Russell on Russellian Monism Donovan Wishon [In Consciousness in the Physical World, eds. Alter and Nagasawa, OUP 2015; Please Cite Published Version] §1 Introduction In recent decades, Russell’s “Neutral Monism” has reemerged as a topic of great scholarly interest among philosophers of mind, philosophers of science, and historians of early analytic philosophy. One of the most controversial points of scholarly dispute regarding Russell’s theory concerns how it best fits into standard classificatory schemes for understanding the relationship between mental phenomena and physical reality. The question is: Is it a genuine form of neutral monism? 1 Is it species of panpsychism (or panexperientialism)? 2 Is it a property dualism or panprotopsychism? Is it a nonstandard version of physicalism or materialism? 3 On one hand, it is hoped that the answer to this question will shed light on how best to understand, on its own terms, Russell’s later philosophical writings. But it is also hoped that the answer will help the growing number of contemporary proponents of “Russellian Monism” better understand how their various versions of it are continuous with, or depart from, their historical point of origin. 4 1 Proponents of this interpretation include Stubenberg (2005/2010, this volume) and Tully (1988, 2003). 2 Stubenberg (this volume) makes a persuasive case against such an interpretation. 3 Proponents of this interpretation include Bostock (2012), Feigl (1975), Landini (2011), Lockwood (1981), Maxwell (1978), and perhaps Stace (1944). 4 Alter and Nagasawa (this volume) and Stubenburg (this volume) rightly note that contemporary versions of Russellian Monism are not intended to be completely faithful to Russell’s Neutral Monism. 1 In my view, the task of classifying Russell’s Neutral Monism is made all the more difficult by the fact that his conception of it evolves in significant ways over the roughly four decades that he advocates it. In fact, I would contend that during this period, Russell holds (at least) three different, but related, ontological views, all of which he labels as “neutral monism”. And though the boundaries between these three views are somewhat nebulous, there are key changes in Russell’s thought that can help us tease them apart. To see this, we must begin by considering key aspects of his early dualism which continue to play important roles in his Neutral Monism, especially his views about acquaintance, knowledge by description, structuralism about physics, and the construction of our physical knowledge. This will be the project of §2-3. In §4, I argue that Russell revises, rather than abandons, his notion of knowledge by acquaintance in 1918 (when he gives up the act-object distinction) and contend that his resulting “neutral monism” remains a partial dualism until his 1921 The Analysis of Mind (hereafter AMi). In §5, I explain how changes in physics leads Russell to reconceptualize his Neutral Monism in The Analysis of Matter (hereafter AMa) and An Outline of Philosophy (hereafter OOP), while challenging the relatively widespread view that his new position is a nonstandard version of physicalism. In §6, however, I argue that after 1940, Russell’s mature Neutral Monism—as presented in Human Knowledge: Its Scope and Limits (hereafter HK), My Philosophical Development (hereafter MPD), and elsewhere—is very plausibly interpreted as a version of “Russellian Physicalism”. 5 §2 Russellian Dualism Many commentators rightly note that Russell’s adoption of Neutral Monism is a gradual affair. In the two decades following his 1898 post-idealist “revolt into pluralism” (alongside Moore), Russell is a self-avowed mind-body dualist (MPD, p. 54). His interests during much of this time are dominated by problems in the philosophy of mathematics and logic, especially regarding his “Contradiction” involving the class of all classes that are not members of themselves (p. 76). Nevertheless, starting in his 1905 “On Denoting” (hereafter OD) and continuing through his well-known works in the 1910s, 5 See Holman (2008), Montero (2010, this volume), Pereboom (2011, this volume), Stoljar (2001, 2006, this volume), and Strawson (1999) for some recent incarnations of Russellian Physicalism. 2 Russell develops a sophisticated theory of knowledge resting on the fundamental notion of “knowledge by acquaintance”. 6 At the heart of Russell’s theory of knowledge is the distinction, drawn from the writings of William James (1885, 1890), between two logically distinct kinds of knowledge: knowledge of things and knowledge of truths (POP, p. 44). 7 Knowledge of things is a matter of a subject simply being aware of particulars and universals such that the subject is in a position to think and talk about them. In contrast, knowledge of truths is a matter of the subject having a “take” on the objects of his or her awareness, paradigmatically in the form of judgments about them. Whereas the latter can be evaluated in terms of truth or falsity, there is simply no sense to be made of the truth or falsity of the former—either the subject is aware of the relevant objects, or he or she isn’t. 8 For Russell, there are two ways a subject can be aware of things. 9 A subject can be directly aware of things, “without the intermediary of any process of inference or any knowledge of truths”, by being presented with them in experience (POP, p. 46). Russell calls this kind of knowledge of things “knowledge by acquaintance”. A subject can also be indirectly aware of things by description in cases where “in virtue of some general principle, the existence of a thing answering to this description can be inferred from the existence of something with which [the subject is] acquainted” (p. 45). Russell calls this kind of knowledge of things “knowledge by description”. And unlike the case of knowledge by acquaintance, the possession of 6 For a more thorough discussion of Russell’s views on acquaintance and its role in thought and talk, see my “Russellian Acquaintance and ‘Frege’s Puzzle’ ” (Forthcoming). 7 James gets this distinction from John Grote’s 1865 Exploratio Philosophica. 8 This is the only sense in which knowledge of things, by acquaintance of otherwise, is infallible. In Chapter XII of POP, Russell says, “Our knowledge of truths, unlike our knowledge of things, has an opposite, namely error. So far as things are concerned, we may know them or not know them, but there is no positive state of mind which can be described as erroneous knowledge of things, so long, at any rate, as we confine ourselves to knowledge by acquaintance. Whatever we are acquainted with must be something; we may draw wrong inferences from our acquaintance, but acquaintance itself cannot be deceptive” (p. 119). In Wishon (2012), I further contend that acquaintance does not provide subjects with discriminating knowledge, revelatory knowledge, fully-disclosing knowledge, or transparent knowledge of its objects. 9 Russell is not entirely consistent in his uses of the terms “acquaintance” and “knowledge of things”, even within the same works. Sometimes he identifies them, but other times he treats acquaintance as one kind of knowledge of things, in which case he allows for the possibility of knowledge of things by description. Given that knowledge by description puts one in a position to think and talk about things, but doesn’t all by itself assert that something is thus-and-so, I prefer the latter practice. 3 knowledge by description requires the antecedent possession of knowledge of truths about things known by acquaintance, including truths about general principles. 10 Both kinds of knowledge of things play crucial roles in Russell’s theory of knowledge. Knowledge by acquaintance is the ultimate enabling condition for all thought and talk. Such direct conscious awareness of things puts a subject in a position to attend to them, to introduce genuine names for them, and to acquire knowledge of truths about them. 11 By exploiting this knowledge of truths about the objects of acquaintance, knowledge by description then enables the subject to extend thought and talk beyond the confines of his or her personal experience. Thus, knowledge by description is the crucial material that makes scientific (and everyday) knowledge of truths about the external world possible. But it all starts from knowledge by acquaintance (POP, p. 48). From 1903 until 1918, Russell thinks it important, for a number of reasons, that acquaintance is a dual (mental) relation holding between distinct relata, where one constituent of the relational fact is the mental subject and the other is the object of acquaintance. First of all, he wishes to avoid “Brentano’s view that in sensation there are three elements: act, content, and object” (MPD, p. 134). 12 For as he expresses in his famous 1904 “Letter to Frege”, Russell worries that if our awareness of objects is mediated through contents (or senses) we never truly acquire empirical knowledge of the world outside the mind. 13 Second, he thinks that the act-object distinction in epistemic relations is needed to resist idealisms of various sorts, including those of Berkeley and the British Monistic Idealists. 