Essays in Experimental Logic

Chapter 11: The Existence of the World as a Logical Problem

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Of the two parts of this paper the first is a study in formal analysis. It attempts to show that there is no problem, logically speaking, of the existence of an external world. Its point is to show that the very attempt to state the problem involves a self-contradiction: that the terms cannot be stated so as to generate a problem without assuming what is professedly brought into question. The second part is a summary endeavor to state the actual question which has given rise to the unreal problem and the conditions which have led to its being misconstrued. So far as subject-matter is concerned, it supplements the first part; but the argument of the first part in no way depends upon anything said in the second. The latter may be false and its falsity have no implications for the first.


There are many ways of stating the problem of the existence of an external world. I shall make that of Mr. Bertrand Russell the basis of my examinations, as it is set forth in his recent book Our Knowledge of the External World as a Field for Scientific Method in Philosophy. I do this both because his statement is

(282) one recently made in a book of commanding importance, and because it seems to me to be a more careful statement than most of those in vogue. If my point can be made out for his statement, it will apply, a fortiori, to other statements. Even if there be those to whom this does not seem to be the case, it will be admitted that my analysis must begin somewhere. I cannot take the space to repeat the analysis in application to differing modes of statement with a view to showing that the method employed will yield like results in all cases. But I take the liberty of throwing the burden upon the reader and asking him to show cause why it does not so apply.

After rejecting certain familiar formulations of the question because they employ the not easily definable notions of the self and independence, Mr. Russell makes the following formulation: Can we "know that objects of sense . . . . exist at times when we are not perceiving them?" (op. cit., p. 75). Or, in another mode of statement: "Can the existence of anything other than our own[1] hard data be inferred from the existence of those data?" (pp. 73 and 83).

I shall try to show that identification of the " data of sense" as the sort of term which will generate the problem involves an affirmative answer to the question—that it must have been answered in the affirmative be-

(283) -fore the question can be asked. And this, I take it, is to say that it is not a question at all. A point of departure may be found in the following passage: "I think it must be admitted as probable that the immediate objects of sense depend for their existence upon physiological conditions in ourselves, and that, for example, the colored surfaces which we see cease to exist when we shut our eyes" (p. 64). I have not quoted the passage for the sake of gaining an easy victory by pointing out that this statement involves the existence of physiological conditions. For Mr. Russell himself affirms that fact. As he points out, such arguments assume precisely the "common sense world of stable objects" professedly put in doubt (p. 85). My purpose is to ask what justification there is for calling immediate data "objects of sense." Statements of this type always call color visual, sound auditory, and so on. If it were merely a matter of making certain admissions for the sake of being able to play a certain game, there would be no objection. But if we are concerned with a matter of serious analysis, one is bound to ask, Whence come these adjectives? That color is visual in the sense of being an object of vision is certainly admitted in the common-sense world, but this is the world we have left. That color is visual is a proposition about color and it is a proposition which color itself does not utter. Visible or visual color is already a "synthetic" proposition. not a term nor an analysis of a single term. That color is seen, or is

(284) visible, I do not call in question; but I insist that fact already assumes an answer to the question which Mr. Russell has put. It presupposes existence beyond the color itself. To call the color a "sensory" object involves another assumption of the same kind but even more complex-involving, that is, even more existence beyond the color.

I see no reply to this statement except to urge that the terms "visual" and "sensory" as applied to the object are pieces of verbal supererogation having no force in the statement. This supposititious answer brings the matter to a focus. Is it possible to institute even a preliminary disparaging contrast between immediate objects and a world external to them unless the term "sensory" has a definite effect upon the meaning assigned to immediate data or objects? Before taking up this question I shall, however, call attention to another implication of the passage quoted. It appears to be implied that existence of color and "being seen" are equivalent terms. At all events, in similar arguments the identification is frequently made. But by description all that is required for the existence of color is certain physiological conditions. They may be present and color exist and yet not be seen. Things constantly act upon the optical apparatus in a way which fulfils the conditions of the existence of color without color being seen. This statement does not involve any dubious psychology about an act of attention. I only mean that the argument implies

(285) over and above the existence of color something called seeing or perceiving — noting is perhaps a convenient neutral term. And this clearly involves an assumption of something beyond the existence of the datum — and this datum is by definition an external world. Without this assumption the term "immediate" could not be introduced. Is the object immediate or is it the object of an immediate noting ? If the latter, then the hard datum already stands in connection with something beyond itself.

