Thomas Reid.

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

. (page 98 of 114)
Online LibraryThomas ReidThe works of Thomas Reid, D.D.; now fully collected, with selections from his umpublished letters → online text (page 98 of 114)
Font size
QR-code for this ebook

stitution, we rely with assurance upon their
testimony, without seeking a reason for
doing so. This assurance, Mr Locke ac-
knowledges, deserves the name of know-
ledge. But those external things are not
ideas, nor are their attributes and relations
the agreements and disagreements of ideas,
but the agreements and disagreements of
things which are not ideas. [551]

To reconcile this to the theory of ideas,
Mr Locke says, That it is the aotual receiv-
ing of ideas from without that gives us notice
of the existence of those external things.

This, if understood literally, would lead
us back to the doctrine of Aristotle, that
our ideas or species come from without
from the external objects, and are the image
or form of those objects. But Mr Locke,
I believe, meant no more by it, but that
our ideas of sense must have a cause, and
that we are not the cause of them our-

[549-55] 1



Bishop Berkeley acknowledges all this,
and shews very clearly that it does not
afford the least shallow of reason for the
belief of any material object — nay, that
there can be nothing external that has any
resemblance to our ideas but the ideas of
other minds.

It is evident, therefore, that the agree-
ments and disagreements of ideas can give
us no knowledge of the existence of any
material thing. If any knowledge can be
attained of things which are not ideas, that
knowledge is a perception of agreements
and disagreements ; not of ideas, but of
things that are not ideas.

As to the existence of a deity, though
Mr Locke was aware that Des Cartes, and
many after him, had attempted to prove it
merely from the agreements and disagree-
ments of ideas ; yet " he thought it an
ill way of establishing that truth, and si-
lencing Atheists, to lay the whole stress of so
important a point upon that sole founda-
tion." And, therefore, he proves this
point, with great strength and solidity, from
our own existence, and the existence of the
sensible parts of the universe. [552] By
memory, Mr Locke says, we have the
knowledge of the past existence of several
things. But all conception of past exist-
ence, as well as of external existence, is
irreconcileable to the theory of ideas ; be-
cause it supposes that there may be imme-
diate objects of thought, which are not ideas
presently existing in the mind.

I conclude, therefore, that, if we have
any knowledge of our own existence, or of
the existence of what we see about us, or of
the existence of a Supreme Being, or if
we have any knowledge of things past by
memory, that knowledge cannot consist in
perceiving the agreements and disagree-
ments of ideas.

This conclusion, indeed, is evident of
itself. For, if knowledge consists solely in
the perception of the agreement or disagree-
ment of ideas, there can be no knowledge of
any proposition, which does not express
some agreement or disagreement of ideas ;
consequently, there can be no knowledge of
any proposition, which expresses either the
existence, or the attributes or relations of
things, which are not ideas. If, therefore,
the theory of ideas be true, there can be no
knowledge of anything but of ideas. And,
on the other hand, if we have any know-
ledge of anything besides ideas, that theory
must be false.

There can be no knowledge, no judgment
or opinion about things which are not im-
mediate objects of thought. This I take to
be self-evident. If, therefore, ideas be the
only immediate objects of thought, they
must be the only things in nature of which
we can have any knowledge, and about

which we can have any judgment or

This necessary consequence of the com-
mon doctrine of ideas Mr Hume saw, and
has made evident in his " Treatise of
Human Nature ;" but the use he made of
it was not to overturn the theory with which
it is necessarily connected, but to overturn
all knowledge, and to leave no ground to
believe anything whatsoever. If Mr Locke
had seen this consequence, there is reason
to think that he would have made another
use of it. [553]

That a man of Mr Locke's judgment and
penetration did not perceive a consequence
so evident, seems indeed very strange ; and
I know no other account that can be given of
it but this — that the ambiguity of the word
idea has misled him in this, as in several
other instances. Having at first defined
ideas to be whatsoever is the object of the
understanding when we think, he takes it
very often in that unlimited sense ; and so
everything that can be an object of thought
is an idea. At other times, he uses the
word to signify certain representative images
of things in the mind, which philosophers
have supposed to be immediate objects of
. thought. At other times, things conceived
abstractly, without regard to their exist-
ence, are called ideas. Philosophy is much
indebted to Mr Locke for his observations
on the abuse of words. It is pity he did
not apply these observations to the word
idea, the ambiguity and abuse of which has
very much hurt his excellent Essay.