14 And third, he maintains that without viewing acquaintance as a dual relation, we cannot produce an 10 On page 46 of POP, he says, “knowledge of things, when it is of the kind we call knowledge by acquaintance, is essentially simpler than any knowledge of truths, and logically independent of knowledge of truths, though it would be rash to assume that human beings ever, in fact, have acquaintance with things without at the same time knowing some truth about them. Knowledge of things by description, on the contrary, always involves…some knowledge of truths as its source and grounds”. Emphasis added. 11 The meanings of “genuine names” are just their referents. For more on these issues, see Wishon (2012). 12 Elsewhere, Russell associates this view with Meinong and Frege. See Russell (1904b) and (1905). 13 Also see MPD, p. 134. 14 See, for instance, Chapters IV and XIV of POP. 4 adequate analysis of various cognitive phenomena such as consciousness, belief, memory, and selectively-based indexical and demonstrative thought. 15 But despite great continuity in Russell’s view of the nature and epistemic role of acquaintance during this period, his views about the objects of our acquaintance are in a state of flux. In the early years after his break from British Monistic Idealism, Russell (like Moore) is a naïve realist who “rejoiced in the thought that grass is really green, in spite of the adverse opinion of all philosophers from Locke onwards” (MPD, p. 61-2). However, by the time of his 1910 Philosophical Essays (hereafter PE), Russell places substantial restrictions on the objects of our acquaintance. 16 A number of philosophical arguments concerning perceptual experience, including the argument from qualitative variation, the argument from hallucinations/dreams, and the argument from science, convince Russell that the objects we are directly aware of in sensation are sense-data rather than the ones of ordinary commonsense. 17 Among the candidates for other particulars with which we can be directly aware of are introspectible mental phenomena (including acquaintance itself), remembered past sense-data and mental phenomena, and (perhaps) the self (POP, p. 48-51). In addition, we can be acquainted with many universals, including general principles, through conceiving them (p. 51-2 and Chapters VII-X). Except in the case of introspectible mental phenomena and (perhaps) the self, the objects of our acquaintance are external to the mind, even in Russell’s most restrictive periods. In his view, “the faculty of being acquainted with things other than itself is the main characteristic of a mind” and “acquaintance with objects essentially consists in a relation between the mind and something other than a mind” (POP, p. 42). This is important because “it is this that constitutes the mind’s power of knowing things” (p. 42). So it is a mistake to see sense-data as any kind of psychological entity. Rather, sense-data are sensed “qualities”, such as colors, shapes, textures, hardness, etc., which are independent of the mind, but which cannot be strictly proved to exist when not sensed. 18 Nevertheless, based on a number of 15 Incidentally, Russell cites this last set of considerations as his strongest grounds for rejecting James’ Neutral Monism. See Russell (1992, p. 30-2) and (1918/1998, p. 153). For more detailed discussion, see Tully (1988, 2003). 16 Most commentators believe that such restrictions are already in place in 1905 in “On Denoting”. See, for example, Proops (2011, Forthcoming). However, I argue against the standard interpretation in Wishon (2012). It is also questioned in Soames (2003) and Kripke (2005). 17 See PE, p. 181-3, POP, Chapters I-IV, and “The Ultimate Constituents of Matter”, p. 126-7. 18 POP, p. 9-11 and Papers, 6, p. 135-6 and 185-6. 5 non-deductive inferences, we have good reason to think that they are at least caused by the objects of physics, and are therefore signs of them (p. 11). And by the time of his 1914 “The Relation of Sense-Data to Physics” (hereafter RSDP), Russell asserts that sense-data are literally physical in nature. 19 §3 From Sense-Data to Knowledge of the Physical World Two of the most pressing concerns for Russell during his dualist phase (as afterwards) are (1) how we derive scientific knowledge from the immediate data of experience, and (2) how such scientific knowledge can be verified on the basis of experience. Regarding physics in particular, he is concerned with the question of how it is that we acquire knowledge of the existence of a material world beyond the confines of personal experience, as well as what we can legitimately infer about its nature. In general outline, his answer is that we acquire knowledge about the existence and nature of the material world by means of knowledge by description and non-demonstrative inference. Like all knowledge of truths, such knowledge about matter “is infected with some degree of doubt” (POP, p. 135). 20 But when it comes to the 19 Russell leaves open the possibility that they are also mental, noting that this would be (partially) compatible with the neutral monism of James. That is, the very same qualities that make up the physical world could, when grouped according to psychological laws, be literally part of a subject’s mind as well. He says, “I propose to assert that sense-data are physical, while yet maintaining that they probably never persist unchanged after ceasing to be data… If there were, as some have held, a logical impossibility in sense-data persisting after ceasing to be data, that certainly would tend to show that they were mental; but if, as I contend, their non-persistence is merely a probable inference from empirically ascertained causal laws, then it carries no such implication with it, and we are quite free to treat them as part of the subject-matter of physics” (RSDP, p. 112). Even still, Russell’s view at this time is incompatible with James’ neutral monism on a different front—for he still embraces a fundamental mental subject and an act-object distinction regarding the mental relation of acquaintance. Thanks to Leopold Stubenberg for helpful discussion of these issues. 20 Contrary to widespread misinterpretation, Russell is no Cartesian when it comes to epistemology. In point of fact, he is quite explicit that “a theory which ignored this fact [i.e. that all knowledge of truths has some degree of doubt] would be plainly wrong” (POP, p. 135). On his view, “philosophy should show us the hierarchy of our instinctive beliefs, beginning with those we hold most strongly… [and] it should take care to show that, in the form in which they are finally set forth, our instinctive beliefs do not clash, but form a harmonious system… [But] it is of course possible that all or any of our beliefs may be mistaken, and therefore all ought to be held with at least some degree of doubt” (p. 25). Emphasis added. See Proops (forthcoming a, forthcoming b) and Wishon (2012). 6 material world, our epistemic situation is even more precarious than this. For all we can know about it, through science or other means, is its structure. Though this acceptance of structuralism about our physical knowledge is often associated solely with Russell’s neutral monist phase, it is already in place in 1912 during his dualist phase. One reason for which he embraces structuralism is that he simply sees it as part of scientific practice (POP, p. 27-8). But he also sees it as a consequence of our sensory acquaintance being restricted to sense-data caused by physical objects, together with considerations of perceptual variation. From this, he infers that physical objects, which we know purely by description, plausibly differ in quality from the sense-data they cause. However, we do not know what the intrinsic natures of these qualities are. Indeed, he asserts, “we find that, although the relations to physical objects have all sorts of knowable properties, derived from their correspondence with the relations of sensedata, the physical objects themselves remain unknown in their intrinsic nature, so far at least as can be discovered by means of the senses” (p. 34). 