And this brings us to a further point. The sense objects are repeatedly spoken of as "known." For example: "It is obvious that since the senses give knowledge of the latter kind [believed on their own account, without the support of any outside evidence] the immediate facts perceived by sight or touch or hearing do not need to be proved by argument but are completely self-evident" (p. 68). Again, they are spoken of as "facts of sense"[2] (p. 70), and as facts going along, for knowledge, with the laws of logic (p. 7a). I do not know what belief or knowledge means here: nor do I understand what is meant by a fact being evidence for itself.[3] But obviously

(286) Mr. Russell knows, and knows their application to the sense object. And here is a further assumption of what, by definition, is a world external to the datum. Again, we have assumed in getting a question stated just what is professedly called into question. And the assumption is not made the less simple in that Mr. Russell has defined belief as a case of a triadic relation, and said that without the recognition of the three-term relation the difference between perception and belief is inexplicable (p. 50).

We come to the question passed over. Can such terms as "visual," "sensory," be neglected without modifying the force of the question — that is, without affecting the implications which give it the force of a problem? Can we "know that objects of sense, or very similar objects, exist at times when we are not perceiving them ? Secondly, if this cannot be known, can we know that other objects, inferable from objects of sense but not necessarily resembling them, exist either when we are perceiving the objects of sense or at any other time" (p. 75) ?

I think a little reflection will make it clear that without the limitation of the term "perceiving" by the term "sense" no problem as to existence at other times

(287) can possibly arise. For neither (a) reference to time nor (b) limitation to a particular time is given either in the fact of existence of color or of perceiving color. Mr. Russell, for example, makes allusion to "a patch of color which is momentarily seen" (p. 76). This is the sort of thing that may pass without challenge in the common-sense world, but hardly in an analysis which professes to call that world in question. Mr. Russell makes the allusion in connection with discriminating between sensation as signifying "the mental event of our being aware" and the sensation as object of which we are aware — the sense object. He can hardly be guilty, then, in the immediate context, of proceeding to identify the momentariness of the event with the momentariness of the object. There must be some grounds for assuming the temporal quality of the object — and that "immediateness" belongs to it in any other way than as an object of immediate seeing. What are these grounds?

How is it, moreover, that even the act of being aware is describable as "momentary"? I know of no way of so identifying it except by discovering that it is delimited in a time continuum. And if this be the case, it is surely superfluous to bother about inference to "other times." They are assumed in stating the question — which thus turns out again to be no question. It may be only a trivial matter that Mr. Russell speaks of "that patch of color which is momentarily seen when we look at the table" (p. 76, italics

(288) mine). I would not attach undue importance to such phrases. But the frequency with which they present themselves in discussions of this type suggests the question whether as matter of fact "the patch of color" is not determined by reference to an object —the table— and not vice versa. As we shall see later, there is good ground for thinking that Mr. Russell is really engaged, not in bringing into question the existence of an object beyond the datum, but in redefining the nature of an object, and that the reference to the patch of color as something more primitive than the table is really relevant to this reconstruction of traditional metaphysics. In other words, it is relevant to defining an object as a constant correlation of variations in qualities, instead of defining it as a substance in which attributes inhere — or a subject of predicates.

a) If anything is an eternal essence, it is surely such a thing as color taken by itself, as by definition it must be taken in the statement of the question by Mr. Russell. Anything more simple, timeless, and absolute than a red can hardly be thought of. One might question the eternal character of the received statement of, say, the law of gravitation on the ground that it is so complex that it may depend upon conditions not yet discovered and the discovery of which would involve an alteration in the statement. If 2 plus 2 equal 4 be taken as an isolated statement, it might be conceived to depend upon hidden conditions and to be alterable with them. But by conception

