The Crazyist Metaphysics of Mind
Department of Philosophy
University of California at Riverside
Riverside, CA 92521-0201
eschwitz at domain- ucr.edu
February 19, 2014
The Crazyist Metaphysics of Mind
Crazyism about X is the view that something that it would be crazy to believe must be among the core truths about X. In this essay, I argue that crazyism is true of the metaphysics of mind. A position is “crazy” in the intended sense if it is contrary to common sense and we are not epistemically compelled to believe it. Crazyism can be treated as the conjunction of two sub-theses: (1.) that something contrary to common sense must be true and (2.) that whatever that true thing is, we are not epistemically compelled to believe it. I defend the first thesis on grounds of the probable incoherence of folk metaphysics, from which it follows that any fully fleshed-out metaphysics will inevitably conflict with some piece of that incoherent story. I defend the second thesis on three grounds: peer disagreement, lack of a compelling method for resolving metaphysical disputes about the mind, and the dubiousness of the general cosmological claims with which metaphysical claims about the mind are entangled.
The Crazyist Metaphysics of Mind
Bizarre views are a hazard of metaphysics. The metaphysician starts, seemingly, with some highly plausible initial commitments or commonsense intuitions – that there is a prime number between 2 and 5, that I could have had eggs for breakfast, that squeezing the clay statue would destroy the statue but not the lump of clay. She thinks long and hard about what, exactly, these claims imply. In the end, she finds herself positing a realm of abstract Platonic entities, or the real existence of an infinite number of possible worlds, or a huge population of spatiotemporally coincident things on her mantelpiece. I believe that there is not a single broad-ranging exploration of the fundamental issues of metaphysics that doesn’t, by the end, entangle its author in seeming absurdities. Rejection of these seeming absurdities then becomes the commonsense starting point of a new round of metaphysics, by other philosophers, which in turn generates a complementary bestiary of metaphysical strangeness. Thus are philosophers happily employed.
I see three possible explanations of why philosophical metaphysics is never thoroughly commonsensical:
First possible explanation. A thoroughly commonsensical metaphysics wouldn’t sell. It would be too boringly obvious, perhaps. Or maybe it would lack a kind of elegant serviceability or theoretical panache. Or maybe it would conflict too sharply with what we think we know from science. The problem with this explanation is that there should be at least a small market for a thoroughly commonsensical philosophy, even if that philosophy is gauche, tiresome, and scientifically stale. Common sense might not be quite as fun as Nietzsche’s eternal recurrence or Leibniz’s windowless monads; it might not be as elegantly useful as Lewis’s possible worlds or as scientifically current as __________ [insert ever-changing example]; but a commonsensical metaphysics ought to be attractive to at least a certain portion of philosophers. At least it ought to command attention as a foil. It oughtn’t be so downmarket as to be entirely invisible.
Second possible explanation. Metaphysics is very difficult. A thoroughly commonsensical metaphysics is out there to be discovered; we simply haven’t found it yet. If all goes well, someday someone will piece it all together, top to bottom, with no serious violence to common sense anywhere in the system. I fear this is wishful thinking against the evidence. In the next several sections I will discuss the case of the metaphysics of mind in particular.
Third possible explanation. Common sense is incoherent in matters of metaphysics. Contradictions thus inevitably flow from it, and no coherent metaphysical system can respect it all. Although ordinary common sense serves us fairly well in practical maneuvers through the social and physical world, common sense has proven an unreliable guide in cosmology, probability theory, microphysics, neuroscience, macroeconomics, evolutionary biology, structural engineering, medicine, topology…. If, as it seems to, metaphysics more closely resembles these latter endeavors than it resembles reaching practical judgments, we might excusably doubt the dependability of common sense as a guide to metaphysics. Undependability doesn’t imply incoherence, of course. But it seems a natural next step in this case, and it would tidily explain the historical fact at hand.
On the first explanation, we could easily enough invent a thoroughly commonsensical metaphysical system if we wanted one, but we don’t want one. On the second explanation, we do want one, or enough of us do, but we haven’t yet managed to construct it. On the third explanation, we can’t have one. I hope you’ll agree with me that the third has at least some prima facie merit.
Common sense might be culturally variable. So whose common sense do I take to be at issue in this argument? I suspect it doesn’t matter. All metaphysical systems in the philosophical canon, I’m inclined to think, conflict both with the common sense of their milieu and with current Western common sense. Eternal recurrence, windowless monads, and the real existence of an infinitude of possible worlds were never part of any society’s common sense.
Some readers will disagree about the existence of the phenomenon I aim to explain; they will think that there is a thoroughly commonsensical metaphysics on the market. To some extent, I’m simply taking as a premise that there is none, and I’m inviting you to agree based on your own reading of historical and contemporary metaphysics. Maybe the premise will appeal better, though, if I highlight its intended scope. It concerns only broad-ranging explorations of fundamental metaphysical issues, especially the issues where seeming absurdities congregate: mind and body, causation, identity, the catalogue of entities that really exist. Some skating treatments and some deep treatments of narrow issues might dodge the charge.