21 What’s more, all inferences to the intrinsic nature of physical objects are tenuous. In POP, Russell notes that the most natural hypothesis is that the qualities of physical objects are “more or less like” sense-data such that “physical objects will, for example, really have colours, and we might, by good luck, see an object as of the colour it really is” (p. 35). However, he maintains that the argument from science shows us that we experience the same sense-data regardless of whether the physical object causing them has color, and so “it is quite gratuitous to suppose that physical objects have colours” (p. 35). In fact, Russell thinks that “if physical objects do have an independent existence, they must differ very widely from sense-data”, and so “the truth about physical objects must be strange… [and] it may be unattainable” (p. 37-8). He does not long remain content to rest our knowledge of physical reality on tenuous non-demonstrative inferences, however. Starting in his unpublished 1912 “On Matter” (hereafter OM), and culminating in his 1914 Our Knowledge of the External World (hereafter OKEW), Russell begins to deploy his method of logical analysis to “construct” our knowledge of physics from a small store of knowledge of truths about sense-data and general principles, together with assumptions which have a relatively high degree of 21 And in remarks long anticipating Frank Jackson’s (1982) knowledge argument, he says “we can know all [and only] those things about physical space which a man born blind might know through other people about the space of sight; but the kind of things which a man born blind could never know about the space of sight we also cannot know about physical space. We can know the properties of the relations required to preserve the correspondence with sense-data, but we cannot know the nature of the terms between which the relations hold” (POP, p. 32). 7 self-evidence. 22 His goal is to provide our body of physical knowledge with as firm a foundation as possible (short of certainty), just as he attempts to do in the case of constructing our body of mathematical knowledge out of that of logic. Thus, in the first instance, this constructive project is an epistemic one, rather than an ontological one. 23 If we are to draw metaphysical conclusions about the world our constructed physical theory describes, we must still rely on non-demonstrative inferences to do so. One of the most important parts of Russell’s construction of physics is the construction of our knowledge of matter from more (epistemically) basic physical phenomena. After coming to the view in 1914 that the sensedata we are acquainted with are literally physical, he sees them as the most obvious material from which to construct this knowledge (RSDP, p. 111). 24 And despite having an attraction to methodological solipsism, Russell thinks that the construction of matter requires assuming the existence of two further sorts of inferred entities: (1) the sense-data of other people, and (2) qualities differing significantly from sense-data only in that they happen to be unsensed, which he calls sensibilia (p. 116-7). He characterizes the latter as follows: 22 Many Russell scholars will dispute one or both of my claims that his constructions were (a) epistemic in character, but (b) not aimed at answering the skeptic once and for all. I cannot hope to settle this issue here. Instead, I will simply point to the following remarks Russell makes in his 1922 “Physics and Perception” while clarifying his aims in OKEW: “I have never called myself a phenomenalist, but I have no doubt sometimes expressed myself as though this were my view. In fact, however, I am not a phenomenalist. For practical purposes, I accept the truth of physics, and depart from phenomenalism so far as may be necessary for upholding the truth of physics. I do not, of course, hold that physics is certainly true, but only that it has a better chance of being true than philosophy has. Having accepted the truth of physics, I try to discover the minimum of assumptions required for its truth, and to come as near to phenomenalism as I can. But I do not in the least accept the phenomenalist philosophy as necessarily right, nor do I think that its supporters always realise what a radical destruction of ordinary beliefs it involves” (p. 480). 23 Russell compares his project to Peano’s in arithmetic: it does not, all by itself, have straightforward ontological implications. For an insightful discussion of Russell’s method, see Hager (2003). It is also worth noting that Russell deploys his version of Ockham’s Razor—“Whenever possible, substitute constructions out of known entities for inferences to unknown entities”—primarily in the epistemological project of constructing physics (1924, p. 326). In metaphysical matters, he often relies heavily on ontological parsimony, but his inferences are frequently guided by competing principles. His arguments against metaphysical solipsism are notable examples. 24 He puts it even clearer a year later in “The Ultimate Constituents of Matter” when he says, “I believe that the actual data of sensation, the immediate objects of sight or hearing, are extra mental, purely physical, and among the ultimate constituents of matter” (p. 96). 8 We have not the means of ascertaining how things appear from places not surrounded by brain and nerves and sense-organs, because we cannot leave the body; but continuity makes it not unreasonable to suppose that they present some appearance at such places. Any such appearance would be included among sensibilia. If per impossible—there were a complete human body with no mind inside it, all those sensibilia would exist, in relation to that body, which would be sense-data if there were a mind in the body. What the mind adds to sensibilia, in fact, is merely awareness: everything else is physical or physiological” (RSDP, p. 111). Thus, like sense-data, un-sensed sensibilia (if they exist) are qualities that are literally part of physical reality. 25 With such assumptions in place, Russell proposes that we treat the persisting material entities of physics as collections of appropriately related sense-data and sensibilia, at different locations and times, grouped together into “biographies” based largely on considerations of (presumed) continuity and causal-dynamical connectedness (RSDP, p. 124-6). 26 And by generalizing this strategy, he takes it to be possible, at least in principle, to construct the description of the world provided by physics by means of functions from sense-data and qualities assumed to be similar in kind to them. Of course, we have no way of knowing with any assurance the actual intrinsic nature of the un-sensed portions of physical reality; but we at least have a picture of it that accords well with what we know about it through acquaintance and physical theory. §4 Russellian Neutral Monism In 1918, Russell’s views about the nature of acquaintance take a radical change, resulting eventually in equally radical changes to his views about the relationship between mind and matter (MPD, p. 134). In particular, for a number of reasons, he “became convinced that William James had been right 25 Regarding the coherence and plausibility of un-sensed sensibilia, Russell remarks, “it may be thought monstrous to maintain that a thing can present any appearance at all in a place where no sense organs and nervous structure exist through which it could appear. I myself do not feel the monstrosity; nevertheless I should regard these supposed appearances only in the light of a hypothetical scaffolding, to be used while the edifice of physics is being raised, though possibly capable of being removed as soon as the edifice is completed” (RSDP, p. 117). 26 For a more detailed discussion of Russell’s construction of matter, see Stubenberg (this volume). 9 in denying the relational character of sensations” (p. 134). For one thing, in his 1919 “On Propositions” (hereafter OP), he comes to the view that in experience, we are presented neither with a mental subject (which he questioned as early as 1911 in “Knowledge by Acquaintance and Knowledge by Description” and rejected in his unpublished 1913 Theory of Knowledge) nor with mental acts or relations. So we have no empirical reason for taking them to be fundamental constituents of the world. 27 For another, he ceases to think that a relational account of mental occurrences is required to explain the possibility of knowledge of the external world, resist idealism, or provide an adequate analysis of consciousness, belief, memory, and selectively-based indexical and demonstrative thought. Hence we have no theoretical grounds for holding the view, either. Consequently, we no longer have any reason to think we know of the mental subject or acts even by description. However, Russell does not abandon acquaintance altogether, contrary to prevailing interpretation. 28 Rather, following James’ “Does ‘Consciousness’ Exist?” (this volume), he gives up the view that sensation is a relation between numerically distinct relata: a mental subject and physical sense-data. In its place, Russell adopts James’ view that the (self-presenting) qualities we are aware of in sensation are literally part of both our minds and physical reality (OP, p. 306). As he later puts it in AMi, “the sensation that we have when we see a patch of colour simply is that patch of colour, an actual constituent of the physical world, and part of what physics is concerned with” (p. 142). But, he continues, “it does not follow that the patch of colour is not also psychical, unless we assume that the physical and the psychical cannot overlap, which I no longer consider a valid assumption. If we admit—as I think we should—that the patch of colour may be both physical and psychical, the reason for distinguishing the sense-datum from the sensation disappears” (AMi, p. 143). 