The psychopathology of metaphysics: Depersonalization and the problem of reality

According to a common philosophical intuition, the deep nature of things is hidden from us, and the world as we know it through perception and science is, just like a dream, shadows, or a computer simulation, somehow shallow and lacking in reality. This “intui-tion of unreality” clashes with a strong, but perhaps more naive, intuition to the effect that the world as we know it seems perfectly real. Shadows, dreams, or in-formational structures appear too unreal to be identical to the world as we know it! This clash between the two intuitions forms the basis of the “problem of reality.” In the late nineteenth century psychiatrists encountered patients they referred to as “metaphysician doubters” who constantly questioned the reality of the world. This essay draws on studies of these patients in

peculiar.They bore exclusively on the reality of things around him and on his own reality.Ball coined the term "metaphysician doubter" to describe his patient's condition: "As for his preoccupations, they bear on the self and the real existence of the objects he perceives.He reproduces, without knowing it, the ideas and often the very expressions of the great philosophers who probed these abysses; but, less fortunate than Descartes, he cannot manage to conclude 'I think, therefore I am'" (Ball 1883, 44; all translations from French are mine).
This patient had a hard time describing exactly what was happening to him and why he could not help doubting the reality of things.Indeed, everything seemed to have the same apparent properties as before.As he said, objects "keep the same forms and colors" and "do everything the way they normally do."Still, they seemed "funny, strange," and as a result the "whole world seemed to him like a gigantic hallucination."In an attempt to summarize his condition, he said, "[T]he way I see things does not reflect what they are or that they exist, hence the doubt" (Ball 1883, 43).
This "metaphysician doubter," as Ball called him, or "pathological metaphysician," was not an isolated case.In the late nineteenth century, his condition was found to be rather common.At that time, psychologists were often doctors in philosophy, and they were prone to check that such pathological metaphysicians were not usually acquainted with philosophy at all and that their disorder could not accordingly be accounted for by poorly digested philosophical readings."These … ideas could stem," says Hesnard (1909, 144), "in a philosopher, from a metaphysical doctrine concerning the outside world.But we have carefully looked, in all our patients, for such external origins, and could never find one."In a 1909 book that describes many such pathological metaphysicians, the great psychologist Pierre Janet, who was both a medical doctor and a philosopher, lamented, "[W]hen one has seen many of these pathological doubters [scrupuleux], one comes to sadly wondering whether philosophical speculation is a disease of the human mind" (Janet 1909, 302).
I do not believe that philosophy is a mental disease, nor that Janet really believed such a thing.I would like to argue, however, that pathological metaphysicians such as these can teach us something philosophically important, and indeed help us solve, or maybe dissolve, an important and perennial problem in the phenomenology and epistemology of metaphysics, which I call "the problem of reality." Let me note at the outset that although I will talk a lot about the sense of reality, I will not try to define the term "reality" right away.In his Principia, Descartes (1969, AT I:x) famously claimed that "reality" is in itself a clear notion and that any attempt to define it would make it more obscure than it is.I am not sure about that last part, but I believe that we do have a clear enough notion of reality to start with-a notion that depends at least in part on the way things seem, perceptually, when they do seem real to us-and that the proper characterization of this notion of reality is precisely part of the "problem of reality" I attempt to solve in this paper. 1 This "problem of reality" stems from the conflict between two strong intuitions.According to the first intuition, the deep nature of things is hidden from us, and the world as we know it (through perception and science) is somehow shallow and lacking in reality.For all we know, philosophers have claimed for centuries, we might just be facing shadows in a cave.We might just be dreaming.We might just be brains in a vat.Or else we might just be sims in a gigantic computer simulation.There is, or there might be, say these philosophers, a deeper and so to speak more real layer of reality-call it "ultimate" or "metaphysical reality"-but it is hidden from perception by our senses and our scientific endeavors.
cursory.It will suffice, however, to outline two simple structuralist arguments for the claim that experience and science are metaphysically mute.In order get a better grip on this problem and put forward a menu of options for solving it, in section 2 I step back a little from recent structuralist debates to present a much broader, but also more precise, version of the problem of reality.Finally, I argue that the study of the "pathological metaphysicians" mentioned above allows us to solve, or rather dissolve, the problem of reality (sections 3 and 4).A study of them strongly suggests that even though it is not introspectively obvious, our experience is not normally metaphysically mute but talks to us about the deepest nature of things around us.It suggests, moreover, that our experience is reliable when it talks that way (section 5).In the final section, I draw on promising psychological theories of "pathological metaphysicians" to solve the meta-problem of reality-that is, to understand why experience has seemed metaphysically mute or unreliable to most philosophers throughout history.
This article, as should already be clear, is very ambitious and might sound too far-reaching.Its ambition prevents some of its claims from being fully substantiated in a fully detailed and perfectly rigorous analytic style.Yet, I believe that this very ambition can be useful to the research community in many ways.It allows us to step back from a whole field of study, to delineate a fruitful research program at the intersection of metaphysics, psychology, and psychopathology, build bridges between the analytic and continental traditions, and spark thought-provoking discussion that more focused analytical pieces might have nipped in the bud.

| T H E ST RUCT U R A L I ST PROBL E M OF R E A L I T Y: T H E M ETA PH YSICA L SI L E NC E OF E X PE R I E NC E
The observation that experience is metaphysically mute has been repeated again and again by modern philosophers since at least Descartes. 2Here is a natural line of thinking, empiricist, or Kantian in inspiration, that might lead to that claim-call it the "no acquaintance argument."It starts by arguing that my experience of the world around me is mediated in many ways and does not directly acquaint me with its objects.Accordingly, it can only tell me how the properties of individuals relate to me-the experiences they are disposed to produce in me-not what these properties are in themselves, independently of how they relate to me-call this the intrinsic nature of properties.Likewise, because it only accesses them through their (qualitative) properties, my experience does not tell me what individuals are in themselves, independently of their (qualitative) properties-call this the particular nature of individuals.
Let me illustrate these two points successively.My visual experience tells me that this apple is round and green, that this lovely person is approaching, that she's tall, smiling, slightly amused, perhaps.It is mute about what greenness or height are in themselves.It just tells me the way they look to me, the way, that is, they relate to me and my experiences, nothing about the intrinsic nature that underlies these relations.And just as it is mute about the deep nature of their properties, my experience seems to be mute about the deep nature of individuals.Indeed, it tells me what properties this apple, Malum, and my wife, Anaïs, have-greenness, tallness-nothing about their particular nature: nothing about the very things that have these properties and that make them different from perfect doubles with the same (qualitative) properties.
This line of thinking might also be supported, in a more straightforward manner, by the following "direct argument" to the effect: • I could have the very same experiences I actually have, • if greenness or tallness had different intrinsic natures underlying their disposition to produce certain experiences, • or if Malum and my wife had been replaced by perfect doubles Mala and Anays (that differ from Malum and Anaïs only by their particular natures), • and these experiences would be just as correct as they are.
On the view just outlined, properties have an intrinsic nature that is more fundamental than their relational features, and individuals have a particular nature that is more fundamental than their properties.The intrinsic nature of properties and the particular nature of particulars are more real because they characterize what properties and particulars are in themselves, as opposed to the way they relate to other things, and most notably the way they appear to us.Yet each time we can only know the less fundamental and less real of these connected entities through experience.Experience is metaphysically silent.

| The metaphysical silence of science
A similar line of thought applies to scientific (rather than perceptual) knowledge.It is true that science seems in a better position than experience to reveal the deep nature of things.Is it not science that taught us that there is an intrinsic property underlying the appearance of green and that it is a certain range of reflectance?Could not science, likewise, precisely describe the lump of matter that arguably distinguishes Malum from a perfect double such as Mala and thus reveal Malum's particular nature?
Science does seem to bootstrap its way out of the mere testimony of experience to tell us what things are in themselves-their deep nature as opposed to the way they seem to us.Fundamentally, however, science also stops short of the deep nature of things.The reason is that science accounts for the nature of ordinary individuals and properties in terms of descriptions of what happens at a more fundamental level.Yet, at the most fundamental level of elementary particles and basic forces, entities are always defined scientifically in purely relational and general terms, by the role they play in the laws of fundamental physics: by what they do, that is, rather than by what they are in themselves.If we consider, for example, an individual electron, science will tell us nothing about its particular nature.Nor will it tell us anything about the intrinsic nature of its electric charge or of its mass.It will tell us only that this electron has charge -e and mass m and spin ½, as well as a certain velocity and a certain position.But these properties are in turn defined, scientifically, by what things with the properties are generally disposed to do.The charge -e is defined by the way things with this charge interact with other electric or magnetic objects.The mass m is defined by the way objects with this mass resist acceleration, and so on.So, whereas experience can tell us only what properties individuals have and how these properties relate to us (the way these appear to us), at a fundamental level, science can only tell us about what properties individuals have and what these properties do (the way they relate to other properties).We might say that science is fundamentally mute about the deep nature of things or that it is mute about the deepest nature of things.This point was nicely expressed by Bertrand Russell: "All that physics gives us is certain equations giving abstract properties of their changes.But as to what it is that changes, and what it changes from and to-as to this, physics is silent" (Russell 1927(Russell /2007, 18), 18).Now let us say that a property either defined by its causal role (by what it does) or (fully) grounded on properties so defined, is structural.Let us say moreover that an individual (fully)

