Thomas Reid.

The works of Thomas Reid, D.D.; now fully collected, with selections from his umpublished letters online

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hardness, are perceived by means of sens-
ations of touch ; whence they rashly con-
cluded, that these sensations must be images
and resemblances of figure, extension, and

The received hypothesis of ideas natur-
ally led them to this conclusion : and indeed
cannot consist with any other ; for, accord-
ing to that hypothesis, external things
must be perceived by means of images of
them in the mind ; and what can those
images of external things in the mind be, but
the sensations by which we perceive them ?

This, however, was to draw a conclusion
from a hypothesis against fact. We need
not have recourse to any hypothesis to
know what our sensations are, or what
they are like. By a proper degree of re-
flection and attention we may understand
them perfectly, and be as certain that they
are not like any quality of body, as we can
be, that the toothache is not like a triangle.
How a sensation should instantly make us
conceive and believe the existence of an
external thing altogether unlike to it, I do
not pretend to know ; and when I say that
the one suggests the other, I mean not to
explain the manner of their connection,
but to express a fact, which every one may
be conscious of— namely, that, by a law of
our nature, such a conception and belief
constantly and immediately follow the sens-

Bishop .Berkeley gave new light to this
subject, by shewing, that the qualities of
an inanimate thing, such as matter is con-
ceived to be, cannot resemble any sensa-
tion ; that it is impossible to conceive any-
thing like the sensations of our minds, but
the sensations of other minds. Every one
that attends properly to his sensations must
assent to this ; yet it had escaped all the
philosophers that came before Berkeley;
it had escaped even the ingenious Locke,
who had so much practised reflection on
the operations of his own mind. So diffi-
cult it is to attend properly even to our
own feelings. They are so accustomed to
pass through the mind unobserved, and
instantly to make way for that which na-
ture intended them to signify, that it is
extremely difficult to stop, and survey
them ; and when we think we have ac-
quired this power, perhaps the mind still
fluctuates between the sensation and its
associated quality, so that they mix to-
gether, and present something to the ima-
gination that is compounded of both. Thus,
in a globe or cylinder, whose opposite sides
are quite unlike in colour, if you turn it
slowly, the colours are perfectly distinguish-
able, and their dissimilitude is manifest ;
but if it is turned fast, they lose their dis-
tinction, and seem to be of one and the same




No succession can be more quick than
that of tangible qualities to the sensations
with which nature has associated them:
but when one has once acquired the art
of making them separate and distinct ob-
jects of thought, he will then clearly per-
ceive that the maxim of Bishop Berkeley,
above-mentioned, is self-evident ; and that
the features of the face are not more un-
like to a passion of the mind which they
indicate, than the sensations of touch are
to the primary qualities of body.

But let us observe what use the Bishop
makes of this important discovery. Why,
he concludes, that we can have no con-
ception of an inanimate substance, such as
matter is conceived to be, or of any of its
qualities ; and that there is the strongest
ground to believe that there is no existence
in nature but minds, sensations, and ideas :
if there is any other kind of existence , it
must be what we neither have nor can
have any conception of. But how does
this follow ? Why, thus : We can have
no conception of anything but what resem-
bles some sensation or idea in our minds ;
but the sensations and ideas in our minds
can resemble nothing but the sensations
and ideas in other minds ; therefore, the
conclusion is evident. This argument, we
see, leans upon two propositions. The last
of them the ingenious author hath, indeed,
made evident to all that understand his
reasoning, and can attend to their own
sensations : but the first proposition he
never attempts to prove ; it is taken from
the doctrine of ideas, which hath been so
universally received by philosophers, that
it was thought to need no proof-

We may here again observe, that this
acute writer argues from a hypothesis against
fact, and against the common sense of man-
kind. That we can have no conception of
anything, unless there is some impression,
sensation, or idea, in our minds which re-
sembles it, is indeed an opinion which hath
been very generally received among philo-
sophers ; but it is neither self-evident, nor
hath it been clearly proved ; and therefore
it hath been more reasonable to call in
question this doctrine of philosophers, than
to discard the material world, and by that
means expose philosophy to the ridicule of
all men who will not offer up common
sense as a sacrifice to metaphysics.

