Thomas Reid.

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

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a train of thought or reasoning without the
use of language. Words are the signs of
our thoughts ; and the sign is so associated
with the thing signified, that the last can
hardly present itself to the imagination,
without drawing the other along with it.

A man who would compose in any lan-
guage must think in that language. If he
thinks in one language what he would ex-
press in another, he thereby doubles his
labour ; and, after all, his expressions will
have more the air of a translation than of
an original.

This shews that our thoughts take their
colour in some degree from the language
we use ; and that, although language ought
always to be subservient to thought, yet
thought must be, at some times and in some
degree, subservient to language.

As a servant that is extremely useful and
necessary to his master, by degrees acquires
an authority over him, so that the master
must often yield to the servant, such is the
case with regard to language. Its inten-
tion is to be a servant to the understanding ;
but it is so useful and so necessary that we
cannot avoid being sometimes led by it when
it ought to follow. We cannot shake off
this impediment — we must drag it along
with us ; and, therefore, must direct our
course, and regulate our pace, as it permits.
Language must have many imperfections
when applied to philosophy, because it was
not made for that use. In the early periods
of society, rude and ignorant men use cer-
tain forms of speech, to express their wants,
their desires, and their transactions with
one another. Their language can reach no
farther than their speculations and notions ;
and, if their notions be vague and ill-defined,
the words by which they express them must
be so likewise.

It was. a grand and noble project of
Bishop Wilkins* to invent a philosophical
language, which should be free from the
imperfections of vulgar languages. Whether
this attempt will ever succeed, so far as to
be generally useful, I shall not pretend to
determine. The great pains taken by that
excellent man in this design have hitherto
produced no effect. Very few have ever
entered minutely into his views ; far less
have his philosophical language and his real
character been brought into use. [668]

He founds his philosophical language and
real character upon a systematical division
and subdivision of all the things which may
be expressed by language ; and, instead of
the ancient division into ten categories, has
made forty categories, or summa genera.
But whether this division, though made by
a very comprehensive mind, will always suit
the various systems that may be introduced,
and all the real improvements that may be
made in human knowledge, may be doubted.
The difficulty is still greater in the sub-
divisions ; so that it is to be feared that
this noble attempt- of a great genius will
prove abortive, until philosophers have the
same opinions and the same systems in the
various branches of human knowledge.

There is more reason to hope that the
languages used by philosophers may be
gradually improved in copiousness and in
distinctness; and that improvements in
knowledge and in language may go hand in
hand and facilitate each other. But I fear
the imperfections of language can never be
perfectly remedied while our knowledge us

However this may be, it is evident that
the imperfections of language, and much
more the abuse of it, are the occasion of
many errors ; and that in many disputes
which have engaged learned men, the differ-
ence has been partly, and in some wholly,
about the meaning of words.

Mr Locke found it necessary to employ a
fourth part of his " Essay on Human Un-
derstanding" about words, their various
kinds, their imperfection and abuse, and
the remedies of both ; and has made many
observations upon these subj ects well worthy
of attentive perusal. [669]

D. The fourth class of prejudices are the
idola theatri, by which are meant prejudice*
arising from the systems or sects in which
we have been trained, or which we have

A false system once fixed in the mind,
becomes, as it were, the medium - through
which we see objects : they receive a tinc-
ture from it, and appear of another colour
than when seen by a pure light.

Upon the same subject, a Platonist, 3

* See above, p. 403, note.— H.




Peripatetic, and an Epicurean, will think
differently, not only in matters connected
with his peculiar tenets, but even in things
remote from them.