27 In OP, he says, “I have to confess that the theory which analyses a presentation into act and object no longer satisfies me. The act, or subject, is schematically convenient, but not empirically discoverable. It seems to serve the same sort of purpose as is served by points and instants, by numbers and particles and the rest of the apparatus of mathematics. All these things have to be constructed, not postulated: they are not stuff of the world, but assemblages which it is convenient to be able to designate as if they were single things. The same seems to be true of the subject, and I am at a loss to discover any actual phenomenon which could be called an ‘act’ and could be regarded as a constituent of a presentation” (p. 305). 28 In MPD, he simply asserts that “such words as ‘awareness’, ‘acquaintance’, and ‘experience’ had to be re-defined” (p. 136). And later he says, “I have maintained a principle, which still seems to me completely valid, to the effect that, if we can understand what a sentence means, it must be composed entirely of words denoting things with which we are acquainted or definable in terms of such words” (p. 169). Emphasis added. In §6, we’ll see that he makes crucial use of acquaintance in HK, for instance on page 245. 10 By giving up the act-object distinction concerning sensation, Russell took his first and most important step towards embracing a James-inspired neutral monism. On his understanding, the core of James’ view is that “the mental and the physical are not distinguished by the stuff of which they are made, but only by their causal laws” (OP, p. 299). In other words, the qualities of which we are directly aware in sensation are intrinsically neither mental nor physical (and hence “neutral”); they are made mental or physical (or both) by being part of causal processes that are either psychological or physical (or both). 29 Comparing matters to the dual classification systems of the old British Post Office Directory, Russell remarks that on this view, “a sensation may be grouped with a number of other occurrences by a memorychain, in which case it becomes part of a mind; or it may be grouped with its causal antecedents, in which case it appears as part of the physical world” (MPD, p. 139). One of the key upshots of James’ neutral monism, in Russell’s estimation, is that it allows us to dispense with the mental subjects as fundamental entities. On the view, mental subjects just are constructions composed of transitory neutral qualities organized in accordance with psychological laws so as to form the right kind of “perspectives” at particular times and “biographies” across time (AMi, p. 296). Thus, while there are mental subjects, they are constructed entities rather than fundamental ones. The latter are merely “logical fictions”—it is useful for certain purposes to feign as if there are such things, but there is no reason to assume “either that they exist or that they don’t exist” (OP, p. 306). 30 It is important to note that at the time of OP, Russell’s commitment to this version of neutral monism is partial and provisional. While he agrees with James that what essentially distinguishes psychology form physics is not a matter of the “stuff” investigated but rather a matter of the causal laws studied, he is not yet ready to conclude that there is in fact only one kind of fundamental (neutral) stuff in the world (OP, p. 299). 31 On the contrary, he asserts that “when we come to consider the stuff of the two sciences, it would seem that there are some particulars which obey only physical laws (namely, unperceived material things), some which obey only psychological 29 For Russell, whether qualities are mental or physical is an extrinsic matter which in no way changes their intrinsic natures, just as an individual can become an uncle or aunt due to purely extrinsic circumstances. 30 He remarks that “the practical effect of this is the same as if we assumed that [fundamental mental selves] did not exist, but the theoretical attitude is different” (OP, p. 306). See Stubenberg (this volume) for more on Russell’s views of the mental subject as a logical construction. 31 See Bostock (2012, p. 174-6) for a more detailed interpretation along these lines. 11 laws (namely, images, at least), and some which obey both (namely, sensations. Thus sensations will be both physical and mental, while images will be purely mental” (p. 299). Moreover, it is not just that images are purely mental because they happen to be part of causal processes that are purely psychological (when they just as well could have been part of physical causal processes, were the world arranged differently). 32 Rather, given the state of psychology and physics at the time, Russell is led to the conclusion that “it is impossible to escape the admission of images as something radically distinct from sensations, particularly as being not amenable to the laws of physics” (OP, p. 296). 33 Thus it is relatively clear that Russell still accepts dualism, at least provisionally, at the time of OP. But at the same time, he admits, “I do not pretend to know whether the distinction between [physical and psychological laws] is ultimate and irreducible. I say only that it is to be accepted practically in the present state of science” (p. 299). In contrast, there is little question that Russell embraces a comprehensive version Neutral Monism by the time of his 1921 AMi. 34 Though he provisionally suggests his earlier OP view of the relation between mind and matter at its outset, he asserts in the final chapter that in the course of investigation, “we found no way of defining images except through their causation; in their intrinsic character they appeared to have no universal mark by which they could be distinguished from sensations” (p. 287). On this new version of Neutral Monism, minds are logical constructions composed of transitory sensations and images, both of which are genuinely neutral qualities, grouped together in a single process of “mnemic causation” (AMi, p. 306). 35 Russell characterizes mnemic causation as a process in which the “proximate cause [of an event] consists not merely of a present event, but this together with a past event” (p. 85). As illustrations of “mnemic phenomena”, he includes acquired habits, images “copied” from past sensations, psychological associations, non-sensational elements in perception, memories, and thoughts. While Russell maintains that the characteristic of an event having both present and past events as its proximate cause is not wholly confined to living organisms, he insists that “in the case of dead matter, …such 32 I would like to thank Russell Wahl for pressing such a reading of the passages in OP. 33 Emphasis added. 34 Though see Bostock (2012) and Landini (2011) for the opposing view. 35 These qualities are “genuinely neutral” because they, together with similar transitory qualities lying outside any mind, literally compose “matter” (a logical construction) when grouped in accordance with physical causal laws. 12 phenomena are less frequent and important than in the case of living organisms, and it is far less difficult to invent satisfactory hypotheses as to the microscopic changes in structure which mediate between the past occurrence and the present changed response” (AMi, p. 78). 36 Hence, paradigmatic mnemic phenomena are “those responses of an organism which, so far as hitherto observed facts are concerned, can only be brought under causal laws by including past occurrences in the history of the organism as part of the causes of the present response” (p. 78). And, he adds, they are “usually of a kind that is biologically advantageous to the organism” (p. 78). In fact, Russell takes very seriously the possibility “that mnemic causation may be reducible to ordinary physical causation in nervous tissue” (AMi, p. 303). At first glance, this lends some credibility to those that question whether his Neutral Monism was really neutral, rather than a nonstandard version of materialism. 37 In fact, Russell himself notes that his view is reminiscent of materialism when understood as “the view that all mental phenomena are causally dependent upon physical phenomena” (p. 303). And while he “does not profess to know” whether mnemic causation is reducible in this way, he concedes that “the bulk of the evidence points to the materialistic answer as the more probable” (p. 303). However, Russell soon afterwards makes clear that his ontological view is not one of materialism. On the contrary, he maintains, “an ultimate scientific account of what goes on in the world, if it were ascertainable, would resemble psychology rather than physics” and “such an account would not be content to speak, even formally, as though matter, which is a logical fiction, were the ultimate reality” (AMi, p. 305-6). In fact, he continues, “it is probable that the whole science of mental occurrences, especially where its initial definitions are concerned, could be simplified by the development of the fundamental unifying science in which the causal laws of particulars are sought, rather than the causal laws of those systems of particulars that constitute the material units of physics” (p. 306-7). As we have seen, Russell takes the relevant particulars to be transitory qualities that are intrinsically neither mental nor material, but that compose both when grouped in appropriate ways. And if a fundamental science of these neutral particulars could be developed, he argues, “[it] would cause physics to become derivative, in the sort of way in which theories of the constitution of the atom make chemistry derivative from physics; it would also cause psychology 36 Giving an example of a mnemic phenomenon concerning “dead matter”, he remarks, “magnetized steel looks just like steel which has not been magnetized, but its behavior is in some ways different” (AMi, p. 78). 