Thomas Reid.

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

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others are easily learned in consequence of
it. The distance of the object, joined with
its visible magnitude, is a sign of its real
magnitude : and the distance of the several
parts of an object, joined with its visible
figure, becomes a sign of its real figure.
Thus, when I look at a globe which stands
before me, by the original powers of sight
I perceive only something of a circular
form, variously coloured. The visible figure
hath no distance from the eye, no convexity,
nor hath it three dimensions ; even its length
and breadth are incapable of being mea-
sured by inches, feet, or other linear mea-
sures. But, when I have learned to per-
ceive the distance of every part of this
object from the eye, this perception gives it
convexity, and a spherical figure ; and adds
a third dimension to that which had but
two before. The distance of the whole
object makes me likewise perceive the real
magnitude ; for, being accustomed to ob-
serve how an inch or a foot of length affects
the eye at that distance, I plainly perceive
by my eye the linear dimensions of the
globe, and can affirm with certainty that
its diameter is about one foot and three

It was shewn in the 7th section of
this chapter that the visible figure of a
body may, by mathematical reasoning, be
inferred from its real figure, distance, and
position, with regard to the eye: in like
manner, we may, by mathematical reason-
ing, from the visible figure, together with
the distance of the several parts of it from
the eye, infer the real figure and position.
But this last inference is not commonly
made by mathematical reasoning, nor, in-
deed, by reasoning of any kind, but by cus-

The original appearance which the colour
of an object makes to the eye, is a sensa-
tion for which we. have no name, because
it is used merely as a sign, and is never made
an object of attention in common life : but
this appearance, according to the different
circumstances, signifies various things. If
a piece of cloth, of one uniform colour, is
laid so that part of it is in the sun, and part
in the shade, the appearance of colour, in



these different parts, is very different : yet
we perceive the colour to be the same ; we
interpret the variety of appearance as a
sign of light and shade, and not as a sign
of real difference in colour. But, if the
eye could he so far deceived as not to per-
ceive the difference of light in the two
parts of the cloth, we should, in that case,
interpret the variety of appearance to signify
a variety of colour in the parts of the cloth.

Again, if we suppose a piece of cloth
placed as before, but having the shaded part
so much brighter in the colour that it gives
the same appearance to the eye as the more
enlightened part, the sameness of appear-
ance will here be interpreted to signify a
variety of colour, because we shall make
allowance for the effect of light and shade.

When the real colour of an object is
known, the appearance of it indicates, in
some circumstances, the degree of light
or shade ; in others, the colour of the cir-
cumambient bodies, whose rays are reflected
by it ; and, in other circumstances, it indi-
cates the distance or proximity of the ob-
ject — as was observed in the last section ;
and by means of these, many other things
are suggested to the mind. Thus, an un-
usual appearance in the colour of familiar
objects may be the diagnostic of a disease
in the spectator. The appearance of things
in myroom may indicate sunshine or cloudy
weather, the earth covered with snow or
blackened with rain. It hath been ob-
served, that the colour of the sky, in a
piece of painting, may indicate the country
of the painter, because the Italian sky is
really of a different colour from the Flemish.

It was already observed, that the original
and acquired perceptions which we have
by our senses, are the language of nature
to man, which, in many respects, hath a
great affinity to human languages. The
instances which we have given of acquired
perceptions, suggest this affinity — that, as,
in human languages, ambiguities are often
found, so this language of nature in our ac-
quired perceptions is not exempted from
them. .We have seen, in vision particu-
larly, that the same appearance to the eye,
may, in different circumstances, indicate
different things. Therefore, when the cir-
cumstances are unknown upon which the
interpretation of the signs depends, their
meaning must be ambiguous ; and when the
circumstances are mistaken, the meaning
of the signs must also be mistaken.