We ought, however, to do this justice
both to the Bishop of Cloyne and to the
author of the " Treatise of Human Nature,"
to acknowledge, that their conclusions are
justly drawn from the doctrine of ideas,
which has been so universally received.
On the other hand, from the character of
Bishop Berkeley, and of his predecessors,
Des Cartes, Locke, and Malebranche, we
may venture to say, that, if they had seen

all the consequences of this doctrine, as
clearly as the author before mentioned did,
they would have suspected it vehemently,
and" examined it more carefully than they
appear to have done.

The theory of ideas, like the Trojan
horse, had a specious appearance both of
innocence and beauty ; but if those philo-
sophers had known that it carried in its
belly death and destruction to all science
and common sense, they would not have
broken down their walls to give it admit-

That we have clear and distinct con-
ceptions of extension, figure, motion, and
other attributes of body, which are neither
sensations, nor like any sensation, is a fact
of which we may be as certain as that we
have sensations. And that all mankind
have a fixed belief of an external material
world — a belief which is neither got by rea-
soning nor education, and a belief which
we cannot shake off, even when we seem
to have strong arguments against it and
no shadow of argument for it — is likewise a
fact, for which we have all the evidence
that the nature of the thing admits. These
facts are phsenomena of human nature,
from which we may justly argue against
any hypothesis, however generally received.
But to argue from a hypothesis against
facts, is contrary to the rules of true philo-



Section I.


The advances made in the knowledge of
optics in the last age and in the present,
and chiefly the discoveries of Sir Isaac
Newton, do honour, not to philosophy only,
but to human nature. Such discoveries
ought for ever to put to shame the ignoble
attempts of our modern sceptics to depre-
ciate the human understanding, and to dis-
pirit men in the search of truth, by repre-
senting the human faculties as fit for no-
thing but to lead us into absurdities aud

Of the faculties called the five senses,
sight is without doubt the noblest. The
rays of light, which minister to this sense,
and of which, without it, we could never
have had the least conception, are the
most wonderful and astonishing part of
the inanimate creation. We must be satis-
fied of this, if we consider their extreme
minuteness ; their inconceivable velocity ;



the regular variety of colours which they
exhibit; the invariable laws according
to which they are acted upon by other
bodies, in their reflections, inflections, and
r. fractions, without the least change of
their original properties ; and the facility
with which they pervade bodies of great
density and of the closest texture, without
resistance, without crowding or disturbing
one another, without giving the least sensi-
ble impulse to the lightest bodies.

The structure of the eye, and of all its ap-
purtenances, the admirable contrivances of
nature for performing all its various exter-
nal and internal motions, and the variety
in the eyes of different animals, suited to
their several natures and ways of life,
clearly demonstrate this organ to be a mas-
terpiece of Nature's work. And he must
be very ignorant of what hath been dis-
covered about it, or have a very strange
cast of understanding, who can seriously
doubt whether or not the rays of light
and the eye were made for one another,
with consummate wisdom, and perfect skill
in optics.

If we shall suppose an order of beings,
endued with every human faculty but that
of sight, how incredible would it appear to
such beings, accustomed only to the slow
informations of touch, that, by the addition
of an organ, consisting of a ball and socket
of an inch diameter, they might be enabled,
in an instant of time, without changing
their place, to percei\e the disposition of a
whole army or the order of a battle, the
figure of a magnificent palace or all the
variety of a landscape ! If a man were by
feeling to find out the figure of the peak of
Teneriffe, or even of St Peter's Church at
Rome, it would be the work of a lifetime.*
It would appear still more incredible to
such beings as we have supposed, if they
were informed of the discoveries which
may be made by this little organ in
things far beyond the reach of any other
sense : that by means of it we can find
our way in the pathless ocean ; that we
can traverse the globe of the earth, deter-
mine its figure and dimensions, and deli-
neate every region of it ; — yea, that we
can measure the planetary orbs, and make
discoveries in the sphere of the fixed stars.
Would it not appear still more astonish-
ing to such beings, if they should be farther
informed, that, by means of this same organ,
we can perceive the tempers and disposi-
tions, the passions and affections, of our
fellow-creatures, even when they want most
to conceal them ?— that, when the tongue