BILLON
grounded on structural properties is structural. 3A primitive intrinsic property and an individual irreducible to (qualitative) properties are nonstructural in this sense (causal roles are general properties).On the line of thought just presented, experience can teach us only what the structural properties of ordinary objects are, and science can teach us only what the most fundamental structural properties are.Neither can tell us anything about the deep nature of things-the intrinsic nature of the most basic structural properties, such as charge and mass, and the particular nature of the most basic individuals, such as electrons.
But if this line of thought is indeed warranted, how can we hope to know the deep nature of things and get any metaphysical knowledge-that is, any knowledge of the deep nature of things?Structuralists typically answer that we should give up such hope.Either things have no deep nature (no nature, that is, underlying their structural properties) or their deep nature is unknowable.Humbly, we had better acknowledge that, at bottom, the world, or at least the world as we know it, just contains properties defined by what they do to other properties; it contains no intrinsic properties and no genuine particulars underlying them.Electrons, for example, would be mere clusters of properties-mass m, charge -e, spin ½-and their properties would be defined by what they do to other things, not by something intrinsic that underlies their doing those things.The world as we know it, then, would be nothing but a network of inter-defined properties, a pure structure whose elements are characterized merely by their place in the structure.There might be something beneath the structure, but it is impossible to know what it is or whether it is indeed there.
This structuralist idea has become extremely influential in the philosophy of science and metaphysics, and it is probably (mutatis mutandis) the default view of most researchers today.Some critics have suggested that such structuralism is threatened by a vicious circularity because it implies that everything is defined by what it does to other things and so that at some point some things must be defined in terms of themselves.But if a thing A is defined by what it does to B and B is defined by what it does to A, won't A be ill-defined?Echoing Chesterton's saying that "[w]e cannot all live by taking in each other's washing," Russell claimed that "[t]here are many possible ways of turning some things hitherto regarded as 'real' into mere laws concerning the other things.Obviously there must be a limit to this process, or else all the things in the world will merely be each other's washing" (Russell 1927(Russell /2007).He has been followed by a couple of contemporary philosophers, such as Phillip Goff (2017, 137-40) and Uriah Kriegel (2019).We know, however, that circular definitions are not always problematic.In arithmetic, the number 1 is arguably defined by what it does to other numbers when you add it to them, but other numbers are defined in reference to the number 1, by how many times you need to add 1 to zero in order to get these numbers.Yet, numbers are perfectly well defined. 43 There are debates about the best way to define "structural" (see, e.g., Newman 1928, Stoljar 2006, 152, Chalmers 2022, 406-12) and different ways to settle these debates, but these differences won't matter in what follows.So far as I know, all definitions agree that a primitive and intrinsic property or a particular nature (the kind of property, sometimes called haecceity, that distinguishes two qualitative doubles from each other) are not structural, that a property defined by its causal role is structural and that a property grounded on structural properties should count as structural as well-which is all I need.My definition is inspired by the works of Derk Pereboom on that matter (see Pereboom 2011 and2013).I say more about the structuralist traditions below.One might want to add spatial relations to causal ones in the definition of structural properties.For simplicity, I will assume that, as argued by Chalmers (2012Chalmers ( , 2022)), space is reducible to its causal role, so that spatial relations reduce to causal ones.Dissenting readers can add "and spatial" to each instance of "causal" in my paper. 4John Ryder (2013, 56) has already claimed that circularities can be philosophically benign and that pragmatic arguments typically involve such benign circularities.More to the point, he answers some classical "circularity objections" to relational metaphysics by claiming that they beg the question (86-87).On whether, or rather when, circular definitions and explanations are vicious, see Billon 2019.The idea that numbers are defined circularly is arguably implied by common forms of mathematical formalism and structuralism (see Shapiro 1997).It might probably be denied by a Platonist.Here and below, I assume a form of mathematical structuralism.

| The intuition of reality
The main problem with the structuralist idea that the world (as we know it) is fundamentally a mere structure is that it seems completely at odds with the way the world ordinarily seems to us (and, as we have seen, van Fraasen [2006], Goff [2017, 140], and Kriegel [2019] acknowledge a problem of this sort as well).There seem to be things that, unlike numbers, have a form of inner depth or metaphysical thickness and cannot be reduced to (in the sense of being fully grounded on) mere placeholders in a network of relational properties.There seem to be things that are nonstructural.Consider individuals such as my wife and me (or substitute us with you and one of your relatives).We do seem to have a particular nature that distinguishes us from perfect doubles and to be irreducible to our properties.Indeed, I can easily imagine a symmetrical world of eternal recurrence in which we have an infinity of doppelgängers that differ from us only by their particular nature.Or take properties such as the painful character of the sensations in my neck.The pain seems to have a primitive intrinsic nature that directly appears to me: seemingly, the primitive intrinsic nature of my pain is indeed just the way it feels.Even though this is slightly more controversial, I would say the same about the greenness of Malum.When I look at Malum, I do seem to see the primitive intrinsic nature of its greenness: it is nothing, apparently, but the apparent green primitive quality covering its surface (a primitive quality Chalmers [2012] has called "Edenic" to insist on that fact that even though it seems to be instantiated, it never really is). 5  More broadly, pure structures, like numbers and other mathematical entities, seem somehow too thin, too abstract, and too ghostly, one might say, to account for reality.They seem to lack the metaphysical depth and substantiality that we spontaneously attribute to ordinary things.They seem, so to speak, not to be "real" enough.This is what I called, in the Introduction, the intuition of reality, an intuition whose clash with the structuralist arguments above constitutes the problem of reality.
Structuralists typically bite the bullet at this point.They grant that the world as we know it does not contain genuine individuals, only bundles of properties, and that what I know when I know Anaïs, Malum, or me myself are not genuine individuals, only bundles of properties.They also grant that what I know when I know the greenness of Malum is not a primitive intrinsic quality.According to them, the world as we know it is not, in fact, different from a mere structure in which all individuals and properties are defined in terms of certain causal relations, and hence are not different from a very rich and detailed computer simulation that would implement that structure. 6They grant, finally, that we might have the intuition that such a purely structural world would be merely virtual and unreal, and cannot be the world we inhabit.But they claim that we can, and should, discount this intuition. 7Chalmers thus argues that modern science has shown us that this intuition cannot be correct: it pictures the world as 5 So-called primitivists about color advocate the existence of primitive, intrinsic, colors, and they usually do so on phenomenological grounds (see, e.g., Johnston 1992, Yablo 1995, and Cutter 2018).Conversely, many of their opponents grant, like Chalmers, that there seems to be primitive intrinsic colors. 6On the connection between structure and information and, relatedly, between structuralism and the digitalist idea that we might be living in a computer simulation, see Chalmers 2022, chaps. VIII, XXI, and XXII and esp. 412-15.This connection stems, very roughly, from the fact that a structure is defined entirely by the causal relations between a set of items independently of the deep nature of these items.Likewise, a program is defined by a series of causal transitions, independently of the substrate on which it is realized.If, moreover, implementation is construed as an isomorphism that preserves the causal structure, it seems that any kind of structure-even that of our whole world-could be implemented by a well-programmed and powerful enough computer.It is a form of structuralism that warrants Wheeler's (1989) influential "it from bit" claim to the effect that the physical world is purely informational.
7 Some structuralists accordingly deny the idea that at a fundamental level metaphysics should study the intrinsic nature of properties and the particular nature of individuals that science fails to reveal.Typically, they assign to it the more modest goal of finding out the ontology to which our scientific theories are more or less implicitly committed (Ladyman and Ross 2007).
Rationally minded structuralists might claim that the world as we know it somehow outstrips a mere structure.According to them, even though we do not know the deep nature of things, we can at least know, through a form of rational intuition, that things do have such a deep nature-an intrinsic know-not-what underlying properties, a particular know-not-what underlying individuals.They might thus endorse what is sometimes called an epistemic rather than ontic form of "structural realism."That does not substantially change their way of addressing the problem of reality, though.Whereas for ontic structural realists the world as we know it is akin to a pure informational structure, for epistemic structural realists it is akin to an informational structure that is realized somewhere on some totally unknown substrate. 8For both kinds of structural realists, however, the world as we know it is not different from a gigantic computer simulation.The influence of structuralism probably goes some way toward explaining the incredible popularity of the thesis, advocated both by philosophers such as David Chalmers, Eric Steinhart, and Nick Borstrom and by Silicon Valley figures such as Ray Kurzweil and Elon Musk, to the effect that neither experience nor science provides good reason against the hypothesis that we live in a computer simulation, and that this "simulation hypothesis" might well be true (see Borstrom 2003and 2011, Steinhart 2014, Chalmers 2007;2010;2012;2022).