This is the case in all the phsenomena
which we call fallacies of the senses ; and
particularly in those which are called
fallacies in vision. The appearance of
things to the eye always corresponds to the
fixed laws of Nature ; therefore, if we speak
properly, there is no fallacy in the senses.
Nature always speaketh the same language,

and useth the same signs in the same cir-
cumstances ; but we sometimes mistake
the meaning of the signs, either through
ignorance of the laws of Nature, or through
ignorance of the circumstances which attend
the signs.*

To a man unacquainted with the prin-
ciples of optics, almost every experiment
that is made with the prism, with the magic
lanthorn, with the telescope, with the mi-
croscope, seems to produce some fallacy in
vision. Even the appearance of a common
mirror, to one altogether unacquainted with
the effects of it, would seem most remark-
ably fallacious. For how can a man be
more imposed upon, than in seeing that
before him which is really behind him ?
How can he be more imposed upon, than
in being made to see himself several yards
removed from himself? Yet children,
even before they can speak their mother-
tongue, learn not to be deceived by these
appearances. These, as well as all the
other surprising appearances produced by
optical glasses, are a part of the visual lan-
guage, and, to those who understand the
laws of Nature concerning light and colours,
are in nowise fallacious, but have a dis-
tinct and true meaning.

Section XXIV.


The objects of human knowledge are in-
numerable ; but the channels by which it
is conveyed to the mind are few. Among
these, the perception of external things by
our senses, and the informations which we
receive upon human testimony, are not the
least considerable ; and so remarkable is
the analogy between these two, and the
analogy between the principles of the mind
which are subservient to the one and those
which are subservient to the other, that,
without further apology, we shall consider
them together.

In the testimony of Nature given by the
senses, as well as in human testimony given
by language, things are signified to us by
signs : and in one as well as the other, the
mind, either by original principles or by
custom, passes from the sign to the concep-
tion and belief of the things signified.

We have distinguished our perceptions

• This is Ihe doctrine of Aristotle ; who holds
that the senses never deceive us in relation to their
proper objects H.

t Compare Mr Stewart's " Elements," vol. I.,
ch. ii., 5 *, p. 247. Second edition. Campbell
"On Miracles," Part 1,5 1. Smith's •• Theory ol
Moral Sentiment," vol II., p. 383. Sixth edition —



into original and acquired ; and language,
into natural and artificial. Between
acquired perception and artificial language,
there is a great analogy ; but still a greater
between original perception and natural

The signs in original perception are sens-
ations, of which Nature hath given us a great
variety, suited to the variety of the things
signified by them. Nature hath established
a real connection between the signs and the
things signified; andNature hath also taught
us the interpretation of the signs — so that,
previous to experience, the sign suggests
the thing signified, and create the belief of

The signs in natural language are features
of the face, gestures of the body, and modu-
lations of the voice ; the variety of which is
suited to the variety of the things signified
by them. Nature hath established a, real
connection between these signs, and the
thoughts and dispositions of the mind which
are signified by them ; and Nature hath
taught us the interpretation of these signs ;
so that, previous to experience, the signs
suggest the thing signified, and create the
belief of it.

A man in company, without doing good
or evil, without uttering an articulate sound,
may behave himself gracefully, civilly,
politely ; or, on the contrary, meanly,
rudely, and impertinently. We see the
dispositions of his mind by their natural
signs in his countenance and behaviour, in
the same manner as we perceive the figure
and other qualities of bodies by the sensa-
tions which nature hath connected with

The signs in the natural language of the
human countenance and behaviour, as well
as the signs in our original perceptions,
have the same signification in all climates
and in all nations ; and the skill of inter-
preting them is not acquired, but innate.

In acquired perception, the signs are
either sensations, or things which we per-
ceive by means of sensations. The con-
nection between the sign and the thing sig-
nified, is established by nature; and we
discover this connection by experience;
but not without the aid of our original per-
ceptions, or of those which we have already
acquired. After this connection is dis-
covered, the sign, in like manner as in
original perception, always suggests the
things signified, and creates the belief of

In artificial language, the signs are arti-
culate sounds, whose connection with the
things signified by them, is established by
the will of men; and, in learning our
mother tongue, we discover this connection
by experience ; but not without the aid of
natural language, or of what we had before

attained of artificial language. And, after
this connection is discovered, the sign, as
in natural language, always suggests the
thing signified, and creates the belief of it.