(288) we are dealing in the case of the colored surface with an ultimate, simple datum. It can have no implications beyond itself, no concealed dependencies. How then can its existence, even if its perception be but momentary, raise a question of "other times" at all?

b) Suppose a perceived blue surface to be replaced by a perceived red surface — and it will be conceded that the change, or replacement, is also perceived. There is still no ground for a belief in the temporally limited duration of either the red or the blue surface. Anything that leads to this conclusion would lead to the conclusion that the number two ceases when we turn to think of an atom. There is no way then of escaping the conclusion that the adjective "sense" in the term "sense object" is not taken innocently. It is taken as qualifying (for the purposes of statement of the problem) the nature of the object. Aside from reference to the momentariness of the mental event a reference which is expressly ruled out — there is no way of introducing delimited temporal existence into the object save by reference to one and the same object which is perceived at different times to have different qualities. If the same object —however object be defined— is perceived to be of one color at one time and of another color at another time, then as a matter of course the color-datum of either the earlier or later time is identified as of transitory duration. But equally, of course, there is no question of inference to "other times." Other times have already been used

(290) to describe, define, and delimit this (brief) time. A moderate amount of unbiased reflection will, I am confident, convince anyone that apart from a reference to the same existence perduring through different times while changing in some respect, no temporal delimitation of the existence of such a thing as sound or color can be made. Even Plato never doubted the eternal nature of red; he only argued from the fact that a thing is red at one time and blue at another to the unstable, and hence phenomenal, character of the thing. Or, put in a different way, we can know that a red is a momentary or transitory existence only if we know of other things which determine its beginning and cessation.

Mr. Russell gives a specific illustration of what he takes to be the correct way of stating the question in an account of what, in the common-sense universe of discourse, would be termed walking around a table. If we exclude considerations to which we have (apart from assuming just the things which are doubtful) no right, the datum turns out to be something to be stated as follows: "What is really known[4] is a correlation of muscular and other bodily sensations with changes in visual sensations" (p. 77). By "sensations" must be meant sensible objects, not mental events. This statement repeats the point already

(291) dealt with: "muscular," "visual," and "other bodily" are all terms which are indispensable and which also assume the very thing professedly brought into question: the external world as that was defined. "Really known" assumes both noting and belief, with whatever complex implications they may involve — implications which, for all that appears to the contrary, may be indefinitely complex, and which, by Mr. Russell's own statement, involve relationship to at least two other terms besides the datum. But in addition there appears the new term "correlation." I cannot avoid the conclusion that this term involves an explicit acknowledgment of the external world.

Note, in the first place, that the correlation in question is not simple: it is threefold, being a correlation of correlations. The "changes in visual sensations" (objects) must be correlated in a temporal continuum; the "muscular and other bodily sensations" (objects) must also constitute a connected series. One set of changes belongs to the serial class "visual"; the other set to the serial class "muscular." And these two classes sustain a point-to-point correspondence to each other — they are correlated.

I am not raising the old question of how such complex correlations can be said to be either "given" or "known" in sense, though it is worth a passing notice that it was on account of this sort of phenomenon that Rant postulated his threefold intellectual synthesis of apprehension, reproduction, and

(292) recognition in conception; and that it is upon the basis of necessity for such correlations that the rationalists have always criticized sensationalist empiricism. Personally I agree that temporal and spatial qualities are quite as much given in experience as are particulars —in fact, as I have been trying to show, particulars can be identified as particulars only in a relational complex. My point is rather (1) that any such given is already precisely what is meant by the "world"; and (ii) that such a highly specified correlation as Mr. Russell here sets forth is in no case a psychological, or historical, primitive, but is a logical primitive arrived at by an analysis of an empirical complex.

