"A man must be forsaken by all the gods to dream that the world we

see outside of us, filling space in its three dimensions, moving down

the inexorable stream of time, governed at each step by Causality's

invariable law,--but in all this only following rules which we may

prescribe for it in advance of all experience,--to dream, I say, that

such a world should stand there outside of us, quite objectively real

with no complicity of ours, and thereupon by a subsequent _act_,

through the instrumentality of mere sensation, that it should enter

our head and reconstruct a duplicate of itself as it was outside. For

what a poverty-stricken thing is this mere sensation! Even in the

noblest organs of sense it is nothing more than a local and specific

feeling, susceptible within its kind of a few variations, but always

strictly subjective and containing in itself nothing objective,

nothing resembling a perception. For sensation of every sort is and

remains a process in the organism itself. As such it is limited to

the territory inside the skin and can never, accordingly, _per se_

contain anything that lies outside the skin or outside ourselves....

Only when the Understanding ... is roused to activity and brings its

sole and only form, the _law of Causality_, into play, only then does

the mighty transformation take place which makes out of subjective

sensation objective intuition. The Understanding, namely, grasps by

means of its innate, _a priori_, ante-experiential form, the given

sensation of the body as an _effect_ which as such must necessarily

have a _cause_. At the same time the Understanding summons to its aid

the form of the outer sense which similarly lies already preformed in

the intellect (or brain), and which is Space, in order to locate that

cause outside of the organism.... In this process the Understanding,

as I shall soon show, takes note of the most minute peculiarities

of the given sensation in order to construct in the outer space a

cause which shall completely account for them. This operation of the

Understanding is, however, not one that takes place discursively,

reflectively, _in abstracto_, by means of words and concepts; but is

intuitive and immediate.... Thus the Understanding must first create

the objective world; never can the latter, already complete _in

se_, simply promenade into our heads through the senses and organic

apertures. For the senses yield us nothing further than the raw

material which must be first elaborated into the objective conception

of an orderly physical world-system by means of the aforesaid simple

forms of Space, Time, and Causality.... Let me show the great chasm

between sensation and perception by showing how raw the material is

out of which the fair structure is upreared. Only two senses serve

objective perception: touch and sight. They alone furnish the data

on the basis whereof the Understanding, by the process indicated,

erects the objective world.... These data in themselves are still

no perception; that is the Understanding's work. If I press with my

hand against the table, the sensation I receive has no analogy with

the idea of the firm cohesion of the parts of this mass: only when my

Understanding passes from the sensation to its cause does it create

for itself a body with the properties of solidity, impenetrability,

and hardness. When in the dark I lay my hand on a surface, or grasp a

ball of three inches diameter, in either case the same parts of the

hand receive the impression: but out of the different contraction of

the hand in the two cases my Understanding constructs the form of the

body whose contact caused the feeling, and confirms its construction

by leading me to move my hand over the body. If one born blind

handles a cubical body, the sensations of his hand are quite uniform

on all sides and in all directions,--only the corners press upon a

smaller part of his skin. In these sensations, as such, there is

nothing whatever analogous to a cube. But from the felt resistance

his Understanding infers immediately and intuitively a cause thereof,

which now presents itself as a solid body; and from the movements

of exploration which the arms made whilst the feelings of the hands

remained constant he constructs, in the space known to him _a priori_,

the body's cubical shape. Did he not bring with him ready-made the

idea of a cause and of a space, with the laws thereof, there never

could arise, out of those successive feelings in his hand, the

image of a cube. If we let a string run through our closed hand, we

immediately construct as the cause of the friction and its duration in

such an attitude of the hand, a long cylindrical body moving uniformly

in one direction. But never out of the pure sensation in the hand

could the idea of movement, that is, of change of position in space

by means of time, arise: such a content can never lie in sensation,

nor come out of it. Our Intellect, antecedently to all experience,

must bear in itself the intuitions of Space and Time, and therewithal

of the possibility of motion, and no less the idea of Causality, to

pass from the empirically given feeling to its cause, and to construct

the latter as a so moving body of the designated shape. For how great

is the abyss between the mere sensation in the hand and the ideas

of causality, materiality, and movement through Space, occurring

in Time! The feeling in the hand, even with different contacts and

positions, is something far too uniform and poor in content for it

to be possible to construct out of _it_ the idea of Space with its

three dimensions, of the action of bodies on each other, with the

properties of extension, impenetrability, cohesion, shape, hardness,

softness, rest, and motion--in short, the foundations of the objective

world. This is only possible through Space, Time, and Causality ...

being preformed in the Intellect itself,... from whence it again

follows that the perception of the external world is essentially an

intellectual process, a work of the Understanding, _to which sensation

furnishes merely the occasion,_ and the data to be interpreted in each

particular case."[264]

I call this view mythological, because I am conscious of no such

Kantian machine-shop in my mind, and feel no call to disparage the

powers of poor sensation in this merciless way. I have no introspective

experience of mentally producing or creating space. My space-intuitions

occur not in two times but in one. There is not one moment of passive

inextensive sensation, succeeded by another of active extensive

perception, but the form I see is as immediately felt as the color

which fills it out. That the higher parts of the mind come in, who can

deny? They add and subtract, they compare and measure, they reproduce

and abstract. They inweave the space-sensations with intellectual

relations; but _these_ relations are the same when they obtain between

the elements of the space-system as when they obtain between any of the

other elements of which the world is made.

The essence of the Kantian contention is that there are not _spaces_,

but _Space_--one infinite continuous _Unit_--and that our knowledge of

_this_ cannot be a piecemeal sensational affair, produced by summation

and abstraction. To which the obvious reply is that, if any known thing

bears on its front the _appearance_ of piecemeal construction and

abstraction, it is this very notion of the infinite unitary space of

the world. It is a _notion_, if ever there was one; and no intuition.

Most of us apprehend it in the barest symbolic abridgment: and if

perchance we ever do try to make it more adequate, we just add one

image of sensible extension to another until we are tired. Most of us

are obliged to turn round and drop the thought of the space in front of

us when we think of that behind. And the space represented as near to

us seems more minutely subdivisible than that we think of as lying far

away.

* * * * *

The other prominent German writers on space are also 'psychical

stimulists.' Herbart, whose influence has been widest, says 'the

resting eye sees no space,'[265] and ascribes visual extension to the

influence of movements combining with the non-spatial retinal feelings

so as to form gradated series of the latter. A given sensation of such

a series reproduces the idea of its associates in regular order, and

its idea is similarly reproduced by any one of them with the order

reversed. Out of the fusion of these two contrasted reproductions comes

the form of space[266]--Heaven knows how.

The obvious objection is that mere serial order is a _genus_, and

space-order a very peculiar species of that _genus_; and that, if the

terms of reversible series became by that fact coexistent terms in

space, the musical scale, the degrees of warmth and cold, and all other

ideally graded series ought to appear to us in the shape of extended

corporeal aggregates,--which they notoriously do not, though we may of

course _symbolize_ their order by a spatial scheme. W. Volkmann von

Volkmar, the Herbartian, takes the bull here by the horns, and says the

musical scale _is_ spatially extended, though he admits that its space

does not belong to the real world.[267] I am unacquainted with any

other Herbartian so bold.

* * * * *

To Lotze we owe the much-used term 'local sign.' He insisted that

space could not emigrate directly into the mind from without, but

must be _reconstructed_ by the soul; and he seemed to think that the

first reconstructions of it by the soul must be super-sensational. But

why sensations themselves might not be the soul's _original_ spatial

reconstructive acts Lotze fails to explain.

* * * * *

Wundt has all his life devoted himself to the elaboration of a

space-theory, of which the neatest and most final expression is to be

found in his Logik (ii. 457-60). He says:

"In the eye, space-perception has certain constant peculiarities

which prove that no single optical sensation by itself possesses

the extensive form, but that everywhere in our perception of space

heterogeneous feelings combine. If we simply suppose that luminous

sensations _per se_ feel extensive, our supposition is shattered by

that influence of movement in vision which is so clearly to be traced

in many normal errors in the measurement of the field of view. If

we assume, on the other hand, that the movements and their feelings

are alone possessed of the extensive quality, we make an unjustified

hypothesis, for the phenomena compel us, it is true, to accord an

influence to movement, but give us no right to call the retinal

sensations indifferent, for there are no visual ideas without retinal

sensations. If then we wish rigorously to express the given facts, we

can ascribe a spatial constitution only to _combinations_ of retinal

sensations with those of movement."

Thus Wundt, dividing theories into 'nativistic' and 'genetic,' calls

his own a genetic theory. To distinguish it from other theories of the

same class, he names it a 'theory of complex local signs.'

"It supposes two systems of local signs, whose relations--taking the

eye as an example--we may think as ... the measuring of the manifold

local-sign system of the retina by the simple local-sign system of

the movements. In its psychological nature this is a process of

associative synthesis: it consists in the fusion of both groups of

sensations into a product, whose elementary components are no longer

separable from each other in idea. In melting wholly away into the

product which they create they become consciously undistinguishable,

and the mind apprehends only their resultant, the intuition of space.

Thus there obtains a certain analogy between this psychic synthesis

and that chemical synthesis which out of simple bodies generates a

compound that appears to our immediate perception as a homogeneous

whole with new properties."

Now let no modest reader think that if this sounds obscure to him it is

because he does not know the full context; and that if a wise professor

like Wundt can talk so fluently and plausibly about 'combination' and

'psychic synthesis,' it must surely be because those words convey a so

much greater fulness of positive meaning to the scholarly than to the

unlearned mind. Really it is quite the reverse; _all_ the virtue of

the phrase lies in its mere sound and skin. Learning does but make one

the more sensible of its inward unintelligibility. Wundt's 'theory' is

the flimsiest thing in the world. It starts by an untrue assumption,

and then corrects it by an unmeaning phrase. Retinal sensations _are_

spatial; and were they not, no amount of 'synthesis' with equally

spaceless motor sensations could intelligibly make them so. Wundt's

theory is, in short, but an avowal of impotence, and an appeal to

the inscrutable powers of the soul.[268] It confesses that we cannot

analyze the constitution or give the genesis of the spatial quality

in consciousness. But at the same time it says the _antecedents_

thereof are psychical and not cerebral facts. In calling the quality in

question a _sensational_ quality, our own account equally disclaimed

ability to analyze it, but said its antecedents were cerebral, not

psychical--in other words, that it was a _first_ psychical thing. This

is merely a question of probable fact, which the reader may decide.

* * * * *

And now what shall be said of Helmholtz? Can I find fault with a book

which, on the whole, I imagine to be one of the four or five greatest

monuments of human genius in the scientific line? If truth impels I

must fain try, and take the risks. It seems to me that Helmholtz's

genius moves most securely when it keeps close to particular facts. At

any rate, it shows least strong in purely speculative passages, which

in the Optics, in spite of many beauties, seem to me fundamentally

vacillating and obscure. The 'empiristic' view which Helmholtz defends

is that the space-determinations we perceive are in every case products

of a process of unconscious inference.[269] The inference is similar to

one from induction or analogy.[270] We always see that form before us

which _habitually_ would have caused the sensation we now have.[271]

But the latter sensation can never be intrinsically spatial, or its

intrinsic space-determinations would never be overcome as they are so

often by the 'illusory' space-determinations it so often suggests.[272]

Since the illusory determination can be traced to a suggestion of

Experience, the 'real' one must also be such a suggestion: so that

_all_ space intuitions are due solely to Experience.[273] The only

psychic activity required for this is the association of ideas.[274]

But how, it may be asked, can association produce a space-quality not

in the things associated? How can we by induction or analogy infer what

we do not already generically know? Can 'suggestions of experience'

reproduce elements which no particular experience originally contained?

This is the point by which Helmholtz's 'empiristic' theory, as a

_theory_, must be judged. No theory is worthy of the name which leaves

such a point obscure.