37 See Bostock (2012), Landini (2011), and Lockwood (1981). 13 to appear less singular and isolated among sciences” (p. 307). So by all appearances, Russell’s Neutral Monism in AMi is unequivocally neutral. §5 The Analysis of Matter In recent years, a number of commentators have alleged that by the time of Russell’s 1927 AMa, his views about Neutral Monism shift on at least three key issues which suggest, at least to them, that it is to be counted as a nonstandard version of physicalism rather than as a true neutral monism. 38 First, they argue, developments in physical science move Russell to see “events”, rather than transitory particulars, as the fundamental constituents of the world. 39 Second, they rightly note, he becomes increasingly inclined to think that psychological causation is in principle reducible to physical causation. And third, they maintain, he develops a causal theory of perception that some see as at odds with a genuinely neutral monism. 40 In my view, however, the textual evidence suggests that despite any changes, Russell’s monism at the time of AMa is not yet a physicalist one. The main project of AMa in many respects shares the general character of OKEW. As with the earlier work, Russell seeks to give a logical analysis of our physical knowledge such that the propositions of physics can be deduced or constructed from “a few simple hypotheses” about “entities forming part of the empirical world” (AMa, p. 2-5). By doing so, he hopes to explain how our knowledge of physics can be derived from experience, as well as how experience can provide evidence for its truth. In addition, to put physics in as secure of a position as possible (short of certainty), he aims to “construct a metaphysic of matter which shall make the gulf between physics and perception as small, and the inferences involved in the causal theory of perception as little dubious, as possible” (p. 275). Russell mentions several times in AMi that physics, under the influence of relativity theory, has moved towards an event ontology. However, to my knowledge, he doesn’t make explicit his own endorsement of 38 Bostock (2012), Landini (2011), Lockwood (1981), and Feigl (1975). 39 Note that Russell doesn’t abandon his use of the expression ‘particulars’ to designate “the ultimate terms of the physical structure” of the world (AMa, p. 277). He does, however, shift its meaning. In its new use, Russell uses it to designate “something which is concerned in the physical world merely through its qualities or its relations to other things, never through its own structure, if any” (p. 277). He is quick to add that what counts as a ‘particular’ (in this new sense) is relative to the current state of our knowledge; once we discover that the ‘ultimate terms’ of our physical theories have further structure, they cease to be particulars (p. 277-8). 40 See Bostock (2012), pages 190-6. 14 this view until his 1922 “Physics and Perception” (hereafter PP), after having completed a series of papers on relativity and the structure of the atom. In PP, Russell responds to challenges leveled by C. A. Strong (1922) against his accounts of perception in both OKEW and AMi, primarily by arguing that his disagreement with Strong actually concerns the nature of matter. He says, “the main purpose of this whole outlook is, in my view, to fit our perceptions into a physical context, and to show how they might, with sufficient knowledge, become part of physics” (PP, p. 478). And part of this project, he argues, requires giving up outdated views about what physics says about the nature of matter, views which Strong mistakenly continues to accept. According to modern physics, he continues, “a piece -of matter…has two aspects, one gravitational, the other electromagnetic… Both these consist of a field, extending theoretically throughout space-time. The gravitational field consists in a certain distortion of space-time, making it everywhere more or less non-Euclidean, but particularly so in a certain neighbourhood, the neighbourhood in which we say the matter is” (PP, p. 478). Thus, he says, in reality, “what we call one element of matter—say an electron—is represented by a certain selection of things that happen throughout space-time” where “these occurrences are ordered in a fourdimensional continuum [each point of which contains] many such occurrences” (p. 479). However, the orderings of these occurrences can no longer be as simple as the cross-temporal “biographies” of collections of momentary particulars which appeared in AMi. This is because relativity theory shows us that “the time-order of events is a certain extent arbitrary and dependent upon the reference-body” (p. 479). Nevertheless, he argues, “each piece of matter has…a ‘proper time,’ which is indicated by clocks that share its motion; from its own point of view, this proper time may be used to define its history” (p. 479). And as a consequence of all of this, “the objects which are mathematically primitive in physics, such as electrons, protons, and points in space-time, are all logically complex structures composed of entities which are epistemically more primitive, which may be conveniently called ‘events’ ” (AMa, p. 9). Strictly speaking, Russell defines events as “entities or structures occupying a region of space-time which is small in all four dimensions” (AMa, p. 286). Such an event might have some internal structure, but if so, it “has no space-time structure, i.e. it does not have parts which are external to each other in space-time” (p. 286). They may, however, be ‘compresent’ with 15 (that is, overlap with) other events at a single space-time location (p. 294). 41 Less strictly speaking, ‘events’ (“in the broad sense”) have no maximal limit with respect to their duration or, presumably, their spatial extension. Nonetheless, he insists, any event which has such a space-time structure can “be analyzed into a structure of events” which do not (p. 286-7). On Russell’s view, the only events with which we have any acquaintance are our own percepts—sensible qualities such as “patches of colour, noises, smells, hardnesses, etc., as well as perceived spatial relations”—and other events in our conscious mental lives (AMa, p. 257). The role they play in his causal theory of perception resembles in different respects those of the “sensations” of AMi and the earlier “sense-data” of POP and RSDP. As in the case of the latter, percepts are signs of the external physical objects which cause them and to which we make unreflective “physiological inferences” (AMa, p. 190). But, as in the case of the former, there is no act-object distinction between percepts and our awareness of them. Thus, unlike sense-data, percepts are not external to the percipient. On the contrary, Russell insists that “whoever accepts the causal theory of perception is compelled to conclude that percepts are in our heads, for they come at the end of a causal chain of physical events leading, spatially, from the object to the brain of the percipient” (p. 320). Largely based on such causal considerations, Russell draws the notorious conclusion that “what a physiologist sees when he examines a brain is in the physiologist, not in the brain he is examining” (AMa, p. 320). Simply put, his proposal is that perception, properly speaking, is a complex causal process that extends from physical objects in the percipient’s environment to the occurrence of events in the percipient’s brain, the intrinsic qualities of which are numerically identical to the sensible qualities we naively suppose to inhere in the external objects. 42 So returning to the physiologist, if we focus on the brain that is situated at the far end of the causal process, rather than the visual percept whose intrinsic qualities the physiologist is immediately aware of, we can find brain events that are literally thoughts or percepts of the other person. Indeed, Russell asserts, “what is in the brain by the time the physiologist examines it if it is dead, I do not profess to know; but while its owner was alive, parts, at least, of the 41 Putting things this way can be slightly misleading, however, since space-time points are analyzed in terms of the compresence of events, rather than the other way around. 