(i) The statement involves the assumption of two temporal "spreads" which, moreover, are determinately specified as to their constituent elements and as to their order. And these sustain to each other a correlation, element to element. The elements, moreover, are all specifically qualitative and some of them, at least, are spatial. How this differs from the external world of common-sense I am totally unable to see. It may not be a very big external world, but having begged a small external world, I do not see why one should be too squeamish about extending it over the edges. The reply, I suppose, is that this complex defined and ordered object is by conception the object of a single perception, so that the question remains as to the possibility of inferring from it to

(293) something beyond.[5] But the reply only throws us back upon the point previously made. A particular or single event of perceptual awareness can be determined as to its ingredients and structure only in a continuum of objects. That is, the series of changes in color and shape can be determined as just such and such an ordered series of specific elements, with a determinate beginning and end, only in respect to a temporal continuum of things anteceding and succeeding. Moreover, the determination involves an analysis which disentangles qualities and shapes from contemporaneously given objects which are irrelevant. In a word, Mr. Russell's object already extends beyond itself; it already belongs to a larger world.

(ii) A sensible object which can be described as a correlation of an ordered series of shapes and colors with an ordered series of muscular and other bodily objects presents a definition of an object, not a psychological datum. What is stated is the definition of an object, of any object in the world. Barring

(294) ambiguities[6] in the terms "muscular" and "bodily," it seems to be an excellent definition. But good definition or poor, it states what a datum is known to be as an object in a known system; viz., definite correlations of specified and ordered elements. As a definition, it is general. It is not made from the standpoint of any particular percipient. It says: If there be any percipient at a specified position in a space continuum, then the object may be perceived as such and such. And this implies that a percipient at any other position in the space continuum can deduce from the known system of correlations just what the scries of shapes and colors will be from another position. For, as we have seen, the correlation of the series of changes of shape assumes a spatial continuum; hence one perspective projection may be correlated with that of any position in the continuum.

I have no direct concern with Mr. Russell's solution of his problem. But if the prior analysis is correct, one may anticipate in advance that it will consist

( 295) simply in making explicit the assumptions which have tacitly been made in stating the problem — subject to the conditions involved in failure to recognize that they have been made. And I think an analytic reading of the solution will bear out the following statement. His various "peculiar," "private" points of view and their perspectives are nothing but names for the positions and projectional perspectives of the ordinary space of the public worlds. Their correlation by likeness is nothing but the explicit recognition that they are all defined and located, from the start, in one common spatial continuum. One quotation must suffice. "If two men are sitting in a room, two somewhat similar worlds are perceived by them; if a third man enters and sits between them, a third world, intermediate between the two others, begins to be perceived" (pp. 87-88). Pray what is this room and what defines the position (standpoint and perspective) of the two men and the standpoint "intermediate" between them ? If the room and all the positions and perspectives which they determine are only within, say, Mr. Russell's private world, that private world is interestingly complex, but it gives only the original problem over again, not a "solution" of it. It is a long way from likenesses within a private world to likenesses between private worlds. And if the worlds are all private, pray who judges their likeness or unlikeness ? This sort of thing makes one conclude that Mr. Russell's actual procedure is the reverse of

(296) his professed one. He really starts with one room as a spatial continuum within which different positions and projections are determined, and which are readily correlated with one another just because they are projections from positions within one and the same space-room. Having employed this, he, then, can assign different positions to different percipients and institute a comparison between what each perceives and pass upon the extent of the likeness which exists between them.

What is the bearing of this account upon the "empirical datum"? just this: The correlation of correlative series of changes which defines the object of sense perception is in no sense an original historic or psychologic datum. It signifies the result of an analysis of the usual crude empirical data, and an analysis which is made possible only by a very complex knowledge of the world. It marks not a primitive psychologic datum but an outcome, a limit, of analysis of a vast amount of empirical objects. The definition of an object as a correlation of various subcorrelations of changes represents a great advance — so it seems to me — over the definition of an object as a number of adjectives stuck into a substantive; but it represents an improved definition made possible by the advance of scientific knowledge about the commonsense world. It is a definition not only wholly independent of the context in which Mr. Russell arrives at it, but is one which once more and finally)

( 297) assumes extensive and accurate knowledge of just the world professedly called into question.


