Thomas Reid.

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

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acquainted with external things. All the
fertility of human invention seems to have
produced only one hypothesis for this pur-
pose, which, therefore, hath been univer-
sally received ; and that is, that the mind,
like a mirror, receives the images of things
from without, by means of the senses ; so
that their usemustbeto convey these images
into the mind. •

Whether to these images of external
things in the mind, we give the name of
sensible forms , or sensible species, with the
Peripatetics, or the name of ideas of sensa-
tion, with Locke ; or whether, with later
philosophers, we distinguish sensations,
which are immediately conveyed by the
senses, from idtas of sensation, which are
faint copies of our sensations retained in
the memory and imagination ;-|- these are
only differences about words. The hypo-
thesis I have mentioned is common to all
these different systems.

The necessary and allowed consequence
of this hypothesis is, that no material thing,
nor any quality of material things, can be
conceived by us, or made an object oj
thought, until its image is conveyed to the
mind by means of the senses. We shall
examine this hypothesis particularly after-
wards, and at this time only observe, that,
in consequence of it, one would naturally
expect, that to every quality and attribute
uf body we know nr can conceive, there
should be a sensation corresponding, which
is the image. and resemblance of that qua-
lity ; and that the sensations which have
no similitude or resemblance to body, or to
any of its qualities, should give us no con-
ception of a material world, or of anything
belonging to it. These things might be ex-
pected as the natural consequences of the
hypothesis we have mentioned.

Now, we have considered, in this and
the preceding chapters, Extension, Figure,
Solidity, Motion, Hardness, Roughness, as
well as Colour, Heat, and Cold, Sound,
Taste, and Smell. We have endeavoured
to shew that our nature and constitution
lead us to conceive these as qualities of
body, as all mankind have always con-

* This is incorrect, especially as it asserts that
the one universal hypothesis of philosophy was, that
"the mind receives the images of things from with-
out," meaning by these images, immediate or repre.
senrarive objects, different from the modifications of
the thinking subject itself. — H.

+ He refers to Hume: Aristotle, however, and
Hoboes, had previously called Imagination a rfe.aV-
inff sense, — H. ~ " 3



oeived them to be. We have likewise exa-
mined with great attention the various
sensations we have by means of the five
senses, and are not able to find among
them all one single* image of body, or of
any of its qualities. From whence, then,
come those images of body and of its qua-
lities into the mind ? Let philosophers re-
solve this question. All I can say is, that
they come not by the senses. I am sure
that, by proper attention and care, I may
know my sensations, and be able to affirm
with certainty what they resemble, and what
they do not resemble. I have examined
them one by one, and compared them with
matter and its qualities ; and I cannot find
one of them that confesses a resembling

A truth so evident as this — that our sens-
ations are not images of matter, or of any
of its qualities — ought not to yield to a hy-
pothesis such as that above-mentioned, how-
ever ancient, or however universally re-
ceived by philosophers ; nor can there be
any amicable union between the two. This
will appear by some reflections upon the
spirit of the ancient and modern philosophy
concerning sensation.

During the reign of the Peripatetic phi-
losophy, our sensations were not minutely
or accurately examined. The attention
of philosophers, as well as of the vulgar,
was turned to the things signified by them :
therefore, in consequence of the common
hypothesis, it was taken for granted, that
all the sensations we have from external
things, are the forms or images of these
external things. And thus the truth we
have mentioned yielded entirely to the hypo-
thesis, and was altogether suppressed by it.

Des Cartes gave » noble example of
turning our attention inward, and scruti-
nizing our sensations ; and this example
hath been very worthily followed by mo-
dern philosophers, particularly by Male-
branche, Locke, Berkeley, and Hume. The
effect of this scrutiny hath been, a gradual
discovery of the truth above-mentioned — to
wit, the dissimilitude between the sensa-
tions of our minds, and the qualities or
attributes of an insentient inert substance,
such as we conceive matter to be. But
this valuable and useful discovery, in its
different stages, hath still been unhappily
united to the ancient hypothesis — and from
this inauspicious match of opinions, so
unfriendly and discordant in their natures,
have arisen those monsters of paradox and
scepticism with which the modern philoso-
phy is too justly chargeable.