A judicious history of the different sects
of philosophers, and the different methods of
philosophising, which have obtained among
mankind, would be of no small use to direct
men in the search of truth. In such a
history, what would be of the greatest mo-
ment is not so much a minute detail of the
dogmata of each sect, as a just delineation
of the spirit of the sect, and of that point
of view in which things appeared to its
founder. This was perfectly understood,
■and, as far as concerns the theories of mo-
rals, is executed with great judgment and
candour by Dr Smith in his theory of moral

As there are certaiD temperaments of the
body that dispose a man more to one class
of diseases than to another, and, on the

other hand, diseases of that kind, when they
happen by accident, are apt to induce the
temperament that is suited to them — there
is something analogous to this in the dis-
eases of the understanding. [670]

A certain complexion of understanding
may dispose a man to one system of opinions
more than to another ; and, on the other
hand, a system of opinions, fixed in the mind
by education or otherwise, gives that com-
plexion to the understanding which is suited
to them.

It were to be wished, that the different
systems that have prevailed could be classed
according to their spirit, as well as named
from their founders. Lord Bacon has dis-
tinguished false philosophy into the sophis-
tical, the empirical, and the superstitious,
and has made judicious observations upon
each of these kinds. But I apprehend this sub-
ject deserves to be treated more fully by such
a hand, if such a hand can be found. [671]





The power of reasoning is very nearly
allied to that of judging ; and it is of little
consequence in the- common affairs of life
to distinguish them nicely. On this account,
the same name is often given to both. We
include both under the name of reason."
The assent we give to a proposition is called
judgment, whether the proposition be self-
evident, or derive its evidence by reasoning
from other propositions.

Yet there is a distinction between rea-
soning and judging. Reasoning is the pro-
cess by which we pass from one judgment
to another, which is the consequence of it.
Accordingly our judgments are distinguished
into intuitive, which are not grounded upon
any preceding judgment, and discursive,
which are deduced from some preceding
judgment by reasoning.

In all reasoning, therefore, there must be
a proposition inferred, and one or more from
which it is inferred. And this power of
inferring, or drawing a conclusion, is only
another name for reasoning ; the proposi-
tion inferred being called the conclusion,

* See Stewart's " Elements," ii. )>. 12— H.

and the proposition or propositions from
which it is inferred, the premises. [672]

Reasoning may consist of many steps ;
the first conclusion being a premise to a
second, that to a third, and so on, till we
come to the last conclusion. A process
consisting of many steps of this kind, is so
easily distinguished from judgment, that it
is never called by that name. But when
there is only a single step to the conclusion,
the distinction is less obvious, and the pro-
cess is sometimes called judgment, some-
times reasoning.

It is not strange that, in common dis-
course, judgment and reasoning should not
be very nicely distinguished, since they are
in some cases confounded even by logicians.
We are taught in logic, that judgment is
expressed by one proposition, but that rea-
soning requires two or three. But so
various are the modes of speech, that what
in one mode is expressed by two or three
propositions, may, in another mode, be ex-
pressed by one. Thus I may say, God is
pood ; therefore good men shall be happy.
Phis is reasoning, of that kind which logi-
cians call an enthymeme, consisting of an
antecedent proposition, and a conclusion
drawn from it.* But this reasoning may

* The enthymeme is a mere abbreviation of expres-
sion ; in the mental process there is no ellipsis. By



[essay vil,

be expressed by one proposition, thus: —
Because God is good, good men shall be
happy. This is what they call a causal
proposition, and therefore expresses judg-
ment ; yet the enthyraeme, which is reason-
ing, expresses no more.

Reasoning, as well as judgment, must he
true or false : both are grounded upon evi-
dence which may be probable or demonstra-
tive, and both are accompanied with assent
or belief. [673]

The power of reasoning is justly accounted
one of the prerogatives of human nature ;
because by it many important truths have
been and may be discovered, which with-
out it would be beyond our reach ; yet it
seems to be only a kind of crutch to a
limited understanding. "We can conceive
an understanding, superior to human, to
which that truth appears intuitively, which
we can only discover by reasoning. For
this cause, though we must ascribe judg-
ment to the Almighty, we do not ascribe
reasoning to him, because it implies some
defect or limitation of understanding. Even
among men, to use reasoning in things that
are self-evident, is trifling ; like a man
going upon crutches when he can walk
upon his legs.