There are some other opinions of philo-
sophers concerning judgment, of which I
think it unnecessary to say much.

Mr Hume sometimes adopts Mr Locke's
opinion, that it is the perception of the
agreement or disagreement of our ideas ;
sometimes he maintains that judgment and
reasoning resolve themselves into concep-
tion, and are nothing but particular ways
of conceiving objects ; and he says, that an
opinion or belief may most accurately be
defined, a lively idea related to or associated
with a present impression. — Treatise of Hu-
man Nature, vol. I. page 172-

I have endeavoured before, in the first
chapterof this Essay, to shew that judgment
is an operation of mind specifically distinct
from the bare conception of an object. Ihave
also considered his notion of belief, in treating
of the theories concerning memory. [554]

Dr Hartley says — " That assent and dis-
sent must come under the notion of ideas,
being only those very complex intern a 1
feelings which adhere by association to such
clusters of words as are called propositions
in general, or affirmations and negations in

This, if I understand its meaning, agrees
with the opinion of Mr Hume, above mea-
2 F




tioned, and lias therefore been before con-

Dr Priestley has given another definition
of judgment: — " It is nothing more than
the perception of the universal concurrence,
or the perfect coincidence of two ideas ; or
the want of that concurrence or coinci-
dence." This, I think, coincides with Mr
Locke's definition, and therefore has been
already considered.

There are many particulars which deserve
to be known, and which might very properly
be considered in this Essay on judgment ;
concerning the various kinds of propositions
by which our judgments are expressed;
their subjects and predicates; their con-
versions and oppositions : but as these are
to be found in every system of logic, from
Aristotle down to the present age, I think
it unnecessary to swell this Essay with the
repetition of what has been said so often.
The remarks which have occurred to me
upon what is commonly said on these points,
as well as upon the art of syllogism ; the
utility of the school logic, and the improve-
ments that may be made in it, may be found
in a " Short Account of Aristotle's Logic,
with Remarks," which Lord Kames has
honoured with a place in his " Sketches of
the History of Man." [555]



One of the most important distinctions of
our judgments is, that some of them are
intuitive, others grounded on argument.

It is not in our power to judge as we
will. The judgment is carried along neces-
sarily by the evidence, real or seeming,
which appears to us at the time. But, in
propositions that are submitted to our
judgment, there is this great difference —
some are of «uch a nature that a man of
ripe understanding may apprehend them
distinctly, and perfectly understand their
meaning, without finding himself under any
necessity of believing them to be true or
false, probable or improbable. The judg-
ment remains in suspense, until it is in-
clined to one side or another by reasons or

But there are other propositions which
are no sooner understood than they are be-
lieved. The judgment follows the appre-
hension of them necessarily, and both are
equally the work of nature, and the result
of our original powers. There is no search-
ing for evidence, no weighing of arguments ;
the proposition is not deduced or inferred
from another ; it has the light of truth in
itself, and has no occasion to borrow it
from another.

Propositions of the last kind, when they
are used in matters of science, have com-
monly been called axioms ; and on what-
ever occasion they are used, are called first
principles, principles of common sense, com-
mon notions, self-evutent truths. Cicero
calls them naiurte judicia, judicia communir
bus hominum sensibus infixa. Lord Shaftes-
bury expresses them by the words, natural
knowledge, fundamental reason, and common
sense. [556]

What has been said, I think, is sufficient
to distinguish first principles, or intuitive
judgments, from those which may be as-
cribed to the power of reasoning ; nor is it
a just objection against this distinction, that
there may be some judgments concerning
which we may be dubious to which class
they ought to be referred. There is a real
distinction between persons within the
house, and those that are without ; yet it
may be dubious to which the man belongs
that stands upon the threshold.