Well, Helmholtz does so leave it. At one time he seems to fall

back on inscrutable powers of the soul, and to range himself with

the 'psychical stimulists.' He speaks of Kant as having made the

essential step in the matter in distinguishing the content of

experience from that form--space, course--which is given it by the

peculiar faculties of the mind.[275] But elsewhere, again,[276]

speaking of sensationalistic theories which would connect spatially

determinate feelings _directly_ with certain neural events, he says

it is better to assume only such simple psychic activities as we

_know_ to exist, and gives the association of ideas as an instance of

what he means. Later,[277] he reinforces this remark by confessing

that he does not see how any neural process _can_ give rise without

antecedent experience to a ready-made (_fertige_) perception of

space. And, finally, in a single momentous sentence, he speaks of

sensations of _touch_ as if they might be the original material of our

space-percepts--which thus, from the optical point of view, 'may be

assumed as _given_.'[278]

Of course the eye-man has a right to fall back on the skin-man for

help at a pinch. But doesn't this mean that he is a mere eye-man and

not a complete psychologist? In other words, Helmholtz's Optics and

the 'empiristic theory' therein professed must not be understood as

attempts at answering the _general_ question of how space-consciousness

enters the mind. They simply deny that it enters with the first

optical sensations.[279] Our own account has affirmed stoutly that it

enters _then_; but no more than Helmholtz have we pretended to show

_why_. Who calls a thing a first sensation admits he has no theory of

its production. Helmholtz, though all the while without an articulate

theory, makes the world think he has one. He beautifully traces the

immense part which reproductive processes play in our vision of space,

and never--except in that one pitiful little sentence about touch--does

he tell us just what it is they reproduce. He limits himself to

denying that they reproduce originals of a visual sort. And so

difficult is the subject, and so magically do catch-words work on the

popular-scientist ear, that most likely, had he written 'physiological'

instead of 'nativistic,' and 'spiritualistic' instead of 'empiristic'

(which synonyms Hering suggests), numbers of his present empirical

evolutionary followers would fail to find in his teaching anything

worthy of praise. But since he wrote otherwise, they hurrah for him as

a sort of second Locke, dealing another death-blow at the old bugaboo

of 'innate ideas.' His 'nativistic' adversary Hering they probably

imagine--Heaven save the mark!--to be a scholastic in modern disguise.

* * * * *

After Wundt and Helmholtz, the most important anti-sensationalist

space-philosopher in Germany is Professor Lipps, whose deduction

of space from an order of non-spatial differences, continuous yet

separate, is a wonderful piece of subtlety and logic. And yet he has

to confess that continuous differences form in the first instance only

a logical series, which _need_ not appear spatial, and that wherever

it does so appear, this must be accounted a 'fact,' due merely 'to the

nature of the soul.'[280]

Lipps, and almost all the anti-sensationalist theorists except

Helmholtz, seem guilty of that confusion which Mr. Shadworth Hodgson

has done so much to clear away, viz., the confounding the analysis

of an idea with the means of its production. Lipps, for example,

finds that every space we think of can be broken up into positions,

and concludes that in some undefined way the several positions must

have pre-existed in thought before the aggregate space could have

appeared to perception. Similarly Mr. Spencer, defining extension as an

'aggregate of relations of coexistent position,' says "every cognition

of magnitude is a cognition of relations of position,"[281] and "no

idea of extension can arise from the simultaneous excitation" of many

nerves "unless there is a knowledge of their relative positions."[282]

Just so Prof. Bain insists that the very _meaning_ of space is scope

for movement,[283] and that therefore distance and magnitude _can_ be

no original attributes of the eye's sensibility. Similarly because

movement is analyzable into positions occupied at successive moments

by the mover, philosophers (e.g. Schopenhauer, as quoted above)

have repeatedly denied the possibility of _its_ being an immediate

sensation. We have, however, seen that it is the most immediate of all

our space-sensations. Because it can only occur in a definite direction

the impossibility of perceiving it without perceiving its direction has

been decreed--a decree which the simplest experiment overthrows.[284]

It is a case of what I have called the 'psychologist's fallacy':

mere acquaintance with space is treated as tantamount to every sort

of knowledge about it, the conditions of the latter are demanded of

the former state of mind, and all sorts of mythological processes

are brought in to help.[285] As well might one say that because the

world consists of all its parts, therefore we can only apprehend it

at all by having unconsciously summed these up in our head. It is the

old idea of our actual knowledge being drawn out from a pre-existent

potentiality, an idea which, whatever worth it may metaphysically

possess, does no good in psychology.

My own sensationalistic account has derived most aid and comfort

from the writings of Hering, A. W. Volkmann, Stumpf, Le Conte, and

Schön. All these authors allow ample scope to that Experience which

Berkeley's genius saw to be a present factor in all our visual acts.

But they give Experience some grist to grind, which the _soi-distant_

'empiristic' school forgets to do. Stumpf seems to me the most

philosophical and profound of all these writers; and I owe him much. I

should doubtless have owed almost as much to Mr. James Ward, had his

article on Psychology in the Encyclopædia Britannica appeared before my

own thoughts were written down. The literature of the question is in

all languages very voluminous. I content myself with referring to the

bibliography in Helmholtz's and Aubert's works on Physiological Optics

for the visual part of the subject, and with naming in a note the

ablest works in the English tongue which have treated of the subject in

a _general_ way.[286]

* * * * *

[140] Reprinted, with considerable revision, from 'Mind' for 1887.

[141] Prof. Jastrow has found that invariably we tend to

_underestimate_ the amount of our skin which may be stimulated by

contact with an object when we express it in terms of visual space;

that is, when asked to mark on paper the extent of skin affected, we

always draw it much too small. This shows that the eye gets as much

space feeling from the smaller line as the skin gets from the larger

one. Cf. Jastrow: Mind, xi. 546-7; American Journal of Psychology, iii.

53.

[142] Amongst sounds the graver ones seem the most extensive. Stumpf

gives three reasons for this: 1) association with bigger causes; 2)

wider reverberation of the hand and body when grave notes are sung; 3)

audibility at a greater distance. He thinks that these three reasons

dispense us from supposing an immanent extensity in the sensation of

sound as such. See his remarks in the Tonpsychologie, i. 207-211.

[143] Encyclopædia Britannica, 9th Edition, article Psychology, pp. 46,

58.

[144] Philosophical Transactions (1841).

[145] Hermann's Handb. d. Physiol., Bd. iii. 1, §. 575.

[146] _Loc. cit._ §. 572.

[147] Elemente der Psychophysik, ii. 475-6.

[148] See Foster's Text-book of Physiology, bk. iii. c. vi. § 2.

[149] Fechner, who was ignorant of the but lately discovered function

of the semi-circular canals, gives a different explanation of the

organic seat of these feelings. They are probably highly composite.

With me, actual movements in the eyes play a considerable part in

them, though I am hardly conscious of the peculiar feelings in the

scalp which Fechner goes on to describe thus: "The feeling of strained

attention in the different sense-organs seems to be only a muscular

one produced in using these various organs by setting in motion, by a

sort of reflex action, the set of muscles which belong to them. One

can ask, then, with what particular muscular contraction the sense of

strained attention in the effort to recall something is associated? On

this question my own feeling gives me a decided answer; it comes to me

distinctly not as a sensation of tension in the inside of the head, but

as a feeling of strain and contraction in the scalp, with a pressure

from outwards in over the whole cranium, undoubtedly caused by a

contraction of the muscles of the scalp. This harmonizes very well with

the expressions, _sich den Kopf zerbrechen, den Kopf zusammennehmen_.

In a former illness, when I could not endure the slightest effort after

continuous thought, and had no theoretical bias on this question, the

muscles of the scalp, especially those of the back-head, assumed a

fairly morbid degree of sensibility whenever I tried to think." (Elem.

der Psychophysik, ii, 490-91.)

[150] That the sensation in question is one of tactile rather than

of acoustic sensibility would seem proved by the fact that a medical

friend of the writer, both of whose _membranæ tympani_ are quite

normal, but one of whose ears is almost totally deaf, feels the

presence and withdrawal of objects as well at one ear as at the other.

[151] The skin seems to obey a different law from the eye here. If a

given retinal tract be excited, first by a series of points, and next

by the two extreme points, with the interval between them unexcited,

this interval will seem considerably less in the second case than it

seemed in the first. In the skin the unexcited interval feels the

larger. The reader may easily verify the facts in this case by taking

a visiting-card, cutting one edge of it into a saw-tooth pattern, and

from the opposite edge cutting out all but the two corners, and then

comparing the feelings aroused by the two edges when held against the

skin.

[152] Classen, Physiologie des Gesichtssinnes, p. 114; see also A.

Riehl, Der Philosophische Kriticismus, ii. p. 149.

[153] It is worth while at this point to call attention with some

emphasis to the fact that, though the anatomical condition of the

feeling _resembles_ the feeling itself, such resemblance cannot be

taken by our understanding to explain _why_ the feeling should be

just what it is. We hear it untiringly reiterated by materialists and

spiritualists alike that we can see no possible inward reason why a

certain brain-process should produce the feeling of redness and another

of anger: the one process is no more red than the other is angry, and

the coupling of process and feeling is, as far as our understanding

goes, a juxtaposition pure and simple. But in the matter of _spatial_

feeling, where the retinal patch that produces a triangle in the mind

is itself a triangle, etc., it looks at first sight as if the sensation

might be a direct cognition of its own neural condition. Were this

true, however, our sensation should be one of _multitude_ rather

than of continuous extent; for the condition is _number_ of optical

nerve-termini, and even this is only a remote condition and not an

immediate condition. The immediate condition of the feeling is not the

process in the retina, but the process in the brain; and the process

in the brain may, for aught we know, be as unlike a triangle,--nay,

it probably is so,--as it is unlike redness or rage. It is simply a

_coincidence_ that in the case of space one of the organic conditions,

viz., the triangle impressed on the skin or the retina, should lead

to a representation in the mind of the subject observed similar to

that which it produces in the psychological observer. In no other

kind of case is the coincidence found. Even should we admit that we

cognize triangles in space because of our immediate cognition of the

triangular shape of our excited group of nerve-tips, the matter would

hardly be more transparent, for the mystery would still remain, why

are we so much better cognizant of triangles on our finger-tips than

on the nerve-tips of our back, on our eye than on our ear, and on any

of these parts than in our brain? Thos. Brown very rightly rejects the

notion of explaining the shape of the space perceived by the shape of

the 'nervous expansion affected.' "If this alone were necessary, we

should have square inches and half inches, and various other forms,

rectilinear and curvilinear, of fragrance and sound." (Lectures, XXII.)

[154] Musical tones, e.g., have an order of quality independent either

of their space- or time-order. Music comes from the time-order of the

notes upsetting their quality-order. In general, if _a b c d e f g h

i j k_, etc., stand for an arrangement of feelings in the order of

their quality, they may assume _any_ space-order or time-order, as _d

e f a h g_, etc., and still the order of quality will remain fixed and

unchanged.

[155] The whole science of geometry may be said to owe its being to the

exorbitant interest which the human mind takes in _lines_. We cut space

up in every direction in order to manufacture them.

[156] Kant was, I believe, the first to call attention to this last

order of facts. After pointing out that two opposite spherical

triangles, two gloves of a pair, two spirals wound in contrary

directions, have identical inward determinations, that is, have their

parts defined with relation _to each other_ by the same law, and so

must be _conceived_ as identical, he showed that the impossibility

of their mutual superposition obliges us to assign to each figure of

a symmetrical pair a peculiar difference of its own which can only

consist in an _outward_ determination or relation of its parts, no

longer to each other, but to the whole of an objectively outlying space

with its points of the compass given absolutely. This in_con_ceivable

difference is perceived only "through the relation to right and

left, which is a matter of immediate intuition." In these last words

(_welches unmittelbar auf Anschauung geht_--Prolegomena, § 12) Kant

expresses all that we have meant by speaking of up and down, right and

left, as _sensations_. He is wrong, however, in invoking relation to

extrinsic total space as essential to the existence of these contrasts

in figures. Relation to our own body is enough.