I have come to the point of transition to the other part of my paper. A formal analysis is necessarily dialectical in character. As an empiricist I share in the dissatisfaction which even the most correct dialectical discussion is likely to arouse when brought to bear on matters of fact. I do not doubt that readers will feel that some fact of an important character in Mr. Russell's statement has been left untouched by the previous analysis — even upon the supposition that the criticisms are just. Particularly will it be felt, I think, that psychology affords to his statement of the problem a support of fact not affected by any logical treatment. For this reason I append a summary statement as to the facts which are misconstrued by any statement which makes the existence of the world problematic.

I do not believe a psychologist would go as far as to admit that a definite correlation of elements as specific and ordered as that of Mr. Russell's statement is a primitive psychological datum. Many would doubtless hold that patches of colored extensity, sounds, kinaesthetic qualities, etc., are psychologically much more primitive than, say, a table, to say nothing of a group of objects in space or a series of events in time; they would say, accordingly, that there is a

(298) real problem as to how we infer or construct the latter on the basis of the former. At the same time I do not believe that they would deny that their own knowledge of the existence and nature of the ultimate and irreducible qualities of sense is the product of a long, careful, and elaborate analysis to which the sciences of physiology, anatomy, and controlled processes of experimental observation have contributed. The ordinary method of reconciling these two seemingly inconsistent positions is to assume that the original sensible data of experience, as they occurred in infancy, have been overlaid by all kinds of associations and inferential constructions so that it is now a work of intellectual art to recover them in their innocent purity.

Now I might urge that as matter of fact the reconstruction of the experience of infancy is itself an inference from present experience of an objective world, and hence cannot be employed to make a problem out of the knowledge of the existence of that world. But such a retort involves just the dialectic excursus which I am here anxious to avoid. I am on matter-of-fact ground when I point out that the assumption that even infancy begins with such highly discriminated particulars as those enumerated is not only highly dubious but has been challenged by eminent psychologists. According to Mr. James, for example, the original datum is large but confused, and specific sensible qualities represent the result of discrimina-

( 299) -tions. In this case, the elementary data, instead of being primitive empirical data, are the last terms, the limits, of the discriminations we have been able to make. That knowledge grows from a confusedly experienced external world to a world experienced as ordered and specified would then be the teaching of psychological science, but at no point would the mind be confronted with the problem of inferring a world. Into the arguments in behalf of such a psychology of original experience I shall not go, beyond pointing out the extreme improbability (in view of what is known about instincts and about the nervous system) that the starting-point is a quality corresponding to the functioning of a single sense organ, much less of a single neuronic unit of a sense organ. If one adds, as a hypothesis, that even the most rudimentary conscious experience contains within itself the element of suggestion or expectation, it will be granted that the object of conscious experience even with an infant is homogeneous with the world of the adult. One may be unwilling to concede the hypothesis. But no one can deny that inference from one thing to another is itself an empirical event, and that just as soon as such inference occurs, even in the simplest form of anticipation and prevision, a world exists like in kind to that of the adult.

I cannot think that it is a trivial coincidence that psychological analysis of sense perception came into existence along with that method of experimentally

( 300) controlled observation which marks the beginning of modern science. 'Modern science did not begin with discovery of any new kind of inference. It began with the recognition of the need of different data if inference is to proceed safely. It was contended that starting with the ordinary —or customary— objects of perception hopelessly compromised in advance the work of inference and classification. Hence the demand for an experimental resolution of the commonsense objects in order to get data less ambiguous, more minute, and more extensive. Increasing knowledge of the structure of the nervous system fell in with increased knowledge of other objects to make possible a discrimination of specific qualities in all their diversity; it brought to light that habits, individual and social (through influence on the formation of individual habits), were large factors in determining the accepted or current system of objects. It was brought to light, in other words, that factors of chance, habit, and other non-rational factors were greater influences than intellectual inquiry in determining what men currently believed about the world. What psychological analysis contributed was, then, not primitive historic data out of which a world had somehow to be extracted, but an analysis of the world which had been previously thought of and believed in, into data making possible better inferences and beliefs about the world. Analysis of the influences customarily determining belief and inference

(301) was a powerful force in the movement to improve knowledge of the world.