Our original perceptions are few, com-
pared with the acquired ; but, without the
former, we could not possibly attain the
latter. In like manner, natural language
is scanty, compared with artificial ; but,
without the former, we could not possibly
attain the latter.

Our original perceptions, as well as the
natural language of human features and
gestures, must be resolved into particular
principles of the human constitution. Thus,
it is by one particular principle of our con-
stitution that certain features express anger ;
and, by another particular principle, that
certain features express benevolence. It is,
in like manner, by one particular principle
of our constitution that a certain sensation
signifies hardness in the body which I
handle; and it is by another particular
principle that a certain sensation signifies
motion in that body.

But our acquired perceptions, and the
information we receive by means of arti-
ficial language, must be resolved into gene-
ral principles of the human constitution.
When a painter perceives that this picture
is the work of Raphael, that the work of
Titian ; a jeweller, that this is a true dia-
mond, that a counterfeit ; a sailor, that this
is a ship of five hundred ton, that of four
hundred; these different acquired percep-
tions are produced by the same general
principles of the human mind, which have
a different operation in the same person
according as they are variously applied, and
in different persons according to the divers-
ity of their education and manner of life.
In like manner, when certain articulate
sounds convey to my mind the knowledge of
the battle of Pharsalia, and others, the
knowledge of the battle of Poltowa — when a
Frenchman and an Englishman receive the
same information by different articulate
sounds — the signs used in these different
cases, produce the knowledge and belief of
the things signified, by means of the same
general principles of the human constitu-

Now, if we compare the general prin-
ciples of' our constitution, which fit us for
receiving information from our fellow-crea-
tures by language, with the general prin-
ciples which fit us for acquiring the per-
ception of things by our senses, we shall
find them to be very similar in their nature
and manner of operation.

When we begin to learn our mother-
tongue, we perceive, by the help of natural
language, that they who speak to us use
certain sounds to express certain things ;
we imitate the same sounds when we would
o 2



express the same things ; and find that we
are understood.

But here a difficulty occurs which merits
our attention, because the solution of it
leads to some original principles of the hu-
man mind, which are of great importance,
and of very extensive influence. We know
by experience that men have used such
words to express such things ; but all ex-
perience is of the past, and can, of itself,
give no notion or belief of what is future.
How come we, then, to believe, and to rely
upon it with assurance, that men, who have
it in their power to do otherwise, will con-
tinue to use the same words when they
think the same things ? Whence comes
this knowledge and belief — this foresight, we
ought rather to call it — of the future and
voluntary actions of our fellow-creatures ?
Have they promised that they will never
impose upon us by equivocation or falsehood ?
No, they have not. And, if they had, this
would not solve the difficulty; for such
promise must be expressed by words or by
other signs ; and, before we can rely upon
it, we must be assured that they put the
usual meaning upon the signs which express
that promise. No man of common sense
ever thought of taking a man's own word
for his honesty ; and it is evident that we
take his veracity for granted when we lay
any stress upon his word or promise. I
might add, that this reliance upon the de-
clarations and testimony of men is found
in children long before they know what a
promise is.

There is, therefore, in the human mind
an early anticipation, neither derived from
experience, nor from reason, nor from any
compact or promise, that our fellow-crea-
tures will use the same signs in language,
when they have the same sentiments.

This is, in reality, a kind of prescience
of human actions ; and it seems to me to
be an original principle of the human con-
stitution, without which we should be in-
capable of language, and consequently in-
capable of instruction.