| A note on structuralism
The presentation of structuralism and the structuralist arguments for the silence of experience and science that I have given above are very rough.Structuralism is a rich and multifaceted current that is sometimes traced back to Aristotle but today gathers at least three partially different traditions and argumentative strategies. 9 The first structuralist tradition, Kantian in inspiration, starts from the idea that our knowledge depends on the way things causally relate to our experience, as opposed to acquaintance with the things themselves, and is thus severely bounded.This tradition is nicely illustrated by Russell's Analysis of Matter (quoted above).It finds its contemporary expressions in works on the metaphysics of individuals and properties (see, e.g., Armstrong 1997 andShoemaker 1980), in Kantian scholarship (see Langton's [1998] analyses of Kantian humility), or in analytic epistemology of metaphysics (Jackson 1998 andLewis 2009).The second structuralist current is rooted in Klein's Erlangen program (see Ihmig 1999) and Poincaré's (1905 and1908) classical writings in philosophy of science, and it has had a tremendous influence on the French social sciences of the twentieth century.It characterizes objectivity in terms of symmetry invariance 10 and defines structure as what is indeed left invariant by the symmetries of nature, entailing that objective knowledge must be knowledge of structure (see Nozick 2001 for a recent defense, Debs and Redhead 2007 and 8 More precisely, epistemic structural realists might claim to know that for each individual or property in the structure there is something underneath that realizes it.They might accordingly claim that a scenario in which Malum, or what I take to be Malum, is not realized by a single underlying object (but, say, by many different piecemeal, disjunctive, and distributed processes, as imagined in Schwitzgebel 2010) is a skeptical scenario in which there is no genuine apple in front of me.9 It is tempting to assimilate Aristotle's forms to modern structures (see, e.g., Cohen 1992 on the mind as the form of the body and modern functionalism).Aristotle notably claims in various places that matter (as opposed to form) cannot be known in itself (Metaphysics XI.2). 10 In physics, symmetries are transformations that map an "acceptable observer" to another.Something that is symmetry invariant is thus independent of the point of view, and in that sense objective (see Nozick 2001 andBillon 2018).Determining what the symmetries of nature are (or, equivalently, what the acceptable observers are) is, however, far from trivial, and some scientific revolutions such as the discovery of General Relativity seem rooted in revolutions in the understanding of symmetries (see, e.g., Moore 2000, 29, and Nozick 2001, 79-83).14679973, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/meta.12666 by Cochrane France, Wiley Online Library on [19/02/2024].See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions)on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License Dasgupta 2016 for critiques).The last structuralist current is also rooted in the writings of Poincaré (1905), but it was resurrected by Worrall (1989) as a potent move in the late twentieth-century controversy over scientific realism.His idea was that even though scientific change seems to forbid naive forms of scientific realism, there is enough continuity in the structure of succeeding scientific theories to warrant a form of realism about the "structural content" of scientific theories (see Ladyman 2020 for an overview).To take a simple example, Newtonian and Relativist physics might seem so different that they are really talking about different things, but they are structurally continuous: if the speed of light c were infinite, both theories would indeed be structurally identical.
My presentation of the silence of experience has relied on a simplistic version of the first, Kantian "no acquaintance" argumentative strategy and on what I have called the "direct argument." 11The second Klein-Poincaré tradition provides a neat argument for the silence of science: science being objective, it should bear only on what is invariant through the symmetries of nature, that is, the structure of the world.So does the third, Poincaré-Worrall tradition, as it implies that only the structural content of science should be considered as faithfully describing reality.But the silence of science naturally provides, in turn, a nice argument against the intuition of reality.Assuming that reality is correctly described by science, either our experience says nothing about the deep nature of things or what it says is completely misleading.Either way, the intuition of reality must be wrong.Call this "the scientific argument against the intuition of reality."As alluded to above, Chalmers dwells on this scientific argument against the intuition of reality in various places.This argument depends on the claim that scientific knowledge is purely structural.

| THE GENERAL FORM OF THE PROBLEM OF REALITY
How should we solve the problem of reality?In order to answer this question, it will prove useful to step back and give a broader and somehow more formal presentation of this problem.By broader, I mean a presentation that does not presuppose that the contrast between the deep, and perfectly real, nature of things and their superficial properties is that between the nonstructural and the structural.By more formal, I mean a presentation that itemizes more precisely the premises on which the problem of reality depends and tries to simplify them as much as possible.
As I have presented it, the problem of reality presupposes the merely apparent, first, between the real or maximally real, and the non-(maximally) real.
1. Basic realism.Some things are (ultimately, metaphysically) real and some things are only apparent, non-real.
Basic realism has been taken as a starting point of most metaphysical inquiries since Plato.It is explicitly advocated by Peter van Inwagen (2009, 1-5) in the first pages of his popular introduction to metaphysics.Because appearances must be grounded in reality, basic realism is closely tied to the idea some things are more fundamental than others, and that there is so to speak a maximally fundamental layer. 1211 Structuralists in the three different traditions, and in fact structuralists within the same tradition, can disagree with each other.They can even disagree on the best definition of structural properties.I believe, however, that these differences do not matter here, as my presentation could be slightly rephrased to fit most understandings of structural properties. 12The connection between basic realism and foundationalism, however, is not completely straightforward.First, even though basic realism is naturally associated with foundationalism (because appearances must be grounded on something real), it is not totally obvious to me that basic realism could not be made sense of without foundationalism (maybe appearances could all be grounded on reality while reality has no bottom, ungrounded layer).Second, even if foundationalism is true, the fact that something is grounded does not ipso facto make it unreal.As argued by Fine (2001, 27-28), at best realism commits us to the claim that if something is ungrounded, then it is real (it would have to be grounded to be explained away as a mere appearance), and that grounded things can be considered unreal provided "there is no special reason to think that they are real." Foundationalism.Grounded things are all grounded on ungrounded things.
Foundationalism is quite orthodox.It has been recently advocated, en passant, by Kit Fine, Samuel Schaffer, and others (see Schaffer 2010 andFine 2010).As Schaffer (2010, 37) puts it, "[T]here must be a ground of being.If one thing exists only in virtue of another, then there must be something from which the reality of the derivative entities ultimately derives." The problem of reality relies on the intuition of reality, an intuition that we can spell out as follows: 2. The intuition of reality (first pass).The world as we know it seems perfectly real, and this seeming is veridical.
This intuition can be supported on broadly Moorean grounds.Things seem real to us when we perceive them, and we would need very strong reasons to believe that those appearances are systematically misleading.
The problem of reality relies as well on the (metaphysical) silence of experience and science: 3. The silence of experience and science.Experience and science are mute about what is (ultimately) real.
Finally, the problem of reality depends on the idea that 4. ( 2) and ( 3) are inconsistent.
We can get a simpler rendering of the problem of reality if we realize that it is not just the world as we know it that seems to be real to us, but already, in fact, the world as we experience it.
(2*) The intuition of reality (second pass).The world as we experience it seems perfectly real, and this seeming is veridical.
And (2*) is in tension not only with the silence of experience and science but also with the silence of experience alone: Framed this way (as the inconsistency of [2*-3*]), it is clear that the problem of reality is not parasitic on structuralism.It is likewise a problem for the Platonist who takes the most fundamental and most real layer of the world to be constituted by the Idea of the good, or, say, for a priority monist such as Schaffer (2010), who takes it to be the whole cosmos.Indeed, the structuralist version of the problem of reality can be obtained by simply adding something like the proto-structuralist premise (S1) to specify (1): (S1) (Ultimate) reality consists either in the most basic structural facts or else in the nonstructural facts that underly them (facts concerning the intrinsic natures of properties and particular natures of individuals).And adding something like (S2-S3) and (S2) in defense of (3) and (3*), respectively: (S2) Experience can only show us some structural features of things (and maybe the fact that there is something unknown underlying them), not the way they are in themselves.
(S3) Science can only show us some structural features of things (and maybe the fact that there is something unknown underlying them), not the way they are in themselves.
This general formulation also suggests a menu of options for solving the problem of reality.

| The dissolution
Even though basic realism (1) has almost always been taken for granted by philosophers throughout history, one might try to dissolve the problem of reality by denying it.One way to do that would be to argue that realism is parasitic on foundationalism and that foundationalism is false.There are various ways to do so.One could, for example, adopt a perfectly flat, horizontal metaphysics to the effect that there is just one layer of reality and nothing is grounded on anything. 13Alternatively, one might endorse a non-well-founded metaphysics that admits circular chains of grounds-this is sometimes called "a coherentist metaphysics"-or infinite descending chains of grounds-this is sometimes called "an infinitist metaphysics."Both claims would indeed prevent us from making sense of a most fundamental layer of the world and would threaten a natural way to draw the distinction between maximally real things and mere appearances thereof.Non-well-founded metaphysics used to be extremely exotic, if not altogether absent from the Western philosophical tradition.Until ten years ago, it seems to me that no one, except Justus Buchler (1966) and some of his heirswho indeed seem to reject basic realism in favor of a "principle of ontological parity"espoused a metaphysics of this kind. 14Things are slowly changing, though.Many philosophers have recently argued that non-well-founded metaphysics constitutes a rather interesting and viable option (see the contributions in the edited volume Bliss and Priest 2018).Even though I have myself some sympathy for this option (see Billon 2022a and forthcoming), I would like to admit foundationalism, and basic realism more broadly, and focus on other ways to deal with the problem of reality.I will also admit with Fine (2001) that ungrounded things are maximally real and that unless we have special reasons to the contrary, grounded things can be considered non-(maximally) real (see my footnote 12 above).