42 According to Alter and Nagasawa (this volume), it is this view “about knowledge and perception” which, together with structuralism about physics, lead Russell to his distinctive version of Russellian Monism. 16 contents of this brain consisted of his percepts, thoughts, and feelings” (p. 320). 43 In claiming that percepts are literally identical to brain events, the most straightforward way to read Russell here is as endorsing some version or other of a physicalist type identity theory. And a number of additional remarks in AMa lend further credibility to such a reading. For instance, he quite plainly says that “percepts are the only part of the physical world that we know otherwise than abstractly” (p. 402). Elsewhere, he contends that “there is no good ground for excluding percepts from the physical world, but several strong reasons for including them. The difficulties that have been supposed to stand in the way seem to me to be entirely due to wrong views as to the physical world, and more particularly as to physical space” (384-5). And again, he insists, “percepts fit into the same causal scheme as physical events, and are not known to have any intrinsic character which physical events cannot have, since we do not know of any intrinsic character which could be incompatible with the logical properties that physics assigns to physical events. There is therefore no ground for the view that percepts cannot be physical events, or for supposing that they are never compresent with other physical events” (p. 384). This final point—that we are ignorant of the intrinsic nature of all but that small corner of the physical world which constitutes our own conscious experience—is what crucially opens the door to Russellian Monisms of various sorts, as all of the contributors to this volume rightly note. As for the rest of physical reality, Russell once again asserts that physical science characterizes it solely in terms of its spatiotemporal and causal structure. As he vividly puts it, “the aim of physics, consciously or unconsciously, has always been to discover what we may call the causal 43 Russell then continues to say, “since his brain also consisted of electrons, we are compelled to conclude that an electron is a grouping of events, and that, if the electron is in the human brain, some of the events composing it are likely to be some of the ‘mental states’ of the man to whom the brain belongs.” Stubenberg reads Russell here as endorsing the view that electrons are made up of either whole percepts or (non-physical) parts of percepts. While he certainly entertains this as a possibility, Russell immediately afterwards suggests that electrons in the brain “are likely to be parts of such ‘mental states’—for it must not be assumed that part of a mental state must be a mental state” (AMa, p. 320). Thus, I read Russell as allowing for the possibility that percepts are made up of electrons and other imperceptible physical events. In my opinion, this second reading also fits better with his earlier claim that “all our percepts are composed of imperceptible parts” as well as his use of phenomenal continua cases to resist the ontological monism of the British Idealists (p. 280-2). For more on Russell’s use of phenomenal continua cases to resist British Idealism as well as Wilfrid Sellars’ 1965 “grain argument” against physicalism, see Wishon (2012). I thank Leopold Stubenberg for helpful discussion of these issues. 17 skeleton of the world” (AMa, p. 391). 44 In fact, he insists, “as regards the world in general, both physical and mental, everything that we know of its intrinsic character is derived from the mental side, and almost everything that we know of its causal laws is derived from the physical side” (p. 402). The importance consequence of these facts, Russell maintains, is that they do away with any grounds for supposing there to be a deep ontological gulf between the mental and the physical. In his opinion, philosophers have struggled to solve the mind-body problem largely because they have mistaken conceptions of both the nature of physical science and the world it describes. Indeed, he says: Both materialism and idealism have been guilty, unconsciously and in spite of explicit disavowals, of a confusion in their imaginative picture of matter. They have thought of the matter in the external world as being represented by their percepts when they see and touch, whereas these percepts are really part of the matter of the percipient’s brain. By examining our percepts it is possible—so I have contended—to infer certain formal mathematical properties of external matter, though the inference is not demonstrative or certain. But by examining our percepts we obtain knowledge which is not purely formal as to the matter of our brains (AMa, p. 382). What’s more, he argues, once we recognize our mistaken conception of matter for what it is, we pave the way for a far more integrated picture of where the mind fits into reality. For instance, he maintains, “we no longer have to contend with what used to seem mysterious in the causal theory of perception: a series of light-waves or sound-waves or what not suddenly producing a mental event apparently totally different from themselves in character” (AMa, p. 400). 45 Indeed, he similarly remarks in OOP: 44 “It is perhaps surprising that there should be such a skeleton,” he continues, “but physics seems to prove that there is, particularly when taken in conjunction with the evidence that percepts are determined by the physical character of their stimuli. There is reason—though not quite conclusive reason—for regarding physics as causally dominant, in the sense that, given the physical structure of the world, the qualities of its events, in so far as we are acquainted with them, can be inferred by means of correlations” (p. 391). 45 In Religion and Science, Russell further argues that the difference between conscious perception and non-conscious phenomena in the natural world is a genuinely vague matter. He says, “we say that we are ‘conscious,’ but that sticks and stones are not; we say that we are ‘conscious’ when awake but not when asleep. We certainly mean something when we say this, and we mean something that is true… When we say we are ‘conscious,’ we mean two things: on the one hand, that we react in a certain way to our environment; on the other, that we seem to find, on looking within, some quality in our thoughts and feelings which we do not find in inanimate 18 Having realized the abstractness of what physics has to say, we no longer have any difficulty in fitting the visual sensation into the causal series. It used to be thought “mysterious” that purely physical phenomena should end in something mental. That was because people thought they knew a lot about physical phenomena, and were sure they differed in quality from mental phenomena (p. 154). But, he continues: We now realize that we know nothing of the intrinsic quality of physical phenomena except when they happen to be sensations, and therefore there is no reason to be surprised that some are sensations, or to suppose that the others are totally unlike sensations. The gap between mind and matter has been filled in, partly by new views on mind, but much more by the realization that physics tells us nothing as to the intrinsic character of matter (p. 154). In point of fact, he asserts, given that physical causal laws are plausibly more fundamental than psychological ones, “mind is merely a cross-section in a stream of physical causation, and there is nothing odd about its being both an effect and a cause in the physical world” (p. 156). Putting together all of the changes in Russell’s views after AMi, it is entirely unsurprising that many commentators have interpreted him as having abandoned a genuinely neutral monism by the time of AMa. However, there is good reason to be skeptical of these claims. Most importantly, in the closing paragraph of Chapter I he says: To show that the traditional separation between physics and psychology, mind and matter, is not metaphysically defensible will be one of the purposes of this work; but the two will be brought objects… So long as it could be supposed that one ‘perceives’ things in the outer world, one could say that, in perception, one was ‘conscious’ of them. Now we can only say that we react to stimuli, and so do stones, though the stimuli to which they react are fewer. So far, therefore, as external ‘perception’ is concerned, the difference between us and a stone is only one of degree. The more important part of the notion of ‘consciousness’ is concerned with what we discover by introspection. We not only react to external objects, but know that we react… [But] to know that we see something is not really a new piece of knowledge, over and above the seeing, unless it is in memory… [However] memory is a form of habit, and habit is characteristic of nervous tissue, though it may occur elsewhere, for example in a roll of paper which rolls itself up again if it is unwound” (130-2). Recently, Brogaard (2010) has also argued, in a