The wise and beneficent Author of Na-
ture, who intended that we should be social
creatures, and that we should receive the
greatest and most important part of our
knowledge by the information of others,
hath, for these purposes, implanted in our
natures two principles that tally with each

The first of these principles is, a pro-
pensity to speak truth, and to use the signs
of language so as to convey our real sen-
timents. This principle has a powerful
operation, even in the greatest liars ; for
where they lie once, they speak truth a
hundred times. Truth is.always uppermost,
and is the natural issue of the mind. It
requires no art or training, no inducement

or temptation, but only that we yield to n
natural impulse. Lying, on the contrary,
is doing violence to our nature ; and is
never practised, even by the worst men,
without some temptation. Speaking truth
is like using our natural food, which we
would do from appetite, although it an-
swered no end ; but lying is like taking
physic, which is nauseous to the taste, and
which no man takes but for some end which
he cannot otherwise attain.

If it should be objected, That men may
be influenced by moral or political consider-
ations to speak truth, and, therefore, that
their doing so is no proof of such an origi-
nal principle as we have mentioned — I
answer, First, That moral or political con-
siderations can have no influence until we
arrive at years of understanding and reflec-
tion ; and it is certain, from experience,
that children keep to truth invariably, be-
fore they are capable of being influenced by
such considerations. Secondly, When we
are influenced by moral or political con-
siderations, we must be conscious of that
influence, and capable of perceiving it upon
reflection. Now, when I reflect upon my
actions most attentively, I am not conscious
that, in speaking truth, I am influenced on
ordinary occasions by any motive, moral or
political. I find that truth is always at the
door of my lips, and goes forth sponta-
neously, if not held back. It requires
neither good nor bad intention to bring it
forth, but only that I be artless andunde-
signing. There may indeed be temptations
to falsehood, which would be too strong for
the natural principle of veracity, unaided
by principles of honour or virtue; but
where there is no such temptation, we speak
truth by instinct — and this instinct is the
principle I have been explaining.

By this instinct, a real connection is
formed between our words and our thoughts,
and thereby the former become fit to be
signs of the latter, which they could not
otherwise be. And although this connec-
tion is broken in every Instance of lying
and equivocation, yet these instances being
comparatively few, the authority of human
testimony is only weakened by them, but
not destroyed.

Another original principle implanted in
us by the Supreme Being, is a disposition
to confide in the veracity of others, and to
believe what they tell us. This is the
counterpart to the former ; and, as that
maybe called the principle of veracity, we
shall, for want of a more proper name, call
this the prinoiple of credulity. It is un-
limited in children, until they meet with
instances of deceit and falsehood; and it
retains a very considerable degree of strength
through life.

If Nature had left the mind of the speaker



in aquitibrio, without any inclination to
the side of truth more than to that of false-
hood, children would lie as often as they
speak truth, until reason was so far ripened
as to suggest the imprudence of lying, or
conscience, as to suggest its immorality.
And if Nature had left the mind of the
hearer in aquilibrio, without any inclina-
tion to the side of belief more than to that
of disbelief, we should take no man's word
until we had positive evidence that he
spoke truth. His testimony would, in this
case, have no more authority than his
dreams ; which may be true or false, but
no man is disposed to believe them, on this
account, that they were dreamed. It is
evident that, in the matter of testimony,
the balance of human judgment is by nature
inclined to the side of belief ; and turns to
that side of itself, when there is nothing
put into the opposite scale. If it was not
so, no proposition that is uttered in dis-
course would be believed, until it was
examined and tried by reason ; and most
men would be unable to find reasons for
believing the thousandth part of what is
told them. Such distrust and incredulity
would deprive us of the greatest benefits of
society, and place us in a worse condition
than that of savages.

Children, on this supposition, would be
absolutely incredulous, and, therefore, ab-
solutely incapable of instruction : those who
had little knowledge of human life, and of
the manners and characters of men, would
be in the next degree incredulous : and the
most credulous men would be those of
greatest experience, and of the deepest
penetration ; because, in many cases, they
would be able to find good reasons for
believing testimony, which the weak and
the ignorant could not discover.