[157] In the eyes of many it will have seemed strange to call a

relation a mere line, and a line a mere sensation. We may easily learn

a great deal _about_ any relation, say that between two points: we may

divide the line which joins these, and distinguish it, and classify

it, and find out _its_ relations by drawing or representing new lines,

and so on. But all this further industry has naught to do with our

_acquaintance_ with the relation itself, in its first intention. So

cognized, the relation _is_ the line and nothing more. It would indeed

be fair to call it something less; and in fact it is easy to understand

how most of us come to feel as if the line were a much grosser thing

than the relation. The line is broad or narrow, blue or red, made by

this object or by that alternately, in the course of our experience;

it is therefore independent of any one of these accidents; and so,

from viewing it as no one of _such_ sensible qualities, we may end

by thinking of it as something which cannot be defined except as the

negation of all sensible quality whatever, and which needs to be put

_into_ the sensations by a mysterious act of 'relating thought.'

Another reason why we get to feel as if a space-relation must be

something other than the mere feeling of a line or angle is that

between two positions we can potentially make any number of lines and

angles, or find, to suit our purposes, endlessly numerous relations.

The sense of this indefinite potentiality cleaves to our words when we

speak in a general way of 'relations of place,' and misleads us into

supposing that not even any single one of them can be exhaustively

equated by a single angle or a single line.

[158] This often happens when the warm and cold points, or the round

and pointed ones, are applied to the skin within the limits of a single

'Empfindungskreis.'

[159] Vierordt, Grundriss der Physiologie, 5te Auflage (1877), pp. 326,

436.

[160] Vorlesungen üb. Menschen- u. Thierseele (Leipzig, 1863), i. 214.

See also Ladd's Physiological Psychology, pp. 396-8, and compare the

account by G. Stanley Hall (Mind, x. 571) of the sensations produced

by moving a blunt point lightly over the skin. Points of cutting pain,

quivering, thrilling, whirling, tickling, scratching, and acceleration,

alternated with each other along the surface.

[161] Of the anatomical and physiological conditions of these facts we

know as yet but little, and that little need not here be discussed.

Two principal hypotheses have been invoked in the case of the retina.

Wundt (Menschen- u. Thierseele, i. 214) called attention to the changes

of color-sensibility which the retina displays as the image of the

colored object passes from the fovea to the periphery. The color alters

and becomes darker, and the change is more rapid in certain directions

than in others. This alteration in general, however, is one of which,

_as such_, we are wholly unconscious. We see the sky as bright blue

all over, the modifications of the blue sensation being interpreted by

us, not as differences in the objective color, but as distinctions in

its locality. Lotze (Medizinische Psychologie, 333, 355), on the other

hand, has pointed out the peculiar tendency which each particular point

of the retina has to call forth that movement of the eyeball which

will carry the image of the exciting object from the point in question

to the _fovea_. With each separate tendency to movement (as with each

actual movement) we may suppose a peculiar modification of sensibility

to be conjoined. This modification would constitute the peculiar local

tingeing of the image by each point. See also Sully's Psychology, pp.

118-121. Prof. B. Erdman has quite lately (Vierteljahrsschrift f. wiss.

Phil., x. 324-9) denied the existence of all evidence for such immanent

_qualia_ of feeling characterizing each locality. Acute as his remarks

are, they quite fail to convince me. On the skin the _qualia_ are

evident, I should say. Where, as on the retina, they are less so (Kries

and Auerbach), this may well be a mere difficulty of discrimination not

yet educated to the analysis.

[162] 1852, p. 331.

[163] Maybe the localization of intracranial pain is itself due to

such association as this of local signs with each other, rather than

to their qualitative similarity in neighboring parts (_supra_, p.

19); though it is conceivable that association and similarity itself

should here have one and the same neural basis. If we suppose the

sensory nerves from those parts of the body beneath any patch of skin

to terminate in the same sensorial brain-tract as those from the skin

itself, and if the excitement of any one fibre tends to irradiate

through the whole of that tract, the feelings of all fibres going to

that tract would presumably both have a similar intrinsic quality,

and at the same time tend each to arouse the other. Since the same

nerve-trunk in most cases supplies the skin and the parts beneath, the

anatomical hypothesis presents nothing improbable.

[164] Unless, indeed, the foot happen to be spontaneously tingling or

something of the sort at the moment. The whole surface of the body is

always in a state of semi-conscious irritation which needs only the

emphasis of attention, or of some accidental inward irritation, to

become strong at any point.

[165] It is true that the inside of the forearm, though its

discriminative sensibility is often less than that of the outside,

usually rises very prominently into consciousness when the latter is

touched. Its _æsthetic_ sensibility to contact is a good deal finer. We

enjoy stroking it from the extensor to the flexor surface around the

ulnar side more than in the reverse direction. Pronating movements give

rise to contacts in this order, and are frequently indulged in when the

back of the forearm feels an object against it.

[166] These facts were first noticed by Wundt: see his Beiträge, p.

140, 202. See also Lamansky, Pflüger's Archiv, xi. 418.

[167] So far all has been plain sailing, but our course begins to be so

tortuous when we descend into minuter detail that I will treat of the

more precise determination of locality in a long note. When _P_ recalls

an ideal line leading to the fovea the line is felt in its entirety

and but vaguely; whilst _P_, which we supposed to be a single star of

actual light, stands out in strong distinction from it. The ground of

the distinction between _P_ and the ideal line which it terminates is

manifest--_P_ being vivid while the line is faint; _but why should P

hold the particular position it does, at the end of the line, rather

than anywhere else--for example, in its middle?_ That seems something

not at all manifest.

To clear up our thoughts about this latter mystery, let us take the

case of an actual line of light, none of whose parts is ideal. The

feeling of the line is produced, as we know, when a multitude of

retinal points are excited together, each of which _when excited

separately_ would give rise to _one_ of the feelings called local

signs. Each of these signs is the feeling of a small space. From their

simultaneous arousal we might well suppose a feeling of larger space

to result. But why is it necessary that _in_ this larger spaciousness

the sign _a_ should appear always at one end of the line, _z_ at the

other, and _m_ in the middle? For though the line be a unitary streak

of light, its several constituent points can nevertheless break out

from it, and become alive, each for itself, under the selective eye of

attention.

The uncritical reader, giving his first careless glance at the

subject, will say that there is no mystery in this, and that 'of

course' local signs must appear alongside of each other, each in its

own place;--there is no other way possible. But the more philosophic

student, whose business it is to discover difficulties quite as much

as to get rid of them, will reflect that it is conceivable that the

partial factors might fuse into a larger space, and yet not each be

located within it any more than a voice is _located_ in a chorus. He

will wonder how, after combining into the line, the points _can_ become

severally alive again: the separate puffs of a 'sirene' no longer

strike the ear after they have fused into a certain pitch of sound.

He will recall the fact that when, after looking at things with one

eye closed, we double, by opening the other eye, the number of retinal

points affected, the new retinal sensations do not as a rule appear

_alongside_ of the old ones and additional to them, but merely make the

old ones seem larger and nearer. Why should the affection of new points

on the _same_ retina have so different a result? In fact, he will

see no sort of logical connection between (1) the original separate

local signs, (2) the line as a unit, (3) the line with the points

discriminated in it, and (4) the various nerve-processes which subserve

all these different things. He will suspect our local sign of being a

very slippery and ambiguous sort of creature. Positionless at first,

it no sooner appears in the midst of a gang of companions than it is

found maintaining the strictest position of its own, and assigning

place to each of its associates. How is this possible? Must we accept

what we rejected a while ago as absurd, and admit the points each to

have position _in se_? Or must we suspect that our whole construction

has been fallacious, and that we have tried to conjure up, out of

association, qualities which the associates never contained?

There is no doubt a real difficulty here; and the shortest way of

dealing with it would be to confess it insoluble and ultimate. Even if

position be not an intrinsic character of any one of those sensations

we have called local signs, we must still admit that there is

_something about_ every one of them that stands for the potentiality of

position, and is the _ground_ why the local sign, when it gets placed

at all, gets placed _here_ rather than _there_. If this 'something' be

interpreted as a physiological something, as a mere nerve-process, it

is easy to say in a blank way that when it is excited alone, it is an

'ultimate fact' (1) that a positionless spot will appear; that when it

is excited together with other similar processes, but _without_ the

process of discriminative attention, it is another 'ultimate fact'

(2) that a unitary line will come; and that the final 'ultimate fact'

(3) is that, when the nerve-process is excited _in combination with_

that other process which subserves the feeling of attention, what

results will be the line with the local sign inside of it determined

to a particular place. Thus we should escape the responsibility of

explaining, by falling back on the everlasting inscrutability of the

psycho-neural nexus. The moment we call the ground of localization

physiological, we need only point out _how_, in those cases in which

localization occurs, the physiological process _differs_ from those

in which it does not, to have done all we can possibly do in the

matter. This would be unexceptionable logic, and with it we might let

the matter drop, satisfied that there was no self-contradiction in

it, but only the universal psychological puzzle of how a new mode of

consciousness emerges whenever a fundamentally new mode of nervous

action occurs.

But, blameless as such tactics would logically be on our part, let us

see whether we cannot push our theoretic insight a little farther.

It seems to me we can. We cannot, it is true, give a reason why the

line we feel when process (2) awakens should have its own peculiar

shape; nor can we explain the essence of the process of discriminative

attention. But we can see why, if the brute facts be admitted that

a line may have one of its parts singled out by attention at all,

and that that part may appear in relation to other parts at all, the

relation must be _in the line itself_,--for the line and the parts are

the only things supposed to be in consciousness. And we can furthermore

suggest a reason why parts appearing thus in relation to each other in

a line should fall into an immutable order, and each within that order

keep its characteristic place.

If a lot of such local signs all have any quality which evenly augments

as we pass from one to the other, we can arrange them in an ideal

serial order, in which any one local sign must lie below those with

more, above those with less, of the quality in question. It must divide

the series into two parts,--unless indeed it have a maximum or minimum

of the quality, when it either begins or ends it.

Such an ideal series of local signs in the mind is, however, not yet

identical with the feeling of a line in space. Touch a dozen points on

the skin _successively_, and there seems no necessary reason why the

notion of a definite line should emerge, even though we be strongly

aware of a gradation of quality among the touches. We may of course

symbolically arrange them in a line in our thought, but we can always

distinguish between a line symbolically thought and a line directly

felt.

But note now the peculiarity of the nerve-processes of all these local

signs: though they may give no line when excited successively, when

excited _together_ they do give the actual sensation of a line in

space. The sum of them is the neural process of that line; the sum of

their feelings is the feeling of that line; and if we begin to single

out particular points from the line, and notice them by their rank, it

is impossible to see how this rank can _appear_ except as an actual

fixed space-position sensibly felt as a bit of the total line. The

scale itself appearing as a line, rank in it must appear as a definite

part of the line. If the seven notes of an octave, when heard together,

appeared to the sense of hearing as an outspread _line_ of sound--which

it is needless to say they do not--why then no one note could be

discriminated without being localized, according to its pitch, _in_ the

line, either as one of its extremities or as some part between.

But not alone the gradation of their quality arranges the local-sign

feelings in a scale. Our _movements_ arrange them also in a time-scale.

