Critiques and Addresses by Thomas Henry Huxley

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[Footnote 1: Locke, "Human Understanding," Book II. chap. viii. Sec.Sec. 14,
15.]

Thus far then materialists and idealists are agreed. Locke and
Berkeley, and all logical thinkers who have succeeded them, are of
one mind about secondary qualities--their being is to be perceived or
known--their materiality is, in strictness, a spirituality.

But Locke draws a great distinction between the secondary qualities of
matter, and certain others which he terms "primary qualities." These
are extension, figure, solidity, motion and rest, and number; and he
is as clear that these primary qualities exist independently of the
mind, as he is that the secondary qualities have no such existence.

"The particular bulk, number, figure, and motion of the parts
of fire and snow are really in them, whether anyone's senses
perceive them or not, and therefore they may be called real
qualities, because they really exist in those bodies; but
light, heat, whiteness, or coldness, are no more really in
them, than sickness, or pain, is in manna. Take away the
sensation of them; let not the eyes see light or colours, nor
the ears hear sounds; let the palate not taste, nor the nose
smell; and all colours, tastes, odours and sounds, as they are
such particular ideas, vanish and cease, and are reduced to
their causes, i.e. bulk, figure, and motion of parts.

"18. A piece of manna of sensible bulk is able to produce in
us the idea of a round or square figure; and, by being removed
from one place to another, the idea of motion. This idea of
motion represents it as it really is in the manna moving; a
circle and square are the same, whether in idea or existence,
in the mind or in the manna; and thus both motion and figure
are really in the manna, whether we take notice of them or no:
this everybody is ready to agree to."

So far as primary qualities are concerned, then, Locke is as
thoroughgoing a realist as St. Anselm. In Berkeley, on the other
hand, we have as complete a representative of the nominalists and
conceptualists--an intellectual descendant of Roscellinus and of
Abelard. And by a curious irony of fate, it is the nominalist who is,
this time, the champion of orthodoxy, and the realist that of heresy.

Once more let us try to work out Berkeley's principles for ourselves,
and inquire what foundation there is for the assertion that extension,
form, solidity, and the other "primary qualities," have an existence
apart from mind. And for this purpose let us recur to our experiment
with the pin.

It has been seen that when the finger is pricked with a pin, a state
of consciousness arises which we call pain; and it is admitted that
this pain is not a something which inheres in the pin, but a something
which exists only in the mind, and has no similitude elsewhere.

But a little attention will show that this state of consciousness is
accompanied by another, which can by no effort be got rid of. I not
only have the feeling, but the feeling is localized. I am just as
certain that the pain is in my finger, as I am that I have it at all.
Nor will any effort of the imagination enable me to believe that the
pain is not in my finger.

And yet nothing is more certain than that it is not, and cannot be, in
the spot in which I feel it, nor within a couple of feet of that spot.
For the skin of the finger is connected by a bundle of fine nervous
fibres, which run up the whole length of the arm, with the spinal
marrow and brain, and we know that the feeling of pain caused by the
prick of a pin is dependent on the integrity of those fibres. After
they have been cut through close to the spinal cord, no pain will be
felt, whatever injury is done to the finger; and if the ends which
remain in connection with the cord be pricked, the pain which arises
will appear to have its seat in the finger just as distinctly as
before. Nay, if the whole arm be cut off, the pain which arises from
pricking the nerve stump will appear to be seated in the fingers, just
as if they were still connected with the body.

It is perfectly obvious, therefore, that the localization of the
pain at the surface of the body is an act of the mind. It is an
_extradition_ of that consciousness, which has its seat in the
brain, to a definite point of the body--which takes place without our
volition, and may give rise to ideas which are contrary to fact. We
might call this extradition of consciousness a reflex feeling, just
as we speak of a movement which is excited apart from, or contrary to,
our volition, as a reflex motion. Locality is no more in the pin than
pain is; of the former, as of the latter, it is true that "its being
is to be perceived," and that its existence apart from a thinking mind
is not conceivable.

The foregoing reasoning will be in no way affected, if, instead of
pricking the finger, the point of the pin rests gently against it, so
as to give rise merely to a tactile sensation. The tactile sensation
is referred outwards to the point touched, and seems to exist there.
But it is certain that it is not and cannot be there really, because
the brain is the sole seat of consciousness; and, further, because
evidence, as strong as that in favour of the sensation being in the
finger, can be brought forward in support of propositions which are
manifestly absurd.