Who might count as a thoroughly commonsensical metaphysician? Aristotle, I’ve sometimes heard. Or Scottish “common sense” philosopher Thomas Reid. Or G.E. Moore, famous for his “Defence of Common Sense” (1925). Or “ordinary language” philosopher P.F. Strawson. Or Wittgenstein. But Aristotle didn’t envision himself as developing a commonsensical view: In the introduction to the Metaphysics Aristotle says that the conclusions of sophisticated inquiries such as his own will often seem “wonderful” to the untutored and contrary to their initial opinions (4th c. BCE/1928); and Aristotle generally conceives his project as in part to distinguish the true from the false in common opinion. Moore, though fierce in wielding common sense against his foes, seems unable to preserve all commonsense commitments when he develops his positive views in detail, for example in his waffling about “sense data” (1922, 1953, 1957). Strawson struggles similarly, especially in his 1985 book, where he can find no satisfactory commonsense account of mental causation. Wittgenstein does not clearly commit to a detailed metaphysical system. Reid I will discuss briefly in section vi.
The argument of this section is an empirical explanatory or “abductive” argument. The empirical fact to be explained is that all metaphysical systems defy common sense. An attractive possible explanation of this fact, I submit, is that common sense is incoherent on matters metaphysical, so that no self-consistent and detailed metaphysical system can satisfy all commonsense constraints.
It doesn’t follow that we must abandon appeals to common sense in metaphysics. Perhaps we could abandon common sense if we had some clearly superior tool to use instead – but we don’t. Or so I will argue in sections ix and x.
Let’s call a position bizarre if it’s contrary to common sense. And let’s say that a position is contrary to common sense just in case most people without specialized training on the issue confidently, but perhaps implicitly, believe it to be false. This usage traces back to Cicero, who calls principles that ordinary people assume to be obvious “sensus communis” and who describes violation of common sense as the orator’s “worst possible fault” – presumably because the orator’s views will then be regarded as ridiculous by his intended audience (1st c. BCE/2001, p. 60, De Oratore I.ii.12). Common sense is what it seems ridiculous to deny.
To call a position bizarre is not necessarily to repudiate it. The truth is sometimes strange. Relativity theory is bizarre. Various bizarre things are true about the infinite. Common sense errs, and we can be justified in thinking so.
Despite the limitations of common sense, we are not ordinarily justified in believing bizarre things without compelling evidence. In the matters it traverses, common sense serves as an epistemic starting point that we reject only with sufficient warrant. To believe something bizarre on thin grounds – for example, to think that the world was created five minutes ago, or that you are constantly cycling through different immaterial souls (assuming you have no special warrant for these views) – seems crazy. I stipulate, then, the following technical definition of a crazy position: A position is crazy if it’s bizarre and we are not epistemically compelled to believe it.
One needn’t, of course, be clinically insane to accept crazy views, and not all crazy views are as crazy as the two just mentioned. Many philosophers and some scientists embrace positions contrary to common sense and for which the evidence is less than compelling. In fact, to convert a position from crazy to merely bizarre might be the highest form of academic success. Einstein, Darwin, and Copernicus (or maybe Kepler) all managed the conversion – and in the case at least of Copernicus common sense eventually relented. Intellectual risk-takers nurture the crazy and see what marvels bloom. The culture of contemporary Anglophone academia, perhaps especially philosophy, overproduces craziness like a plant produces seeds.
Crazyism about a topic, then, is the view that something crazy must be among the core truths about that topic. Crazyism can be justified when we have good reason to believe that one among several bizarre views must be true about the topic in question but where the balance of evidence leaves no individual view decisively supported over all the others. We might find ourselves rationally compelled to believe that either T1, T2, T3, or T4 must be true, where each of the T’s is crazy.
Crazyism might be justified in interpreting quantum mechanics. The “many worlds” interpretation, for example, seems to sharply conflict with ordinary common sense. And it also seems that the balance of evidence does not compellingly favor this view over all competitors. Thus, the view is crazy in the sense defined. If the same holds for all viable interpretations of quantum mechanics, then crazyism would be warranted in that domain.
I will argue below that crazyism is warranted in the metaphysics of mind. I will argue that any well developed materialist metaphysics will be crazy, in the intended sense of the term. I will argue the same for any well developed dualist metaphysics. And the same for idealism (well developed or not). And the same for positions that reject all three of these views or aim to reconcile or compromise among them. But some metaphysical theory of this sort must be true – that is, either some form of materialism, dualism, or idealism must be true or some sort of rejection or compromise approach must be true. So something crazy must be among the core truths in the metaphysics of mind.
To be crazy, a position must be both bizarre and uncompelled by the evidence. Let’s consider bizarreness first, and let’s consider materialism first.
