Russell - A Very Short Indroduction (11 page)

Neutral monism

James argued that the single kind of metaphysically ultimate raw material is arranged in different patterns by its interrelations, some of which we call ‘mental’ and some ‘physical’. James said his view was prompted by dissatisfaction with theories of consciousness, which is merely the wispy inheritor of old-fashioned talk about ‘souls’. He agreed that thoughts exist; what he denied is that they are entities. They are, instead, functions: there is ‘no aboriginal stuff or quality of being, contrasted with that of which material objects are made, out of which our thoughts of them are made; but there is a function in experience which thoughts perform, and for the performance of which this quality of being is invoked. That function is
knowing
’ (James,
Essays in Radical Empiricism
, 3–4).

In James’s view the single kind of ‘primal stuff’, as he called it, is ‘pure experience’. Knowing is a relation into which different portions of primal stuff can enter; the relation itself is as much part of pure experience as its relata.

Russell could not accept quite all of this view. He thought that James’s use of the phrase ‘pure experience’ showed a lingering influence of idealism, and rejected it; he preferred the use made by others of the term ‘neutral stuff’, a nomenclatural move of importance because whatever the primal stuff is, it has to be able – when differently arranged – to give rise to what could not appropriately be called ‘experience’, for example stars and stones. But even with this modified view Russell only partially agreed. It is right to reject the idea of consciousness as an entity, he said, and it is partly but not wholly right to consider both mind and matter as composed of neutral stuff which in isolation is neither; especially in regard to sensations – an important point for Russell, with his overriding objective of marrying physics and perception. But he insisted that certain things belong only to the mental world (images and feelings) and others only to the physical world (everything which cannot be described as experience). What distinguishes them is the kind of causality that governs them; there are two different kinds of causal law, one applicable only to psychological phenomena, the other only to physical phenomena. Hume’s law of association exemplifies the first kind, the law of gravity the second. Sensation obeys both kinds, and is therefore truly neutral.

Adopting this version of neutral monism obliged Russell to abandon some of his earlier views. One important change was that he gave up the notion of ‘sense-data’. He did this because sense-data are objects of mental acts, whose existence he had now rejected; therefore, since there can be no question of a relation between non-existent acts and supposed objects of those acts, there can be no such objects either. And because there is no distinction between sensation and sense-datum – that is, because we now understand that the sensation we have in seeing, for example, a colour-patch
just is
the colour-patch itself – we need only one term here, for which Russell adopts the name ‘percept’.

Before accepting neutral monism Russell had objected to it on a number of grounds, one being that it could not properly account for belief. And as noted, even when he adopted the theory he did so in a qualified form; mind and matter overlap on common ground, but each has irreducible aspects. Nevertheless what at last persuaded him was the fact, as it seemed to him, that psychology and physics had come very close: the new physics both of the atom and of relativistic space-time had effectively dematerialized matter, and psychology, especially in the form of behaviourism, had effectively materialized mind. From the internal viewpoint of introspection, mental reality is composed of sensations and images. From the external viewpoint of observation, material things are composed of sensations and sensibilia. A more or less unified theory therefore seems possible by treating the fundamental difference as one of arrangement: a mind is a construction formed of materials organized in one way, a brain more or less the same materials organized in another.

A striking feature of this view is, surprisingly, how idealist it is. Russell had, as noted, charged James with residual idealism. But here he is arguing something hardly distinguishable: that minds are composed of sensed percepts – namely, sensations and images – and matter is a logical fiction constructed of unsensed percepts. Now Russell had often insisted (using his earlier terminology) that sense-data and sensibilia are ‘physical’ entities, in somewhat the sense in which, if one were talking about an item of sensory information in a nervous system, that datum would be present as impulses in a nerve or activity in a brain. But then nerves and brains, as objects of physical theory, are themselves to be understood as constructions from sensations and sensibilia, not as traditionally understood ‘material substance’, a concept which physics has shown to be untenable. At the end of
AMd
Russell accordingly says that ‘an ultimate scientific account of what goes on in the world, if it were ascertainable, would resemble psychology rather than physics . . . [because] psychology is nearer to what exists’ (
AMd
305, 308). This explains Russell’s notorious claim that ‘brains consist of thoughts’ and that when a physiologist looks at another person’s brain, what he ‘sees’ is a portion of his own brain (Schilpp,
Philosophy of Bertrand Russell
, 705).

For robuster versions of materialism this aspect of Russell’s view is hard to accept. But it is not the only difficulty with his version of neutral monism. Not least is the fact that he failed in his main aim, which was to refute the view that consciousness is essential to the distinction between mental and physical phenomena. He had not of course attempted to analyse consciousness quite away; his aim was rather to reduce its importance for the mind–matter question. But images, feelings, and sensations, which play so central a role in his theory, stubbornly remain
conscious
phenomena, whereas the sensibilia (by definition often unsensed), which constitute the greater part of matter, are not. Russell accepted this, but tried to specify a criterion of difference which did not trade on these facts, namely, the criterion of membership of different causal realms. But whereas that difference is open to question – and even if it exists might be too often hard to see – the consciousness difference is clear cut.

