Thomas Reid.

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

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examination. For, if the principles of mo-
rals be not a matter of judgment, but of



feeling only, there can be no demonstration
of them ; nor can any other reason be given
for them, but that men are so constituted
by the Author of their being as to contem-
plate with pleasure the actions we call vir-
tuous, and with disgust those we call vicious.

It is not, therefore, to be expected that
the philosophers of this class should think
this opinion of Mr Locke worthy of ex-
amination, since it is founded upon what
they think a false hypothesis. But if our
determinations in morality be real judg-
ments, and, like all other judgments, be
either true or false, it is not unimportant
to understand upon what kind of evidence
those judgments rest.

The argument offered by Mr Locke,
to shew that morality is capable of demon-
stration, is, " That 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
perfectly discovered, in which consists per-
fect knowledge."

It is true, that the field of demonstration
is the various relations of things conceived
abstractly, of which we may have perfect
and adequate conceptions. And Mr Locke,
taking all the things which moral words
stand for to be of this kind, concluded that
morality is as capable of demonstration as

I acknowledge that the names of the
virtues and vices, of right and obligation,
of liberty and property, stand for things
abstract, which may be accurately defined,
or, at least, conceived as distinctly and
adequately as mathematical quantities. And
thence, indeed, it follows, that their mutual
relations may be perceived as clearly and
certainly as mathematical truths. [682]

Of this Mr Locke gives two pertinent
examples. The first — " Where there is no
property, there is no injustice, is," says he,
" a proposition as certain as any demon-
stration in Euclid."

When injustice is defined to be a viola-
tion of property, it is as necessary a truth,
that there can be no injustice where there
is no property, as that you cannot take
from a man that which he has not.

The second example is, " That no
government allows absolute liberty." This
is a truth no less certain and necessary.

Such abstract truths I would call meta-
physical rather than moral. We give the
name of mathematical to truths that ex-
press the relations of quantities considered
abstractly; all other abstract truths may
be called metaphysical. But if those men-
tioned by Mr Locke are to be called moral
truths, I agree with him that there are
many such that are necessarily true, and
that have all the evidence that mathemati-
cal truths can have.
T682, 6831 '

It ought, however, to be remembered,
that, as was before observed, the relations
of things abstract, perceivable by as, ex-
cepting those of mathematical quantities,
are few, and, for the most part, immediately
discerned, so as not to require that train
of reasoning which we call demonstration.
Their evidence resembles more that of
mathematical axioms than mathematical

This appears in the two propositions
given as examples by Mr Locke. The first
follows immediately from the definition of
injustice ; the second from the definition of
government. Their evidence may more
properly be called intuitive than demon-
strative. And this I apprehend to be the
case, or nearly the case, of all abstract
truths that are not mathematical, for the
reason given in the last chapter. [683]

The propositions which I think are pro-
perly called moral, are those that affirm
some moral obligation to be, or not to be
incumbent on one or more individual per-
sons. To such propositions, Mr Locke's
reasoning does not apply, because the sub-
jects of the proposition are not things whose
real essence may be perfectly known. They
are the creatures of God ; their obligation
results from the constitution which God
hath given them, and the circumstances
in which he hath placed them. That an
individual hath such a constitution, and is
placed in such circumstances, is not an
abstract and necessary, but a contingent
truth. It is a matter of fact, and, there-
fore, not capable of demonstrative evidence,
which belongs only to necessary truths.

The evidence which every man hath of
his own existence, though it be irresistible,
is not demonstrative. And the same thing
may be said of the evidence which every
man hath, that he is a moral agent, and
under certain moral obligations. In like
manner, the evidence we have of the exist-
ence of other men, is not demonstrative ;
nor is the evidence we have of their being
endowed with those faculties which make
them moral and accountable agents.

If man had not the faculty given him by
God of perceiving certain things in conduct
to be right, and others to be wrong, and of
perceiving his obligation to do what is right,
and not to do what is wrong, he would not
be a moral and accountable being.

