both Charlemagne and Chilpéric” (Citton 2006, citing Mon-tesquieu at 77).

But if materialism is granted, should selfhood be located (a) in a set of relations, as a structurally defined feature, a "ratio of motion and rest" in Spinozist terms (as in *Ethics* IIp13s), (b) in an actualized, temporal, finite biological entity – with additional individuat-ing features to be specified involving its homeostatic equilibrium, its immune system, and so forth, or (c) purely in processes, such as Locke's continuity of consciousness over time?

Recall that Locke's celebrated theory of personal identity was in large part intended to avoid having to locate the latter in a merely material substance: "[those] who place Thought in a purely material, animal Constitution, void of an immaterial Substance" plainly "con-ceive personal Identity preserved in something else than Identity of Substance: as animal Identity is preserved in Identity of Life, and not of Substance" (Locke 1975, II.xxvii.12.). In addition to this "identity of Life," humans have a form of reflexive self-consciousness, a type of "privileged access" to ourselves in our ability to remember our past – despite prob-lems such as potentially fabricated memories – which we do not have in relation to others, including the narratives of others.

We are dealing here with memory, a type of privileged access crucial enough for it to be constitutive of personal identity itself. Yet Locke doesn't hold that memory *per se* is the guarantor of personal identity. This is what I termed a "processual" definition of selfhood: it explicitly aims to replace any substantial definition – including, of course a materialist definition. Of course, Locke is frequently agnostic about tensions between immaterialism and materialism, but in the present context he seems to lean in one direction: "the more probable opinion is that this consciousness is annexed to, and the affection of one individual immaterial Substance."<fnref n="14" />

<footnote n="14">14 Locke 1975, II.xxvii.25. However, two points allow for differing interpretations: the first, the extent to which Locke is “agnostic” about materialism, and the second, the extent to which Diderot’s materialist</footnote>
Is a materialist approach to personal identity instantly invalidated, or at least weakened, by Locke's anti-substantialist theory? Yes, if it meant understanding what a self or individual is (granted, these are not identical terms!) in strictly aggregative terms. To be clear, concepts of selfhood and of individuality are often run into each other in the texts of the period, as has been observed by Udo Thiel in one of the best studies of the topic (Thiel 2006, 296). But Locke's important insights are not fatal to a more organismic (and thus also relational) concept of self. That sentience is a feature of advanced organisms is taken by Diderot as an empirical fact (deriving from experiments such as Haller's on the nervous system: cf. Wolfe 2014; Duchesneau 2017). Granted, for a "Cartesian" or "Kantian", empirical facts are certainly not relevant to a decision about the nature of the mind, but that is a problem beyond the scope of this paper.

Recall Diderot's distinction between merely spatial and mechanical contiguity, and properly organic, indeed organismic, continuity: the latter concept includes an existential, processual, temporal dimension, in the sense that an organism is not just a "snapshot" of an organism. To cite Olson again, "For any organism x and any y, if and only if x's life is y's life." And the sophisticated materialist theorist of personal identity, not least a biologically inspired materialist, should not be unaware of the simple fact that the cells in our bodies change over time (an example which Locke thought was fatal to a naïve substantialist-materialist theory of personal identity). As Diderot himself reflects in *Rêve*: "through all the vicissitudes I experience in the course of my duration, given that I may not possess a single one of the molecules I was composed of at birth, how did I remain myself to others and to myself?" (Diderot 1975–, XVII, 163). Here the Spinozist point that what it is to be me is not so much a fixed set of material parts, but rather a *ratio*, is applicable. Think also of the case of our immune system (Pradeu 2012), which is neither reducible to a "thing" located at one fixed point in time and space, nor a *cosa mentale* which the biologically nourished materialist can say nothing about.

Yet the structural answer (which corresponds in more detail to what I have called "externalism") does not exhaust the materialist treatment of personal identity. In fact, Locke's emphasis on memory can be integrated therein, despite the seeming paradox (since it was intended to reject the material substantiality of the self). This integration is notably possible because of the shift in our understanding of memory as itself a cerebral function. That is, Locke rejects material criteria for personal identity and asserts the criterion of memory; but we would say today that the mechanisms of memory are cerebral functions! As Ludwig