In a word, if credulity were the effect of
reasoning and experience, it must grow up
and gather strength, in the same proportion
as reason and experience do. But, if it is
the gift of Nature, it will be strongest in
childhood, and limited and restrained by
experience ; and the most superficial view
of human life shews, that the last is really
the case, and not the first. *

It is the intention of Nature, that we
should be carried in arms before we are able
to walk upon our legs ; and it is likewise
the intention of Nature, that our belief
should be guided by the authority and rea-
son of others, before it can be guided by
our own reason. The weakness of the in-
fant, and the natural affection of the mother,
plainly indicate the former ; and the natural
credulity of youth, and authority of age, as
plainly indicate the latter. The infant, by

• See,contra, Priestley's" Examination," p. 86.
".Brown's Lect." lect. Ixxxiv.— H.

proper nursing and care, acquires strength
to walk without support. Reason hath
likewise her infancy, when she must be
carried in arms : then she leans entirely
upon authority, by natural instinct, as if
she was conscious of her own weakness ;
and, without this support, she becomes ver-
tiginous. When brought to maturity by
proper culture, she begins to feel her own
strength, and leans less upon the reason of
others ; she learns to suspect testimony in
some cases, and to disbelieve it in others ;
and sets bounds to that authority to which
she was at first entirely subject. But still,
to the end of life, she finds a necessity ot
borrowing light from testimony, where she
has none within herself, and of leaning,
in some degree, upon the reason of others,
where she is conscious of her own imbe-

And as, in many instances, Reason, even
in her maturity, borrows aid from testi-
mony, so in others she mutually gives aid
to it, and strengthens its authority. For,
as we find good reason to reject testimony in
some cases, so in others we find good reason
to rely upon it with perfect security, in our
most important concerns. The character,
the number, and the disinterestedness of
witnesses, the impossibility of collusion, and
the incredibility of their concurring in their
testimony without collusion, may give an
irresistible strength to testimony, compared
to which its native and intrinsic authority
is very inconsiderable.

Having now considered the general prin-
ciples of the human mind which fit us for
receiving information from our fellow-crea-
tures, by the means of language, let us next
consider the general principles which fit us
for receiving the information of Nature by
our acquired perceptions.

It is undeniable, and indeed is acknow-
ledged by all, that when we have found two
things to have been constantly conjoined in
the course of nature, the appearance of one
of them is immediately followed by the con-
ception and belief of the other. The for-
mer becomes a natural sign of the latter;
and the knowledge of their constant conjunc-
tion in time past, whether got by experience
or otherwise, is sufficient to make us rely
with assurance upon the continuance of that

This process of the human mind is so
familiar that we never think of inquiring
into the principles upon which it is founded.
We are apt to conceive it as a self-evident
truth, that what is to come must be similar
to what is past. Thus, if a certain degree
of cold freezes water to-day, and has been
known to do so in all time past, we have
no doubt but the same degree of cold will
freeze water to-morrow, or a year hence.
That this is a truth which all men believe aa



soon as they understand it, I readily admit ;
but the question is, Whence does its evi-
dence arise ? Not from comparing the
Ideas, surely. -For, when I compare the
idea of cold with that of water hardened
into a transparent solid body, I can per-
ceive no connection between them : no man
can shew the one to be the necessary effect
of the other ; no man can give a shadow of
reason why Nature hath conjoined them.
But do we not learn their conjunction from
experience ? True ; experience informs
us that they have been conjoined in time
past ; but no man ever had any experience
of what is future : and this is the very
question to be resolved, How we come to
believe that the future will be like the
past ? Hath the Author of nature pro-
mised this ? Or were we admitted to his
council, when he established the present
laws of nature, and determined the time
v>of their continuance. No, surely. In-
deed, if we believe that there is a wise and
good Author of nature, we may see a good
reason why he should continue the same

Online LibraryThomas ReidThe works of Thomas Reid, D.D.; now fully collected, with selections from his umpublished letters → online text (page 45 of 114)