different context, that ‘consciousness’ is a vague term. 19 together, not by subordinating either to the other, but by displaying each as a logical structure composed of what, following Dr. H. M. Sheffer, we shall call “neutral stuff”. (AMa, p. 10) In fact, Russell further contends in OOP, “in a completed science, the word ‘mind’ and the word ‘matter’ would both disappear, and would be replaced by causal laws concerning ‘events’, the only events known to us otherwise than in their mathematical and causal properties being percepts” (p. 292-3). As a consequence, both psychology and physics would cease to be independent sciences. Instead, Russell argues, they would both be reducible to what he calls “chrono-geography”, an imagined future science which he suggests “begins with events having space-time relations and does not assume at the outset that certain strings of them can be treated as persistent material units or as minds” (p. 294). Shortly thereafter, in his 1935 Religion and Science (hereafter RS), Russell makes similar pronouncements. While he claims on one hand that “physics and chemistry are supreme throughout” the world, he insists on the other that “the distinction between what is mental and what is physical is only one of convenience” (p. 203). Indeed, he continues, “the technique of physics was developed under the influence of a belief in the metaphysical reality of ‘matter’ which now no longer exists, and the new quantum mechanics has a different technique which dispenses with false metaphysics” (p. 204). Likewise, he says, “the technique of psychology, to some extent, was developed under a belief in the metaphysical reality of the ‘mind’ ” (p. 204). However, he suggests, “it seems possible that, when physics and psychology have both been completely freed from these lingering errors, they will both develop into one science dealing neither with mind nor matter, but with events, which will not be labeled either ‘physical’ or ‘mental’ ” (p. 204). While there remains some room for interpretation, remarks such as these strongly suggest that Russell continues to embrace a genuine neutral monism well after the writing of AMa. §6 Towards Russellian Physicalism? Thus far, I have made the case that Russell’s Neutral Monism encompasses two related, but distinct, views about the relation between the mind and physical reality. First, according to the Neutral Monism of Russell’s 1919 OP, there are particulars which are purely material, images which are purely mental, and sensations which are both mental and material—and hence genuinely neutral. Plausibly, this version of Neutral Monism is an ontological dualism in all but name. Second, according to the Neutral 20 Monism of AMi, both minds and matter are composed from more fundamental constituents of the world—initially labeled ‘transitory particulars’ and later ‘events’—which are intrinsically neither mental nor physical, but which become mental and/or physical in virtue of playing roles in psychological and/or physical causal processes. Arguably, this version of Neutral Monism is a genuine neutral monism, one which Russell seemingly embraced well after many commentators have alleged. In what follows, I will suggest that there are strong, though far from dispositive, grounds for thinking that Russell’s Neutral Monism shifts again during the 1940s—this time seemingly into a version of Russellian Physicalism. 46 To my knowledge, the first indication of this shift occurs in his 1944 “Reply to Criticisms” (hereafter Reply) in the Library of Living Philosophers volume on his work. In the course of clarifying and addressing challenges to his Neutral Monism of AMi, Russell notes two points on which his views have importantly changed. Firstly, he becomes increasingly confident that mnemic causation, which he previously regarded as the causal process which renders events psychological, is fully reducible to physiological causal processes in the brain. 47 (And there is no hint here, or in later work, that Russell continues to imagine physical causation to be reducible, in turn, to chrono-geography.) Secondly, and more importantly, he revealingly remarks that “I find myself in ontology increasingly materialistic, and in theory of knowledge increasingly subjectivistic” (Reply, p. 700). 48 Elaborating on this shortly thereafter, Russell says, “I wish to distinguish sharply between ontology and epistemology. In ontology I start by accepting the truth of physics; in epistemology I ask myself: Given the truth of physics, what can be meant by an organism having ‘knowledge,’ and what knowledge can it have?” (p. 700, emphasis added). 46 I won’t here address the question of whether Russellian Physicalism genuinely counts as a version of physicalism. While I am inclined to think some versions do, making such a case is a project for another occasion. 47 He says, “As regards ‘mnemic causation, I agree with Mr. [John] Laird that the hypothesis of causes acting at a distance is too violent, and I should therefore now explain habits by means of modifications of brain structure” (Reply, p. 700). 48 We must be careful not to conclude that Russell is here endorsing run-of-the-mill materialism. For he continues to repudiate it as late as 1959 in a letter to the editor originally published in Encounter in which he says, “I do not, in fact, think that either mind or matter is part of the stuff of the world. I think that minds and bits of matter are convenient aggregations, like cricket clubs or football clubs” (Yours Faithfully, p. 292). Rather, I suspect, the view to which he is increasingly attracted is what Maxwell (this volume) later calls “nonmaterialist physicalism”, one according to which both matter and minds are constructed from physical events. My thanks to Russell Wahl for bringing this letter to my attention. 21 In my view, these remarks suggest a significant transition in how Russell conceives of the mind-body problem, especially when considered in light of what he says elsewhere in his later work. In particular, there is compelling evidence that he no longer views the distinction between the mind and physical reality to be in any sense ontological in character. It is not a matter of intrinsic differences between mental and physical phenomena or even between psychological or physical causal processes. For seemingly, on his new view all events and causal processes are fundamentally physical in nature. 49 Instead, the real root of the mind-body problem is epistemic in character; it is the result of the radical differences in the kinds of knowledge we have of the events which make up physical reality. Further evidence for this interpretation occurs a few pages later when he remarks, “beyond certain very abstract mathematical properties physics can tell us nothing about the character of the physical world. But there is one part of the physical world which we know otherwise than through physics, namely that part in which our thoughts and feelings are situated. These thoughts and feelings, therefore, are members of the atoms (or minimal material constituents) of our brains” (Reply, p. 706, emphasis added). By the time of his 1948 HK, his last systematic foray into issues of epistemology and metaphysics, Russell makes his change in view even more explicit. There he reports, “my own belief is that the ‘mental’ and the ‘physical’ are not so disparate as is generally thought. I should define a ‘mental’ occurrence as one which some one knows otherwise than by inference; the distinction between ‘mental’ and ‘physical’ therefore belongs to theory of knowledge, not to metaphysics” (HK, p. 224). And not long afterwards he says, What, then, do we know about the physical world? Let us first define more exactly what we mean by a ‘physical’ event. I should define it as an event which, if known to occur, is inferred and which is not known to be mental. And I define a ‘mental’ event (to repeat) as one with which some one is acquainted otherwise than by inference. Thus a ‘physical’ event is one which is either totally unknown, or, if known at all, is not known to any one except by inference—or, perhaps we should say, is not known to be known to any one except by inference (p. 245). On a straightforward reading of these remarks, mental phenomena are not distinguishable by any ontological feature they possess, but rather by the fact that a subject is acquainted with them (in the post-OP non-relational sense). In 49 Consequently, there is more to physical reality than we might naively suppose. 22 contrast, physical phenomena will include all of the events describable, in causal and structural terms, by physics. Hence, if it turns out that the events describable by physics include all of those with which conscious subjects are acquainted, mental events will turn out to be a subclass of the physical events that make up reality. And there is compelling evidence that Russell thinks that mental events are indeed identical to events in the brain which, with respect to their causal and structural features, physics can in principle provide a full descriptive characterization. 