<footnote>theory of memory can nevertheless be said to be Lockean or not (if personal identity is constituted by
the processual unification of thoughts and actions through memory, one can be "neutral" as regards
the substrate of this process: it is material in Diderot, but Locke would not have to disagree with this).
Thiel notes that some early critics of Locke even thought that Locke deliberately accounted for personal
identity in terms of consciousness and memory, and not in terms of the same substance, so as to open
the door for a materialist account of the mind: thus, Isaac Watts suspected that Locke "is so very sollici-
tous to make the *same Substance* unnecessary to *Personal Identity*, that so he may maintain his supposed
Possibility of Matter being made capable of Thinking" (Watts, *Philosophical Essays*, 3rd ed 1742, 302, cit.
Thiel 2011, 150). I thank Udo Thiel for discussion about this point.</footnote>
Büchner put it, “memory is merely the product of material combinations” (Büchner 1870, 131). Indeed, Diderot himself described memory as a “corporeal quality” (*EP* , in Diderot 1975–, XVII, 335) but also appeals to it in very Lockean ways, for instance when he criti- cizes Hemsterhuis’ version of a traditional immaterialist concept of personhood, stressing that without the memory attached to a series of actions, the individual, moving from sleep to wakefulness and back again, would barely be able to take note of her own existence. At the same time, this apparently “processual” rather than “substantial” concept is also integrated in Diderot’s conception of what I called above “the organic self”, as when he asserts that “the history of the life and the self of each animal is composed of the memory of its successive impressions” (*Rêve*, DPV XVII, 155). The structural here has become the corporeal, and/or the cerebral.<fnref n="15" />

Conclusion

The materialist theory of self need not be blind to or dismissive of all features of interior-
ity. While it is necessarily deflationary or reductionist towards selfhood qua interiority,
certainly as something foundational (the early modern materialist could very well have
said "You are *not* authoritative about what is happening in you, but only about what *seems*
to be happening in you." Dennett 1991, 96), the theory can, notably, integrate degrees of
embodied selfhood, qua biological individuality, given that it is not an outright physical-
ism (although depending how much a given thinker builds into their physics, like Hobbes
and his "small beginnings of motion" which account for both physical and mental forms
of striving,<fnref n="16" /> one can arguably go some distance towards an account of volitional and
other parts of mental life on such a physicalist basis...). Instead of denying the existence
of interiority, the materialist should try and locate it within the physical world, within the
overall framework of explanation (as Spinoza did). But since this materialism is not strictly
a physicalism but can appeal to biological information, it offers plenty of ways to under-
stand individuality, selfhood or agency – as in the “immunological self” (Pradeu 2012).
The articulation of externalism and the specifically biological or embodied dimensions
of certain forms of materialism can be expressed in a mantra of social psychology (here,

<footnote n="15">15 In this sense, Diderot may be an interesting “problem case” for the opposition between scholars such as Mijuskovic and Thiel, for Thiel rejects Mijuskovic’s claim that materialist theories seek to establish “personal identity on a model of bodily identity” (Mijuskovic 1974, 105) and emphasizes instead the Lockean dimension, according to which materialist theories of personal identity accept arguments against material-substantial continuity (Thiel 1998, 69). In this paper, Thiel suggested that “French materialist *philosophes* do not concern themselves very much with the special problem of personal identity” (Thiel 1998, 63n.); perhaps Diderot’s *Rêve de D’Alembert* merits a revision of this claim. (Thiel updated his views in his 2015 paper.)</footnote>

<footnote n="16">16 Hobbes 1976, chapter 33, § 2, 407; *De Cive*, IX, 9, in Hobbes 1992, II, 120, and Hobbes 1994, XXI, 1.</footnote>
prominent social psychologist Roy Baumeister): “Everywhere in the world, self starts with body.” (Baumeister 1999, 2).

The point is not that the materialist theory of self, for instance in Diderot’s version, encompasses all the positive features of all other theories of self without any of their negative features, but that classic oppositions between a world of agency, value, intentional states and privacy, and a “merely spatial” and/or mechanical and by extension somehow dehumanized world, need serious revision. This overlaps with a related problem concerning early modern materialism, when it is understood as somehow necessarily mechanistic (Wolfe 2017).

The theory as I have reconstructed it essentially comprises a “relational”, externalist metaphysics and a biological vision of individuality. The advantage of the biological perspective is that it preserves a certain realism; the power but also the danger of externalism as an ontology of relations, and of the reduction of personal identity, is that they lose trace of any existence of the self (as Spinoza was often reproached: the “selfhood” of one finite mode among others does not seem like the most appealing defence of the self). But this advantage – unless one has a kind of transcendental criterion with which to automatically reject any confusion between the self and the “feeling of organic unity” – brings with it the danger of “biologism”, and of a metaphysics of the organism, in which the fact that certain features of selfhood seem to be present in (some parts of) the biological world allow for a kind of a re-transcendentalization, notably of “the organism”. Hence the materialist theory of the self is a mobile (and modular) set of concepts, with its advantages and its disadvantages, its diversity and its limitations. Future histories or philosophical *survols* of the self might consider it worthy of inclusion.

## Acknowledgments

I wish to thank Udo Thiel for his comments on an earlier version of this paper, as well as Judit Szalai and an anonymous reviewer for their further suggestions.

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