The power of reasoning — that is, of draw-
ing a conclusion from a chain of premises —
may with some propriety be called an art.
" All reasoning," says Mr Locke, " is
search and casting about, and requires
pains and application." It resembles the
power of walking, which is acquired by use
and exercise. Nature prompts to it, and
has given the power of acquiring it ; but
must be aided by frequent exercise before
we are able to walk. After repeated efforts,
much stumbling, and many falls, we learn
to walk ; and it is in a similar manner that
we learn to reason.

But the power of judging in self-evidei:t
propositions, which are clearly understood,
may be compared to the power of swallow-
ing our food. It is purely natural, and there-
fore common to the learned and the un-
learned, to the trained and the untrained.
It requires ripeness of understanding, and
freedom from prejudice, but nothing else.

I take it for granted that there are self-
evident principles. Nobody, I think, de-
nies it. And if any man were so sceptical
as to deny that there is any proposition
that is self-evident, I see not how it would
be possible to convince him by reasoning.

But yet there seems to be great difference
of opinions among philosophers about first
principles. What one takes to be self-evi-
dent, another labours to prove by argu-
ments, and a third denies altogether. [557]

Thus, before the time of Des Cartes, it
was taken for a first principle, that there is
a sun and a moon, an earth and sea, which
really exist, whether we think of them or
not. Des Cartes thought that the exist-
ence of those things ought to be proved by
argument ; arid in this he has been follow-
ed by Malebranche, Arnauld, and Locke.
They have all laboured to prove, by very

eiiAP. iv. j



weak reasoning, the existence of external
objects of sense ; and Berkeley and Hume,
sensible of the weakness of their arguments,
have been led to deny their existence alto-

The ancient philosophers granted, that
all knowledge must be grounded on first
principles, and that there is no reasoning
w.thout them. The Peripatetic philosophy
was redundant rather than deficient in n st
principles. Perhaps the abuse of them in
that ancient system may have brought
them into discredit in modern times ; for,
as the best things may be abused, so that
abuse is apt to give a disgust to the thing
itself ; and as one extreme often leads into
the opposite, this seems to have been the
case in the respect paid to first principles
in ancient and modern times.

Des Cartes thought one principle, express-
ed in one word, coyilo, a sufficient foundation
for his whole system, and asked no more.

Mr Locke seems to think first principles
of very small use. Knowledge consisting,
according to him, in the perception of the
agreement or disagreement of our ideas ;
when we have clear ideas, and are able to
compare them together, we may always fa-
bricate first principles as often as we have
occasion for them. Such differences we find
among philosophers about first principles.

It is likewise a question of some moment,
whether the differences among men about
first principles can be brought to any issue ?
When in disputes one man maintains that
to be a first principle which another denies,
commonly both parties appeal to common
sense, and so the matter rests. Now, is
there no way of discussing this appeal ? Is
there no mark or criterion, whereby first
principles that are truly such, may be dis-
tinguished from those that assume the cha-
racter without a just title ? I shall humbly
offer in the following propositions what
appears to me to be agreeable to truth in
these matters, always ready to change my
opinion upon conviction. [558]

1. First, I hold it to be certain, and even
demonstrable, that all knowledge got by
reasoning must be built upon first princi-

( This is as certain as that every house
^ust have a foundation. The power of

,asoning, in this respect, "resembles the
nechanical powers or engines ; it must
have a fixed point to rest upon, otherwise
it spends its force in the air, and produces
no effect.

When we examine, in the way of ana-
lysis, the evidence of any proposition, either
we find it self-evident, or it rests upon one
or more propositions that support it. The
same thing may be said of the propositions

* So Aristotle, pturie*. — H.
[458. 559]

that support it, and of those that support
them, as far back as we can go. But we
cannot go back in this track to infinity.
Where then must this analysis stop ? It
is evident that it must stop only when we
come to propositions which support all that
are built upon them, but are themselves
supported by none — that is, to self-evident