For example, the hairs and nails are utterly devoid of sensibility,
as everyone knows. Nevertheless, if the ends of the nails or hairs
are touched, ever so lightly, we feel that they are touched, and the
sensation seems to be situated in the nails or hairs. Nay more, if a
walking-stick a yard long is held firmly by the handle and the other
end is touched, the tactile sensation, which is a state of our own
consciousness, is unhesitatingly referred to the end of the stick; and
yet no one will say that it _is_ there.

Let us now suppose that, instead of one pin's point resting against
the end of my finger, there are two. Each of these can be known to
me, as we have seen, only as a state of a thinking mind, referred
outwards, or localized. But the existence of these two states, somehow
or other, generates in my mind a host of new ideas, which did not make
their appearance when only one state was present.

For example, I get the ideas of co-existence, of number, of distance,
and of relative place or direction. But all these ideas are ideas of
relations, and imply the existence of something which perceives those
relations. If a tactile sensation is a state of the mind, and if
the localization of that sensation is an act of the mind, how is it
conceivable that a relation between two localized sensations should
exist apart from the mind? It is, I confess, quite as easy for me to
imagine that redness may exist apart from a visual sense, as it is to
suppose that co-existence, number, and distance can have any existence
apart from the mind of which they are ideas.

Thus it seems clear that the existence of some, at any rate, of
Locke's primary qualities of matter, such as number and extension,
apart from mind, is as utterly unthinkable as the existence of colour
and sound under like circumstances.

Will the others--namely, figure, motion and rest, and
solidity--withstand a similar criticism? I think not. For all these,
like the foregoing, are perceptions by the mind of the relations
of two or more sensations to one another. If distance and place are
inconceivable, in the absence of the mind, of which they are ideas,
the independent existence of figure, which is the limitation of
distance, and of motion, which is change of place, must be equally
inconceivable. Solidity requires more particular consideration, as it
is a term applied to two very different things, the one of which is
solidity of form, or geometrical solidity; while the other is solidity
of substance, or mechanical solidity.

If those motor nerves of a man by which volitions are converted into
motion were all paralysed, and if sensation remained only in the palm
of his hand (which is a conceivable case), he would still be able to
attain to clear notions of extension, figure, number, and motion, by
attending to the states of consciousness which might be aroused by the
contact of bodies with the sensory surface of the palm. But it does
not appear that such a person could arrive at any conception of
geometrical solidity. For that which does not come in contact with the
sensory surface is non-existent for the sense of touch; and a solid
body, impressed upon the palm of the hand, gives rise only to the
notion of the extension of that particular part of the solid which is
in contact with the skin.

Nor is it possible that the idea of outness (in the sense of
discontinuity with the sentient body) could be attained by such a
person; for, as we have seen, every tactile sensation is referred to
a point either of the natural sensory surface itself, or of some
solid in continuity with that surface. Hence it would appear that the
conception of the difference between the Ego and the non-Ego could
not be attained by a man thus situated. His feelings would be his
universe, and his tactile sensations his "moenia mundi." Time would
exist for him as for us, but space would have only two dimensions.

But now remove the paralysis from the motor apparatus, and give the
palm of the hand of our imaginary man perfect freedom to move, so as
to be able to glide in all directions over the bodies with which it is
in contact. Then with the consciousness of that mobility, the notion
of space of three dimensions--which is "_Raum_" or "room" to move with
perfect freedom--is at once given. But the notion that the tactile
surface itself moves, cannot be given by touch alone, which is
competent to testify only to the fact of change of place, not to its
cause. The idea of the motion of the tactile surface could not, in
fact, be attained, unless the idea of change of place were accompanied
by some state of consciousness, which does not exist when the tactile
surface is immoveable. This state of consciousness is what is termed
the muscular sense, and its existence is very easily demonstrable.