Whenever a stimulus passes from point _a_ of the skin or retina to

point _f_, it awakens the local-sign feelings in the perfectly definite

time-order _abcdef_. It cannot excite _f_ until _cde_ have been

successively aroused. The feeling _c_ sometimes is preceded by _ab_,

sometimes followed by _ba_, according to the movement's direction;

the result of it all being that we never feel either _a, c,_ or _f_,

without there clinging to it faint reverberations of the various

time-orders of transition in which, throughout past experience, it

has been aroused. To the local sign _a_ there clings the tinge or

tone, the penumbra or fringe, of the transition _bcd_. To _f_, to _c_,

there cling quite different tones. Once admit the principle that a

feeling may be tinged by the reproductive consciousness of an habitual

transition, even when the transition is not made, and it seems entirely

natural to admit that, if the transition be habitually in the order

_abcdef_, and if _a, c,_ and _f_ be felt separately at all, _a_ will be

felt with an essential _earliness_, _f_ with an essential _lateness_,

and that _c_ will fall between. Thus those psychologists who set

little store by local signs and great store by movements in explaining

space-perception, would have a perfectly definite time-order, due to

motion, by which to account for the definite order of positions that

appears when sensitive spots are excited all at once. Without, however,

the preliminary admission of the 'ultimate fact' that this collective

excitement shall feel like a _line_ and nothing else, it can never be

explained why the new order should needs be an order of _positions_,

and not of merely ideal serial rank. We shall hereafter have any amount

of opportunity to observe how thoroughgoing is the participation of

motion in all our spatial measurements. Whether the local signs have

their respective qualities evenly graduated or not, the feelings of

transition must be set down as among the _veræ causæ_ in localization.

But the gradation of the local signs is hardly to be doubted; so we may

believe ourselves really to possess two sets of reasons for localizing

any point we may happen to distinguish from out the midst of any line

or any larger space.

[168] M. Binet (Revue Philosophique, Sept. 1880, page 291) says we

judge them locally different as soon as their sensations differ enough

for us to distinguish them as qualitatively different when successively

excited. This is not strictly true. Skin-sensations, different enough

to be discriminated when _successive_, may still fuse locally if

excited both at once.

[169] It may, however, be said that even in the tongue there is a

determination of bitter flavors to the back and of acids to the front

edge of the organ. Spices likewise affect its sides and front, and a

taste like that of alum localizes itself, by its styptic effect on the

portion of mucous membrane, which it immediately touches, more sharply

than roast pork, for example, which stimulates all parts alike. The

pork, therefore, tastes more spacious than the alum or the pepper.

In the nose, too, certain smells, of which vinegar may be taken as

the type, seem less spatially extended than heavy, suffocating odors,

like musk. The reason of this appears to be that the former inhibit

inspiration by their sharpness, whilst the latter are drawn into the

lungs, and thus excite an objectively larger surface. The ascription of

height and depth to certain notes seems due, not to any localization of

the sounds, but to the fact that a feeling of vibration in the chest

and tension in the gullet accompanies the singing of a bass note,

whilst, when we sing high, the palatine mucous membrane is drawn upon

by the muscles which move the larynx, and awakens a feeling in the roof

of the mouth.

The only real objection to the law of partial stimulation laid down

in the text is one that might be drawn from the organ of hearing;

for, according to modern theories, the cochlea may have its separate

nerve-termini exclusively excited by sounds of differing pitch, and

yet the sounds seem all to fill a common space, and not necessarily

to be arranged alongside of each other. At most the high note is felt

as a thinner, brighter streak against a darker background. In an

article on Space, published in the Journal of Speculative Philosophy

for January, 1879, I ventured to suggest that possibly the auditory

nerve termini might be "excited all at once by sounds of any pitch,

as the whole retina would be by every luminous point if there were

no dioptric apparatus affixed." And I added: "Notwithstanding the

brilliant conjectures of the last few years which assign different

acoustic end-organs to different rates of air-wave, we are still

greatly in the dark about the subject; and I, for my part, would

much more confidently reject a theory of hearing which violated the

principles advanced in this article than give up those principles for

the sake of any hypothesis hitherto published about either organs of

Corti or basilar membrane." Professor Rutherford's theory of hearing,

advanced at the meeting of the British Association for 1886, already

furnishes an alternative view which would make hearing present no

exception to the space-theory I defend and which, whether destined to

be proved true or false, ought, at any rate to make us feel that the

Helmholtzian theory is probably not the last word in the physiology of

hearing. Stepano, ff. (Hermann und Schwalbe's Jahresbericht, xv. 404,

Literature 1886) reports a case in which more than the upper half of

one cochlea was lost without any such deafness to deep notes on that

side as Helmholtz's theory would require.

[170] Donaldson, in Mind, x. 399, 577; Goldscheider, in Archiv f.

(Anat. u.) Physiologie; Blix, in Zeitschrift für Biologie. A good

résumé may be found in Ladd's Physiol. Psychology, part ii. chap. iv.

§§ 21-23.

[171] I tried on nine or ten people, making numerous observations on

each, what difference it made in the discrimination of two points

to have them alike or unlike. The points chosen were (1) two large

needle-heads, (2) two screw-heads, and (3) a needle-head and a

screw-head. The distance of the screw-heads was measured from their

centres. I found that when the points gave diverse qualities of

feeling (as in 3), this facilitated the discrimination, but much less

strongly than I expected. The difference, in fact, would often not be

perceptible twenty times running. When, however, one of the points

was endowed with a rotary movement, the other remaining still, the

doubleness of the points became much more evident than before. To

observe this I took an ordinary pair of compasses with one point blunt,

and the movable leg replaced by a metallic rod which could, at any

moment, be made to rotate _in situ_ by a dentist's drilling-machine, to

which it was attached. The compass had then its points applied to the

skin at such a distance apart as to be felt as one impression. Suddenly

rotating the drill-apparatus then almost always made them seem as two.

[172] This is only another example of what I call 'the psychologist's

fallacy'--thinking that the mind he is studying must necessarily be

conscious of the object after the fashion in which the psychologist

himself is conscious of it.

[173] Sitzb. der. k. Akad. Wien, Bd. lxxii., Abth. 8 (1875).

[174] Zeitschrift für Biologie, xii. 226 (1876).

[175] Vierteljahrsch. für wiss. Philos., ii. 377.

[176] Exner tries to show that the structure of the faceted eye of

articulates adapts it for perceiving motions almost exclusively.

[177] Schneider tries to explain why a sensory surface is so much more

excited when its impression moves. It has long since been noticed how

much more acute is discrimination of successive than of simultaneous

differences. But in the case of a moving impression, say on the retina,

we have a summation of both sorts of difference; whereof the natural

effect must be to produce the most perfect discrimination of all.

[Illustration: FIG. 53.]

In the left-hand figure let the dark spot B move, for example, from

right to left. At the outset there is the simultaneous contrast of

black and white in B and A. When the motion has occurred so that the

right-hand figure is produced, the same contrast remains, the black

and the white having changed places. But in addition to it there is

a double successive contrast, first in A, which, a moment ago white,

has now become black; and second in B, which, a moment ago black,

has now become white. If we make each single feeling of contrast = 1

(a supposition far too favorable to the state of rest), the sum of

contrasts in the case of motion will be 3, as against 1 in the state

of rest. That is, our attention will be called by a treble force to

the difference of color, provided the color begin to move.--(Cf. also

Fleischl, Physiologische Optische Notizen, 2te Mittheilung, Wiener

Sitzungsberichte, 1882.)

[178] Brown, Bain, J. S. Mill, and in a modified manner Wundt,

Helmholtz, Sully, etc.

[179] M. Ch. Dunan, in his forcibly written essay 'l'Espace Visuel et

l'Espace Tactile' in the Revue Philosophique for 1888, endeavors to

prove that surfaces alone give no perception of extent, by citing the

way in which the blind go to work to gain an idea of an object's shape.

If surfaces were the percipient organ, he says, "both the seeing and

the blind ought to gain an exact idea of the size (and shape) of an

object by merely laying their hand flat upon it (provided of course

that it were smaller than the hand), and this because of their direct

appreciation of the amount of tactile surface affected, and with no

recourse to the muscular sense.... But the fact is that a person

born blind never proceeds in this way to measure objective surfaces.

The only means which he has of getting at the size of a body is that

of running his finger along the lines by which it is bounded. For

instance, if you put into the hands of one born blind a book whose

dimensions are unknown to him, he will begin by resting it against

his chest so as to hold it horizontal; then, bringing his two hands

together at the middle of the edge opposite to the one against his

body, he will draw them asunder till they reach the ends of the edge

in question; and then, and not till then, will he be able to say what

the length of the object is" (vol. xxv. p. 148). I think that anyone

who will try to appreciate the size and shape of an object by simply

'laying his hand flat upon it' will find that the great obstacle is

that he _feels the contours_ so imperfectly. The moment, however, the

hands move, the contours are emphatically and distinctly felt. All

perception of shape and size is perception of contours, and first of

all these must be made _sharp_. Motion does this; and the impulse to

move our organs in perception is primarily due to the craving which we

feel to get our surface-sensations sharp. When it comes to the naming

and measuring of objects in terms of some common standard we shall

see presently how movements help also; but no more in this case than

the other do they help, because the quality of extension itself is

contributed by the 'muscular sense.'

[180] Fechner describes (Psychophysik, i. 132) a 'method of

equivalents' for measuring the sensibility of the skin. Two compasses

are used, one on the part A, another on the part B, of the surface. The

points on B must be adjusted so that their distance apart appears equal

to that between the points on A. With the place A constant, the second

pair of points must be varied a great deal for every change in the

place B, though for the same A and B the relation of the two compasses

is remarkably constant, and continues unaltered for months, provided

but few experiments are made on each day. If, however, we practise

daily their difference grows less, in accordance with the law given in

the text.

[181] Prof. Jastrow gives as the result of his experiments this general

conclusion (Am. Journal of Psychology, iii. 53): "The space-perceptions

of disparate senses are themselves disparate, and whatever harmony

there is amongst them we are warranted in regarding as the result

of experience. The spacial notions of one deprived of the sense of

sight and reduced to the use of the other space-senses must indeed

be different from our own." But he continues: "The existence of the

striking disparities between our visual and our other space-perceptions

without confusing us, and, indeed, without usually being noticed, can

only be explained by the tendency to interpret all dimensions _into

their visual equivalents_." But this author gives no reasons for

saying 'visual' rather than 'tactile;' and I must continue to think

that probabilities point the other way so far as what we call real

magnitudes are concerned.

[182] Cf. Lipps on 'Complication,' Grundtatsachen, etc., p. 579.

[183] Ventriloquism shows this very prettily. The ventriloquist talks

without moving his lips, and at the same time draws our attention to a

doll, a box, or some other object. We forthwith locate the voice within

this object. On the stage an actor ignorant of music sometimes has to

sing, or play on the guitar or violin. He goes through the _motions_

before our eyes, whilst in the orchestra or elsewhere the music is

performed. But because as we listen we see the actor, it is almost

impossible not to _hear_ the music as if coming from where he sits or

stands.

[184] Cf. Shand, in Mind, xiii. 340.

[185] See, e.g., Bain's Senses and Intellect, pp. 366-7, 371.

[186] When, for example, a baby looks at its own moving hand, it sees

one object at the same time that it feels another. Both interest its

attention, and it locates them together. But the felt object's size is

the more constant size, just as the felt object is, on the whole, the

more interesting and important object; and so the retinal sensations

become regarded as its signs and have their 'real space-values'

interpreted in tangible terms.

[187] The incoherence of the different primordial sense-spaces _inter

se_ is often made a pretext for denying to the primitive bodily

feelings any spatial quality at all. Nothing is commoner than to hear

it said: "Babies have originally no spatial perception; for when a

baby's toe aches he does not place the pain in the toe. He makes no

definite movements of defence, and may be vaccinated without being

held." The facts are true enough; but the interpretation is all wrong.

What really happens is that _the baby does not place his 'toe' in the

pain_; for he knows nothing of his 'toe' as yet. He has not attended

to it as a visual object; he has not handled it with his fingers; nor

have its normal organic sensations or contacts yet become interesting

enough to be discriminated from the whole massive feeling of the foot,

or even of the leg to which it belongs. In short, the toe is neither

a member of the babe's optical space, of his hand-movement space, nor

an independent member of his leg-and-foot space. It has actually no

mental existence yet save as this little pain-space. What wonder, then,

if the pain seem a little space-world all by itself? But let the pain

once associate itself with these other space-worlds, and its space

will become part of their space. Let the baby feel the nurse stroking

the limb and awakening the pain every time her finger passes towards

the toe; let him look on and see her finger on the toe every time

the pain shoots up; let him handle his foot himself and get the pain

whenever the toe comes into his fingers or his mouth; let moving the

leg exacerbate the pain,--and all is changed. The space of the pain

becomes identified with that part of each of the other spaces which

gets felt when it awakens; and by their identity with _it_ these parts

are identified with each other, and grow systematically connected as

members of a larger extensive whole.