The materialist (or “physicalist”) position is difficult to characterize precisely. This might be a problem for the view – though if so, I’m inclined to think that it’s just a manifestation of a more general problem that I’ll discuss in section x. As a working approximation, let’s characterize materialism as the view that everything in the universe is composed of, or reducible to, or most fundamentally, material stuff, where “material stuff” means things like elements of the periodic table and the various particles or waves or fields that interact with or combine to form such elements, whatever those particles, waves, or fields might be, as long as they are spatial and not intrinsically mental. The two historically most important competitor positions are idealism and substance dualism, both of which assert the existence of an immaterial soul.
Materialism per se might be bizarre. People have a widespread, and maybe developmentally and cross-culturally deep, tendency to believe that they are more than just material stuff. Not all unpopular views violate common sense, however, by my definition of “common sense” above. It depends how confidently the opposing view is held; and that’s a bit difficult to assess in this case.
However, my thesis not that materialism per se is bizarre, but rather the weaker thesis that any well-developed materialist view – any view developed in enough detail to commit on specific metaphysical issues about, for example, mental causation and the distribution of consciousness among actual and hypothetical systems – will inevitably be bizarre.
I offer four considerations in support of this claim.
Antecedent plausibility. As noted above, traditional commonsense folk opinion has proven radically wrong about central issues in physics, biology, and cosmology. On broad inductive grounds, scientifically inspired materialists ought to be entirely unsurprised if there are similarly sharp conflicts between commonsense opinion and the best materialist theories of consciousness. It seems likely that folk opinion about the nature of mentality will have mostly been shaped by evolutionary and social pressures ill-tuned to the metaphysical truth about cases outside the usual run of daily life, such as pathological, science fiction, and phylogenetically remote cases. Materialists have reason to suspect serious shortcomings in the folk psychological materials from which commonsense judgments must ultimately be constructed.
Leibniz’s mill and Crick’s oscillations. Leibniz asks the reader to imagine entering into a thinking machine as though one were entering a mill. Looking around, he says, one will only see parts pushing each other – nothing to explain perceptual experience (1714/1989, p. 215 [§ 17]). Frank Jackson’s (1986) “Mary” and the “zombies” of Robert Kirk (1974) and David Chalmers (1996) draw on a similar thought: Something in us appears to rebel against the idea, central to materialism, that particular motions or configurations of particular bits of material stuff could ever give rise to, or explain, or constitute, full-color conscious experience without the addition of something extra. And the more particular the materialist’s commitments, it seems, the stiffer the resistance. Francis Crick (1994) equates human consciousness with synchronized 40-hertz oscillations in the subset of neurons corresponding to an attended object. Nicholas Humphrey (1992, 2011) equates consciousness with reentrant feedback loops in an animal’s sensory system. Both Crick and Humphrey report that popular audiences vigorously resist their views. Common sense fights them hard; their views are not just tepidly unintuitive. When a theorist commits to a particular materialist account – this material process is what consciousness comes down to! – doing so seems to vividly reveal the inescapable bizarreness of materialist theorizing about the mind.
Mad pain, Martian pain, or the denial of local supervenience. There are several issues on which materialist views are, I think, forced to select among commitments any one of which violates common sense. Lewis sets up one such issue in his classic “Mad pain and Martian pain” (1980). Simple versions of materialism appear to imply that to be in pain is either just to be in a particular brain state or, alternatively, to be in a state that plays a particular causal or functional role relating the system’s inputs and outputs (views often associated with Smart 1959 and Putnam 1965 respectively). But reflection reveals both options to have bizarre implications. If pain requires being in a particular brain state, then no being constructed very differently than us – no hypothetical Martian, for example, who operates by internal hydraulics rather than by neurons with axons and dendrites – could experience pain, no matter how pain-like her outward behavioral patterns. However, if pain, instead, requires being in a particular functional role, then no being, no “mad man”, could experience pain that was caused in unusual ways (say, by moderate exercise on an empty stomach) and in turn caused unusual reactions (say, finger-snapping and concentration on mathematics). Also on the second view (a point not emphasized by Lewis), any weirdly constructed system – maybe made out of beer cans and windmills (Searle 1984) or out of people trading messages in China (Block 1978/2007) – could experience pain if it instantiates the right types of transition states between its inputs and its outward behavior. In this way, the simplest materialist theories seem to compel a choice between competing bizarrenesses.