Relatedly, the intentionality which characterizes consciousness cannot be left out of accounts of knowledge; memory and perception are inexplicable without it. Russell later acknowledged this point, and gave it as a reason in
MPD
for having to return to the question of perception and knowledge in later writings.
Russell also later came to abandon the idea – anyway deeply unsatisfactory from the point of view of a theory supposed to be both
neutral
and
monist –
that images and feelings are essentially mental, that is, not wholly reducible to neutral stuff; for in a very late essay he says; ‘An event is not rendered either mental or material by any intrinsic quality, but only by its causal relations. It is perfectly possible for an event to have both the causal relations characteristic of physics and those characteristic of psychology. In that case, the event is both mental and material at once’ (
Portraits from Memory
(1958), 152). This, for consistency, is what he should have argued in
AMd
itself, where only sensations have this character. But this view in turn generates another problem, which is that it comes into unstable tension with a view to which Russell returned after
AMd
, namely, that the causes of percepts are inferred from the occurrence of the percepts themselves. As noted earlier, Russell wavered between treating physical things as logical constructions of sensibilia and as entities inferred as the causes of perception; he held this latter view in
PP
and returned to it after
AMd
. But on the face of it, one is going to need a delicate connection between one’s metaphysics and one’s epistemology in order to hold both that minds and things are of one stuff, and that things are the unknown external inferred causes of what happens in minds. So those parts of the legacy of
AMd
which remain in his later thinking raise considerable difficulties for his later views about matter.

Realism and perception

One of the chief reasons for Russell’s reversion to a realistic, inferential view about physical things was the difficulty inherent in the notion of unsensed sense-data or, in the later terminology, percepts. As noted above, the idea had been to replace inferred entities with logically constructed ones, an application of the analytical technique. lf physical things can be logically constructed out of actual and possible sensedata, then two desiderata have been realized at once: the theory is empirically based, and inferred entities have been shaved away by Ockham’s razor. But it is obvious, and the point has already been made, that the idea of unsensed sense-data (or unperceived percepts) is, if not indeed contradictory, at least problematic. It makes sense – although, without a careful gloss, it is metaphysically questionable – to talk of the existence of
possibilities
of sensation; but to talk of the existence of
possible sensations
arguably does not (note Russell’s definition of sensibilia as entities having the ‘same metaphysical and physical status as sense-data without necessarily being data to any mind’). If the choice lay between inferred material particulars and non-actual perceptions existing unperceived, it would seem best to plump for the former. In effect, this is what Russell himself came to think; and unsensed sensations went out of the window. But he did not return to the cruder form of inferential realism held in
PP
; something more ingenious, but no more successful, was up his sleeve, as explained shortly.

Another reason for Russell’s reversion to realism was his recognition that the notion of causality is problematic for phenomenalism. Things in the world seem to affect one another causally in ways that are difficult to account for properly by mere reports of sense-experiences. Moreover, a causal theory of perception is a natural and powerful way of explaining how experience itself arises. In Russell’s mature philosophy of science, contained in
AMt
and
Human Knowledge
(1948), he did not opt for a Lockean view which says that our percepts resemble their causal origins – the so-called ‘picture-original’ theory – because we cannot be directly acquainted with things, and therefore cannot expect to know their qualities and relations. Rather, he now argued, changes in the world and our perceptions are correlated, or co-vary, at least for orders of things in the world that our perceptual apparatus is competent to register (we do not, for example, perceive electrons swarming in the table, so there is no associated covariation of world and perception at that level). The correspondence between percepts and things is one of
structure
at the appropriate level: ‘Whatever we infer from perceptions it is only structure that we can validly infer; and structure is what can be expressed by mathematical logic’ (
AMt
254). And this means that we have to be ‘agnostic’ about all but the physical world’s mathematical properties, which is what physics describes (
AMt
270).

Russell had come to think that the best candidate for what is metaphysically most basic in the world is the ‘event’. Objects are constructed out of events in the following way: the world is a collection of events, most of which cluster together around a multitude of ‘centres’, thus constituting individual ‘objects’. Each cluster radiates ‘chains’ of events, which interact with and react upon chains radiating from other centres – among which are perceivers. When a chain interacts with the events constituting the perceptual apparatus of a perceiver, the last link in the chain is a percept. Since everything is ultimately constituted of events, they are in effect the ‘neutral stuff’ of which minds and material things are made. Minds are clusters of events connected by ‘mental’ relations, not least among them
memory; otherwise there is no metaphysical difference between mind and matter. Finally, the interrelations of event-chains is what scientific causal laws describe.

This view enabled Russell to formulate the argument he had long been trying to state satisfactorily, namely, that percepts are parts of things. For on this view it is not the case that there are events which constitute things, and then in addition other events which are perceptions of those things; rather, there are just events constituting the object, some of which are percepts – these being the terminal events of the chains radiating from the object which interact with events constituting the perceiver.

This theory is inferential not in the earlier sense in which the causes of percepts, lying inaccessibly beyond a veil of perception, are guessed from the nature of the percepts themselves. Rather, the inference is
from
certain terminal events, namely, percepts – which are interactions between (to put the matter heuristically) ‘mental’ events and that level of structure in the rest of the event world with which the ‘mental’ events are capable of interacting – to the clusters and chains of events constituting the world as a whole

In
AMt
the core of the theory is the idea that knowledge of the world is purely structural. We know the qualities and relations as well as the structure of percepts, but we know only the structure of external events, not their qualities. This seems somewhat reminiscent of Locke’s distinction between primary and secondary qualities, but it is not; Russell is saying that all we can infer from our percepts is the structure of the qualities and relations of things, not the qualities and relations themselves; and that this is the limit of knowledge.

This theory has a fatal flaw, which was quickly recognized by the mathematician M. H. A. Newman and set out in an article published soon after the appearance of
AMt
. It is that since our knowledge of the structure of events is not a mere result of our stipulating them, but is manifestly non-trivial, it follows that our inferential knowledge cannot be limited solely to questions of structure. This is because – to put the point by a rough analogy – a number of different worlds could be abstractly definable as having the same structure, and if they were, knowledge of their structure alone could not separate them and in particular could not individuate the ‘real’ one. If science genuinely consists of discoveries about the world through observation and experiment, the distinction between what we observe and what we infer cannot therefore be collapsed into a distinction between pure structure and qualities.