[188] 'Pourquoi les Sensations visuelles sont elles étendues?' in

Revue Philosophique, iv. 167.--As the proofs of this chapter are being

corrected, I receive the third 'Heft' of Münsterberg's Beiträge zur

Experimentellen Psychologie, in which that vigorous young psychologist

reaffirms (if I understand him after so hasty a glance) more radically

than ever the doctrine that muscular sensation proper is our one means

of measuring extension. Unable to reopen the discussion here, I am in

duty bound to call the attention of the reader to Herr M.'s work.

[189] Even if the figure be drawn on a board instead of in the air, the

variations of contact on the finger's surface will be much simpler than

the peculiarities of the traced figure itself.

[190] See for example Duchenne, Electrisation localisée, pp. 727, 770,

Leyden; Virchow's Archiv, Bd. xlvii. (1869).

[191] E.g., Eulenburg, Lehrb. d. Nervenkrankheiten (Berlin), 1878, i. 3.

[192] 'Ueber den Kraftsinn,' Virchow's Archiv, Bd. lxxvii. 134.

[193] Archiv f. (Anat. u) Physiologie (1889), pp. 369, 540.

[194] Direction in its 'first intention,' of course; direction with

which so far we merely become _acquainted_, and _about_ which we know

nothing save perhaps its difference from another direction a moment ago

experienced in the same way!

[195] I have said hardly anything about associations with visual space

in the foregoing account, because I wished to represent a process which

the blind and the seeing man might equally share. It is to be noticed

that the space suggested to the imagination when the joint moves, and

projected to the distance of the finger-tip, is not represented as any

_specific_ skin-tract. What the seeing man imagines is a visible path;

what the blind man imagines is rather a generic image, an abstraction

from many skin-spaces whose local signs have neutralized each other,

and left nothing but their common vastness behind. We shall see as we

go on that this generic abstraction of space-magnitude from the various

local peculiarities of feeling which accompanied it when it was for

the first time felt, occurs on a considerable scale in the acquired

perceptions of blind as well as of seeing men.

[196] The ideal enlargement of a system of sensations by the mind is

nothing exceptional. Vision is full of it; and in the manual arts,

where a workman gets a tool larger than the one he is accustomed to

and has suddenly to adapt all his movements to its scale, or where he

has to execute a familiar set of movements in an unnatural position of

body; where a piano-player meets an instrument with unusually broad or

narrow keys; where a man has to alter the size of his handwriting--we

see how promptly the mind multiplies once for all, as it were, the

whole series of its operations by a constant factor, and has not to

trouble itself after that with further adjustment of the details.

[197] Pflüger's Archiv, xlv. 65.

[198] Untersuchungen im Gebiete der Optik, Leipzig (1863), p. 188.

[199] Problems of Life and Mind, prob. vi. chap. iv. § 45.

[200] Volkmann, _op. cit._ p. 189. Compare also what Hering says of

the inability in his own case to make after-images seem to move when

he rolls his closed eyes in their sockets; and of the insignificance

of his feelings of convergence for the sense of distance (Beiträge zur

Physiologie, 1881-2, pp. 31, 141). Helmholtz also allows to the muscles

of convergence a very feeble share in producing our sense of the third

dimension (Physiologische Optik, 649-59).

[201] Compare Lipps, Psychologische Studien (1885), p. 18, and the

other arguments given on pp. 12 to 27. The most plausible reasons

_for_ contractions of the eyeball-muscles being admitted as original

contributors to the perception of extent, are those of Wundt,

Physiologische Psychologie, ii. 96-100. They are drawn from certain

constant errors in our estimate of lines and angles; which, however,

are susceptible, all of them, of different interpretations (see

some of them further on).--Just as my MS. goes to the printer, Herr

Münsterberg's Beiträge zur experimentellen Psychologie, Heft 2, comes

into my hands with experiments on the measurement of space recorded in

it, which, in the author's view, prove the feeling of muscular strain

to be a principal factor in our vision of extent. As Münsterberg worked

three hours a day for a year and a half at comparing the length of

lines, seen with his eyes in different positions; and as he carefully

averaged and 'percented' 20,000 observations, his conclusion must be

listened to with great respect. Briefly it is this, that "our judgments

of size depend on a comparison of the intensity of the feelings of

movement which arise in our eyeball-muscles as we glance over the

distance, and which fuse with the sensations of light" (p. 142). The

facts upon which the conclusion is based are certain constant errors

which Münsterberg found according as the standard or given interval was

to the right or the left of the interval to be marked off as equal to

it, or as it was above or below it, or stood in some more complicated

relation still. He admits that he cannot explain all the errors in

detail, and that we "stand before results which seem surprising and

not to be unravelled, because we cannot analyze the elements which

enter into the complex sensation which we receive." But he has no

doubt whatever of the general fact "that the movements of the eyes

and the sense of their position when fixed exert so decisive an

influence on our estimate of the spaces seen, that the errors cannot

possibly be explained by anything else than the movement-feelings and

their reproductions in the memory" (pp. 166, 167). It is presumptuous

to doubt a man's opinion when you haven't had his experience; and

yet there are a number of points which make me feel like suspending

judgment in regard to Herr M.'s _dictum_. He found, for example, a

constant tendency to underestimate intervals lying to the right, and

to overestimate intervals lying to the left. He ingeniously explains

this as a result of the habit of _reading_, which trains us to move our

eyes easily along straight lines from left to right, whereas in looking

from right to left we move them in curved lines across the page. As we

_measure intervals as straight lines_, it costs more muscular effort

to measure from right to left than the other way, and an interval

lying to the left seems to us consequently longer than it really is.

Now I have been a reader for more years than Herr Münsterberg; and yet

with me there is a strongly pronounced error the other way. It is the

rightward-lying interval which to me seems longer than it really is.

Moreover, Herr M. wears concave spectacles, and looked through them

with his _head fixed_. May it not be that some of the errors were due

to distortion of the retinal image, as the eye looked no longer through

the centre but through the margin of the glass? In short, with all the

presumptions which we have seen against muscular contraction being

definitely felt as length, I think that there may be explanations of

Herr M.'s results which have escaped even his sagacity; and I call for

a suspension of judgment until they shall have been confirmed by other

observers. I do not myself doubt that our feeling of seen extent may

be _altered_ by concomitant muscular feelings. In Chapter XVII (pp.

28-30) we saw many examples of similar alterations, interferences

with, or exaltations of, the sensory effect of one nerve-process

by another. I do not see why currents from the muscles or eyelids,

coming in at the same time with a retinal impression, might not make

the latter seem bigger, in the same way that a greater _intensity_ in

the retinal stimulation makes it seem bigger; or in the way that a

greater extent of surface excited makes the color of the surface seem

stronger, or if it be a skin-surface, makes its heat seem greater;

or in the way that the coldness of the dollar on the forehead (in

Weber's old experiments) made the dollar seem heavier. But this is a

_physiological_ way; and the bigness gained is that of the retinal

image after all. If I understand Münsterberg's meaning, it is quite

different from this: the bigness belongs to the muscular feelings, as

such, and is merely _associated_ with those of the retina. _This_ is

what I deny.

[202] Archiv f. (Anat. u.) Physiol. (1889), p. 543.

[203] _Ibid._ p. 496.

[204] _Ibid._ p. 497. Goldscheider thinks that our muscles do not

even give us the feeling of _resistance_, that being also due to the

articular surfaces; whilst _weight_ is due to the tendons. _Ibid._ p.

541.

[205] "Whilst the memories which we seeing folks preserve of a man all

centre round a certain exterior form composed of his image, his height,

his gait, in the blind all these memories are referred to something

quite different, namely, _the sound of his voice_." (Dunan, Rev. Phil.,

xxv. 357.)

[206] Vol. xxv. pp. 357-8.

[207] P. 135.

[208] Essay conc. Hum. Und., bk. ii. chap. ix. § 8.

[209] Philosophical Transactions, 1841. In T. K. Abbot's Sight and

Touch there is a good discussion of these cases. Obviously, positive

cases are of more importance than negative. An under-witted peasant,

Noé M., whose case is described by Dr. Dufour of Lausanne (Guerison

d'un Aveugle né; 1876) is much made of by MM. Naville and Dunan; but

it seems to me only to show how little _some_ people can deal with new

experiences in which others find themselves quickly at home. This man

could not even tell whether one of his first objects of sight moved or

stood still (p. 9).

[210] What may be the physiological process connected with this

increased sensation of depth is hard to discover. It seems to have

nothing to do with the parts of the retina affected, since the mere

inversion of the picture (by mirrors, reflecting prisms, etc.),

without inverting the head, does not seem to bring it about; nothing

with sympathetic axial rotation of the eyes, which might enhance

the perspective through exaggerated disparity of the two retinal

images (see J. J. Müller, 'Raddrehung u. Tiefendimension,' Leipzig

Acad. Berichte, 1875, page 124), for one-eyed persons get it as

strongly as those with two eyes. I cannot find it to be connected

with any alteration in the pupil or with any ascertainable strain

in the muscles of the eye, sympathizing with those of the body. The

exaggeration of distance is even greater when we throw the head over

backwards and contract our superior recti in getting the view, than

when we bend forward and contract the inferior recti. Making the eyes

diverge slightly by weak prismatic glasses has no such effect. To me,

and to all whom I have asked to repeat the observation, the result

is so marked that I do not well understand how such an observer as

Helmholtz, who has carefully examined vision with inverted head, can

have overlooked it. (See his Phys. Optik, pp. 488, 723, 728, 772.) I

cannot help thinking that anyone who can explain the exaggeration of

the depth-sensation in this case will at the same time throw much light

on its normal constitution.

[211] "In Froriep's Notizen (1838, July), No. 133, is to be found a

detailed account, with a picture, of an Esthonian girl, Eva Lauk,

then fourteen years old, born with neither arms nor legs, which

concludes with the following words: 'According to the mother, her

intellect developed quite as fast as that of her brother and sisters;

in particular, she came as quickly to a right judgment of the size and

distance of visible objects, although, of course, she had no use of

hands.'" (Schopenhauer, Welt als Wille, ii. 44.)

[212] Physiol. Optik, p. 438. Helmholtz's reservation of 'qualities'

is inconsistent. Our judgments of light and color vary as much as our

judgments of size, shape, and place, and ought by parity of reasoning

to be called intellectual products and not sensations. In other places

he does treat color as if it were an intellectual product.

[213] It is needless at this point to consider what Helmholtz's views

of the nature of the intellectual space-yielding process may be. He

vacillates--we shall later see how.

[214] _Op. cit._ p. 214.

[215] Before embarking on this new topic it will be well to shelve,

once for all, the problem of what is the physiological process that

underlies the distance-feeling. Since one-eyed people have it, and

are inferior to the two-eyed only in measuring its gradations, it can

have no exclusive connection with the double and disparate images

produced by binocular parallax. Since people with closed eyes,

looking at an after-image, do not usually see it draw near or recede

with varying convergence, it cannot be simply constituted by the

convergence-feeling. For the same reason it would appear non-identical

with the feeling of accommodation. The differences of apparent

parallactic movement between far and near objects as we move our head

cannot constitute the distance-sensation, for such differences may be

easily reproduced experimentally (in the movements of visible spots

against a background) without engendering any illusion of perspective.

Finally, it is obvious that visible faintness, dimness, and smallness

_are_ not _per se_ the feeling of visible distance, however much in the

case of well-known objects they _may_ serve as signs to suggest it.