Locke saw clearly, and proved incon-
testably, that the sensations we have by
taste, smell, and hearing, as well .as the

' One tingle — a common but faulty pleonasm. — H.

sensations of colour, heat, and cold, are
nut resemblances of anything^ in bodies ;
and in this he agrees with Des Cartes and
Malebranche. Joining this opinion with
the hypothesis, it follows necessarily, that
three senses of the five are cut off from
giving us any intelligence of the material
world, as being altogether inept for that
office. Smell, and taste, and sound, as well
as colour and heat, can have no more rela-
tion to body, than anger or gratitude ; nor
ought the former to be called qualities of
body, whether primary or secondary, any
more than the latter. For it was natural
and obvious to argue thus from that hypo-
thesis : If heat, and colour, and sound
are real qualities of body, the sensations
by which we perceive them must be re-
semblances of those qualities ; but these
sensations are not resemblances ; there-
fore, those are not real qualities of body.

We see, then, that Locke, having found
that the ideas of secondary qualities are no
resemblances, was compelled, by a hypo-
thesis common to all philosophers, to deny
that they are real qualities of body. It
is more difficult to assign a reason why,
after this, he should call them secondary
qualities ; for this name, if I mistake not,
was of his invention.* Surely he did not
mean that they were secondary qualities of
the mind ; and I do not see with what pro-
priety, or even by what tolerable license,
he could call them secondary qualities of
body, after finding that they were no qua-
lities of body at all. In this, he seems to
have sacrificed to Common Sense, and to
have been led by her authority even in
opposition to his hypothesis. The same
sovereign mistress of our opinions that led
this philosopher to call those things second-
ary qualities of body, which, according to his
principles and reasonings, were no qualities
of body at all, hath led, not the vulgar of
all ages only, but philosophers also, and
even the disciples of Locke, to believe them
to be real qualities of body — she hath led
them to investigate, by experiments, the
nature of colour, and sound, and heat, in
bodies- Nor hath this investigation been
fruitless, as it must have been if there had
been no such thing in bodies ; on the con-
trary, it hath produced very noble and
useful discoveries, which make a very con-
siderable part of natural philosophy. If,
then, natural philosophy be not a dream,
there is something in bodies which we call
colour, and heat, and sound. And if this
be so, the hypothesis from which the con-

• The terms First anrl Second, or Primary and
Secondary qualities, were no more an invention of
Locke than the distinction which he applied them to
denote. The terms First and Second Qualities,
as I have noticed, in the Aristotelian philosophy,
marked out, however, a different distribution ox
qualities than that in question.— H.



trary is concluded, must be false : for the
argument, leading; to a false conclusion,
recoils against the hypothesis from which
it was drawn, and thus directs its force
backward. If the qualities of body were
known to us only by sensations that resem-
ble them, then colour, and sound, and
heat could be no qualities of body ; but
these are real qualities of body ; and, there-
fore, the qualities of botty are not known
only by means of sensations that resemble

But to proceed. What Locke had proved
with regard to the sensations we have by
smell, taste, and hearing, Bishop Berkeley
proved no less unanswerably with regard
to all our other sensations ;* to wit, that
none of them can in the least resemble the
qualities of a lifeless and insentient being,
such as matter is conceived to be. Mr
Hume hath confirmed this by his authority
and reasoning. This opinion surely looks
with a very malign aspect upon the old hypo-
thesis ; yet that hypothesis hath still been
retained, and conjoined with it. And what
a brood of monsters hath this produced !

The first-born of this union, and, per-
haps, the most harmless, was, That the
secondary qualities of body were mere sens-
ations of the mind. To pass by Male-
branche's notion of seeing all things in the
ideas of the divine mind,-|- as a foreigner,
never naturalized in this island ; the next
was Berke'ey's system, That extension,
and figure, and hardness, and motion — that
land, and sea, and houses, and our own
bodies, as well as those of our wives, and
children, and friends — are nothing but ideas
of the mind : and that there is nothing
existing in nature, but minds and ideas.