Let us again consider a synthetical proof of
any kind, where we begin with the premises,
and pursue a train of consequences, until we
come to the last conclusion or thing to be
proved. Here we must begin, either with
self-evidentpropositionsorwithsuch as have
been already proved. When the last is the
case, the proof of the propositions, thus as-
sumed, is a part of our proof; and the
proof is deficient without it. Suppose then
the deficiency supplied, and the proof com-
pleted, is it not evident that it must set out
with self-evident propositions, and that the
whole evidence must rest upon them ? So
that it appears to be demonstrable that,
without first principles, analytical reasoning
could have no end, and synthetical reason-
ing could have no beginning ; and that
every conclusion got by reasoning must
rest with its whole weight upon first princi-
ples, as the building does upon its founda-
tion. [559]

2. A second proposition is, That some
first principles yield conclusions that are
certain, others such as are probable, in va-
rious degrees, from the highest probability
to the lowest.

In just reasoning, the strength or weak-
ness of the conclusion will always corre-
spond to that of the principles on which it is

In a matter of testimony, it is self-evi-
dent that the testimony of two is better
than that of one, supposing them equal in
character, and in their means of knowledge ;
yet the simple testimony may be true, and
that which is preferred to it may be false.

When an experiment has succeeded in
several trials, and the circumstances have
been marked with care, there is a self-evi-
dent probability of its succeeding in a new
trial ; but there is no certainty. The pro-
bability, in some cases, is much greater
than in others ; because, in some cases, it
is much easier to observe all the circum-
stances that may have influence upon the
event than in others. And it is possible
that, after many experiments made with
care, our expectation may be frustrated in
a succeeding one, by the variation of some
circumstance that has not, or perhaps
could not be observed.

Sir Isaac Newton has laid it down as a

first principle in natural philosophy, (hat a

property which has been found in all bodies

upon which we have had access to make




experiments, and which has always been
found in its quantity to be in exact propor-
to the quantity of matter in every body, is
to be held as an universal property of mat-
ter. [560]

This principle, as far as I know, has
never been called in question. The evi-
dence we have, that all matter is divisible,
movable, solid, and inert, is resolvable
into this principle ; and, if it be not true,
we cannot have any rational conviction that
all matter has those properties. From the
same principle that great man has shewn
that we have reason to conclude that all
bodies gravitate towards each other.

This principle, however, has not that
kind of evidence which mathematical axioms
have. It is not a necessary truth, whose
contrary is impossible ; nor did Sir Isaac
ever conceive it to be such. And, if it
should ever be found, by just experiments,
that there is any part in the composition of
some bodies which has not gravity, the
fact if duly ascertained, must be admitted
as an exception to the general law of gra-

In games of chance, it is a first principle
that every side of a die has an equal chance
to be turned up ; and that, in a lottery,
every ticket has an equal chance of being
drawn out. From such first principles as
these, which are the best we can have in
such matters, we may deduce, by demon-
strative reasoning, the precise degree of
probability of every event in such games.

But the principles of all this accurate
and profound reasoning can never yield a
certain conclusion, it being impossible to
supply a defect in the first principles by any
accuracy in the reasoning that is grounded
upon them. As water, by its gravity, can
rise no higher in its course than the foun-
tain, however artfully it be couducted ; so
no conclusion of reasoning can have a
greater degree of evidence than the first
principles from which it is drawn.

From these instances, it is evident that,
as there are some first principles that yield
conclusions of absolute certainty, so there
are others that ean only yield probable con-
clusions ; and that the lowest degree of
probability must be grounded on first prin-
ciples as well as absolute certainty.*

3. A third proposition is, That it would
contribute greatly to the stability of human
knowledge, and consequently to the im-
provement of it, if the first principles upon
which the various parts of it are grounded
were pointed out and ascertained.

We have ground to think so, both from
facts, and from the nature of the thing.