Lewis offers an escape: To be in pain is to be in a state that plays the functional role of pain for the right population. That state might be one particular type of brain state for human beings, and a very different type of interior state for hydraulic Martians; and “mad” cases might be cases in which that state is realized in that individual but doesn’t play its usual functional role. More generally, to be in pain on Lewis’s account and most subsequent materialist accounts is to be in a physical state that normally plays a certain causal role, where “normally” can be understood in various ways, e.g., with reference to a population or with reference to the developmental or evolutionary history of the organism (Dretske 1995; Tye 1995, 2009). On this option, pain no longer supervenes locally: Whether one is in pain depends on how one’s current biophysical configuration is seated in the broader universe, e.g., on who else is in your group or on events in the past. But now new bizarrnesses blossom forth. If pain depends on the past, then you and I might be molecule-for-molecule identical with each other now, screaming and writhing equally, equally cursing our maker, but because of differences in personal or evolutionary history, you’re in pain and I’m not. If pain depends, instead, on what is currently normal for your species or group, that could change with selective genocide or a speciation event beyond your ken. Strange forms of anesthesia! The issue thus appears to present a trilemma for the materialist: either accept neural chauvinism (no Martian pain), accept flat-footed functionalism (beer can pain and no mad pain), or deny local supervenience (anesthesia by speciation or genocide). Even if some materialist view can evade all three horns, it seems a reasonable conjecture that no well developed materialist view can simultaneously respect all our commonsense judgments about this cluster of issues.
Group consciousness. It would be bizarre, I hope you’ll agree, to suppose that the United States has a stream of conscious experience over and above the conscious experiences of the people who compose it. Yet it is unclear by what materialist standard the United States, considered as a concrete entity with people as some or all of its parts, lacks consciousness. The subparts of the United States (people and groups of people) are massively informationally interconnected and mutually dependent, including in incredibly fancy self-regulating feedback loops. The United States gathers, stores, and manipulates information, at the group level, as a result of these interconnections, seeming to represent its internal and external conditions, including in complex ways that transcend the understanding of any single individual. Using those informational representations, the United States responds, (semi-)intelligently and self-protectively, in a coordinated way, to opportunities and threats. The United States shows skillful attunement to environmental inputs in warring and spying on other nations, refining and updating its representations and action patterns over a long history. These are the kinds of capacities and structures that materialists typically regard as the heart of mentality. Nations do all these things via the behavior of their subparts, of course; but on materialist views individual people also do what they do via the behavior of their subparts. A planet-sized alien who squints might see individual members of the United States as so many buzzing pieces of a somewhat diffuse body consuming bananas and automobiles, invading Iraq, exuding waste.
Even if the United States lacks a little something needed for consciousness, it seems we ought at least hypothetically be able to change that thing, and so generate a stream of experience. We presumably needn’t go nearly as far as Block does in his famous “Chinese nation” example (1978/2007) – an example in which the country of China implements the exact functional structure of someone’s mind for an hour – unless we suppose, bizarrely, that consciousness is only possible among beings with almost exactly our psychology at the finest level of functional detail. If we are willing to attribute consciousness to relatively unsophisticated beings (frogs? rabbits?), it seems that the United States acts with as much coordination and intelligence, if on a larger scale.
In Schwitzgebel (forthcoming), I explore this issue in detail. If we accept, with most materialists, and with at least one strand of common sense, that oddly formed aliens could be conscious, then we should also accept that group entities could in principle be conscious. If we also accept, with most materialists and with common sense, that rabbits are conscious, we should accept that even relatively dumb group entities could be conscious. And finally, the United States would seem to be a relatively dumb group entity of the relevant sort, if standard materialist criteria are applied without bias. What blinds us to this fact, I suspect, is mainly morphological prejudice against spatially distributed entities and against large entities whose mechanisms we can see (one materialist diagnosis of people’s reaction to Leibniz’s mill, discussed above). The materialist can try to dodge this conclusion in several ways – for example, she could deny that conscious entities can have other conscious entities as parts or she could assert that consciousness requires specific architectural constraints that the U.S. does not satisfy – but such attempted escapes always seem to bring different bizarre consequences in their train.
I don’t expect to convince you, in this brief presentation, that the United States is literally phenomenally conscious. I don’t draw that conclusion myself, though I do regard it as an open possibility. What I do hope seems plausible is this: Any well-developed materialist view of consciousness will probably have to commit to the literal phenomenal consciousness of groups of people under some conditions jarring to common sense – unless, alternatively, the view is bizarrely restrictive about the conditions under which consciousness can arise (e.g., denying the possibility of rabbit or alien consciousness). Materialists have not yet really begun to explore this nest of issues, but once they do so, it seems unrealistically optimistic to hope that sharp violations of common sense can be entirely avoided.
The literal group-level consciousness of the United States, anesthesia by genocide, beer-can pain – those are the kind of strikingly weird bizarrenesses I have in mind. I have expanded upon these points because I believe materialism is often presented in a sketchy way that masks the bizarre theoretical choices that are swiftly forced upon the thoughtful materialist. Even if I have failed in my choice of specific examples, I hope that the general point is still plausible on broad, inductive grounds, and in light of our knowledge of the kinds of factors that presumably shape nonspecialists’ opinions about the metaphysics of mind. The more we learn about cosmology, microphysics, mathematics, and other such foundational matters, both cosmic and a priori, the grosser the violations of common sense seem to become. The materialist should expect no lesser weirdness from the metaphysics of mind.