| The philosophers' solution
Denying the intuition of reality (2*) is by far the most popular option to solve this problem among philosophers-call this the philosophers' solution.
13 Karen Bennett (2011) suggests that this is a viable metaphysics.14 I thank a Metaphilosophy referee for bringing to my attention the works of Buchler. Buchler (1966) calls foundationalism the "principle of ontological priority," and he rejects it in favor of a "principle of ontological parity."He might seem to endorse a form of infinitism, as he argues that the world is made of "natural complexes," which are themselves made of "natural complexes" ( 14), but he also argues that classical examples of ontological dependence involve, in reality, a form of codependence (45-46), which suggests he also countenances a form of metaphysical coherentism.Cohenrentism and infinitism are not in any case inconsistent with each other (see the introduction in Bliss and Priest 2018 and, in the context of Buchler's thought, Wallace 1999).As I understand him, Buchler simply rejects traditional, well-founded notions of ground or ontological dependence that forbid metaphysical loops or infinite regresses.
Advocates of the philosophers' solution can simply deny that things seem perfectly real to us through experience and claim that this naive phenomenological claim cannot stand philosophical scrutiny.This is typically done by reinstating some of the arguments for the silence of experience that we have envisioned so far, be it the conceivability argument to the effect that we can conceive of having the same experiences in an unreal (shadowy, oneiric, simulated) environment, the related "direct argument" stating that our experience stops short of the deep nature of things, and the Kantian "no acquaintance" structuralist argument for the silence of experience to the effect that we can at best perceive the causal dispositions of ordinary objects, not their deep nature.More interestingly, foes of (2*) can also try to debunk our sense of reality, arguing that it is metaphysically insignificant.Hume and Kant have, for example, espoused a shallow, "deflationary" account of our sense of reality or existence that has proven extremely influential.On that account, being aware of an individual as really existing is nothing over and above being aware of that individual, and the sense of reality is itself, so to speak, not metaphysically committal (see Billon 2023b).
Alternatively, advocates of the philosophers' intuition can grant that we have an impression of perfect metaphysical realness but deny that it is reliable.To that effect, they can invoke what we have called the scientific argument for the silence experience, by claiming that the scientific picture of the world is purely structural and that unless our experience is metaphysically silent, it will be massively deceptive (Chalmers 2022, 436-37).

| The naive solution
Philosophers who reject the silence of experience (3*) in favor of the intuition of reality-call this "the naive (or, maybe, wannabe naive) solution"-are rare but not altogether inexistent.
Consider, first, subjective idealists who claim that everything is grounded on experience ("ideas").According to them, our experiences are the most fundamental and most real elements, and by (so to speak) telling us about themselves, they tell us about the deepest nature of things, that is, about ultimate reality.
Maybe more interestingly, the silence of experience has also been rejected by philosophers (i) who acknowledge that the world could exist without our (or God's) experiences (and are thus not subjective idealists), (ii) and who grant the proto-structuralist claim (S1) to the effect that the most fundamental layer of reality consists either in the most basic structural facts or else in the nonstructural facts that underly them.The thinkers I am thinking of argue that there is one important exception to the claim that experience is metaphysically mute concerning everything: experience itself and, maybe, the subject of experience.Inspired by the works of Maine de Biran (1812/1981), Schopenhauer (1819Schopenhauer ( /1969, § 17), § 17), and some of their indirect heirs (including Russell, Brentano, Bergson, and the late phenomenologist Michel Henry), 15 these philosophers have argued that even though our experiences seem metaphysically mute about the outside world, they disclose their own deepest nature to us when we have them. 16When you are in pain, as we have already noticed, it indeed seems that you do not just get to know how pain appears to you or what pain makes you do, but really what pain is fundamentally and intrinsically.Trying to build our whole metaphysics on this inner exception, these philosophers have all advocated what Kriegel (2019) aptly calls an "introverted metaphysics," that is, a metaphysics to the effect that the deep nature of things and its relation to their superficial, structural properties is akin to 15 On Russell and Brentano on the silence of experience, see Kriegel 2019.The "introverted medium" of metaphysical insight is diversely called "immediate consciousness," "intuition," and "instinct" by Bergson, who contrasts it with "reflective consciousness," "intelligence," and "reflection" (see Bergson 1896 and Le Lannou 2001 for a synoptic view of Bergson's metaphysics).The introverted medium of metaphysical insight is called "immanence" by Michel Henry (2015), who contrasts it with the "transcendence" of intentionality. 16The silence of experience has also been denied, so to speak locally, by primitivists about colors such as Johnston (1992), Campbell (1993), Yablo (1995), and Cutter (2018), who believe that we are perceptually acquainted with colors' deep nature.experience and the way it relates to its structural properties.The simplest way to do this is to claim that the deepest nature of everything is in fact experiential.It would be, for example, because of a form of experience that the electric charge of electrons does what it does to other things.This conclusion, known as panpsychism, is definitely weird: it implies that everything has mental properties.But it might seem to solve the problem of reality: the world as we know it would be more real than a mere structure because we get to know its deepest substrate through introspection.Panpsychism has been endorsed by many contemporary philosophers, including Phillip Goff (2017), Hedda Morch (2021), and Galen Strawson (2006aand 2006b), and it has become rather popular.Introverted metaphysics need not get that weird, however.Kriegel argues that the analogy between experience and the deepest nature of electrons and photons posited by introverted empiricists might be much weaker than panpsychism assumes.Even though I have never seen it fully and convincingly articulated, I do not want to suppose that such a maneuver cannot yield a plausible metaphysics.Nor do I want to suppose that the incredulous stare at panpsychism (which I share) is a decisive objection against it.I do believe that neither subjective idealism nor introverted metaphysics can really save the naive intuition of reality concerning outside objects, but I can suspend my judgment on that matter at this stage, as we will see later that they encounter bigger worries. 17

| The conciliatory solution
A last way to solve the problem of reality is to deny claim (4*) (the claim to the effect that the intuition of reality (2*) and the silence of experience (3*) are inconsistent).Claim (4*) might seem analytic.If the world as I experience it seems perfectly real, and if this impression is veridical, experience cannot be mute about what is (ultimately) real.One could, however, try to reject (4*) by claiming that there are different concepts or ways of being (ultimately, metaphysically) real, and that (4*) equivocates on them.The idea, here, would be that there is a sense of reality, call it "perfect reality," for which experience is indeed metaphysically mute (3*) or unreliable, and for which the intuition of reality (2*) is indeed false.Yet our "intuition of reality" would not be completely misleading, for there is another sense of "real," call it "simple" or "imperfect reality," for which the intuition of reality is true and the silence of experience is false.More specifically, even if we accept (3*) and reject (2*), understood as claims bearing on perfect reality, we could accept (2**) and reject (3**): (2**) The intuition of (at least) imperfect reality.The world as we experience it seems at least imperfectly real, and this seeming is veridical.
(3**) The (proto)metaphysical silence of experience.Experience is mute about imperfect reality.This conciliatory approach (which grants something both to the philosophical and the naive solution and is accordingly rather appealing) can be attributed to Chalmers (2022).He precisely distinguishes "perfect reality" from "imperfect reality," where: • perfect reality corresponds to the Edenic world covered with nonstructural qualities (such as perfect primitive colors), that perfectly match our experiences, and 17 For subjective idealism, see Bennett 1971, § 34.Bennett argues that Berkeley's solution to this problem (of accounting for the intuition of reality for outside objects) commits him to a form of "phenomenalism" to the effect that objects are not just collections of ideas, as per subjective idealism proper, but complex logical constructions involving counterfactual conditionals (of the form "if I were to move to … I would have such and such experience").• imperfect reality corresponds to the structural properties (such as the disposition to cause color experiences in us) associated with these nonstructural properties.
For Chalmers, experience isn't metaphysically mute, but inasmuch as it isn't mute, it is unreliable.So even though (3*) is false, (2*) is true: experience talks about perfect reality but falsely so.Crucially, however, if Chalmers's distinction between perfect and imperfect reality is to yield a genuine (as opposed to merely verbal) solution his proponent must show, to the effect that even though it is imperfect, imperfect reality is so to speak real enough to deserve the name-that is, that imperfect reality is simply real.Chalmers does tackle this task, and his 2022 monograph can be read as a book-length argument to the effect that even though it is the kind of reality we would encounter in a virtual simulated world, imperfect reality is indeed real enough to be considered real.His argument is long and complex.It relies, however, on the three following claims: • Science describes our world as only imperfectly real, and we should not expect the world to be more real than science allows.• Imperfectly real things can pass a couple of tests that are critical for reality (they can exist, be causally efficient, mind-independent, and authentic).• And, crucially, imperfectly real things can pass roughly (if not perfectly) a last critical test for reality, the test of non-illusoriness: imperfect reality indeed corresponds roughly (if not perfectly) to the way the world seems to us-because imperfect reality has the same structure as the perfect reality that appears to us-and is thus roughly (if not perfectly) non-illusory.
It is not time to assess conciliatory solutions, such as those Chalmers offers, that invoke a form of ambiguity of "reality" to reject claim (4*).We should just remember, at this stage, that they depend on showing that imperfect reality is real enough, and more specifically, in the case of Chalmers's, on showing that being roughly non-illusory (in the sense of having the sale structure as [apparent] perfect reality) is being real enough.
Let us take stock.We have seen that the problem of reality presupposes basic realism and relies on three additional premises.The most common way of solving it, the philosophers' solution, consists in denying the intuition of reality (2*).It has been a staple of philosophical theorizing throughout history that deep or ultimate reality is hidden from sight.Structuralism provides new ways to back up the rejection of (2*).As we have seen, subjective idealists and introspective metaphysicians have put forward "naive (or, maybe, wannabe naive) solutions" that reject the silence of experience and try to vindicate the intuition of reality.Finally, some philosophers, such as Chalmers, try to help us bite the "unreality bullet" by claiming that albeit untrue for a certain, perfect conception of reality, the intuition of reality can be saved for "imperfect reality" (2**).In the next section, I try to show that the study of "metaphysical doubters" such as Ball's patient can help us reject the idealist's and the introverted metaphysician's naive solution and put forward a new, trivial solution to the problem of reality, a solution that denies, just like subjective idealists and introverted metaphysicians, that experience is metaphysically silent and endorses the intuition of reality, but a solution that is far less counterintuitive.The study of these patients also strongly suggests, we will see, that Chalmers's imperfect reality is simply not real enough to deserve the name and that his conciliatory solution is a dead end.
Although I believe this move could be justified independently, I will, for the sake of simplicity, assume in what follows that the best formulation of the problem of reality is the contemporary formulation we started with, in terms of structural versus nonstructural properties.More precisely, I will assume the proto-structuralist premise (S1) to the effect that the world consists of structural properties plus, maybe, their deep intrinsic nature and the deep particular nature of particulars instantiating them.