A certain maximum distance-value, however, being given to the field of

view of the moment, whatever it be, the feelings that accompany the

processes just enumerated become so many _local signs_ of the gradation

of distances within this maximum depth. They help us to subdivide and

measure it. Itself, however, is felt as a unit, a total distance-value,

determining the vastness of the whole field of view, which accordingly

appears as an abyss of a certain volume. And the question still

persists, what neural process is it that underlies the sense of this

distance-value?

Hering, who has tried to explain the gradations within it by the

interaction of certain native distance-values belonging to each point

of the two retinæ, seems willing to admit that the _absolute_ scale of

the space-volume within which the natively fixed relative distances

shall appear is _not_ fixed, but determined each time by 'experience

in the widest sense of the word' (_Beiträge_, p. 344). What he calls

the _Kernpunkt_ of this space-volume is the point we are momentarily

fixating. The absolute scale of the whole volume depends on the

absolute distance at which this _Kernpunkt_ is judged to lie from

the person of the looker. "By an alteration of the localization of

the _Kernpunkt_, the _inner_ relations of the seen space are nowise

altered; this space in its totality is as a fixed unit, so to speak,

displaced with respect to the self of the looker" (p. 345). But what

constitutes the localization of the _Kernpunkt_ itself at any given

time, except 'Experience,' i.e., higher cerebral and intellectual

processes, involving memory, Hering does not seek to define.

Stumpf, the other sensationalist writer who has best realized the

difficulties of the problem, thinks that the primitive sensation

of distance must have an immediate physical antecedent, either in

the shape of "an organic alteration accompanying the process of

accommodation, or else given directly in the specific energy of the

optic nerve." In contrast with Hering, however, he thinks that it is

the _absolute_ distance of the spot fixated which is thus primitively,

immediately, and physiologically given, and not the relative distances

of other things about this spot. These, he thinks, are originally

seen in what, broadly speaking, may be termed one plane with it.

Whether the distance of this plane, considered as a phenomenon of

our primitive sensibility, be an invariable datum, or susceptible

of fluctuation, he does not, if I understand him rightly, undertake

dogmatically to decide, but inclines to the former view. For him then,

as for Hering, higher cerebral processes of association, under the

name of 'Experience,' are the authors of fully one-half part of the

distance-perceptions which we at any given time may have.

Hering's and Stumpf's theories are reported for the English reader by

Mr. Sully (in Mind, iii. pp. 172-6). Mr. Abbott, in his Sight and Touch

(pp. 96-8), gives a theory which is to me so obscure that I only refer

the reader to its place, adding that it seems to make of distance a

fixed function of retinal sensation as modified by focal adjustment.

Besides these three authors I am ignorant of any, except Panum, who

may have attempted to define distance as in any degree an immediate

sensation. And with them the direct sensational share is reduced to a

very small proportional part, in our completed distance-judgments.

Professor Lipps, in his singularly acute Psychologische Studien (p.

69 ff.), argues, as Ferrier, in his review of Berkeley (Philosophical

Remains, ii. 330 ff.), had argued before him, that it is _logically

impossible_ we should perceive the distance of anything from the eye

by sight; for a _seen_ distance can only be between _seen_ termini;

and one of the termini, in the case of distance from the eye, is

the eye itself, which is not seen. Similarly of the distance of two

points behind each other: the near one _hides_ the far one, no space

is seen between them. For the space between two objects to be _seen_,

both must appear _beside_ each other, then the space in question will

be _visible_. On no other condition is its visibility possible. The

conclusion is that things can properly be seen only in what Lipps calls

a surface, and that our knowledge of the third dimension must needs be

conceptual, not sensational or visually intuitive.

But no arguments in the world can prove a feeling which actually exists

to be impossible. The feeling of depth or distance, of farness or

awayness, does actually exist as a fact of our visual sensibility. All

that Professor Lipps's reasonings prove concerning it is that it is

not linear in its character, or in its immediacy fully homogeneous and

consubstantial with the feeling of literal distance between two seen

termini; in short, that there are _two_ sorts of optical sensation,

each inexplicably due to a peculiar neural process. The neural

process is easily discovered, in the case of lateral extension or

spreadoutness, to be the number of retinal nerve-ends affected by the

light; in the case of protension or mere farness it is more complicated

and, as we have concluded, is still to seek. The two sensible

qualities unite in the primitive visual bigness. The measurement of

their various amounts against each other obeys the general laws of

all such measurements. We discover their equivalencies by means of

objects, apply the same units to both, and translate them into each

other so habitually that at last they get to seem to us even quite

similar in kind. This final appearance of homogeneity may perhaps be

facilitated by the fact that in binocular vision two points situated

on the prolongation of the optical axis of _one_ of the eyes, so that

the near one hides the far one, are by the _other_ eye seen laterally

apart. Each eye has in fact a foreshortened lateral view of the other's

line of sight. In The London Times for Feb. 8, 1884, is an interesting

letter by J. D. Dougal, who tries to explain by this reason why

two-eyed rifle-shooting has such advantages over shooting with one eye

closed.

[216] Just so, a pair of spectacles held an inch or so from the eyes

seem like one large median glass. The faculty of seeing stereoscopic

slides single without an instrument is of the utmost utility to the

student of physiological optics, and persons with strong eyes can

easily acquire it. The only difficulty lies in dissociating the degree

of accommodation from the degree of convergence which it usually

accompanies. If the right picture is focussed by the right eye, the

left by the left eye, the optic axes must either be parallel or

converge upon an imaginary point some distance behind the plane of the

pictures, according to the size and distance apart of the pictures.

The accommodation, however, has to be made for the plane of the

pictures itself, and a near accommodation with a far-off convergence is

something which the ordinary use of our eyes never teaches us to effect.

[217] These two observations prove the law of identical direction

only for objects which excite the foveæ or lie in the line of direct

looking. Observers skilled in indirect vision can, however, more or

less easily verify the law for outlying retinal points.

[218] This essay, published in the Philosophical Transactions, contains

the germ of almost all the methods applied since to the study of

optical perception. It seems a pity that England, leading off so

brilliantly the modern epoch of this study, should so quickly have

dropped out of the field. Almost all subsequent progress has been made

in Germany, Holland, and, _longo intervallo_, America.

[219] This is no place to report this controversy, but a few

bibliographic references may not be inappropriate. Wheatstone's

own experiment is in section 12 of his memoir. In favor of his

interpretation see Helmholtz, Phys. Opt., pp. 737-9; Wundt, Physiol.

Psychol., 2te Aufl. p. 144; Nagel, Sehen mit zwei Augen, pp. 78-82.

Against Wheatstone see Volkmann, Arch. f. Ophth., v. 2-74, and

Untersuchungen, p. 266; Hering, Beiträge zur Physiologie, 29-45,

also in Hermann's Hdbch. d. Physiol., Bd. iii. 1 Th. p. 435; Aubert,

Physiologie d. Netzhaut, p. 322; Schön, Archiv f. Ophthal., xxiv. 1.

pp. 56-65; and Donders, _ibid._ xiii. 1. p. 15 and note.

[220] When we see the finger the whole time, we usually put it in the

line joining object and left eye if it be the left finger, joining

object and right eye if it be the right finger. Microscopists,

marksmen, or persons one of whose eyes is much better than the other,

almost always refer directions to a single eye, as may be seen by the

position of the shadow on their face when they point at a candle-flame.

[221] Professor Joseph Le Conte, who believes strongly in the

identity-theory, has embodied the latter in a pair of laws of the

relation between positions seen single and double, near or far, on

the one hand, and convergences and retinal impressions, on the other,

which, though complicated, seems to me by far the best descriptive

formulation yet made of the normal facts of vision. His account

is easily accessible to the reader in his volume 'Sight' in the

International Scientific Series, bk. ii. c. 8, so I say no more about

it now, except that it does not solve any of the difficulties we are

noting in the identity-theory, nor account for the other fluctuating

perceptions of which we go on to treat.

[222] Naturally it takes a smaller object at a less distance to cover

by its image a constant amount of retinal surface.

[223] Archiv f. Ophthal., Bd. xvii. Abth. 2, pp. 44-6 (1871).

[224] A. W. Volkmann, Untersuchungen, p. 253.

[225] Philosophical Transactions, 1852, p. 4.

[226] Physiol. Optik, 649-664. Later this author is led to value

convergence more highly. Arch. f. (Anat. u.) Physiol. (1878), p. 322.

[227] Anomalies of Accommodation and Refraction (New Sydenham Soc.

Transl., London, 1864), p. 155.

[228] These strange contradictions have been called by Aubert

'secondary' deceptions of judgment. See Grundzüge d. Physiologischen

Optik (Leipzig, 1876), pp. 601, 615, 627. One of the best examples of

them is the small size of the moon as first seen through a telescope.

It is larger and brighter, so we see its details more distinctly and

judge it nearer. But because we judge it so much nearer we think it

must have grown smaller. Cf. Charpentier in Jahresbericht, x. 430.

[229] Revue Philosophique, iii. 9, p. 220.

[230] See Chapter XXIV.

[231] The only exception seems to be when we expressly wish to abstract

from particulars, and to judge of the general 'effect.' Witness ladies

trying on new dresses with their heads inclined and their eyes askance;

or painters in the same attitude judging of the 'values' in their

pictures.

[232] The importance of Superposition will appear later on.

[233] Physiol. Optik, p. 817.

[234] Bowditch and Hall, in Journal of Physiology, vol. iii. p. 299.

Helmholtz tries to explain this phenomenon by unconscious rotations

of the eyeball. But movements of the eyeball can only explain such

appearances of movements as are the same over the whole field. In the

windowed board one part of the field seems to move in one way, another

part in another. The same is true when we turn from the spiral to look

at the wall--the _centre_ of the field alone swells out or contracts,

the margin does the reverse or remains at rest. Mach and Dvorak have

beautifully proved the impossibility of eye-rotations in this case

(Sitzungsber. d. Wiener Akad., Bd. lxi.). See also Bowditch and Hall's

paper as above, p. 300.

[235] Bulletins de l'Acad. de Belgique, xxi. 2; Revue Philosophique,

vi. pp. 223-5; Physiologische Psychologie, 2te Aufl. p. 103. Compare

Münsterberg's views, Beiträge, Heft 2, p. 174.

[236] Physiol. Optik, pp. 562-71.

[237] Physiol. Psych., pp. 107-8.

[238] Grundtatsachen des Seelenlebens, pp. 526-30.

[239] Cf. _supra_, vol. I. p. 515 ff.

[240] See Archiv f. Ophthalm., v. 2, 1 (1859), where many more examples

are given.

[241] Untersuchungen, p. 250; see also p. 242.

[242] I pass over certain difficulties about double images, drawn from

the perceptions of a few squinters (e.g. by Schweigger, Klin. Untersuch

über das Schielen, Berlin, 1881; by Javal, Annales d'Oculistique,

lxxxv. p. 217), because the facts are exceptional at best and very

difficult of interpretation. In favor of the sensationalistic or

nativistic view of one such case, see the important paper by Von Kries,

Archiv f. Ophthalm., xxiv. 4, p. 117.

[243] Physiologische Untersuchungen im Gebiete der Optik, v.

[244] Cf. E. Mach, Beiträge zur Analyse der Empfindungen, p. 87.

[245] Cf. V. Egger, Revue Philos., xx. 488.

[246] Loeb (Pflüger's Archiv, xl. 274) has proved that muscular changes

of adaptation in the eye for near and far distance are what determine

the form of the relief.

[247] The strongest passage in Helmholtz's argument against sensations

of space is relative to these fluctuations of seen relief: "Ought one

not to conclude that if sensations of relief exist at all, they must be

so faint and vague as to have no influence compared with that of past

experience? Ought we not to believe that the perception of the third

dimension may have arisen _without_ them, since we now see it taking

place as well _against_ them as _with_ them?" (Physiol. Optik, p. 817.)