* The thing would be impossible. Let any one
try by touch to ascertain the figure of a room, with
which he is previously unacquainted, and not alto-
gether of the usual shape, and he will find that
'ouch will afford him iiut slender aid — H.

is taught most artfully to lie and dissemble,
the hypocrisy should appear in the counte-
nance to a discerning eye ? — and that, by
this organ, we can often perceive what is
straight and what is crooked in the mind as
well as in the body ? How many myste-
rious things must a blind man believe, if he
will give credit to the relations of those
that see ? Surely he needs as strong a
faith as is required of a good Christian.

It is not therefore without reason that
the faculty of seeing is looked upon, not
only as more noble than the other senses,
but as having something in it of a nature
superior to sensation. The evidence of
reason is called seeing, not feeling, smelling,
or lusting. Yea, we are wont to express
the manner of the Divine knowledge by see-
ing, as that kind of knowledge which is
most perfect in us.

Section II.




Notwithstanding what hath been said of
the dignity and superior nature of this
faculty, it is worthy of our observation, that
there is very little of the knowledge ac-
quired by sight, that may not be communi-
cated to a man born blind. One who never
saw the light, may be learned and knowing
in every science, even in optics ; and may
make discoveries in every branch of philo-
sophy. He may understand as much as
another man, not only of the order, dis-
tances, and motions of the heavenly bodies ;
but of the nature of light, and of the laws
of the reflection and refraction of its rays.
He may understand distinctly how thos-e
laws produce the phenomena of the rain-
bow, the prism, the camera obscura. and
the magic lanthorn, and all the powers of
the microscope and telescope. This is a
fact sufficiently attested by experience.

In order to perceive the reason of it, we
must distinguish the appearance that objects
make to the eye, from the things suggested
by that appearance : and again, in the visi-
ble appearance of objects, we must dis-
tinguish the appearance of colour from
the appearance of extension, figure, and
motion. First, then, as to the visible
appearance of the figure, and motion, and
extension of bodies, I conceive that a man
born blind may have a distinct notion, if
not of the very things, at least of something
extremely like to them. May not a blind
man be made to conceive that a body mov-
ing directly from the eye, or directly to-
wards it, may ap] ear to be at rest ? and
that the same motion may appear quicker



or slower, according as it is nearer to the
eye or farther off, more direct or more ob-
lique ? May he not be made to conceive,
that a plain surface, in a certain position,
may appear as a straight line, and vary
its visible figure, as its position, or the posi-
tion of the eye, is varied ? — that a circle
seen obliquely will appear an ellipse ; and
a square, a rhombus, or an oblong rec-
tangle ? Dr Saunderson understood the
projection of the sphere, and the common
rules of perspective ; and if he did, he
must have understood all that I have men-
tioned. If there were any doubt of Dr
Saunderson's understanding these things, I
could mention my having heard him say in
conversation, that he found great difficulty
in understanding Dr Halley's demonstra-
tion of that proposition, that the angles
made by the circles of the sphere, are equal
to the angles made by their representatives
in the stereographic projection ; but, said
he, when I laid aside that demonstration,
and considered the proposition in my own
way, I saw clearly that it must be true.
Another gentleman, of undoubted credit
and judgment in these matters, who had
part in this conversation, remembers it

As to the appearance of colour, a blind
man must be more at a loss ; because he
hath no perception that resembles it. Yet
he may, by a kind of analogy, in part sup-
ply this defect. To those who see, a scar-
let colour signifies an unknown quality
in bodies, that makes to the eye an ap-
pearance which they are well acquainted
with and have often observed — to a blind
man, it signifies an unknown quality, that
makes to the eye an appearance which he
is unacquainted with. But he can conceive
the eye to be variously affected by differ-
ent colours, as the nose is by different
smells, or the ear by different sounds.
Thus he can conceive scarlet to differ from
blue, as the sound of a trumpet does
from that of a drum ; or as the smell of
an orange differs from that of an apple.
It is impossible to know whether a scarlet
colour has the same appearance to me
which it hath to another man ; and, if the
appearances of it to different persons dif-
fered as much as colour does from sound,
they might never be able to discover this
difference. Hence, it appears obvious,
that a blind man might talk long about
colours distinctly and pertinently ; and, if
you were to examine him in the dark about
the nature, composition, and beauty of them,
he might be able to answer, so as not to
betray his defect.