The progeny that followed, is still more
frightful ; so that it is surprising, that one
could be found who had the courage to act
the midwife, to rear it up, and to usher it
into the world. No causes nor effects ; no
substances, material or spiritual ; no evi-
dence, even in mathematical demonstration ;
no liberty nor active power ; nothing exist-
ing in nature, but impressions and ideas
following each other, without time, place,
or subject. Surely no age ever produced
such a system of opinions, justly deduced
with great acuteness, perspicuity, and ele-
gance, from a principle universally received.

* Bayle, before Berkeley, shewed that the reason.
ing of Malebranche against the external reality of
the secondary qualities, when carried to its legitimate
issue, subverted also that of the primary.— H,

t Malebranche, it should bo observed, distin-
guished more precisely than Des Cartes, or any pre-
vious philosopher, primary from secondary quali-
ties; and perception {idee) from sensation (senti-
ment.") He regarded the sensation of the secondary
qualities as the mere subjective feeling which the
human mind had of its own affections ; but I he per-
ception of the primary he considered as an objective
rntuition it obtained of these, as represented in the
divine mind — H.

The hypothesis we have mentioned is the
father of them all. The dissimilitude of
our sensations and feelings to external things,
is the innocent mother of most of them.

As it happens sometimes, in an arith-
metical operation, that two errors balance
one another, so that the conclusion is little
or nothing affected by them ; but when one
of them is corrected, and the other left, we
are led farther from the truth than by both
together : so it seems to have happened in
the Peripatetic philosophy of sensation,
compared with the modern. The Peripa-
tetics adopted two errors ; but the last
served as a corrective to the first, and ren-
dered it mild and gentle ; so that their
system had no tendency to scepticism.
The moderns have retained the first of those
errors, but have gradually detected and
corrected the last. The consequence hath
been, that the light we have struck out hath
created darkness, and scepticism hath ad-
vanced hand in hand with knowledge,
spreading its melancholy gloom, first over
the material world, and at last over the
whole face of nature. Such a phaenomeno n
as this, is apt to stagger even the lovers of
light and knowledge, while its cause is latent ;
but, when that is detected, it may give hopes
that this darkness shall not be everlasting,
but that it shall be succeeded by a more
permanent light.

Section VII.


Although there is no resemblance, nnr,
as far as we know, any necessary connec-
tion, between that quality in a body which
we call its colour, and the appearance which
that colour makes to the eye, it is quite
otherwise with regard to its figure and mag-
nitude. There is certainly a resemblance,
and a necessary connection, between the
visible figure and magnitude of a body, and
its real figure and magnitude ; no man can
give a reason why a scarlet colour affects
the eye in the manner it does ; no man can
be sure that it affects his eye in the same
manner as it affects the eye of another,
and that it has the same appearance to him
as it has to another man ; — but we can assign
a reason why a circle placed obliquely to
the eye, should appear in the form of an
ellipse. The visible figure, magnitude, and
position may, by mathematical reasoning,
be deduced from the real ; and it may be
demonstrated, that every eye that sees dis-
tinctly and perfectly, must, in the same
situation, see it under this form, and no
other. Nay, we may venture to affirm,
that a man born blind, if he were instructed
in mathematics would be able to determine



tlie visible figure of a body, when its real
figure, distance, and position, are given.
Dr Saunderson understood the projection
of the sphere, and perspective. Now, I
require no more knowledge in a blind man,
in order to his being able to determine the
visible fig re of bodies, than that he can
project the outline of a given body, upon
the surface of a hollow sphere, whose centre
is in the eye. This projection is the visible
figure he wants : for it is the same figure
with that which is projected upon the
tunica retina in vision.