What reasoning is, can be understood
only by a man who has reasoned, and who
is capable of reflecting upon this operation
of his own mind. We can define it only by
synonymous words or phrases, such as in-
ferring, drawing a conclusion, and the like.
The very notion of reasoning, therefore, can
enter into the mind by no other channel
than that of reflecting upon the operation
of reasoning in our own minds ; and the
notions of premises and conclusion, of a
syllogism and all its constituent parts, of
an enthymeme, sorites, demonstration, pa-
ralogism, and many others, have the same

It is nature, undoubtedly, that gives us
the capacity of reasoning. When this is
wanting, no art nor education can supply it.
But this capacity may be dormant through
life, like the seed of a plant, which, for want
of heat and moisture, never vegetates. This
is probably the case of some savages.

Although the capacity be purely the gift
of nature, and probably given in very dif-
ferent degrees to different persons ; yet the
power of reasoning seems to be got by habit,
as much as the power of walking or running.
Its first exertions we are not able to recol-
lect in ourselves, or clearly to discern in
others. They are very feeble, and need to
be led by example, and supported by autho-
rity. By degrees it acquires strength,
chiefly by means of imitation and exer-
c ise. [674]

mthiimeme, Aristotle also meant something very dif-
ferent trom what is vulgarly supposed.— H.

The exercise of reasoning on various sub.
jects not only strengthens the faculty, but
furnishes the mind with a store of materials.
Every train of reasoning, which is familiar,
becomes a beaten track in the way to many
others. It removes many obstacles which
lay in our way, and smooths many roads
which we may have occasion to travel in
future disquisitions.

When men of equal natural parts apply
their reasoning power to any subject, the
man who has reasoned much on the same
or on similar subjects, has a like advantage
over him who has not, as the mechanic
who has store of tools for his work, has of
him who has his tools to make, or even to

In a train of reasoning, the evidence of
every step, where nothing is left to be sup-
plied by the reader or hearer, must be im-
mediately discernible to every man of ripe
understanding who has a distinct compre-
hension of the premises and conclusion, and
who compares them together. To be able
to comprehend, in one view, a combination
of steps of this kind, is more difficult, and
seems to require a superior natural ability.
In all, it may be much improved by habit.

But the highest talent in reasoning is the
invention of proofs ; by which, truths re-
mote from the premises are brought to light.
In all works of understanding, invention
has the highest praise 1 it requires an ex-
tensive view of what relates to the subject,
and a quickness in discerning those affinities
and relations which may be subservient tc
the purpose.

In all invention there must be some end
in view : and sagacity in finding out the
road that leads to this end, is, I think, what
we call invention. In this chiefly, as I ap-
prehend, and in clear and distinct concep-
tions, consipts that superiority of under-
standing which we call genivs. [675]

In every chain of reasoning, the evidence
of the last conclusion «an be no greater than
that of the weakest link of the cham, what-
ever may be the strength of the rest.

The most remarkable distinction of rea-
sonings is, that some are probable, others

In every step of demonstrative reason-
ing, the inference is necessary, and we per-
ceive it to be impossible that the conclusion
should not follow from the premises. In
probable reasoning, the connection between
the premises and the conclusion is not neces-
sary, nor do we perceive it to be impossible
that the first should be true while the last
is false.

Henee, demonstrative reasoning has no
degrees, nor can one demonstration be
stronger than another, though, in relation
to our faculties, one may be more easilv
comprehended than another. Every do.



monstration gives equal strength to the con-
clusion, and leaves no possibility of its being

It was, I think, the opinion of all the
ancients, that demonstrative reasoning can
be applied only to truths that are necessary,
and not to those that are contingent. In
this, I believe, they judged right. Of all
created things, the existence, the attributes,
and, consequently, the relations resulting
from those attributes, are contingent. They
depend upon the will and power of Him who
made them. These are matters of fact, and
admit not of demonstration.