H E ST U DY OF P SYC HOPAT HOLOGY
Ball's patient, as we have seen, said, "[T]he way I see things does not reflect what they are or that they exist, hence the doubt."He was clear, however, that he perceived that "things keep the same forms and colors" and "do everything the way they normally do."What, then, was modified in the way he saw things?Ball talked of "a loss of the feeling of reality" and the "feeling of oneself," and his patient indeed insisted that his experience had lost some aspects they normally had, which used to disclose not only that things are real but also what they are beyond the way they relate to him and other things, beyond, that is, what they do.Given that the deep nature of things is precisely that (what they are beyond what they do), and given, as we have seen, that it is supposed to account for their reality, this patient's testimony suggests that our experience normally says something (correct or incorrect) about that deep nature of things so that the silence of experience (3*) is false.Given that patients like this one can sometimes deny the reality of themselves and their experiences but not of outside things (see, e.g., Lambert et al. 2001), they also suggest, against idealist solutions and introverted solutions, that our sense of the metaphysical reality of inner things is not primary with regard to that of inner things.There might thus be a new way to deny the silence of experience, endorse the intuition of reality, and solve the problem of reality: we could simply argue that ordinary experiences of internal and external items do reveal the deep nature of things.
In order to make this promising hypothesis more precise and to assess it, we should look more precisely at other "pathological metaphysician doubters."The precise condition of Ball's patient is something we now characterize as depersonalization, depersonalization disorder (DPD), or depersonalization derealization disorder.DPD is a psychiatric condition defined by long-lasting impressions of the unreality of oneself and one's mental states (call this "trait depersonalization" [DP]) and of the world around one (call this "trait derealization" [DR]) without delusional ideas.Things seem unreal to the subjects with DPD, but they know that everything is still real.DPD would afflict 1 to 2 percent of the population, and it has been relatively well studied since it was discovered at the end of the nineteenth century (see, e.g., Dugas and Moutier 1911, Sierra 2009, and Simeon and Abugel 2006).Some reports of DPD patients are even more strikingly metaphysical than those gathered by Ball.A patient of Dugas's (Dugas is the philosopher and de facto psychologist who coined the term "depersonalization" in 1898), for example, explained that after a crisis of depersonalization, he was finally reminded that "there is a real substrate [my emphasis] to what seemed just like a dream of life" (Dugas and Moutier 1911). 18The dream hypothesis has in fact always been commonly evoked.A patient of Janet's explained: "It seemed to me that I did not exist anymore at all, that I could see, but that it wasn't me who was seeing, that I could hear, but that it wasn't me who was hearing; I wasn't sure of anything.It seemed to me that both objects and I were nothing but a dream anymore.This state annoyed me tremendously" (Janet 1903, 56-57).
Instead of a dream or (like Ball's patient) a gigantic hallucination, some early patients said that they felt as though they were living in a fictional world.Nowadays, many patients readily evoke a gigantic computer simulation.One of them, who devotes a blog entry on the topic, says: "For most people, this [the simulation hypothesis] is a fun little theory that has little basis in reality.For persons with derealization, however, this is not simply a fun theory to think about, but instead, a question that we have to constantly tell ourselves not to pursue."Another describes his experience as follows: "From my experience, it feels like I'm stuck in a virtual reality simulator-I know I'm me, I know my thoughts and actions are my own, but my surroundings 18 Psychologists today are still amazed, sometimes, by the way DPD can turn people who were not otherwise interested in metaphysics into genuine philosophers (see, e.g., https:// www.psych ology today.com/ intl/ blog/ the-searc h-self/ 201610/ deper sonal izati on-philo sophi cal-aware ness and Simeon and Abugel 2006).don't seem to be real.(I imagine it's a bit like what Neo feels when he goes back into the Matrix after being freed.)" 19 These reports strongly suggest that DPD patients lack a sense of reality for the things they perceive because these things seem to them to be lacking the metaphysical depth, the substantiality, that would make them differ from a mere computer simulation.Now all accounts of DPD agree that the patients' impression of unreality stems from an anomalous experience (rather than, say, from abnormal beliefs or desires, or abnormal reasoning).Because patients explicitly talk of something lacking in their experience that used to be there, all accounts also agree that their experience is anomalous in that it lacks some aspects it used to have. 20Combined, these three claims seem to confirm the idea that contrary to the silence of experience (3*) and to the common structuralist assumption (S2), we do normally experience all the things we perceive as having a genuine metaphysical depth that sets them apart from mere placeholders in a structure-or mere simulated objects.This conclusion, it should be noted, would also explain why the assumption to the contrary is so widespread.Being normally universal, the metaphysical aspects of our experiences that underscore the sense of reality would also be elusive, for the simple reason that, unlike DPD patients, we lack the contrast cases that could make it salient.Finally, it has been observed that DP (the impression that one and one's mental states are unreal) and DR (the impression that outer things seem unreal) do not always occur together in DPD.More specifically, while pure DR is so rare that its existence is still controversial, pure DP is not totally uncommon (see, e.g., Lambert et al. 2001). 21This strongly suggests that, pace introverted metaphysicians, the sense of reality for outer things does not depend on the sense of reality for oneself or one's experiences.
I believe that these conclusions are indeed correct.One might, however, object that they remain fragile.They indeed rely on the two following claims that probably deserve further scrutiny: • (R1) Reality as substantiality.There is a sense of "real" in which something is unreal if it is unsubstantial, that is, if it has no underlying particular or fundamentally intrinsic nature, or if it has one but the nature is "too abnormal"-in the way the substrate of a virtual world realized on a supercomputer would intuitively be too abnormal to confer substantiality to it. 22The world, in a computer simulation, is paradigmatically unreal in that sense. 23• (R2) The sense of (un)reality in DPD is a sense of (in)substantiality.The lack of sense of reality in DPD, that is derealization, involves, maybe among other things, the lack of sense of substantiality. 19 These reports can be found, respectively, here (https:// secre tlady spider.wordp ress.com/ 2019/ 05/ 10/ the-matri x-simul ated-reali ty-andderea lizat ion/ ) and here (https:// psych centr al. com/ blog/ panic/ 2013/ 02/ the-matri x-has-you-on-disso ciati on-and-feeli ngs-of-detac hment# 1).You can find many other testimonies invoking the simulation hypothesis on patients' forums and blogs or in case studies such as Chard 2020. 20The only exception I know is Dub (2021), who argues that although DPD patients might have something lacking in their experiences, their conditions should be explained by an extra emotion of unreality.21 See Sierra et al. 2002, Lambert et al. 2001, and Mayer-Gross (1935) for arguments to the effect that pure DR exists.Some patients describe the onset of DR as preceding that of DP (Hesnard 1909, 145).Statistical analyses on large-scale samples can be found in Baker et al. 2003, Sierra et al. 2005, and Simeon et al. 2008.  2It might be wondered whether just any abnormality in the intrinsic and particular character implies unreality in that sense.It seems to me that this is not the case, for the following reason.Suppose we all take our world to be a virtual world realized on a rather slow computer, and that we think that we have a special form of intuition that backs up this belief.Suppose, then, that some philosopher argues that our world is in fact realized on a super-fast quantum computer.We would probably think "If she is right, then our intuition is misleading."I doubt, however, we would even be tempted to think "Gosh!If she is right, everything is unreal."If, however, she argued that our world is realized in a disorganized fashion on hundreds of computers on which many operators need to intervene almost every second, we might feel tempted by a thought such as this one.See Schwitzgebel 2017, § 6 and § 9, for speculations on (too) abnormal implementations.