Suppose the back of my hand to rest upon a table, and a sovereign to
rest upon the upturned palm, I at once acquire a notion of extension,
and of the limit of that extension. The impression made by the
circular piece of gold is quite different from that which would be
made by a triangular, or a square, piece of the same size, and thereby
I arrive at the notion of figure. Moreover, if the sovereign slides
over the palm, I acquire a distinct conception of change of place
or motion, and of the direction of that motion. For as the sovereign
slides, it affects new nerve-endings, and gives rise to new states of
consciousness. Each of them is definitely and separately localized by
a reflex act of the mind, which, at the same time, becomes aware of
the difference between two successive localizations; and therefore of
change of place, which is motion.

If, while the sovereign lies on the hand, the latter being kept quite
steady, the fore-arm is gradually and slowly raised; the tactile
sensations, with all their accompaniments, remain exactly as they
were. But, at the same time, something new is introduced; namely, the
sense of effort. If I try to discover where this sense of effort seems
to be, I find myself somewhat perplexed at first; but, if I hold the
fore-arm in position long enough, I become aware of an obscure sense
of fatigue, which is apparently seated either in the muscles of the
arm, or in the integument directly over them. The fatigue seems to be
related to the sense of effort, in much the same way as the pain which
supervenes upon the original sense of contact, when a pin is slowly
pressed against the skin, is related to touch.

A little attention will show that this sense of effort accompanies
every muscular contraction by which the limbs, or other parts of the
body, are moved. By its agency the fact of their movement is known;
while the direction of the motion is given by the accompanying tactile
sensations. And, in consequence of the incessant association of the
muscular and the tactile sensations, they become so fused together
that they are often confounded tinder the same name.

If freedom to move in all directions is the very essence of that
conception of space of three dimensions which we obtain by the sense
of touch; and if that freedom to move is really another name for the
feeling of unopposed effort, accompanied by that of change of place,
it is surely impossible to conceive of such space as having existence
apart from that which is conscious of effort.

But it may be said that we derive our conception of space of three
dimensions not only from touch, but from vision; that if we do not
feel things actually outside us, at any rate we see them. And it was
exactly this difficulty which presented itself to Berkeley at the
outset of his speculations. He met it, with characteristic boldness,
by denying that we do see things outside us; and, with no less
characteristic ingenuity, by devising that "New Theory of Vision"
which has met with wider acceptance than any of his views, though it
has been the subject of continual controversies.[1]

[Footnote 1: I have not specifically alluded to the writings of
Bailey, Mill, Abbott, and others, on this vexed question, not because
I have failed to study them carefully, but because this is not a
convenient occasion for controversial discussion. Those who are
acquainted with the subject, however, will observe that the view I
have taken agrees substantially with that of Mr. Barley.]

In the "Principles of Human Knowledge," Berkeley himself tells us how
he was led to those views which he published in the "Essay towards the
New Theory of Vision."

"It will be objected that we see things actually without, or
at a distance from us, and which consequently do not exist in
the mind; it being absurd that those things which are seen at
the distance of several miles, should be as near to us as our
own thoughts. In answer to this, I desire it may be considered
that in a dream we do oft perceive things as existing at a
great distance off, and yet, for all that, those things are
acknowledged to have their existence only in the mind.

"But for the fuller clearing of this point, it may be worth
while to consider how it is that we perceive distance and
things placed at a distance by sight. For that we should in
truth see external space and bodies actually existing in it,
some nearer, others further off, seems to carry with it some
opposition to what hath been said of their existing nowhere
without the mind. The consideration of this difficulty it
was that gave birth to my 'Essay towards the New Theory of
Vision,' which was published not long since, wherein it is
shown that distance, or outness, is neither immediately of
itself perceived by sight, nor yet apprehended, or judged
of, by lines and angles or anything that hath any necessary
connection with it; but that it is only suggested to our
thoughts by certain visible ideas and sensations attending
vision, which, in their own nature, have no manner of
similitude or relation either with distance, or with things
placed at a distance; but by a connection taught us by
experience, they come to signify and suggest them to us, after
the same manner that words of any language suggest the ideas
they are made to stand for; insomuch that a man born blind and
afterwards made to see, would not, at first sight, think the
things he saw to be without his mind or at any distance from
him."

The key-note of the Essay to which Berkeley refers in this passage is
to be found in an italicized paragraph of section 127:--

"_The extensions; figures, and motions perceived by sight are
specifically distinct from the ideas of touch called by the
same names; nor is there any such thing as an idea, or kind of
idea, common to both senses_."