We have seen how far a blind man may
go in the knowledge of the appearances
which things make to the eye. As to the
things which are suggested by them or

inferred from them, although he could
never discover them of himself, yet he may
understand them perfectly by the inform-
ation of others. And everything of this
kind that enters into our minds by the eye,
may enter into his by the ear. Thus, for
instance, he eould never, if left to the di-
rection of his own faculties, have dreamed
of any such thing as light ; but he can be
informed of everything we know about
it. He can conceive, as distinctly as we,
the minuteness and velocity of its rays,
their various degrees of refrangibility and
reflexibility, and all the magical powers
and virtues of that wonderful element.
He could never of himself have found out,
that there are such bodies as the sun,
moon, and stars ; but he may be informed
of all the noble discoveries of astrono-
mers about their motions, and the lawf
of nature by which they are regulated.
Thus, it appears, that there is very little
knowledge got by the eye, which may not
be communicated by language to those who
have no eyes.

If we should suppose that it were as
uncommon for men to see as it is to be
born blind, would not the few who had
this rare gift appear as prophets and in-
spired teachers to the many ? We conceive
inspiration to give a man no new faculty,
but to communicate to him, in a new way,
and by extraordinary means, what the fa-
culties common to mankind can apprehend,
and what he can communicate to others
by ordinary means. On the supposition
we have made, sight would appear to the
blind very similar to this ; for the few who
had this gift, could communicate the know-
ledge acquired by it to those who had it
not. They could not, indeed, convey to
the blind any distinct notion of the manner
in which they acquired this knowledge. A
ball and socket would seem, to a blind
man, in this case, as improper an instru-
ment for acquiring such a variety and ex-
tent of knowledge, as a dream or a vision.
The manner in which a man who sees,
discerns so many things by means of the
eye, is as unintelligible to the blind, as (he
manner in which a man may be inspired
with knowledge by the Almighty, is to
us. Ought the blind man, therefore, with-
out examination, to treat all pretences to
the gift of seeing as imposture ? Might he
not, if he were candid and tractable, find
reasonable evidence of the reality of this
gift in others, and draw great advantages
from it to himself ?

The distinction we have made between
the visible appearances of the objects of
sight, and things suggested by them, is ne-
cessary to give us a just notion of the in-
tention of nature in giving us eyes. If we
attend duly to (he operation of our mind



tn the use of this faculty, we shall perceive
that the visible appearance of objects is
hardly ever regarded by us. It is not at
all made an object of thought or reflec-
tion, but serves only as a sign to introduce
to the mind something else, which may be
distinctly conceived bythose who neversaw.
Thus, the visible appearance of things in
my room varies almost every hour, accord-
ing as the day is clear or cloudy, as the sun
is in the east, or south, or west, and as my
eye is in one part of the room or in an-
other ; but I never think of these variations,
otherwise than as signs of morning, noon,
or night, of a clear or cloudy sky. A book
or a chair has a different appearance to the
eye, in every different distance and posi-
tion ; yet we conceive it to be still the
same ; and, overlooking the appearance, we
immediately conceive the real figure, dis-
tance, and posiiion of the body, of which
its visible or perspective appearance is a
sign and indication.