If man be endowed with such a faculty,
there must be some things which, by this
faculty, are immediately discerned to be
right, and others to be wrong ; and, there-
fore, there must be in morals, as in other
sciences, first principles which do not de.
rive their evidence from any antecedent
principles, but may be said to be intuitively

Moral truths, therefore, may be divided



[essay vii.

into two classes — to wit, such as are self-
evident to every man whose understanding
and moral faculty are ripe, and such as are
deduced by reasoning from those that are
self-evident. If the first be not discerned
without reasoning, the last never can be so
by any reasoning. [684]

If any man could say, with sincerity, that
he is conscious of no obligation to consult
his own present and future happiness ; to
be faithful to his engagements ; to obey his
Maker ; to injure no man ; I know not
what reasoning, either probable or demon-
strative, I could use to convince him of any
moral duty. As you cannot reason in
mathematics with a man who denies the
axioms, as little can you reason with a man
in morals who denies the first principles of
morals. The man who does not, by the light
of his own mind, perceive some things in
conduct to be right, and others to be wrong,
is as incapable of reasoning about morals
as a blind man is about colours. Such a
man, if any such man ever was, would be
no moral agent, nor capable of any moral

Some first principles of morals must be
immediately discerned, otherwise we have
no foundation on which others can rest, or
from which we can reason.

Every man knows certainly, that, what he
approves in other men, he ought to do in
like circumstances, and that he ought not to
do what he condemns in other men. Every
man knows that he ought, with candour, to
use the best means of knowing his duty.
To every man who has a conscience, these
things are self-evident. They are imme-
diate dictates of our moral faculty, which is
a part of the human constitution ; and every
man condemns himself, whether he will or
not, when he knowingly acts contrary to
them. The evidence of these fundamental
principles of morals, and of others that
might be named, appears, therefore, to me
to be intuitive rather than demonstrative.

The man who acts according to the dic-
tates of his conscience, and takes due pains
to be rightly informed of his duty, is a per-
fect man with regard to morals, and merits
no blame, whatever may be the imperfec-
tions or errors of his understanding;. He
who knowingly acts contrary to them, is
conscious of guilt, and self-condemned.
Every particular action that falls evidently
within the fundamental rules of morals, is
evidently his duty; and it requires no rea-
soning to convince him that it is so. [685]

Thus, I think it appears, that every man
of common understanding knows certainly,
and without reasoning, the ultimate ends
he ought to pursue, and that reasoning is
necessary only to discover the most proper
means of attaining them ; and in this, in-
deed, a good man may often be in doubt.

Thus, a magistrate knows that it is his
duty to promote the good of the community
which hath intrusted him with authority ;
and to offer to prove this to him by reason/" 1
ing, would be to affront him. But whether
such a scheme of conduct in his office, or
another, may best serve that end, he may
in many cases be doubtful. I believe, in
such cases, he can very rarely have demon-
strative evidence. His conscience deter-
mines the end he ought to pursue, and he
has intuitive evidence that his end is good ;
but prudence must determine the means
of attaining that end ; and prudence can
very rarely use demonstrative reasoning,
but must rest in what appears most -oba-

I apprehend, that, in every kind of duty
we owe to God or man, the case is similar —
that is, that the obligation of the most
general rules of duty is self-evident ; that
the application of those rules to particular
actions is often no less evident ; and that,
when it is not evident, but requires reason-
ing, that reasoning can very rarely be of
the demonstrative, but must be of the pro-
bable kind. Sometimes it depends upon
the temper, and talents, and circumstances
of the man himself; sometimes upon the
character and circumstances of others ;
sometimes upon both ; and these are things
which admit not of demonstration. [686]
Every man is bound to employ the talents
which God hath given him to the best pur-
pose ; but if, through accidents which he
could not foresee, or ignorance which was
invincible, they be less usefully employed
than they might have been, this will not be
imputed to him by his righteous Judge-
It is a common and a just observation,
that the man of virtue plays a surer game
in order to obtain his end than the man of
the world. It is not, however, because he
reasons better concerning the means of
attaining his end ; for the children of this
world are often wiser in their generation
than the children of light. But the reason
of the observation is, that involuntary
errors, unforeseen accidents, and invincible
ignorance, which affect deeply all the con-
cerns of the present world, have no effect
upon virtue or its reward.

In the common occurrences of life, a man
of integrity, who hath exercised his moral
faculty in judging what is right and what
is wrong, sees his duty without reasoning,
as he sees the highway. The cases that
require reasoning are few, compared with
those that require none ; and a man may
be very honest and virtuous who cannot
reason, and who knows not what demon-
stration means.