One alternative to materialism is dualism, the view that people are not wholly material entities but rather possess immaterial souls in addition to their material bodies. (By “dualism”, unqualified, I mean substance dualism, which posits an immaterial soul. “Property dualism” I will discuss briefly below.) Although dualism has merits as a first pass at a commonsense metaphysics of mind, from the 17th century to the present, the greatest philosophers of the Western world have universally found themselves forced into bizarre views when attempting to articulate the metaphysics of immateriality. I regard this history as significant empirical evidence that a well developed metaphysics of substance dualism will unavoidably be bizarre.
Attempts at commonsense dualism founder, it seems, on at least two broad issues: the causal powers of the immaterial mind and the class of beings with immaterial minds. I assume readers are broadly familiar with dualism’s troubled history on these matters. How can the immaterial soul affect a material world? Do only human beings have immaterial souls, or do non-human animals also have them – and if the latter, how do we avoid the slippery slope to panpsychism?
Let’s briefly consider two dualists whose views are sometimes thought to be close to common sense: Reid and Descartes.
Reid’s explicit and philosophically motivated commitment to common sense often leads him to refrain from advancing detailed metaphysical views – which is of course no harm to my thesis. However, in accord with my thesis, on those occasions where Reid does develop views on the metaphysics of dualism, he appears unable to sustain his commitment to common sense. On the scope of mentality, Reid is either silent or embraces panpsychism: He attributes immaterial souls to vegetables (esp. in 1774-1778/1995, 3.X), but it’s unclear whether Reid thinks such immateriality is sufficient for mentality (leading to a view of mentality as radically abundant) or not (in which case Reid did not develop a criterion of non-human mentality and so his view is not “well developed” in the relevant sense). On causal powers, Reid regards material events as causally epiphenomenal: Only immaterial beings have genuine causal power. Physical objects cannot produce motion or change, or even to cohere into shapes, without the regular intervention of immaterial beings (1774-1778/1995; 1788/2010). Reid recognizes that this view conflicts with the commonsense opinions of ordinary people – though he says this mistake of the “vulgar” does them no harm (see 1788/2010, IV.3). Despite his general commitment to common sense, Reid explicitly acknowledges that on some issues human understanding is weak and common sense errs (see also 1785/2002, I.1).
Descartes advocates an interactionist approach to the causal powers of the soul, according to which activities of the soul can influence the brain. Although this view is perhaps somewhat less jarring to common sense than some of the other options, it does suggest an odd and seemingly unscientific view of the behavior of neurons; it requires some contortions to explain how the rational, non-embodied processes of the immaterial soul can be hijacked by drugs and alcohol; and on Descartes’ view, non-human animals have no more thought or sensory experience than does a cleverly made automaton (1649/1991). Descartes’s opponents imagined Descartes flinging a cat out a window while asserting that animals are mere machines – an image intended to illustrate the metaphysical craziness of Descartes, his radical departure from common sense.
The third historically important position is idealism, the view that there is no material world at all but only a world of minds or spirits, in interaction with each other or with God, or wholly solipsistic. As most idealists acknowledge, idealism is not the ordinary view of non-philosophers (e.g., Berkeley 1710-1713/1965, PHK §4). No one, it seems, is born an idealist. They are convinced, against common sense, by metaphysical arguments or by an unusual religious or meditative experience. Idealism also inherits the bizarre choices about causation and the scope of ensoulment that trouble dualist views.
The bizarrenesses of materialism and dualism may not be immediately evident, manifesting only when details are developed and implications clarified. Idealism, in contrast, is bizarre on its face.
There might be an alternative to classical materialism, substance dualism, or idealism; or there might be a compromise position. Maybe Kant’s transcendental idealism (1781/1787/1998) is such an alternative or compromise, or maybe some sort of Russellian (1921, 1927) or Chalmersian (1996) neutral monism or property dualism is. However, I think we could hardly accuse Kant, Russell, or Chalmers of articulating a commonsense view of the metaphysics of mind. Chalmers, for example, offers no good commonsense answer to the problems of immaterial causation and the scope of immateriality, tentatively favoring epiphenomenalism and panpsychism: All information processing systems, even thermostats, have conscious experience or at least “proto-consciousness”, but such immaterial properties play no causal role in their physical behavior. The attractions of Kant, Russell, and Chalmers lie, if anywhere, in their elegance and rigor rather than their commonsensicality.