23
Being substantial in this sense thus involves having a (not too abnormal) intrinsic nature and a (not too abnormal) particular nature.It is worth emphasizing because many authors, especially in the literature on individuals, use the word "substantial" to convey merely the presence of a particular nature.Setting the details apart (when exactly does a substrate count as too abnormal?and so forth), the first claim is not very controversial and is rather widespread.It articulates philosophically the common idea that virtual reality is more virtual than real and that being real involves having a proper substrate (what is controversial is the claim, on which I would like to remain neutral at this stage, that this commonsense idea is correct). 24The sense of "real" involved corresponds to what Chalmers calls "perfect reality," a sense that he considered "outdated" by modern science (Chalmers 2017 and2022).The second claim is not, however, very widespread.Not that many people explicitly disagree with it.The problem is rather that most studies on DPD do not explain in what sense things seem unreal to the patients, and the very few commentators that do take a positive stance on this topic do little to argue for that stance. 25Now, as we have seen, some patients' reports describe the lack of sense of reality in terms of the lack of a substrate underlying the world and compare the unreality of their perceived world to that of a computer simulation.This provides some support for both claims (R1 and R2).It is well known, however, that patients have an extremely hard time explaining in what sense the world seems unreal to them.Also, some reports describing their phenomenology might be highly metaphorical.Others might be incidental, focusing on the consequences of the sense of unreality rather than on the sense of unreality itself.Yet others might merely try to convey the fact that things seem unreal to them, rather than try to explain in what sense they seem unrealand they might accordingly depend on commonsense theories of reality (or what they take those theories to be) rather than on the patient's precise phenomenology of unreality.These are all fair worries.Elsewhere I have devoted a full article to the defense of (R2) (Billon 2022b).Here, I would like to argue that there is a simple argument, relying on objective data rather than on controversial subjective reports, that confirms my interpretation and disconfirms its most plausible rivals.The argument rests on the extremely intriguing fact that the patients' sensorimotor abilities are, so far as we know, objectively normal.
Noticing the patients' common complaints of separation or alienation from the world and the self, or their (slightly less common) comparison of perceptual objects with mere images thereof, early researchers extensively probed the sensorimotor abilities of patients.Except for a few patients of Krishaber (1973) (whose series of patients was biased by the fact that he was an ear, nose, and throat specialist and that his DPD subjects usually had vestibular problems), the researchers found none.Janet, who followed some people with DPD for two or three decades, explained: "To summarize, patients keep a normal perception and sensation of the outer world, but they have lost the feeling of reality that is ordinarily inseparable from these perceptions.And the same goes for the perception of oneself.…They have kept all the psychological functions but they have lost the feeling that we always have… of being real, of being part of the reality of the world" (see Janet 1903, 353-54). 26 These classical clinical observations have been confirmed by modern experimental studies, which found no sensorimotor impairment (Cappon and Banks 1965), even in often neglected modalities such as interoception (Michal et al. 2014).Indeed, so far as we know, the only objective psychological (as opposed to neurophysiological) measures that can distinguish DPD patients from controls rely on attentional tasks, but even there the patients' attentional deficits are very subtle (Guralnik, Schmeidler, andKnutelska 2000 and2007, 24 Even though he believes that a notion of reality such as this one, that classifies virtual reality as unreal is "outdated," Chalmers grants that it is widespread (Chalmers 2017b andChalmers 2022).What he calls "perfect reality" is real in that sense.McDaniel (2017, 159-60) argues interestingly that on some interpretations Nagarjuna's claim that nothing really exists is the claim that everything lacks an intrinsic nature or a particular nature. 25Radovic and Radovic 2002 is an important exception; I tackle its views elsewhere (Billon 2023b).

26
After mentioning the groundbreaking works of Janet, Jaspers (1913/1962, 94) would likewise claim: "[A]wareness of reality may fail us even when we concretely perceive.For instance, it is lost in 'derealization' and 'depersonalization.'"Adler et al. 2014, andSchabinger et al. 2018).They are in fact more subtle than the deficit affecting OCD patients who do not suffer from derealization or depersonalization, which strongly suggests that such a deficit is a consequence rather than a cause of their condition (see Billon 2022b).This is indeed the hypothesis put forward by the studies on attention among DPD patients mentioned above.
The normal sensorimotor abilities mean that the subjects' perception of the causal structure of their environment is normal. 27For if there were causal relations between ourselves and objects outside us or between objects outside that they cannot perceive (but we can), their sensorimotor abilities would differ from ours.Now, I would like to argue (i) that my interpretation (R2) of unreality claims in DPD does not predict that patients' perception of the causal structure of the world should be abnormal and (ii) that it is the most plausible interpretation not predicting this. 28Let us tackle these points in turn.(i) First, according to my interpretation of unreality claims in DPD (R2), the sense of (un) reality in DPD is a sense of (un)substantiality.It is, accordingly, a sense of something that does not depend on the causal structure of the environment, and the perception of which should not depend on the perception of the causal structure of the environment.(R2) does not accordingly predict that people with DPD should perceive the structure of the world in any abnormal way.
(ii) The only accounts that do not predict an abnormal perception of the causal structure of the world are those claiming that the sense of reality does not depend on such perception.But it is hard to make sense of any such account unless it grants (R2).Why?Because it is hard to make sense of the claim that we have a sense of x if x is completely causally idle, and the only way for something independent of the causal structure of the world not to be completely causally idle is arguably to ground the causal structure of the world.
It follows from (i) and (ii) that the most plausible accounts of the sense of reality consistent with the absence of sensorimotor distortion in DPD depict the sense of reality as a sense of substantiality (R2).Patients can clearly see that objects still have the same shape, color, location, depth, and so on that they used to have.They just miss something which they used to perceive and grounded the impression that these things are real, and which is arguably the presence of particular natures or fundamentally intrinsic properties underlying individuals and their manifest properties-what Dugas's patient calls "a substrate." 29

| OT H E R PAT HOLOGICA L M ETA PH YSIC I A NS
DPD, as I have explained, is accompanied by insight, but the same impressions of unreality (of self and world) can be found among some delusional patients.These delusional patients 27 I have assumed that spatial relations are causal relations as well; see my footnote 3 above.

28
When I say that A predicts B, I do not mean that A a priori entails B and is logically inconsistent with non-B (I believe that almost all theories of the sense of (un)reality in DPD are logically consistent with the absence of sensorimotor deficits in DPD).I just mean that A is empirically confirmed by the observation of B and disconfirmed by the observation of non-B, or again (I take this to be equivalent) that the observation of B makes A more probable, and the observation of non-B makes A less probable.

29
How, then, should we interpret the numerous reports of DPD patients suggesting that they lack a normal sense of presencereports claiming that they feel alienated, estranged, or separated from the world and themselves?I would say that patients indeed lack a sense of presence but that this lack is incidental (it is the consequence of the lack of sense of reality rather than its cause or its nature), and that it is accordingly rather peculiar and does not predict any sensorimotor consequence (see Billon 2023b).The idea is that because things in their environment seem unsubstantial, they seem to be merely virtual figures representing the real things they used to be acquainted with, real things that are now, so to speak, in another world.While the real things do not seem present, then, the figures that represent them, and that are structurally like them (and causally efficient like them), do seem present, which explains the absence of sensorimotor alterations.
14679973, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/meta.12666 by Cochrane France, Wiley Online Library on [19/02/2024].See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions)on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License can be considered "pathological metaphysicians" as well, and study of them also supports the claim that we normally have a sense of substantiality for many things we experience.Consider first Cotard delusion, named after the French neurologist Jules Cotard, who studied it extensively in the 1880s: the patients do not just feel as if they or the things around are unreal but bluntly claim that they are unreal (Cotard 1891).Cotard delusion is usually considered the delusional version of DPD, the idea being that Cotard patients share similar experiences with DPD patients but wrongly consider them as showing that things are unreal.Cotard patients can also indulge in long, puzzled metaphysical meditations (see, for example, the patient of Janet's [1928] named Laetitia or the fascinating case report by Martis [1956]).And just as in the case of DPD patients, early clinicians were amazed to discover that Cotard patients generally had no sensorimotor problems (clinicians of the early twentieth century often lumped together DPD and Cotard delusion) (see Billon 2016).
In the 1920s, the psychiatrist Joseph Capgras also pointed out that some patients suffering from depersonalization or derealization believed that some of their relatives had been replaced by perfect doubles (Capgras, Lucchini, and Schiff 1924).This has been termed "Capgras delusion." 30Capgras patients recognize that their relatives have the same properties they used to have (in fact they can spend a lot of time trying to find at least a small difference, such as a mole on the skin, that would back up their belief).Yet it seems to them that some of these relatives have a different particular nature.Daniel Dennett (1996, 111) once said, "Capgras delusion should send shockwaves to philosophy."If, as is commonly assumed by clinicians and neuropsychologists, Capgras delusion stems from the lack of certain normal experiential features, this delusion indeed suggests that our experience is not normally metaphysically mute. 31 That it does not stop short of the qualitative features of things that the patient would share with a perfect double but reveals (or seems to reveal) the particular nature of at least some of its objects.Together, then, DPD, Cotard delusion and Capgras delusion provide some further empirical support for the claim that our experience bears on the particular and intrinsic nature of things.