The power of reasoning, in those that

have it, may be abused in morals, as in

other matters. To a man who uses it with





an upright heart, and a single eye to find
what is his duty, it will be of great use ;
but when it is used to justify what a man
has a strong inclination to do, it will only
serve to deceive himself and others. When
a man can reason, his passions will reason,
and they are the most cunning sophists we
meet with.
.,_ ,Jf the rules of virtue were left to be dis-
covered by demonstrative reasoning, or by
reasoning of any kind, sad would be the
condition of the far greater part of men,
who have not the means of cultivating the
power of reasoning. As virtue is the busi-
ness of all men, the first principles of it are
written in their hearts, in characters so
legible that no man can pretend ignorance
of them, or of his obligation to practise
them. [687]

Some knowledge of duty and of moral
obligation is necessary to all men. With-
out it they could not be moral and account-
able creatures, nor capable of being mem-
bers of civil society. It may, therefore,
be presumed that Nature has put this
knowledge within the reach of all men.
Reasoning and demonstration are weapons
which the greatest part of mankind never
was able to wield. The knowledge that is
necessary to all, must be attainable by all.
We see it is so in what pertains to the
natural life of man.

Some knowledge of things that are useful
and things that are hurtful, is so necessary
to all men, that without it the species would
soon perish. But it is not by reasoning
that this knowledge is got, far less by de-
monstrative reasoning. It is by our senses,
by memory, by experience, by information ;
means of knowledge that are open to all
men, and put the learned and the unlearned,
those who cau reason and those who can-
not, upon a level.

It may, therefore, be expected, from the
analogy of nature, that such a knowledge
of morals as is necessary to all men should
be had by means more suited to the abili-
ties of all men than demonstrative reason-
ing is.

This, I apprehend, is in fact the case.
When men's faculties are ripe, the first
principles of morals, into which all moral
reasoning may be resolved, are perceived
intuitively, and in a manner more analogous
to the perceptions of sense than to the con-
clusions of demonstrative reasoning. [688]

Upon the whole, I agree with Mr Locke,
that propositions expressing the congruities
and incongruities of things abstract, which
moral words stand for, may have all the
evidence of mathematical truths. But this
is not peculiar to things which moral words
stand for. It is common to abstract pro-
positions of every kind. For instance, you
cannot take from a man what he has not.

A man cannot be bound and perfectly free
at the same time. I think no man will
call these moral truths ; but they are neces-
sary truths, and as evident as any in mathe-
matics. Indeed, they are very nearly allied
to the two which Mr Locke gives as in-
stances of moral propositions capable of
demonstration. Of such abstract proposi-
tions, I think it may more properly be said
that they have the evidence of mathemati-
cal axioms, than that they are capable of

There are propositions of another kind,
which alone deserve the name of moral pro-
positions. They are such as affirm some-
thing to be the duty of persons that really
exist. These are not abstract propositions ;
and, therefore, Mr Locke's reasoning does
not apply to them. The truth of all such
propositions depends upon the constitution
and circumstances of the persons to whom
they are applied.

Of such propositions, there are some that
are self-evident to every man that has a
conscience j and these are the principles
from which all moral reasoning must be
drawn. They may be called the axioms of
morals. But our reasoning from these
axioms to any duty that is not self-evident
can very rarely be demonstrative. Nor is this
any detriment to the cause of virtue, because
to act against what appears most probable
in a matter of duty, is as real a trespass
against the first principles of morality, as
to act against demonstration ; and, because
he who has but one talent in reasoning, and
makes the proper use of it, shall be ac-
cepted, as well as he to whom God has
given ten. [689]



The field of demonstration, as has been
observed, is necessary truth : the field of
probable reasoning is contingent truth — jiot
what necessarily must be at all times, but
what is, or was y or shall be.

No contingent truth is capable of strict
demonstration; but necessary truths may
sometimes have probable evidence.

Dr Wallis discovered many important
mathematical truths, by that kind of induc-
tion which draws a general conclusion from
particular premises. This is not strict de-
monstration, but, in some cases, gives as
full conviction as demonstration itself ; and
a man may be certain, that- a truth is de-
monstrable before it ever has been demon-
strated. In other cases, a mathematical
proposition may have such probable evi-
dence from induction or analogy as en-
courages the mathematician to investigata



[essay VII.

its demonstration. But still the reasoning,
proper to mathematical and other necessary
truths, is demonstration ; and that which is
proper to contingent truths, is probable

These two kinds of reasoning differ in
other respects. In demonstrative reason-
ing, one argument is as good as a thousand-
One demonstration may be more elegant
than another ; it may be more easily com-
prehended, or it may be more subservient
to some purpose beyond the present. On
any of these accounts it may deserve a
preference : but then it is sufficient by it-
self ; it needs no aid from another ; it can
receive none. To add more demonstrations
of the same conclusion, would be a kind of
tautology in reasoning ; because one de-
monstration, clearly comprehended, gives
all the evidence we are capable of receiv-
ing. [690]

The strength of probable reasoning, for
the most part, depends not upon any one
argument, but upon many, which unite
their force, and lead to the same conclusion.
Any one of them by itself would be insuf-
ficient to convince ; but the whole taken
together may have a force that is irresistible,
so that to desire more evidence would be
absurd. Would any man seek new argu-
ments to prove that there were such persons
as King Charles I. or Oliver Cromwell ?