Alternatively, maybe there’s no metaphysical fact of the matter here. Maybe the issue is so ill-conceived that debate about it is hopelessly misbegotten (Carnap 1928/1967, 1932/1959; maybe Searle 1992, 2004). Or maybe asking metaphysical questions of this sort takes us too far beyond the proper bounds of language use to be meaningful. But this type of view, too, seems bizarre. The whole famous mind-body dispute is over nothing real, or nothing it makes sense to try to talk about? There is no fact of the matter about whether something in you goes beyond the merely physical or material? We can’t legitimately ask whether some immaterial part of you might transcend the grave? It’s one thing to allow that facts about transcendent existence might be unknowable – an agnostic view probably within the bounds of commonsense options – and it’s one thing to express the view, as some materialists do, that dualists speak gibberish when they invoke the immaterial soul; but it’s quite another thing, a much more radical and unintuitive thing, to say that there is no legitimate sensible interpretation of the dualist-materialist(-idealist) debate, not even sense enough to allow the materialist coherently to express her rejection of the dualist’s transcendent hopes.
I am making an empirical claim about the history of philosophy and offering a psychological explanation for this putative empirical fact. The empirical claim is that all existing well developed accounts of the metaphysics of mind are bizarre. The psychological explanation is that common sense is incoherent with respect to the metaphysics of mind. Common sense, and indeed I think simple logic, requires that one of four options be true: materialism, dualism, idealism, or a compromise/rejection view. And yet common sense conflicts with each option, either on its face or implicitly as revealed when metaphysical choices are made and implications pursued. If common sense is indeed incoherent in the metaphysics of mind, then the empirical claim can be modally generalized: It is not possible to develop a metaphysics of mind that is both coherent and non-bizarre by the standards of current common sense, if that view involves specific commitments on tricky issues like fundamental ontology, mind-body causation, and the scope of mentality. Call this thesis universal bizarreness.
Crazyism requires conjoining universal bizarreness with a second thesis, universal dubiety, to which I will now turn. The universal dubiety thesis is just the thesis that none of the bizarre options compels belief. Even on the fairly thick slicing of the options I’ve been using –materialism vs. dualism vs. idealism vs. compromise/rejection – no one option probably deserves credence in the philosophical community much in excess of 50%.
I offer three arguments for universal dubiety.
An Argument from Disagreement.
When experts disagree about some proposition, doubt about that proposition is the most reasonable response, unless the opinions of experts on one side can be disregarded. Experts disagree about basic issues in the metaphysics of mind, such as the truth of materialism vs. dualism vs. idealism vs. a compromise/rejection view. So unless there is good reason to disregard the opinions of experts on all but one side of the dispute, doubt is the most reasonable response. Usual reasons for discounting experts, such as disproportionate ignorance or bias on all but one side, do not seem to apply to the present case.
Thomas Kelly (2005) has argued that you may disregard peer dissent when you have “thoroughly scrutinized the available evidence and arguments” on which your disagreeing peer’s judgment is based. But we cannot disregard peer disagreement in philosophy of mind on the grounds that this condition is met. The condition is not met. No philosopher has thoroughly scrutinized the evidence and arguments on which all of her disagreeing peers’ views are based. The field is too large. Some philosophers are more expert on the literature on a priori metaphysics, others on arguments in the history of philosophy, others on empirical issues; and these broad literatures further divide into subliteratures and sub-subliteratures with which philosophers are differently acquainted. Furthermore, epistemic peers, though overall similar in intellectual capacity, tend to differ somewhat in the exact profile of virtues they possess. Consequently, even assessing exactly the same evidence and arguments, convergence or divergence with one’s peers should still be epistemically relevant if the evidence and arguments are complicated enough that their thorough scrutiny challenges the upper range of human capacity across several intellectual virtues – a condition that the metaphysics of mind appears to meet. Some philosophers are more careful readers of opponents’ views, some are more facile with complicated formal arguments, some are more imaginative in constructing hypothetical scenarios, etc., and world-class intellectual virtue in any one of these respects can substantially improve the quality of one’s assessments of arguments in the metaphysics of mind. Every philosopher’s preferred metaphysical position is rejected by a substantial proportion of philosophers who are overall approximately as well informed and intellectually virtuous as she is, and who are also in some respects better informed and more intellectually virtuous than she is. Under these conditions, I submit, a high degree of confidence in one’s position is epistemically unwarranted.
Try this thought experiment. You are shut in a seminar room, required to defend your favorite metaphysics of mind for six hours (or six days, if you prefer) against the objections of Ned Block, David Chalmers, Daniel Dennett, and Saul Kripke. Just in case we aren’t now living in the golden age of metaphysics of mind, let’s add Kant, Leibniz, Hume, Zhu Xi, and Aristotle too. (First we’ll catch them up on recent developments.) If you don’t imagine yourself emerging triumphant, then you might want to acknowledge that the grounds for your favorite position might not really be very compelling.
Consider everyone’s favorite philosophy student: She vigorously champions her opinions, while at the same time being intellectually open and acknowledging the very substantial doubt that appropriately flows from her awareness that others think otherwise, despite those others being in some ways better informed and more capable than she is. Even the best professional philosophers still are such students, or should aspire to be, only in a larger classroom.
A No-Method Argument.