50 As noted above, by the time of Reply, he already sees psychological causal processes as fully reducible to physiological causal processes in the brain. And in HK, he goes further in maintaining that physiological causal processes are in all probability fully reducible most immediately to chemical causal processes, and ultimately to macro-level physical processes. In fact, he contends, “there is no reason to suppose living matter subject to any laws other than those to which inanimate matter is subject, and considerable reason to think that everything in the behavior of living matter is theoretically explicable in terms of physics and chemistry” (HK, p. 50). And concerning physiological causal processes in the brain in particular, he says, “on the evidence as it exists the most probable hypothesis is that, in the chain of events from sense-organ to muscle, everything is determined by the laws of macroscopic physics” (p. 56). Thus, it is relatively clear at this point that Russell thinks that mental events just are physical events in the brain with which a subject is acquainted. In any case, this is precisely the view that he unequivocally affirms in his 1958 review of Gilbert Ryle’s The Concept of Mind: My own belief is that the distinction between what is mental and what is physical does not lie in any intrinsic character of either, but in the way in which we acquire knowledge of them. I should call an event ‘mental’ if it is one that somebody can notice or, as Professor Ryle would say, observe. I should regard all events as physical, but I should regard as only physical those which no one knows except by inference (“What is Mind?”, p. 12, emphasis added). One important consequence of the change in Russell’s conception of Neutral Monism is that its neutrality becomes entirely epistemic character. For as he continues to emphasize, given our epistemic limitations we cannot rule out any number of competing hypotheses about the intrinsic nature of the 50 Of course, on Russell’s view physical events have intrinsic natures which elude these descriptions. It is an open question whether he would conceive of these intrinsic natures as additional aspects of physical events, or whether the descriptions simply cannot capture all there is to one and the same aspects. 23 events described by physics with which we lack acquaintance. In fact, he maintains, “the qualities that compose such events are unknown—so completely unknown that we cannot say either that they are, or that they are not, different from the qualities that we know as belonging to mental events” (p. 247). And in MPD, he puts matters even more forcefully: It is not always realized how exceedingly abstract is the information that theoretical physics has to give. It lays down certain fundamental equations which enable it to deal with the logical structure of events, while leaving it completely unknown what is the intrinsic character of the events that have the structure. We only know the intrinsic character of events when they happen to us. Nothing whatever in theoretical physics enables us to say anything about the intrinsic character of events elsewhere. They may be just like events that happen to us, or they may be totally different in strictly unimaginable ways (MPD, p. 18). But while Russell grants, and even insists, that we cannot have conclusive grounds for rejecting panpyschism, idealism, or even dualism for that matter, he takes there to be non-demonstrative inferences which lend greater credibility to the hypothesis that extra-mental events in physical reality differ somewhat in intrinsic character from those with which we are acquainted. Indeed, he contends, “when we come to events in parts of physical space-time where there are no brains, we have still no positive argument to prove that they are not thoughts, except such as may be derived from observation of the differences between living and dead matter coupled with inferences based on analogy or its absence” (HK, p. 246, emphasis added). So we needn’t be forced to embrace idealism or panpsychism. On the other hand, Russell denies that the differences in the intrinsic character of events with which we are and are not acquainted suffice to open an ontological chasm between them. Quite the contrary, he says, “there is supposed to be a gulf between mind and matter, and a mystery which it is held in some degree impious to dissipate. I believe, for my part, that there is no greater mystery than there is in the transformation by the radio of electromagnetic waves into sounds [i.e. sound-waves]. I think the mystery is produced by a wrong conception of the physical world and by a Manichaean fear of degrading the mental world to the level of the supposedly inferior world of matter” (MPD, p. 21-22). 51 Thus, by all appearances, what Russell leaves us with is a Neutral Monism with a greater affinity to Russellian 51 Russell makes clear that instead of “sounds” he should have said “sound-waves” in his aforementioned 1959 letter to the editor in Encounter. 24 Physicalism than any genuinely neutral monism, including his own previously held versions. 52 And if so, then he is not best seen as a proponent of neutral monism—he is best seen as a proponent, at different times, of three different Neutral Monisms: one an ontological dualism, one a genuine neutral monism, and one a Russellian Physicalism. ACKNOWLEDGEMENTS: For helpful comments and feedback, I would like to thank Torin Alter, Heath Hamilton, Bernard Linksy, Leopold Stubenberg, Russell Wahl, and the 52 The strongest objection to this reading is that it is seemingly in tension with several remarks Russell makes in his “Mind and Matter”, which was published in his 1956 Portraits from Memory. For instance, in the penultimate paragraph he says, “a piece of matter is a group of events connected by causal laws, namely the causal laws of physics. A mind is a group of events connected by causal laws, namely, the causal laws of psychology. An event is not rendered either mental or material by an intrinsic quality, but only by its causal relations” (p. 164). And elsewhere in “Mind and Matter”, he remarks, “I do not think it can be laid down absolutely, if the above is right, that there can be no such thing as disembodied mind. There would be disembodied mind if there were groups of events connected according to the laws of psychology, but not according to the laws of physics. We readily believe that dead matter consists of groups of events arranged according to the laws of physics, but not according to the laws of psychology. And there seems no a priori reason why the opposite should not occur” (p. 160). Together, these passages strongly suggest that Russell is still a genuine neutral monist well into the 1950s. However, there are a number of reasons why drawing this conclusion would be hasty. First, it is worth noting that Russell originally presented “Mind and Matter” in lectures in 1950 and it is not inconceivable that the shift in his thinking that started in 1948 hadn’t yet reached full completion only two years later. Second, immediately after noting the a priori possibility of a disembodied mind, Russell insists that “we have no empirical evidence of it” (p. 160) and we have already seen that he thinks that the empirical evidence suggests that psychological causal processes are ultimately reducible to physical causal processes. It is perfectly consistent for Russell to think that there are only physical events and physical processes in the world while granting that we cannot a priori rule out the possibility of disembodied minds. Indeed, given his actual views about knowledge by acquaintance and knowledge by description, I think Russell is plausibly read as what we might call an “a posteriori Russellian Physicalist” (see Alter and Howell, this volume). (It is worth noting that some functionalists would also hold the a priori possibility of disembodied minds to be perfectly compatible with the actual world being entirely physical, though Russell obviously predated any such view.) Third, as noted in footnote 48 above, we must be careful not to conflate something’s being physical with it’s being material. Russell clearly thinks that matter is constructed from more basic elements, but it doesn’t follow that these events are non-physical. On the contrary, there are many places in his later work where he seems quite sensitive to the distinction. Thus, all things considered, I think that there is a stronger case that the later Russell is best interpreted as a Russellian Physicalist, though I grant that there might be alternative ways of interpreting him along the lines of his earlier neutral monism. But any such interpretation would have to address the passages I have noted here which strongly suggest otherwise. My thanks to Leopold Stubenberg for helpful discussion of these issues. 25 students in my 2013 graduate seminar on Bertrand Russell at the University of Mississippi. REFERENCES: Alter, T. and R. Howell. (this volume). 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