There are two branches of human know-

* Compare Stewart's "Elements," ii. p. 38.— H.

ledge in which this method has been followed
—to wit, mathematics and natural philoso-
phy ; in mathematics, as far back as we have
books. It is in this science only, that, for
more than two thousand years since it be-
gan to be cultivated, we find no sects, no
contrary systems, and hardly any disputes ;
or, if there have been disputes, they have
ended as soon as the animosity of par-
ties subsided, and have never been again
revived. The science, once firmly esta-
blished upon the foundation of a few axioms
and definitions, as upon a rock, has grown
from age so age, so as to become the loftiest
and the most solid fabric that human rea-
son can boast.*

Natural philosophy, till less than two
hundred years ago, remained in the same
fluctuating state with the other sciences.
Every new system pulled up the old by
the roots. The system-builders, indeed,
were always willing to accept of the aid
of first principles, when they were of their
side ; but, finding them insufficient to sup-
port the fabric which their imagination had
raised, they were only brought in as auxi-
liaries, and so intermixed with conjectures,
and with lame inductions, that their sys-
tems were like Nebuchadnezzar's image,
whose feet were partly of iron and partly
of clay.

Lord Bacon first delineated the only so-
lid foundation on which natural philoso-
phy can be built ; and Sir Isaac Newton
reduced the principles laid down by Bacon
into three or four axioms, which he calls
rpyulce philosnpkandi. From these, toge-
ther with the phenomena observed by the
senses, which he likewise lays down as
first principles, he deduces, by strict rea-
soning, the propositions contained in the
third book of his "Principia," and in his
" Optics ;" and by this means has raised a
fabric in those two branches of natural
philosophy, which is not liable to be shaken
by doubtful disputation, but stands im-
movable upon the basis of self-evident
principles. [562]

This fabric has been carried on by the
accession of new discoveries; but is no
more subject to revolutions.

The disputes about materia prima, sub-
stantial forms, Nature's abhorring a vatf 8 *
cuum, and bodies having no gravitation
in their proper place, are now no more.
The builders in this work are not put to the
necessity of holding a weapon in one hand
while they build with the other ; their
whole employment is to carry on the work.

Yet it seems to be very probable, that, if
natural philosophy had not been rearedupon
this solid foundation of self-evident princi-
ples, it would have been to this day a field

* See Stewart's ■' Elements," ii. p. n— H.

[SCO, 562]

eiiAi*. iv.



or battle, wherein every inch of ground
would have been disputed, and nothing fixed
and determined.

I acknowledge that mathematics and na-
tural philosophy, especially the former,
have this advantage of most other sciences,
that it is less difficult to form distinct and
determinate conceptions of the objects
about which they are employed ; but, as
this difficulty is not insuperable, it affords
a good reason, indeed, why other sciences
should have a longer infancy ; but no rea-
son at all why they may not at last arrive
at maturity, by the same steps as those of
quicker growth.

The facts I have mentioned may there-
fore lead us to conclude, that, if in other
branches of philosophy the first principles
were laid down, as has been done in ma-
thematics and natural philosophy, and the
subsequent conclusions grounded upon them,
this would make it much more easy to dis-
tinguish what is solid and well supported
from the vain fictions of human fancy. [563]

But, laying aside facts, the nature of the
thing leads to the same conclusion.

For, when any system is grounded upon
first principles, and deduced regularly from
them, we have a thread to lead us through
the labyrinth. The judgment has a distinct
and determinate object. The heterogeneous
parts being separated, can be examined each
by itself.

The whole system is reduced to axioms,
definitions, and deductions. These are ma-
terials of very different nature, and to be
measured by a very different standard ; and
it is much more easy to judge of each, taken
by itself, than to judge of a mass wherein
they are kneaded together without distinc-
tion. Let us consider how we judge of each
of them.

First, As to definitions, the matter is very
easy. They relate only to words, and differ-
ences about them may produce different
ways of speaking, but can never produce
different ways of thinking, while every man
keeps to his own definitions.

But, as there is not a more plentiful source
of fallacies in reasoning than men's using
the same word sometimes in one sense and
at other times in another, the best means
of preventing such fallacies, or of detecting
them when they are committed, is defi-
nitions of words as accurate as can be

Secondly, As to deductions drawn from
principles granted on both sides, I do not
see how they can long be a matter of dis-

Online LibraryThomas ReidThe works of Thomas Reid, D.D.; now fully collected, with selections from his umpublished letters → online text (page 98 of 114)