There is no conscious-ometer. Nor should we expect one soon. There is also no material-world-ometer. The lack of these devices problematizes the metaphysics of mind.
Samuel Johnson kicked a stone. Thus, he said, he refuted Berkeley’s idealism (Boswell 1791/1980, p. 333). Johnson’s proof convinces no one with an inkling of sympathy for Berkeley, nor should it. Yet it’s hard to see what empirical test could be more to the point. Carnap (1928/1967, p. 333-334) imagines an idealist and a non-idealist both measuring a mountain; there is no experiment on which they will disagree. No multiplicity of gauges, neuroimaging equipment, or particle accelerators could give stronger empirical proof against idealism, it seems, than Johnson’s kick. Similarly, Smart, in his influential defense of materialism, admits that no empirical test could distinguish materialism from epiphenomenalist substance dualism (1959, p. 155-156); there is no epiphenomenal-substance-ometer.
Why, then, should we be materialists? Smart appeals to Occam’s razor: Materialism is simpler. But simplicity is a complex business. Arguably, Berkeley’s idealism is simpler than either dualism or materialism and solipsism is simpler yet. And anyhow, simplicity is at best one theoretical virtue among several, to be balanced in the mix. Abstract theoretical virtues like simplicity will, I suggest, attach only indecisively, non-compellingly, to the genuine metaphysical contenders. I’m not sure how to argue for this other than to invite you sympathetically to feel the abstract beauties of some of the contending views other than your favorite. Materialism has its beauty. But so does transcendental idealism, and so does neutral monism.
If you’re willing to commit to materialism, you might still hope at least for a conscious-ometer that we could press against a human or animal head to decide among, say, relatively conservative vs. moderate vs. liberal materialistic views of the abundance or sparseness of consciousness in the world. But even this is too much to hope for, I think, in our philosophical lifetimes. Is a frog conscious? That is, does a frog have a stream of phenomenal experience? If two theorists of consciousness disagree about this matter, no output from an fMRI machine or set of single-cell recordings is likely to resolve their disagreement – not unless they share much more in common than generally is shared by conservatives and liberals about the abundance of consciousness. Similarly intractable, I think, is the dispute about how richly detailed human experience is – about whether, for example, people have constant tactile experience of their feet in their shoes. If such disputes are intractable, we have no firm grounds of choice between approaches to consciousness that are relatively liberal (perhaps even as liberal as panpsychism) and approaches that are relatively conservative (perhaps even as conservative as restricting consciousness to adult human beings in their most self-aware moments). Either there’s something it’s like to be a frog, or there isn’t, or somewhere in-between, or the question is somehow broken. These are substantially different positions, each with some ineliminable plausibility and no broadly acceptable means of empirical test. Our epistemic situation is even worse if we consider the wide variety of hypothetical alien species and artificial human constructions that a well developed metaphysical position must be ready to address.
Thus I suggest: Major metaphysical issues of mind are resistant enough to empirical resolution that none compel belief on empirical grounds; and this situation is unlikely to change in the foreseeable future. Neither do these issues permit resolution by appeal to common sense (which will rebel against all and might be a poor guide anyway), or by appeal to broad, abstract theoretical considerations. I assume there are no logical self-contradictions or irresolvable conceptual incoherences in any of these views, at least insofar as they are well developed real contenders. I see no other means of settling the matter.
I am not recommending epistemic anarchy, in which all metaphysical views deserve equal credence. A view on which people have immaterial souls for exactly seventeen minutes starting on their eighteenth birthday has no merit by the standards of common sense, empirical science, or theoretical elegance and deserves extremely close to zero credence. Furthermore, it seems reasonable to distribute one’s credences unequally among the four main metaphysical options, and then among subsets of those options, on some combination of scientific, commonsensical, and abstract theoretical grounds.
An Argument from Cosmological Crazyism.
If a broad-reaching cosmological crazyism is true, then crazyism in the metaphysics of mind is a natural consequence. If we don’t know how the universe works, we don’t know how the mind fits within it.
I can’t defend cosmological crazyism in detail here, but a few remarks can highlight its plausibility. Consider the bizarreness of quantum mechanics and the lack of consensus about its interpretation, including the fact that some interpretations treat mentality as fundamental (such as the many minds view and some versions of the Copenhagen interpretation). Consider the bizarreness of relativity theory and the apparent conflict between relativity theory and quantum theory. Consider that many cosmologies now posit either a creator who set the physical constants or initial conditions at the time of the Big Bang so as to support the eventual occurrence of life, or some sort of dependence of the universe upon our observation of it, or the real existence of a vast number of universes with different physical constants or conditions. If the number of universes is infinite, as many cosmologists now think, or if there is even a single infinite universe of the right sort, then every event of finite probability will occur an infinite number of times (given certain background assumptions about cosmic diversity). The spontaneous congealment, from relatively disorganized matter, of a molecule-for-molecule twin of any living person is often held to have a very tiny but finite probability. You would, then, be one among an infinite number of actually existing molecule-for-molecule twins of yourself, of diverse origin. (Shades of Nietzsche’s eternal return?) Quantum cosmology has also been interpreted as suggesting the backward causation of the history of the universe by our current acts of scientific observation (Hawking and Mlodinow 2010, p. 140).