A blind man can conceive lines drawn
from every point of the object to the centre
of the eye, making angles. He can con-
ceive that the length of the object will
appear greater or less, in proportion to the
angle which it subtends at the eye; and
that, in like manner, the breadth, and in
general the distance, of any one point of the
object from any other point, will appear
greater or less, in proportion to the angles
which those- distances subtend. He can
easily be made to conceive, that the visible
appearance has no thickness, any more than
a projection of the sphere, or a perspective
draught. He may be informed, that the
eye, until it is aided by experience, does
not represent one object as nearer or more
remote than another. Indeed, he would
probably conjecture this of himself, and be
apt to think that the rays of light must
make the same impression upon the eye,
whether they come from a greater or a less

These are all the principles which we
suppose our blind mathematician to have ;
and these he may certainly acquire by in-
formation and reflection. It is no less
certain, that, from these principles, having
given the real figure and magnitude of a
body, and its position and distance with
regard to the eye, he can find out its visible
figure and magnitude. He can demonstrate
in general, from these principles, that the
visible figure of all bodies will be the same
with that of their projection upon the sur-
face of a hollow sphere, when the eye is
placed in the centre. And he can demon-
strate that their visible magnitude will be
greater or less, according as their projec-
tion occupies a greater or less part of the
surface of this sphere.

To set this matter in another light, let
us distinguish betwixt the position of objects
with regard to the eye, and their distance
from it. Objects that lie in the same right
line drawn from the centre of the eye, have
the same position, however different their
distances from the eye may be : but objects
which lie in different right lines drawn from
the eye's centre, have a different position ;
i na this difference of position is greater or
less i.i proportion to the angle made at the

eye by the right lines mentioned. Having
thus defined what we mean by the position
of objects with regard to the eye, it is evi-
dent that, as the real figure of a body con-
sists in the situation of its several parts
with regard to one another, so its visible
figure consists in the position of its several
parts with regard to the eye ; and, as ho
that hath a distinct conception of the situ-
ation of the parts of the body with regard
to one another, must have a distinct con-
ception of its real figure ; so he that con-
ceives distinctly the position of its several
parts with regard to the eye, must have a
distinct conception of its visible figure.
Now, there is nothing, surely, to hinder a
blind man from conceiving- the position of
the several parts of a body with regard to
the eye, any more than from conceiving
their situation with regard to one another ;
and, therefore, I conclude, that a blind man
may attain a distinct conception of the vis-
ible figure of bodies.*

Although we think the arguments that
have been offered are sufficient to prove
that a blind man may conceive the visible
extension and figure of bodies ; yet, in order
to remove some prejudicesagainstthis truth,
it will be of use to compare the notion which
a blind mathematician might form to him-
self of visible figure, with that which is pre-
sented to the eye in vision, and to observe
wherein they differ.

First, Visible figure is never presented to
the eye but in conjunction with colour :
and, although there be no connection be-
tween them from the nature of the things,
yet, having so invariably kept company to-
gether, we are hardly able to disjoin them
even in our imagination. \ What mightily
increases this difficulty is, that we have
never been accustomed to make visible
figure an object of thought. It is only used
as a sign, and, having served this purpose,
passes away, without leaving a trace behind.
The drawer or designer, whose business it
is to hunt this fugitive form, and to take a
copy of it, finds how difficult his task is,
after many years' labour and practice.
Happy ! if at last he can acquire the art of
arresting it in his imagination, until he can
delineate it. For then it is evident that
he must be able to draw as accurately from
the life as from a copy. But how few
of the professed masters of designing are
ever able to arrive at this degree of perfec-
tion ! It is no wonder, then, that we should
find so great difficulty in conceiving this
form apart from its constant associate,

* The most accurate observations of the blind
from birth evince, however, that their conceptions
of figure are extremely limited. — H.

t In other words, that unextended colour can be
perceived — can be imagined. Of this paradox (wh ch
is also adopted by Mr Stewart) in the sequel — H.



when it is so difficult to conceive it at ail-
But our blind man's notion of visible
figure will not be associated with colour, of
which he hath no conception, but it will,
perhaps, be associated with hardness or
smoothness, with which he is acquainted by
touch. These different associations are apt
to impose upon us, and to make things
seem different, which, in reality, are the

Secondly, The blind man forms the no-
tion of visible figure to himself, by thought,
and by mathematical reasoning from prin-
ciples ; whereas, the man that sees, has it
presented to his eye at once, without any
labour, without any reasoning, by a kind of
inspiration. A man may form to himself
the notion of a parabola, or a cycloid, from
the mathematical definition of those figures,
although he had never seen them drawn or
delineated. Another, who knows nothing
of the mathematical definition of the figures,
may see them delineated on paper, or feel
them cut out in wood. Each may have a
distinct conception of the figures, one by
mathematical reasoning, the other by sense.
Now, the blind man forms his notion of
visible figure in the same manner as the
first of these formed his notion of a para-
bola or a cycloid, which he never saw.