[248] Cf. E. Mach, Beiträge, etc., p. 90, and the preceding chapter of

the present work, p. 86 ff.

[249] I ought to say that I seem always able to see the cross

rectangular at will. But this appears to come from an imperfect

absorption of the rectangular after-image by the inclined plane at

which the eyes look. The cross, with me, is apt to detach itself from

this and then look square. I get the illusion better from the circle,

whose after-image becomes in various ways elliptical on being projected

upon the different surfaces of the room, and cannot then be easily made

to look circular again.

[250] In Chapter XVIII, p. 74, I gave a reason why imaginations

_ought_ not to be as vivid as sensations. It should be borne in mind

that that reason does not apply to these complemental imaginings of the

real shape of things actually before our eyes.

[251] Hermann's Handb. der Physiologie, iii. 1. p. 565-71.

[252] Bulletin de l'Académie de Belgique, 2me Série, xix. 2.

[253] Wundt seeks to explain all these illusions by the relatively

stronger 'feeling of innervation' needed to move the eyeballs

upwards,--a careful study of the muscles concerned is taken to prove

this,--and a consequently greater estimate of the distance traversed.

It suffices to remark, however, with Lipps, that were the innervation

all, a column of S's placed on top of each other should look each

larger than the one below it, and a weathercock on a steeple gigantic,

neither of which is the case. Only the halves of _the same object_ look

different in size, because the customary correction for foreshortening

bears only on the relations of the parts of special _things_ spread out

before us. Cf. Wundt, Physiol. Psych., 2te Aufl. ii. 96-8; Th. Lipps,

Grundtatsachen, etc., p. 535.

[254] Hering would partly solve in this way the mystery of Figs. 60,

61, and 67. No doubt the explanation partly applies; but the strange

cessation of the illusion when we fix the gaze fails to be accounted

for thereby.

[255] Helmholtz has sought (Physiol. Optik, p. 715) to explain the

divergence of the apparent vertical meridians of the two retinæ, by

the manner in which an identical line drawn on the ground before us in

the median plane will throw its images on the two eyes respectively.

The matter is too technical for description here; the unlearned reader

may be referred for it to J. Le Conte's Sight in the Internat. Scient.

Series, p. 198 ff. But, for the benefit of those to whom _verbum

sat_, I cannot help saying that it seems to me that the _exactness_

of the relation of the two meridians--whether divergent or not, for

their divergence differs in individuals and often in one individual at

diverse times--precludes its being due to the mere habitual falling-off

of the image of one objective line on both. Le Conte, e.g., measures

their position down to a sixth of a degree, others to tenths. This

indicates an organic identity in the sensations of the two retinæ,

which the experience of median perspective horizontals may roughly

have agreed with, but hardly can have engendered. Wundt explains the

divergence as usual, by the _Innervationsgefühl_ (_op. cit._. ii. 99

ff.).

[256] Physiol. Optik, p. 547.

[257] "We can with a short ruler draw a line as long as we please on

a plane surface by first drawing one as long as the ruler permits,

and then sliding the ruler somewhat along the drawn line and drawing

again, etc. If the ruler is exactly straight, we get in this way a

straight line. If it is somewhat curved we get a circle. Now, instead

of the sliding ruler we use in the field of sight the central spot of

distinctest vision impressed with a linear sensation of sight, which

at times may be intensified till it becomes an after-image. We follow,

in looking, the direction of this line, and in so doing we slide the

line along itself and get a prolongation of its length. On a plane

surface we can carry on this procedure on any sort of a straight or

curved ruler, but in the field of vision there is for each direction

and movement of the eye only one sort of line which it is possible for

us to slide along in its own direction continually." These are what

Helmholtz calls the 'circles of direction' of the visual field--lines

which he has studied with his usual care. Cf. Physiol. Optik, p. 548 ff.

[258] Cf. Hering in Hermann's Handb. der Physiol., iii. 1, pp. 558-4.

[259] This shrinkage and expansion of the absolute space-value of the

total optical sensation remains to my mind the most obscure part of the

whole subject. It is a real optical sensation, seeming introspectively

to have nothing to do with locomotor or other suggestions. It is easy

to say that 'the Intellect produces it,' but what does that mean? The

investigator who will throw light on this one point will probably clear

up other difficulties as well.

[260] Examination of Hamilton, 3d ed. p. 283.

[261] Senses and Intellect, 3d ed. p. 183.

[262] Exam. of Hamilton, 3d ed. p. 283.

[263] Senses and Intellect, p. 372.

[264] Vierfache Wurzel des Satzes vom zureichenden Grunde, pp. 52-7.

[265] Psychol. als Wissenschaft, § 111.

[266] Psychol. als Wissenschaft, § 113.

[267] Lehrbuch d. Psychol., 2te Auflage, Bd. ii. p. 66. Volkmann's

fifth chapter contains a really precious collection of historical

notices concerning space-perception theories.

[268] Why talk of 'genetic theories'? when we have in the next breath

to write as Wundt does: "If then we must regard the intuition of space

as a product that simply emerges from the conditions of our mental and

physical organization, nothing need stand in the way of our designating

it as one of the _a priori_ functions with which consciousness is

endowed." (Logik, ii. 460.)

[269] P. 430.

[270] Pp. 430, 449.

[271] P. 428.

[272] P. 442.

[273] Pp. 442, 818.

[274] P. 798. Cf. also Popular Scientific Lectures, pp. 301-3.

[275] P. 456; see also 428, 441.

[276] P. 797.

[277] P. 812.

[278] Bottom of page 797.

[279] In fact, to borrow a simile from Prof. G. E. Müller (Theorie

der sinnl. Aufmerksamkeit, p. 38), the various senses bear in the

Helmholtzian philosophy of perception the same relation to the 'object'

perceived by their means that a troop of jolly drinkers bear to the

landlord's bill, when no one has any money, but each hopes that one of

the rest will pay.

[280] Grundtatsachen des Seelenlebens (1883), pp. 480, 591-2.

Psychologische Studien (1885), p. 14.

[281] Psychology, ii. p. 174.

[282] _Ibid._ p. 168.

[283] Senses and Intellect, 3d ed. pp. 366-75.

[284] Cf. Hall and Donaldson in Mind, x. 559.

[285] As other examples of the confusion, take Mr. Sully: "The

_fallacious assumption_ that there can be an idea of distance in

general, apart from particular distances" (Mind, iii. p. 177); and

Wundt: "An indefinite localization, which waits for experience to give

it its reference to real space, stands in contradiction with the very

idea of localization, which means the reference to a determinate point

of space" (Physiol. Psych., 1te Aufl. p. 480).

[286] G. Berkeley: Essay towards a new Theory of Vision; Samuel Bailey:

A Review of Berkeley's Theory of Vision (1842); J. S. Mill's Review of

Bailey, in his Dissertations and Disquisitions, vol. ii; Jas. Ferrier:

Review of Bailey, in 'Philosophical Remains,' vol. ii; A. Bain:

Senses and Intellect, 'Intellect,' chap. i; H. Spencer: Principles

of Psychology, pt. vi. chaps. xiv, xvi; J. S. Mill: Examination of

Hamilton, chap. xiii (the best statement of the so-called English

empiricist position); T. K. Abbott: Sight and Touch, 1861 (the first

English book to go at all minutely into _facts_; Mr. Abbott maintaining

retinal sensations to be originally of space in three dimensions); A.

C. Fraser: Review of Abbott, in North British Review for Aug. 1864;

another review in Macmillan's Magazine, Aug. 1866; J. Sully: Outlines

of Psychology, chap. vi; J. Ward: Encyclop. Britannica, 9th Ed.,

article 'Psychology,' pp. 53-5; J. E. Walter: The Perception of Space

and Matter (1879)--I may also refer to a discussion between Prof. G.

Groom Robertson, Mr. J. Ward, and the present writer, in Mind, vol.

xiii.--The present chapter is only the filling out with detail of an

article entitled 'The Spatial Quale,' which appeared in the Journal of

Speculative Philosophy for January 1879 (xiii. 64).

CHAPTER XXI.[287]

THE PERCEPTION OF REALITY.

BELIEF.

Everyone knows the difference between imagining a thing and believing

in its existence, between supposing a proposition and acquiescing in

its truth. In the case of acquiescence or belief, the object is not

only apprehended by the mind, but is held to have reality. Belief is

thus the mental state or function of cognizing reality. As used in

the following pages, 'Belief' will mean every degree of assurance,

including the highest possible certainty and conviction.

There are, as we know, two ways of studying every psychic state. First,

the way of analysis: What does it consist in? What is its inner nature?

Of what sort of mind-stuff is it composed? Second, the way of history:

What are its conditions of production, and its connection with other

facts?

Into the first way we cannot go very far. _In its inner nature,

belief, or the sense of reality, is a sort of feeling more allied to

the emotions than to anything else._ Mr. Bagehot distinctly calls it

the 'emotion' of conviction. I just now spoke of it as acquiescence.

It resembles more than anything what in the psychology of volition we

know as consent. Consent is recognized by all to be a manifestation of

our active nature. It would naturally be described by such terms as

'willingness' or the 'turning of our disposition.' What characterizes

both consent and belief is the cessation of theoretic agitation,

through the advent of an idea which is inwardly stable, and fills the

mind solidly to the exclusion of contradictory ideas. When this is the

case, motor effects are apt to follow. Hence the states of consent

and belief, characterized by repose on the purely intellectual side,

are both intimately connected with subsequent practical activity.

This inward stability of the mind's content is as characteristic of

disbelief as of belief. But we shall presently see that we never

disbelieve anything except for the reason that we believe something

else which contradicts the first thing.[288] Disbelief is thus an

incidental complication to belief, and need not be considered by itself.

* * * * *

_The true opposites of belief,_ psychologically considered, _are

doubt and inquiry, not disbelief._ In both these states the content

of our mind is in unrest, and the emotion engendered thereby is,

like the emotion of belief itself, perfectly distinct, but perfectly

indescribable in words. Both sorts of emotion may be pathologically

exalted. One of the charms of drunkenness unquestionably lies in the

deepening of the sense of reality and truth which is gained therein.

In whatever light things may then appear to us, they seem more utterly

what they are, more 'utterly utter' than when we are sober. This goes

to a fully unutterable extreme in the nitrous oxide intoxication, in

which a man's very soul will sweat with conviction, and he be all

the while unable to tell what he is convinced of at all.[289] The

pathological state opposed to this solidity and deepening has been

called the questioning mania (_Grübelsucht_ by the Germans). It is

sometimes found as a substantive affection, paroxysmal or chronic, and

consists in the inability to rest in any conception, and the need of

having it confirmed and explained. 'Why do I stand here where I stand?'

'Why is a glass a glass, a chair a chair?' 'How is it that men are only

of the size they are? Why not as big as houses,' etc., etc.[290] There

is, it is true, another pathological state which is as far removed

from doubt as from belief, and which some may prefer to consider the

proper contrary of the latter state of mind. I refer to the feeling

that everything is hollow, unreal, dead. I shall speak of this state

again upon a later page. The point I wish to notice here is simply that

belief and disbelief are but two aspects of one psychic state.

* * * * *

John Mill, reviewing various opinions about belief, comes to the

conclusion that no account of it can be given:

"What," he says, "is the difference _to our minds_ between thinking

of a reality and representing to ourselves an imaginary picture? I

confess I can see no escape from the opinion that the distinction is

ultimate and primordial. There is no more difficulty in holding it

to be so than in holding the difference between a sensation and an

idea to be primordial. It seems almost another aspect of the same

difference.... I cannot help thinking, therefore, that there is in the

remembrance of a real fact, as distinguished from that of a thought,

an element which does not consist... in a difference between the mere

ideas which are present to the mind in the two cases. This element,

howsoever we define it, constitutes belief, and is the difference

between Memory and Imagination. From whatever direction we approach,

this difference seems to close our path. When we arrive at it, we seem

to have reached, as it were, the central point of our intellectual

nature, presupposed and built upon in every attempt we make to explain

the more recondite phenomena of our mental being."[291]

If the words of Mill be taken to apply to the mere subjective analysis

of belief--to the question, What does it feel like when we have

it?--they must be held, on the whole, to be correct. Belief, the sense

of reality, feels like itself--that is about as much as we can say.