When I see a man at the distance of ten
yards, and afterwards see him at the dis-
tance of a hundred yards, his visible ap-
pearance, in its length, breadth, and all its
linear proportions, is ten times less in the
last case than it is in the first ; yet I do not
conceive him one inch diminished by this
diminution of his visible figure. Nay, I
do not in the least attend to this diminution,
even when I draw from it the conclusion
of his being at a greater distance. For such
is the subtilty of the mind's operation in
this case, that we draw the conclusion, with-
out perceiving that ever the premises en-
tered into the mind. A thousand such in-
stances might be produced, in order to shew
that the visible appearances of objects are
intended by nature only as signs or indica-
tions ; and that the mind passes instantly
to the things signified, without making the
least reflection upon the sign, or even per-
ceiving that there is any such thing. It is
in a way somewhat similar, that the sounds
of a language, after it is become familiar,
are overlooked, and we attend only to the
things signified by them.

It is therefore a just and important ob-
servation of the Bishop of Cloyne, That
the visible appearance of objects is a kind
of language used by nature, to inform us
of their distance, magnitude, and figure.
And this observation hath been very happily
applied by that ingenious writer, to the
solution of somepheenomena in optics, which
had before perplexed the greatest masters
in that science. ' The same observation is
further improved by thejudicious Dr Smith,
in his Optics, for explaining the apparent
figure of the heavens, and the apparent
distances and magnitudes of objects seen
with glasses, or by the naked eye.

Avoiding as much as possible the repe-

tition of what hath been said by these ex-
cellent writers, we shall avail ourselves of
the distinction between the signs that nature
useth in this visual language, and the things
signified by them : and in what remains to
be said of sight, shall first make some ob-
servations upon the signs.

Section III.


In this section we must speak of things
which are never made the object of re-
flection, though almost every moment pre-
sented to the mind. Nature intended them
only for signs ; and in the whole course
of life they are put to no other use. The
mind has acquired a confirmed and invet-
erate habit of inattention to them ; for
they no sooner appear, than quick as light-
ning the thing signified succeeds, and en-
grosses all our regard. They have no
name in language ; and, although we are
conscious of them when they pass through
the mind, yet their passage is so quick
and so familiar, that it is absolutely un-
heeded; nor do they leave any footsteps
of themselves, either in the memory or
imagination. That this is the case with
regard to the sensations of touch, hath been
shewn in the last chapter; and it holds
no less with regard to the visible appear-
ances of objects.

I cannot therefore entertain the hope of
being intelligible to those readers who have
not, by pains and practice, acquired the
habit of distinguishing the appearance of
objects to the eye, from the judgment which
we form by sight of their colour, distance,
magnitude, and figure. The only profes-
sion in life wherein it is necessary to make
this distinction, is that of paintini.'. The
painter hath occasion for an abstraction,
with regard to visible objects, somewhat
similar to that which we here require : and
this indeed is the most difficult part of his
art. For it is evident, that, if he could fix
in his imagination the visible appearance of
objects, without confounding it with the
things signified by that appearance, it
would be as easy for him to paint from the
life, and to give every figure its proper
shading and relief, and its perspective pro-
portions, as it is to paint from a copy. Per-
spective, shading, giving relief, and colour-
ing, are nothing else but copying the ap-
pearance which things make to the eye.
We may therefore borrow some light on

Let one look upon any familiar object,
such as a book, at different distances and
in different positions : is he not able to
affirm, upon the tcst'mony of his sight, that



it is the same bonk, the same object, whether
seen at the distance of one foot or of ten,
whether in one position or another ; that
the colour is the same, the dimensions the
same, and the figure the same, as far as
the eye can judge ? This surely must be
acknowledged. The same individual object
is presented to the mind, only placed at
different distances and in different posi-
tions. Let me ask, in the next place,
Whether this object has the same appear-
ance to the eye in these different distances ?
Infallibly it hath not. Kor,

First, However certain our judgment
may be that the colour is the same, it is as
certain that it hath not the same appear-
ance at different distances. There is a
certain degradation of the colour, and a
certain confusion and indistinctness of the
minute parts, which is the natural conse-
quence of the removal of the object to a
greater distance. Those that are not

Online LibraryThomas ReidThe works of Thomas Reid, D.D.; now fully collected, with selections from his umpublished letters → online text (page 31 of 114)