Thirdly, Visible figure leads the man
that sees, directly to the conception of the
real figure, of which it is a sign. But the
blind man's thoughts move in a contrary
direction. For he must first know the real
figure, distance, and situation of the body,
and from thence he slowly traces out the
visible figure by mathematical reasoning.
Nor does his nature lead him to conceive
this visible figure as a sign ; it is a creature
of his own reason and imagination.

Section VIII.


It may be asked, What kind of thing is
this visible figure ? Is it a Sensation, or
an Idea ? If it is an idea, from what sensa-
tion is it copied ? These questions may
seem trivial or impertinent to one who does
not know that there is a tribunal of inqui-
sition erected by certain modern philoso-
phers, before which everything in nature
must answer. The articles of inquisition
are few indeed, but very dreadful in their
consequences. They are only these : Is
the prisoner an Impression or an Idea ?
If an idea, from what impression copied ?
Now, if it appears that the prisoner is
neither an impression, nor an idea copied
from some impression, immediately, with-
out being allowed to offer anything in

arrest of judgment, he is sentenced to pass
out of existence, and to be, in all time to
come, an empty unmeaning sound, or the
ghost of a departed entity. *

Before this dreadful tribunal, cause and
effect, time and place, matter and spirit,
have been tried and cast : how then shall
such a poor flimsy form as visible figure
stand before it ? It must even plead guilty,
and confess that it is neither an impression
nor an idea. For, alas ! it is notorious,
that it is extended in length and breadth ;
it may be long or short, broad or narrow,
triangular, quadrangular, or circular ; and,
therefore, unless ideas and impressions are
extended and figured, it cannot belong to
that category.

If it should still be asked, To what cate-
gory of beings does visible figure then be-
long ? I can only, in answer, give some
tokens, by which those who are better ac-
quainted with the categories, may chance
to find its place- It is, as we have said,
the position of the several parts of a figured
body with regard to the eye. The dif-
ferent positions of the several parts of the
body with regard to the eye, \vhen put to-
gether, make a real figure, which is truly
extended in length and breadth, and which
represents a figure that is extended in
length, breadth, and thickness. In like
manner, a projection of the sphere is a real
figure, and hath length and breadth, but
represents the sphere, which hath three
dimensions. A projection of the sphere,
or -a, perspective view of a palace, is a re-
presentative in the very same sense as visi-
ble figure is ; and wherever they have their
lodgings in the categories, this will be found
to dwell next door to them.

It may farther be asked, Whether there
be any sensation proper to visible figure, by
which it is suggested in vision ? — or by
what means it is presented to the mind ?+

» « Where Entity and Quiddity,

The ghosts of defunct bodies, fly."

Hi dibras.— H.
f " In Dr Reid's ' Inquiry,*" (says Mr Stewart, in
one of his last works, in reference to the following
reasoning,) " he Has introduced a discussion con-
cerning the perception of visible figure, which ha<
puzzled me since the first time (more than forty years
ago) that I read his'work. The discussion relates te
thequestinn, ■ Whethertherebeanysensation propel
to visible figure, by which it is suggested in vision?'
The result ot the argument is, that * our eye might
have been so framed as to suggest the figure of the
object, without suggesting colour or any other quali-
ty ; and, ot consequence, there seems to be no sensa-
tion appropriated to visible figure ; thisijuality being
suggested immediately by the material impression
upon the organ, of which impression we are not
conscious'— lnquiiy, &c chap. vi. $ 8. To my
apprehension, nothing can appear more manifest
than this, that, if there had been no variety in our
sensations of colour, and, still more, if we had had no

Online LibraryThomas ReidThe works of Thomas Reid, D.D.; now fully collected, with selections from his umpublished letters → online text (page 33 of 114)