The field of demonstrative reasoning,
therefore, is the various relations of things
abstract, that is, of things which we con-
ceive, without regard to their existence.
Of these, as they are conceived by the mind,
and are nothing but what they are conceived
to be, we may have a clear and adequate
comprehension. Their relations and attri-
butes are necessary and immutable. They
are the things to which the Pythagoreans
and Platonists gave the name of ideas. I
would beg leave to borrow this meaning of
the word idea from those ancient philoso-
phers, and then I must agree with them,
that ideas are the only objects about which
we can reason demonstratively. [676]

There are many even of our ideas about
which we can carry on no considerable train
of reasoning. Though they be ever so well
defined and perfectly comprehended, yet
their agreements and disagreements are few,
and these are discerned at once. We may
go a step or two in forming a conclusion
with regard to such objects, but can go no
farther. There are others, about which we
may, by a long train of demonstrative rea-
soning, arrive at conclusions very remote
and unexpected.

The reasonings I have met with that can
be called strictly demonstrative, may, I
think, be reduced to two classes. They are
either metaphysical, or they are mathe-

In metaphysical reasoning, the process is
always short. The conclusion is but a step
or two, seldom more, from the first principle
or axiom on which it is grounded, and the
different conclusions depend not one upon

It is otherwise in mathematical reason-
ing. Here the field has no limits. One
proposition leads on to another, that to a
third, and so on without end.

If it should be asked, why demonstrative
reasoning has so wide a field in mathema-
tics, while, in other abstract subjects, it is
confined within very narrow limits, I con-
ceive this is chiefly owing to the nature of
quantity, the object of mathematics.

Every quantity, as it has magnitude, and
is divisible into parts without end, so, in

respect of its magnitude, it has a certain
ratio to every quantity of the kind. The
ratios of quantities are innumerable, such
as, a half, a third, a tenth, double, triple.
[677] All the powers of number are in-
sufficient to express the variety of ratios.
For there are innumerable ratios which
cannot be perfectly expressed by numbers,
such as, the ratio of the side to the diagonal
of a square, or of the circumference of a circle
to the diameter. Of this infinite variety of
ratios, every one may be clearly conceived
and distinctly expressed, so as to be in no
danger of being mistaken for any other.

Extended quantities, such as lines, sur-
faces, solids, besides the variety of relations
they have in respect of magnitude, have no
less variety in respect of figure ; and every
mathematical figure may be accurately
defined, so as to distinguish it from all

There is nothing of this kind in other
objects of abstract reasoning. Some of
them have various degrees ; but these are
not capable of measure, nor can be said to
have an assignable ratio to others of the
kind. They are either simple, or com-
pounded of a few indivisible parts; and
therefore, if we may be allowed the expres-
sion, can touch only in few points. But
mathematical quantities being made up of
parts without number, can touch in innu-
merable points, and be compared in innu-
merable different ways.

There have been attempts made to mea-
sure the merit of actions by the ratios of
the affections and principles of action from
which they proceed. This may perhaps,
in the way of analogy, serve to illustrate
what was before known ; but I do not think
any truth can be discovered in this way.
There are, no doubt, degrees of benevolence,
self-love, and other affections ; but, when
we apply ratios to them, I apprehend we
have no distinct meaning.

Some demonstrations are called direct,
others indirect. The first kind leads directly
to the conclusion to be proved. Of the
indirect, some are called demonstrations ad
absurdum. In these, the proposition con-
tradictory to that which is to be proved is
demonstrated to be false, or to lead to an
absurdity ; whence it follows, that its con-
tradictory — that is, the proposition to be
proved — is true. This inference is grounded
upon an axiom in logic, that of two contra-
dictory propositions, if one be false, the
other must be true.* [678]

Another kind of indirect demonstration
proceeds by enumerating all the supposi-
tions that can possibly be made concerning
the proposition to be proved, and then

* This is called the principle of Excluded Middie-*
Tiz., between two contradictories — H



{essa ir vii.

demonstrating that all of them, excepting
that which is to- be proved, are false ; whence
it follows, that the excepted supposition is
true. Thus, one line is proved to be equal
to another, by proving first that it cannot be
greater, and then that it cannot be less : for
it must be either greater, or less, or equal ;
and two of these suppositions being demon-
strated to be false, the third must be true.