It will be observed that this proposition expressly declares that
extension, figure, and motion, and consequently distance, are
immediately perceived by sight as well as by touch; but that visual
distance, extension, figure, and motion, are totally different in
quality from the ideas of the same name obtained through the sense
of touch. And other passages leave no doubt that such was Berkeley's
meaning. Thus in the 112th section of the same Essay, he carefully
defines the two kinds of distance, one visual, the other tangible:--

"By the distance between any two points nothing more is meant
than the number of intermediate points. If the given points
are visible, the distance between them is marked out by the
number of interjacent visible points; if they are tangible,
the distance between, them is a line consisting of tangible
points."

Again, there are two sorts of magnitude or extension:--

"It has been shown that there are two sorts of objects
apprehended by sight, each whereof has its distinct magnitude
or extension: the one properly tangible, _i.e._ to be
perceived and measured by touch, and not immediately falling
under the sense of seeing; the other properly and immediately
visible, by mediation of which the former is brought into
view."--Sec. 55.

But how are we to reconcile these passages with others which will be
perfectly familiar to every reader of the "New Theory of Vision "? As,
for example:--

"It is, I think, agreed by all, that distance of itself, and
immediately, cannot be seen."--Sec. 2.

"Space or distance, we have shown, is no otherwise the object
of sight than of hearing."--Sec. 130.

"Distance is in its own nature imperceptible, and yet it is
perceived by sight. It remains, therefore, that it is
brought into view by means of some other idea, that is itself
immediately perceived in the act of vision."--Sec. 11.

"Distance or external space."--Sec. 155.

The explanation is quite simple, and lies in the fact that Berkeley
uses the word "distance" in three senses. Sometimes he employs it to
denote visible distance, and then he restricts it to distance in two
dimensions, or simple extension. Sometimes he means tangible distance
in two dimensions; but most commonly he intends to signify tangible
distance in the third dimension. And it is in this sense that he
employs "distance" as the equivalent of "space." Distance in two
dimensions is, for Berkeley, not space, but extension. By taking a
pencil and interpolating the words "visible" and "tangible" before
"distance" wherever the context renders them necessary, Berkeley's
statements may be made perfectly consistent; though he has not always
extricated himself from the entanglement caused by his own loose
phraseology, which rises to a climax in the last ten sections of
the "Theory of Vision," in which he endeavours to prove that a pure
intelligence able to see, but devoid of the sense of touch, could have
no idea of a plane figure. Thus he says in section 156:--

"All that is properly perceived by the visual faculty amounts
to no more than colours with their variations and different
proportions of light and shade; but the perpetual mutability
and fleetingness of those immediate objects of sight
render them incapable of being managed after the manner of
geometrical figures, nor is it in any degree useful that they
should. It is true there be divers of them perceived at once,
and more of some and less of others; but accurately to compute
their magnitude, and assign precise determinate proportions
between things so variable and inconstant, if we suppose
it possible to be done, must yet be a very trifling and
insignificant labour."

If, by this, Berkeley means that by vision alone, a straight line
cannot be distinguished from a curved one, a circle from a square,
a long line from a short one, a large angle from a small one, his
position is surely absurd in itself and contradictory to his own
previously cited admissions; if he only means, on the other hand, that
his pure spirit could not get very far on in his geometry, it may be
true or not; but it is in contradiction with his previous assertion,
that such a pure spirit could never attain to know as much as the
first elements of plane geometry.

Another source of confusion, which arises out of Berkeley's
insufficient exactness in the use of language, is to be found in what
he says about solidity, in discussing Molyneux's problem, whether a
man born blind and having learned to distinguish between a cube and a
sphere, could, on receiving his sight, tell the one from the other
by vision. Berkeley agrees with Locke that he could not, and adds the
following reflection:--

"Cube, sphere, table, are words he has known applied to things
perceivable by touch, but to things perfectly intangible
he never knew them applied. Those words in their wonted
application always marked out to his mind bodies or solid
things which were perceived by the resistance they gave. But
there is no solidity, no resistance or protrusion perceived by
sight."