Prof. Brentano, in an admirable chapter of his _Psychologie_,

expresses this by saying that conception and belief (which he names

_judgment_) are two different fundamental psychic phenomena. What

I myself have called (Vol. I, p. 275) the 'object' of thought may

be comparatively simple, like "Ha! what a pain," or "It-thunders";

or it may be complex, like "Columbus-discovered-America-in-1492,"

or "There-exists-an-all-wise-Creator-of-the-world." In either case,

however, the mere thought of the object may exist as something quite

distinct from the belief in its reality. The belief, as Brentano says,

presupposes the mere thought:

"Every object comes into consciousness in a twofold way, as simply

thought of [_vorgestellt_] and as admitted [_anerkannt_] or

denied. The relation is analogous to that which is assumed by most

philosophers (by Kant no less than by Aristotle) to obtain between

mere thought and desire. Nothing is ever desired without being thought

of; but the desiring is nevertheless a second quite new and peculiar

form of relation to the object, a second quite new way of receiving

it into consciousness. No more is anything judged [i.e., believed or

disbelieved] which is not thought of too. But we must insist that, so

soon as the object of a thought becomes the object of an assenting

or rejecting judgment, our consciousness steps into an entirely new

relation towards it. It is then twice present in consciousness, as

thought of, and as held for real or denied; just as when desire

awakens for it, it is both thought and simultaneously desired." (P.

266.)

The commonplace doctrine of 'judgment' is that it consists in the

combination of 'ideas' by a 'copula' into a 'proposition,' which may

be of various sorts, as affirmative, negative, hypothetical, etc. But

who does not see that in a disbelieved or doubted or interrogative

or conditional proposition, the ideas are combined in the same

identical way in which they are in a proposition which is solidly

believed? _The way in which the ideas are combined is a part of the

inner constitution of the thought's object or content._ That object

is sometimes an articulated whole with relations between its parts,

amongst which relations, that of predicate to subject may be one. But

when we have got our object with its inner constitution thus defined

in a proposition, then the question comes up regarding the object as

a whole: 'Is it a real object? is this proposition a true proposition

or not?' And in the answer _Yes_ to _this_ question lies that new

psychic act which Brentano calls 'judgment,' but which I prefer to call

'belief.'

In every proposition, then, so far as it is believed, questioned, or

disbelieved, four elements are to be distinguished, the subject, the

predicate, and their relation (of whatever sort it be)--these form the

_object_ of belief--and finally the psychic attitude in which our mind

stands towards the proposition taken as a whole--and this is the belief

itself.[292]

Admitting, then, that this attitude is a state of consciousness _sui

generis_, about which nothing more can be said in the way of internal

analysis, let us proceed to the second way of studying the subject of

belief: _Under what circumstances do we think things real?_ We shall

soon see how much matter this gives us to discuss.

THE VARIOUS ORDERS OF REALITY.

Suppose a new-born mind, entirely blank and waiting for experience

to begin. Suppose that it begins in the form of a visual impression

(whether faint or vivid is immaterial) of a lighted candle against a

dark background, and nothing else, so that whilst this image lasts

it constitutes the entire universe known to the mind in question.

Suppose, moreover (to simplify the hypothesis), that the candle is

only imaginary, and that no 'original' of it is recognized by us

psychologists outside. Will this hallucinatory candle be believed in,

will it have a real existence for the mind?

What possible sense (for that mind) would a suspicion have that the

candle was not real? What would doubt or disbelief of it imply? When

_we_, the onlooking psychologists, say the candle is unreal, we mean

something quite definite, viz., that there is a world known to _us_

which _is_ real, and to which we perceive that the candle does not

belong; it belongs exclusively to that individual mind, has no _status_

anywhere else, etc. It exists, to be sure, in a fashion, for it forms

the content of that mind's hallucination; but the hallucination itself,

though unquestionably it is a sort of existing fact, has no knowledge

of _other_ facts; and since those _other_ facts are the realities par

_excellence_ for us, and the only things we believe in, the candle is

simply outside of our reality and belief altogether.

By the hypothesis, however, the _mind which sees the candle_ can spin

no such considerations as these about it, for of other facts, actual

or possible, it has no inkling whatever. That candle is its all, its

absolute. Its entire faculty of attention is absorbed by it. It _is_,

it is _that_; it is _there_; no other possible candle, or quality

of this candle, no other possible place, or possible object in the

place, no alternative, in short, suggests itself as even conceivable;

so how can the mind help believing the candle real? The supposition

that it might possibly not do so is, under the supposed conditions,

unintelligible.[293]

This is what Spinoza long ago announced:

"Let us conceive a boy," he said, "imagining to himself a horse,

and taking note of nothing else. As this imagination involves the

existence of the horse, _and the boy has no perception which annuls

its existence,_ he will necessarily contemplate the horse as present,

nor will he be able to doubt of its existence, however little

certain of it he may be. I deny that a man in so far as he imagines

[_percipit_] affirms nothing. For what is it to imagine a winged

horse but to affirm that, the horse [that horse, namely] has wings?

For if the mind had nothing before it but the winged horse it would

contemplate the same as present, would have no cause to doubt of its

existence, nor any power of dissenting from its existence, unless

the imagination of the winged horse were joined to an idea which

contradicted [_tollit_] its existence." (Ethics, ii. 49, Scholium.)

The sense that anything we think of is unreal can only come, then, when

that thing is contradicted by some other thing of which we think. _Any

object which remains uncontradicted is ipso facto believed and posited

as absolute reality._

Now, how comes it that one thing thought of can be contradicted by

another? It cannot unless it begins the quarrel by saying something

inadmissible about that other. Take the mind with the candle, or the

boy with the horse. If either of them say, 'That candle or that horse,

even when I don't see it, exists in _the outer world_,' he pushes into

'the outer world' an object which may be incompatible with everything

which he otherwise knows of that world. If so, he must take his choice

of which to hold by, the present perceptions or the other knowledge of

the world. If he holds to the other knowledge, the present perceptions

are contradicted, _so far as their relation to that world goes._ Candle

and horse, whatever they may be, are not existents in outward space.

They are existents, of course; they are mental objects; mental objects

have existence as mental objects. But they are situated in their own

spaces, the space in which they severally appear, and neither of those

spaces is the space in which the realities called 'the outer world'

exist.

Take again the horse with wings. If I merely dream of a horse with

wings, my horse interferes with nothing else and has not to be

contradicted. That horse, its wings, and its place, are all equally

real. That horse exists no otherwise than as winged, and is moreover

really there, for that place exists no otherwise than as the place of

that horse, and claims as yet no connection with the other places of

the world. But if with this horse I make an inroad into the _world

otherwise known_, and say, for example, 'That is my old mare Maggie,

having grown a pair of wings where she stands in her stall,' the whole

case is altered; for now the horse and place are identified with a

horse and place otherwise known, and _what_ is known of the latter

objects is incompatible with what is perceived with the former. 'Maggie

in her stall with wings! Never!' The wings are unreal, then, visionary.

I have dreamed a lie about Maggie in her stall.

The reader will recognize in these two cases the two sorts of judgment

called in the logic-books existential and attributive respectively.

The candle exists as an outer reality' is an existential, 'My Maggie

has got a pair of wings' is an attributive, proposition;[294] and

it follows from what was first said that _all propositions, whether

attributive or existential, are believed through the very fact of

being conceived, unless they clash with other propositions believed,

at the same time, by affirming that their terms are the same with the

terms of these other propositions._ A dream-candle has existence, true

enough; but not the same existence (existence for itself, namely, or

_extra mentem meam_) which the candles of waking perception have. A

dream-horse has wings; but then neither horse nor wings are the same

with any horses or wings known to memory. That we can at any moment

think of the same thing which at any former moment we thought of is the

ultimate law of our intellectual constitution. But when we now think

of it incompatibly with our other ways of thinking it, then we must

choose which way to stand by, for we cannot continue to think in two

contradictory ways at once. _The whole distinction of real and unreal,

the whole psychology of belief, disbelief, and doubt, is thus grounded

on two mental facts--first, that we are liable to think differently of

the same; and second, that when we have done so, we can choose which

way of thinking to adhere to and which to disregard._

The subjects adhered to become real subjects, the attributes adhered

to real attributes, the existence adhered to real existence; whilst

the subjects disregarded become imaginary subjects, the attributes

disregarded erroneous attributes, and the existence disregarded an

existence in no man's land, in the limbo 'where footless fancies

dwell.' The real things are, in M. Taine's terminology, the

_reductives_ of the things judged unreal.

THE MANY WORLDS.

Habitually and practically we do not _count_ these disregarded things

as existents at all. For them _Væ victis_ is the law in the popular

philosophy; they are not even treated as appearances; they are treated

as if they were mere waste, equivalent to nothing at all. To the

genuinely philosophic mind, however, they still have existence, though

not the same existence, as the real things. _As_ objects of fancy,

_as_ errors, _as_ occupants of dreamland, etc., they are in their way

as indefeasible parts of life, as undeniable features of the Universe,

as the realities are in their way. The total world of which the

philosophers must take account is thus composed of the realities _plus_

the fancies and illusions.

Two sub-universes, at least, connected by relations which philosophy

tries to ascertain! Really there are more than two sub-universes of

which we take account, some of us of this one, and others of that.

For there are various categories both of illusion and of reality, and

alongside of the world of absolute error (i.e., error confined to

single individuals) but still within the world of absolute reality

(i.e., reality believed by the complete philosopher) there is the

world of collective error, there are the worlds of abstract reality,

of relative or practical reality, of ideal relations, and there is the

supernatural world. The popular mind conceives of all these sub-worlds

more or less disconnectedly; and when dealing with one of them, forgets

for the time being its relations to the rest. The complete philosopher

is he who seeks not only to assign to every given object of his thought

its right place in one or other of these sub-worlds, but he also seeks

to determine the relation of each sub-world to the others in the total

world which _is_.

The most important sub-universes commonly discriminated from each other

and recognized by most of us as existing, each with its own special and

separate style of existence, are the following:

(1) The world of sense, or of physical 'things' as we instinctively

apprehend them, with such qualities as heat, color, and sound, and such

'forces' as life, chemical affinity, gravity, electricity, all existing

as such within or on the surface of the things.

(2) The world of science, or of physical things as the learned conceive

them, with secondary qualities and 'forces' (in the popular sense)

excluded, and nothing real but solids and fluids and their 'laws'

(i.e., customs) of motion.[295]

(3) The world of ideal relations, or abstract truths believed

or believable by all, and expressed in logical, mathematical,

metaphysical, ethical, or æsthetic propositions.

(4) The world of 'idols of the tribe,' illusions or prejudices common

to the race. All educated people recognize these as forming one

sub-universe. The motion of the sky round the earth, for example,

belongs to this world. That motion is not a recognized item of any of

the other worlds; but as an 'idol of the tribe' it really exists. For

certain philosophers 'matter' exists only as an idol of the tribe. For

science, the 'secondary qualities' of matter are but 'idols of the

tribe.'

(5) The various supernatural worlds, the Christian heaven and hell,

the world of the Hindoo mythology, the world of Swedenborg's _visa

et audita_, etc. Each of these is a consistent system, with definite

relations among its own parts. Neptune's trident, e.g., has no status

of reality whatever in the Christian heaven; but within the classic

Olympus certain definite things are true of it, whether one believe

in the reality of the classic mythology as a whole or not. The

various worlds of deliberate fable may be ranked with these worlds of

faith--the world of the _Iliad_, that of _King Lear_, of the _Pickwick

Papers_, etc.[296]