All these kinds of demonstration are used
in mathematics, and perhaps some others.
They have all equal strength. The direct
demonstration is preferred where it can be
had, for this reason only, as I apprehend,
because it is the shortest road to the con-
clusion. The nature of the evidence, and
its strength, is the same in all : only we
are conducted to it by different roads.



What has been said of demonstrative
reasoning, may help us to judge of an opi-
nion of Mr Locke, advanced in several places
of his Essay — to wit, " That morality is
capable of demonstration as well as mathe-

In book III., chap. 11, having observed
that mixed modes, especially thdse belong-
ing to morality, being such combinations of
ideas as the mind puts together of its own
choice, the signification of their names
may be perfectly and exactly defined, he
adds— [679]

Sect. 16. " Upon this ground it is that I
am bold to think that morality is capable of
demonstration as well as mathematics ; since
the precise real essence of the things moral
words stand for may be perfectly known,
and so the congruity or incongruity of the
things themselves be certainly discovered,
in which consists perfect knowledge. Nor
let any one object, That the names of sub-
stances are often to be made use of in mo-
rality, as well as those of modes, from
which will arise obscurity ; for, as to sub-
stances, when concerned in moral dis-
courses, their divers natures are not so
much inquired into as supposed : v. g. When
we say that man is subject to law, we mean
nothing by man but a corporeal rational
creature : what the real essence or other
qualities of that creature are, in this case,
is no way considered."

Again, in book IV., ch. iii., § 18 :— " The
idea of a Supreme Being, whose workman-
ship we are, and the idea of ourselves, being
such as are clear in us, would, I suppose,
if duly considered and pursued, afford such
foundation of our duty and rules of action
as might place morality among the sciences

capable of demonstration. The relation of
other modes may certainly be perceived, as
well as those of number and extension ; and
I cannot see why they should not be cap-
able of demonstration, if due methods were
thought on to examine or pursue their
agreement or disagreement."

He afterwards gives, as instances, two
propositions, as moral propositions of which
we may be as certain as of any in mathe-
matics ; and considers at large what may
have given the advantage to the ideas of
quantity, and made them be thought more
capable of certainty and demonstration. [680]

Again, in the 12th chapter of the same
book, § 7, 8 : — " This, I think, I may say,
that, if other ideas that are the real as well
as nominal essences of their several species
were pursued in the way familiar to mathe-
maticians, they would carry our thoughts
farther, and with greater evidence and
clearness, than possibly we are apt to ima-
gine. This gave me the confidence to
advance that conjecture which I suggest,
chap iii. — viz., That' morality is capable of
demonstration as well as mathematics."

From these passages, it appears that this
opinion was not a transient thought, but
what he had revolved in his mind on dif-
ferent occasions. He offers his reasons for
it, illustrates it by examples, and considers
at length the causes that have led men to
think mathematics more capable of demon-
stration than the principles of morals.

Some of his learned correspondeiits, par-
ticularly his friend Mr Molyneux, urged
and importuned him to compose a system
of morals according to the idea he had ad-
vanced in his Essay ; and, in his answer to
these solicitations, he only pleads other oc-
cupations, without suggesting any change of
his opinion, or any great difficulty in the
execution of what was desired.

The reason he gives for this opinion is
ingenious ; and his regard for virtue, the
highest prerogative of the human species,
made him fond of an opinion which seemed
to be favourable to virtue, and to have a
just foundation in reason.

We need not, however, be afraid that the
interest of virtue may suffer by a free and
candid examination of this question, or in-
deed of any question whatever. For the
interests of truth and of virtue can never
be found in opposition. Darkness and error
may befriend vice, but can never be favour-
able to virtue. [681]

Those philosophers who think that our
determinations in morals are not real judg-
ments — that right and wrong in human con»
duct are only certain feelings or sensations
in the person who contemplates th action
— must reject Mr Locke's opinion without

Online LibraryThomas ReidThe works of Thomas Reid, D.D.; now fully collected, with selections from his umpublished letters → online text (page 107 of 114)