| SA N I T Y, FOL LY, A N D T H E R E L I A BI L I T Y OF OU R SE NSE OF PER F ECT R E A L I T Y
At this point, one might grant that (S2) is wrong and that, against (3*), experience is not metaphysically mute.One might also grant, against introverted metaphysicians, that experience's verdict on outer things does not depend on what it says about oneself.Yet one might wonder whether this suffices to solve the problem of reality.After all, if experience is not metaphysically mute but what it says about (ultimate) reality is unreliable, we still have to reject the intuition of reality.And even if the study of DPD patients shows that experience is not metaphysically mute, it does not show that it is metaphysically reliable.This worry is particularly pressing, since, as we have seen, a leading contemporary structuralist, David Chalmers, grants that experience presents the world as not only real but "Edenically real" or "perfectly real" (Chalmers 2022), and yet he argues that we cannot take this appearance of Edenic or perfect 30 On the close connection between DP, DR, and Capgras delusion, see Janet 1928, Balvet (1936), and Christodoulou 1986.Strangely enough, in the very same paper Capgras and his colleagues (1924, 210) present a "Capgras patient" who explicitly claims to be unsure whether she still exists, yet they deny that Capgras delusion involves depersonalization or derealization.I think that what they mean, by this denial, is that this patient's belief that she does not exist stems from the fact that she does not recognize herself well.It is, however, unclear that this suffices to exclude depersonalization, and many clinicians have subsequently associated DP, DR, and Capgras delusion.31 Common explanations of "monothematic" delusions in general, and common explanations of Capgras delusions in particular, posit an abnormal experience The so-called two-factor explanations, which are the most widespread today, additionally posit some abnormally severe cognitive biases (Davies et al. 2001).

BILLON
reality seriously, because it has been discredited by modern science.We have seen too that Chalmers moreover tries to help us bite the bullet by claiming that even though the intuition of (perfect) reality (2*) is false, the world reliably seems real, albeit only imperfectly so (2**).
How could someone like Chalmers (who grants that the silence of experience is false but rejects the intuition of reality (2*) in favor of the intuition of imperfect reality (2**)) describe the case of pathological metaphysicians?She would of course say, first, that, unlike our normal experiences, the impoverished experiences of pathological metaphysical doubters do not represent the world as being perfectly real.But it seems that she would have to add: The experiences of pathological metaphysicians still represent the world as simply real (if not as perfectly real).
After all, except for their impression of unreality, pathological metaphysicians perceive things exactly like we do.There is no structural fact that we would see but that they do not see, and simple, imperfect reality only differs from perfect reality in some Edenic nonstructural facts.
Given that according to someone like Chalmers the impression of imperfect reality, but not the impression of imperfect reality, is veridical, the advocate of (2**) seems condemned to add: (ii) Pathological metaphysicians see the world better than we do.
The first claim, (i), strikes me as simply implausible: DPD patients and Cotard patients describe the world as it appears to them as totally unreal and replete with things, be they individuals or properties, that do not exist at all.I am not sure they would be convinced by a philosopher trying to explain to them that they just miss perfect Edenic reality and that the virtual, dreamlike world they see is obviously real enough (since it shares the same causal structure with the Edenic world they have lost).Chalmers's main argument for the claim that something not perfectly real can still be genuinely real relies, as we have seen, on the claim that imperfectly real things pass, if only imperfectly, the test of non-illusoriness because perfect and imperfect reality are structurally identical.Crucially, however, Chalmers needs to show that being imperfectly real is being real enough to deserve the name.If I understand him correctly, he tries to do that by claiming (a) that things' causal role or "function" is (a very important) part of our ordinary concept of these things, and that provided it is preserved we can count things as genuinely real (Chalmers 2022, 428-30; see also Chalmers 2006, § § 6-8), and by claiming (b) that, accordingly, all our ordinary beliefs (as opposed to our metaphysical beliefs) would remain true if reality were only imperfect reality (127-28). 32The study of DPD suggests that he is wrong on both points.It suggests, first, that if we saw the world as only imperfectly real, we would not regard our ordinary beliefs as true.Indeed, DPD patients commonly say that things do not seem to exist or to have genuine properties such as real colors, and Cotard patients, who, as we have seen, take DPD experiences at face value (and can reflect quite rationally and philosophically on their situation), may reject all ordinary beliefs.But it is hard to claim that our ordinary beliefs would remain true in situation X if, were the world to seem like X and were we to believe we are suddenly plunged into that situation X, we could not regard our ordinary beliefs as true.Now if the truth or all of our ordinary beliefs indeed depend on perfect reality, then our beliefs matter much more for us than Chalmers assumes. 32Chalmers at various places (e.g., 2022, 429, and 2006, § 8) suggests another, pragmatic argument for his claim: even if the world is completely insubstantial, it is very useful to consider red things as really red (and the world as really real), and we would lose too much if we stopped doing that.This argument, however, is consistent with a form of fictionalism to the effect that calling things that play the red causal role "red" and purely structural things "real" is just a useful fiction.It should be emphasized that my present disagreement with Chalmers is in part metaphilosophical.In order to assess whether imperfectly real is real enough, Chalmers resorts to the classical armchair methodology: he envisions a scenario in which the world is not perfectly real but things keep the same causal role (he believes this scenario is actual, but that does not matter for my point), and he wonders: If that is the case, should we say that our ordinary beliefs are correct and that the world is still real?His answer is yes.He takes this to show that our ordinary concepts of, say, colors and shapes, or meliorated versions of them, still apply to imperfect colors and imperfect shapes, and more important, that our ordinary concept of reality (or meliorated versions of it) still applies to imperfect reality.In order to answer the same question, I use a different method: I wonder what we would say (after reflection) if we were suddenly plunged into a world that seemed only imperfectly real to us and that we believed to be only imperfectly real; I use psychopathology to answer this question.The two methods will yield different results when it is difficult to predict the experiences we would have in the envisioned scenario, that is, when the phenomenology is somehow opaque, and when our best concepts are partly recognitional concepts, that is, concepts whose application is partly grounded on experience.The fact that their experiences confer on people with DPD and Cotard syndrome the disposition to believe that things are unreal, and that they do believe that they are unreal, even after long critical reflection, when they trust their experience, suggests that the phenomenology of reality is indeed opaque and that our best concept of reality is indeed recognitional.
Let us now consider (ii).It is not simply counterintuitive.It goes against some of our intuitions that are the most solid and fundamental, some intuitions that delineate mental sanity from pure folly, that are in the background of all our debates and without which we would probably not be capable of understanding each other, let alone philosophizing.The claim that Cotard, Capgras, or even DPD patients do not see things better than we do might be considered as being part of what Searle (1983) calls "the Background," whose abandonment seems more characteristic of psychosis than wisdom.The contrast between psychosis and wisdom, here, is not just meant as a hyperbolic and picturesque illustration of the Moorean argument for the intuition of reality.DPD, Cotard syndrome, and Capgras syndrome are mental disorders.On the most plausible account, they involve a (harmful) dysfunction of the perceptual system (Wakefield 1992).Yet, our perceptual system is fine-tuned, and whatever its proper function is, it is completely unlikely that a disorder of this system could allow it to better fulfill a function such as "getting a more accurate conception of the world."(Think about the probability that by changing the connection of two wires on a radio receiver it might become capable of receiving some hidden radio waves better!By inverting two wires, you are almost certain to prevent your radio receiver from functioning at all.) 33  It is true that some philosophers and psychiatrists in the phenomenological tradition have suggested that people with schizophrenia are somehow "sick of truth" and can see things better than we do. 34Recently, the Buddhist scholar and philosopher Monima Chadha (ms.) has precisely claimed that DPD patients support the Buddhist no-self theory (presupposing that they see things better than we ordinarily do).I am sensitive myself to the romantic allure of taking the part of delusions and folly.I do not think, however, that this is a philosophically tenable attitude.