Here "solidity" means resistance to pressure, which is apprehended by
the muscular sense; but when in section 154 Berkeley says of his pure
intelligence--

"It is certain that the aforesaid intelligence could have no
idea of a solid or quantity of three dimensions, which follows
from its not having any idea of distance "--

he refers to that notion of solidity which may be obtained by the
tactile sense, without the addition of any notion of resistance in the
solid object; as, for example, when the finger passes lightly over the
surface of a billiard ball.

Yet another source of difficulty in clearly understanding Berkeley
arises out of his use of the word "outness." In speaking of touch
he seems to employ it indifferently, both for the localization of
a tactile sensation in the sensory surface, which we really obtain
through touch; and for the notion of corporeal separation, which is
attained by the association of muscular and tactile sensations. In
speaking of sight, on the other hand, Berkeley employs "outness" to
denote corporeal separation.

When due allowance is made for the occasional looseness and ambiguity
of Berkeley's terminology, and the accessories are weeded out of the
essential parts of his famous Essay, his views may, I believe, be
fairly and accurately summed up in the following propositions:--

1. The sense of touch gives rise to ideas of extension, figure,
magnitude, and motion.

2. The sense of touch gives rise to the idea of "outness," in the
sense of localization.

3. The sense of touch gives rise to the idea of resistance, and thence
to that of solidity, in the sense of impenetrability.

4. The sense of touch gives rise to the idea of "outness," in the
sense of distance in the third dimension, and thence to that of space,
or geometrical solidity.

5. The sense of sight gives rise to ideas of extension, of figure,
magnitude, and motion.

6. The sense of sight does not give rise to the idea of "outness,"
in the sense of distance in the third dimension, nor to that of
geometrical solidity, no visual idea appearing to be without the mind,
or at any distance off (Sec.Sec. 43, 50).

7. The sense of sight does not give rise to the idea of mechanical
solidity.

8. There is no likeness whatever between the tactile ideas called
extension, figure, magnitude, and motion, and the visual ideas which
go by the same names; nor are any ideas common to the two senses.

9. When we think we see objects at a distance, what really happens
is that the visual picture suggests that the object seen has tangible
distance; we confound the strong belief in the tangible distance of
the object with actual sight of its distance.

10. Visual ideas, therefore, constitute a kind of language, by which
we are informed of the tactile ideas which will, or may, arise in us.

Taking these propositions into consideration _seriatim_, it may be
assumed that everyone will assent to the first and second; and that
for the third and fourth we have only to include the muscular sense
tinder the name of sense of touch, as Berkeley did, in order to make
it quite accurate. Nor is it intelligible to me that anyone should
explicitly deny the truth of the fifth proposition, though some
of Berkeley's supporters, less careful than himself, have done so.
Indeed, it must be confessed that it is only grudgingly, and as it
were against his will, that Berkeley admits that we obtain ideas of
extension, figure, and magnitude by pure vision, and that he more than
half retracts the admission; while he absolutely denies that sight
gives us any notion of outness in either sense of the word, and even
declares that "no proper visual idea appears to be without the mind,
or at any distance off." By "proper visual ideas," Berkeley denotes
colours, and light, and shade; and, therefore, he affirms that colours
do not appear to be at any distance from us. I confess that this
assertion appears to me to be utterly unaccountable. I have made
endless experiments on this point, and by no effort of the imagination
can I persuade myself, when looking at a colour, that the colour is
in my mind, and not at a "distance off," though of course I know
perfectly well, as a matter of reason, that colour is subjective. It
is like looking at the sun setting, and trying to persuade oneself
that the earth appears to move and not the sun, a feat I have never
been able to accomplish. Even when the eyes are shut, the darkness
of which one is conscious, carries with it the notion of outness. One
looks, so to speak, into a dark space. Common language expresses the
common experience of mankind in this matter. A man will say that a
smell is in his nose, a taste in his mouth, a singing in his ears, a
creeping or a warmth in his skin; but if he is jaundiced, he does not
say that he has yellow in his eyes, but that everything looks yellow;
and if he is troubled with _muscae volitantes_, he says, not that he
has specks in his eyes, but that he sees specks dancing before his
eyes. In fact, it appears to me that it is the special peculiarity
of visual sensations, that they invariably give rise to the idea of
remoteness, and that Berkeley's dictum ought to be reversed. For I
think that anyone who interrogates his consciousness carefully will
find that "every proper visual idea" appears to be without the mind
and at a distance off.

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