Shall we look, then, to religion for non-bizarre cosmologies? That seems an unlikely source. Creation stories, accounts of the afterlife – especially in the hands of those who would attempt to work out the full ontological implications – seem only a source of further bizarreness.
Another issue is this: If consciousness can be created within artificial networks manipulated by external users – for example in computer programs run by children for entertainment – and if the beings inside those networks can be kept ignorant of their nature, then there could be beings in the universe who are vastly deluded in fundamental matters of metaphysics. Such beings, perhaps, might think they live in a wide world of people like them when in fact they have three-hour lives, isolated from all but their creator and whatever other beings are instantiated in the same artificial environment. There is, I think, a non-negligible possibility that we (I? you?) are such beings. To think that we are in fact such beings is, of course, crazy. But is the possibility too crazy to figure in a disjunction of live cosmological options? Is it more than one order of magnitude crazier than multiverse theory or the typical well developed religious cosmology? There are no commonsense cosmologies left.
Further support for cosmological dubiety comes from our (apparently) miniscule cosmological perspective. If mainstream scientific cosmology is correct, we have seen only a very small, perhaps an infinitesimal, part of reality. We are like fleas on the back of a dog, watching a hair grow and saying, “Ah, so that’s how the universe works!”
There seems to me to be sufficient cosmological uncertainty to cast materialist metaphysics into doubt. For example, if it might be the case that an immaterial entity fashioned the physical constants, then we cannot justifiably rest assured that materialism is true. If there might really exist actual universes so radically different from our own that cognition transpires without the existence of anything we would rightly call material, then materialism is at best a provincial contingency. If we are created within a simulation by outside agents, our experience of objects as necessarily laid out in space and time might be a feature of our programming environment that doesn’t reflect the fundamental structure of the universe (Kant meets cyberpunk).
Scientific cosmology is deeply and pervasively bizarre; it is highly conjectural in its conclusions; it has proven unstable over the decades; and experts persistently disagree on fundamental points. Nor is it even uniformly materialist. If materialism draws its motivation from being securely and straightforwardly the best scientific account of the fundamental nature of things, materialists ought to think twice. I focus on materialism, since it is the dominant view in contemporary metaphysics of mind, but similar considerations cast doubt on dualism, idealism, and compromise/rejection views.
Certain fundamental questions about the metaphysics of mind can’t, it seems, be settled by science, in anything like its current state, or by abstract reasoning. To address these questions we must turn to common sense. If we then have good reason to think that common sense, too, is no reliable guide, we are unmoored. Without common sense as a constraint, the possibilities open up, bizarre and beautiful in their different ways; and once open they refuse to shut. This is crazyism.
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 For helpful comments on drafts or conversation on these topics during the course of writing thanks to Ned Block, Kurt Boughan, Peter Carruthers, Becko Copenhaver, Helen De Cruz, Dan Dennett, Fred Dretske, Sandy Goldberg, Chris Hill, Linus Huang, Bryce Huebner, Jenann Ismael, Hilary Kornblith, Uriah Kriegel, Barry Loewer, Bill Lycan, Pete Mandik, Jozef Muller, Steve Stich, Galen Strawson, Alan Tapper, Nathan Westbrook, Splintered Mind readers, and audiences at University of Cincinnati, Princeton, Harvard, Institut Jean Nicod, and St. Andrews.
 See also Churchland 1981; Stich 1983; Kornblith 1998; Dennett 2005; Ladyman and Ross 2007; and Weinberg, Gonnerman, Buckner, and Alexander 2010; and historically Hume 1740/1978; Kant 1781/1787/1998; Bradley 1893/1930; McTaggart 1908. Even metaphilosophical views that treat metaphysics largely as a matter of building a rigorous structure out of our commonsense judgments often envision conflicts within common sense so that common sense cannot be entirely preserved: e.g., Ayer 1967; Kriegel 2011.
 See Hempel 1980; Crane and Mellor 1990; Chomsky 2009; Montero 1999; Stoljar 2010.
 See also Adams and Dietrich 2004. See Aydede 2009 and Hill 2009 for rather different arguments that the folk metaphysics of pain is incoherent. See Schwitzgebel in preparation for further illustration of the bizarreness of Lewis’s approach to pain.
 See also Edelman 2008, p. 431-433; Koch 2012, p. 131-134.
 Kriegel forthcoming develops a similar argument in more detail, focusing on the ontology of objects as his test case; see also Strawson 2012.
 Image inspired by Hume 1779/1947, §II, p. 147-149.