33
I develop this argument in more detail elsewhere (Billon 2023c).Many people believe that "depressive realism" shows that some mental disorders can make us perceive some things more accurately.Yet the evidence for depressive realism is rather contrasted (Moore and Fresco 2012).There are, moreover, reasons to believe that the most influential results in support of depressive realism cannot be replicated with up-to-date methods and measurement techniques (Dev et al. 2022). 34Since the pioneering works of Blankenburg, the comparison of psychosis with the phenomenologist's bracketing of the "natural attitude" toward the world has given rise to a rich literature that tends to portray people with schizophrenia as "spontaneous philosophers" (Blankenburg 2001, Depraz 2003, Stanghellini 2004; see also Kusters 2016).In this tradition, though, this comparison is not usually construed as a criticism of philosophy but rather, somehow, as praise of psychotics' perspicacity.
We can conclude that the study of pathological metaphysicians shows that our experiences are not metaphysically mute, and there is good reason to believe that when they present the world as being perfectly real we should simply trust them.If, as I have argued, this impression of reality is an impression of substantiality, we should also conclude that our experiences give us some insight into the deep nature of things.The intuition of reality is correct, then, and it is an intuition of substantiality.

| TOWA R D S A M ETA-PROBL E M OF R E A L I T Y
The study of metaphysician doubters and connected delusions still leaves many questions unanswered, and it should definitely be pursued further.I have also remained silent about what is wrong with the classical arguments for the silence of experience and against the intuition of reality.
I hope to have shown, however, that what we know of DPD already suggests that our ordinary experience is not in fact metaphysically mute and that the intuition of reality is in fact quite plausible: experience goes beyond the structural properties of individuals and talks to us about their deepest nature, and we have good reason to trust it on this matter.The world as it spontaneously appears to us, populated with mid-sized objects and people we are acquainted with (each having primitive intrinsic qualities and a particular nature), the world we could call, with Sellars (1962) "manifest," is not a mere appearance but, in fact, metaphysical reality. 35 This naive-one might even say "trivial"-solution to the problem of reality raises a final problem, with which I would like to conclude.Why has the problem of reality been considered a problem in the first place?Why haven't we stayed content with the intuition of reality and dismissed the silence of experience?Certainly the classical arguments against the intuition of reality (which, unlike their conclusion, I have not tried to defuse here) have a certain intuitive appeal.But we might have recognized that and remained adamant that their conclusion is wrong-a bit like most philosophers being adamant that even though we can derive that the claim "This sentence is false" is true and false from very plausible premises, this should not be taken to imply that there are true contradictions.We would have talked about paradoxical arguments against the intuition of reality, but we would not seriously have considered their conclusion.
One answer to this meta-problem of reality, suggested half-jokingly, as we have seen, by Janet, is that philosophers suffer from a mental disorder such as DPD.Janet is not totally alone here.There is a long tradition that contrasts the practice of philosophy with ordinary life and some philosophical conclusions with common sense, to assimilate entire sections of the discipline as a form of mental illness.This tradition, which can be traced back both to ancient criticisms against the skeptics and to the Pauline critique of the philosopher's reason, focused with Descartes (see Darriulat 1996) and Hume (1739Hume ( /1969, 316) , 316) on the supposed links between an excess of philosophical reflection and melancholy-a disease known for leading to episodes of depersonalization and derealization and, in its later stages, sometimes, to Cotard's delusion. 36Even though he rejected the naive solution and endorsed the philosophers' solution, the historian of philosophy and Descartes scholar I mentioned in the Introduction, Ferdinand Alquié, can be regarded as having developed a full 35 This obviously raises a further question that goes well beyond the scope of this paper: How is such a metaphysics consistent with the scientific image of the world?See Bernstein 2021 for interesting suggestions. 36Major milestones in this tradition also include Renaissance and early modern skeptics such as Montaigne (1580/2007, II, § 12), commonsense philosophers (Reid 1764/1983, 10), Schopenhauer's (1969) characterization of solipsism as a disease that should be cured, Nietzsche's (1974) diagnosis of philosophers' search for a hidden reality underlying appearances, and of course Wittgenstein's (1969, § 467) remarks on philosophers' confusing, acontextual, use of ordinary words.See also my footnotes 34 and 38.
14679973, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/meta.12666 by Cochrane France, Wiley Online Library on [19/02/2024].See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions)on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License philosophical system that takes Janet's suggestion extremely seriously. 37Noticing two 1631 letters to Guez de Balzac in which Descartes seems to avow episodes of derealization, Alquié (1955, 27;1956;1974/2023, 329-33) argued that Descartes's rationalism was in fact secretly indebted to some very personal but metaphysically relevant experiential insights-"derealization" insights to the effect that (2*) might be wrong and (3*) true.Alquié later generalized this point, arguing that we were all separated from what is perfectly real (he calls that "Being") and that any authentic philosophy is an endeavor to make explicit something like an experience of derealization toward the "objective world."He argued, finally, that philosophers' experience of derealization or quasi-derealization presupposes a prior but radically elusive experience of perfect realness (Alquié 1979)."No one would become a philosopher," he said in a 1974 note, "if he were not first a little crazy, I mean if he were not led by some feeling of unreality experienced in front of things, to ask himself questions that reasonable people do not ask themselves" (Alquié 1974(Alquié /2023, 331), 331). 38Earlier, he made the point by invoking a general "nostalgia of Being" driving philosophers' reason (Alquié 1955).Like Schopenhauer and Maine de Biran before him, Alquié took the experience of perfect realness that derealization, as he claimed, presupposes to be affective and primarily introverted.Decisively, he also took it to be involved in folly, dreams, and poetry.He, for example, argued that the feeling of reality we have toward dreams and the insights delivered by poetry let us know that the objective world is not all there is to reality and thus let us, so to speak, derealize this objective world.This answer to the meta-problem of reality is interesting, but it is ultimately unconvincing.For most philosophers do not suffer from derealization, and even when they have had derealization-like experiences, the question of why they do not simply dismiss these experiences as pathological and unreliable remains unanswered by Alquié.
Even though he mentions Janet a couple of times and was a great friend of Lacan, Alquié was more interested in surrealism than in psychology.This is unfortunate: had he investigated the psychology of derealization better, he would have found that the experience of perfect reality was not primarily introverted and did not typically depend on folly, dreams, or poetry.It is much more mundane than Alquié suggests it is (and indeed much more widespread than the experience of derealization or quasi-derealization, which he seemed to have regarded as almost always veridical and, so to speak, normal).He would also have found a better response to the meta-problem of reality that fits some aspects of his theory but avoids picturing philosophers as madmen.According to Alquié, we really are separated from perfect reality, even though we can get a hint of its existence through the subjective viewpoint of our "affective consciousness" that is essential to dreams and poetry.Philosophers are more perspicuous than nonphilosophers, on his account, because of the weight they secretly grant to those affective hints (even when they publicly invoke reason), which paradoxically makes them a little crazy ("no one would become a philosopher," he says, "if he were not first a little crazy"). 39 Modern neuropsychology and clinical psychology partly vindicate Alquié on one of these last points.They indeed give us reason to believe that DPD stems from something like a cortico-limbic disconnection dissociating our ordinary experiences from affectivity, depriving 37 Alquié (1906Alquié ( -1985) ) was very close to the Surrealists when he was young.He became an influential professor at the Sorbonne after World War II, where he taught philosophy to a whole generation of important philosophers (including Deleuze and Derrida).He seems to have had an important influence on Michel Henry as well. 38The impetus of this 1974 note comes from a much commented on debate between Foucault and Derrida on the relative role of madness and dreams in Descartes's Second Meditation (Foucault 1972, 55-58, Derrida 1963, and Foucault 1972, 583-603).

39
It might be argued that despite the proximity of their themes, pathological metaphysicians and philosophers differ in the quality of their doubts.The doubts of the former are more affectively intense and akin to the doubts affecting OCD patients rather than to calm Cartesian doubts (see Vazard 2019).I believe, however, that this difference is a matter of degree, and it is not clear to me that all philosophical doubts are perfectly calm and non-obsessional.
these experiences of their normal emotional warmth (Sierra 2009, Gerrans 2019) and disturbing their subject's subjective point of view on the world (Billon 2023a).The sense of reality, as Alquié thought, is indeed affective, or at least very closely tied to affectivity.It is, however, neither rare, oneiric, nor exclusively introverted.If we assume, as I have argued we should, that Janet was right, against Alquié, Chalmers, and almost the whole philosophical tradition, in believing that our normal sense of reality is both metaphysically loaded and accurate, this, in turn, suggests that what is peculiar (and wrong) with metaphysicians is not that they take seriously some elusive affective hints that acquaint them with Being and let them notice its absence in the ordinary world.It is, to the contrary, that they suppress or neglect the role affects and subjectivity should play in philosophical cognition, picturing the good metaphysician as a thoroughly depersonalized subject.By neglecting the subjective point of view and our affective embedding in the world, the philosophical reflection would simultaneously mimic the detached, hyper-objective viewpoint of DPD patients and stumble on the problem of reality.The culprit is the overintellectualism that naturally leads metaphysical inquirers away from lived subjective experience into a realm of gutless speculation where philosophers strangely meet mentally disordered people. 40  ORC I D Alexandre Billon https://orcid.org/0000-0001-8905-0298

R E F E R E NC E S
(3*) The silence of experience.Experience is mute about what is maximally real.Now, arguably, (4*), (2*), and (3*) are inconsistent.