This statement of matters of fact bears out, it will be observed, the conclusions of the dialectical analysis. That brought out the fact that the ultimate and elementary data of sense perception are identified and described as limiting elements in a complex world. What is now added is that such an identification of elements marks a significant addition to the resources of the technique of inquiry devoted to improving knowledge of the world. When these data are isolated from their logical status and office, they are inevitably treated as self-sufficient, and they leave upon our hands the insoluble, because self-contradictory, problem of deriving from them the world of commonsense and science. Taken for what they really are, they are elements detected in the world and serving to guide and check our inferences about it. They are never self-inclosed particulars; they are always —even as crudely given— connected with other things in experience. But analysis gets them in the form where they are keys to much more significant relations. In short, the particulars of perception, taken as complete and independent, make nonsense. Taken as objects discriminated for the purposes of improving, reorganizing, and testing knowledge of the world they are invaluable assets. The material fallacy lying behind the formal fallacy which the first part of this paper noted is the failure to recognize

( 302) that what is doubtful is not the existence of the world but the validity of certain customary yet inferential beliefs about things in it. It is not the common-sense world which is doubtful, or which is inferential, but common-sense as a complex of beliefs about specific things and relations in the world. Hence never in any actual procedure of inquiry do we throw the existence of the world into doubt, nor can we do so without self-contradiction. We doubt some received piece of "knowledge" about some specific thing of that world, and then set to work, as best we can, to rectify it. The contribution of psychological science to determining unambiguous data and eliminating the irrelevant influences of passion and habit which control the inferences of common-sense is an important aid in the technique of such rectifications.


  1. I shall pass over the terms "our own" so far as specific reference is concerned, but the method employed applies equally to them. Who are the "we," and what does "own" mean, and how is ownership established ?
  2. Contrast the statement: "When I speak of a fact, I do not mean one of the simple things of the world, I mean that a certain thing has a certain quality, or that certain things have a certain relation" (P. 51).
  3. In view of the assumption, shared by Mr. Russell, that there is such a thing as non-inferential knowledge, the conception that a thing offers evidence for itself needs analysis. Self-evidence is merely a convenient term for disguising the difference between the indubitably given and the believed in. Hypotheses, for example, are self-evident sometimes, that is, obviously present for just what they are, but they are still hypotheses, and to offer their self-evident character as "evidence" would expose one to ridicule. Meanings may be self-evident (the Cartesian "clear and distinct") and truth dubious.
  4. "Really known" is an ambiguous term. It may signify understood, or it may signify known to be there or given. Either meaning implies reference beyond.
  5. The reply implies that the exhaustive, all-at-once perception of the entire universe assumed by some idealistic writers does not involve any external world. I do not make this remark for the sake of identifying myself with this school of thinkers, but to suggest that the limited character of empirical data is what occasions inference. But it is a fallacy to suppose that the nature of the limitations is psychologically given. On the contrary, they have to be determined by descriptive identifications which involve reference to the more extensive world. Hence no matter how "self-evident" the existence of the data may be, it is never self-evident that they are rightly delimited with respect to the specific inference in process of making.
  6. The ambiguities reside in the possibility of treating the "muscular and other bodily sensations" as meaning something other than data of motion and corporealness-however these be defined. Muscular sensation may be an awareness of motion of the muscles, but the phrase "of the muscles" does not alter the nature of motion as motion; it only specifies what motion is involved. And the long controversy about the existence of immediate "muscular sensations" testifies to what a complex cognitive determination we are here dealing with. Anatomical directions and long experimentation were required to answer the question. Were they psychologically primitive data no such questions could ever have arisen.

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