Such evidence may be compared to a rope
made up of many slender filaments twisted
together. The rope has strength more
than sufficient to bear the stress laid upon
it, though no one of the filaments of which
it is composed would be sufficient for that

It is a common observation, that it is
unreasonable to require demonstration for
things which do not admit of it. It is no
less unreasonable to require reasoning of
any kind for things which are known with-
out reasoning. All reasoning must be
grounded upon truths which are known
without reasoning. In every branch of real
knowledge there must be first principles
whose truth is known intuitively, without
reasoning, either probable or demonstrative.
They are not grounded on reasoning, but
all reasoning is grounded on them. It has
been shewn, that there are first principles
of necessary truths, and first principles of
contingent truths. Demonstrative reason-
ing is grounded upon the former, and pro-
bable reasoning upon the latter.

That we may not be embarrassed by the
ambiguity of words, it is proper to observe,
that there is a popular meaning of probable
evidence, which ought not to be confounded
with the philosophical meaning, above ex-
plained. [691]

In common language, probable evidence
is considered as an inferior degree of evi-

dence, and is opposed to certainty : so that
what is certain is more than probable, and
what is only probable is not certain. Phi-
losophers consider probable evidence, not
as a degree, but as a species of evidence,
which is opposed, not to certainty, but tu
another species of evidence, called demon-

Demonstrative evidence has no degrees ;
but probable evidence, taken in the philo-
sophical sense, has all degrees, from the
very least to the greatest, which we call

That there is such a city as Home, I am
as certain as of any proposition in Euclid ;
but the evidence is not demonstrative, but
of that kind which philosophers call pro-
bable. Yet, in common language, it would
sound oddly to say, it is probable there is
such a city as Rome, because it would
imply some degree of doubt or uncertainty.

Taking probable evidence, therefore, in
the philosophical sense, as it is opposed to
demonstrative, it may have any degrees of
evidence, from the least to the greatest.

I think, in most cases, we measure the
degrees of evidence by the effect they have
upon a, sound understanding, when com-
prehended clearly and without prejudice.
Every degree of evidence perceived by the
mind, produces & proportioned degree of
assent or belief. The judgment may be in
perfect suspense between two contradictory
opinions, when there is no evidence for
either, or equal evidence for both. The
least prepondera.ncy on one side inclines the
judgment in proportion. Belief is mixed
with doubt, more or less, until we come
to the highest degree of evidence, when
all doubt vanishes, and the belief is firm
and immovable. This degree of evidence,
the highest the human faculties can attain,
we call certainty. [692]

Probable evidence not only differs in kind
from demonstrative, but is itself of different
kinds. The chief of these I shall mention,
without pretending to make a complete

The first kind is that of human testimony,
upon which the greatest part of human
knowledge is built.

The faith of history depends upon it, as
well as the judgment of solemn tribunals,
with regard to men's acquired rights, and
with regard to their guilt or innocence,
when they are charged with crimes. A
great part of the business of the judge, of
counsel at the bar, of the historian, the
critic, and the antiquarian, is to canvass
and weigh this kind of evidence; and no
man can act with common prudence in the
ordinary occurrences of life, who has not
some competent judgment of it.

The belief we give to testimony, in many

cases, is not solely grounded upon the vera-





city of the testifier. In a single testimony,
we consider the motives a man might have
to falsify. If there be no appearance of
any such motive, much ore if there be
motives on the other side, his testimony has
weight independent of his moral character.
If the testimony be circumstantial, we con-
sider how far the circumstances agree to-
gether, and with things that are known.
It is so very difficult to fabricate a story
which cannot be detected by a judicious
examination of the circumstances, that it
acquires evidence by being able to bear
such a trial. There is an art in detecting
false evidence in judicial proceedings, well
known to able judges and barristers; so
that I believe few false witnesses leave the
bar without suspicion of their guilt.

When there is an agreement of many
witnesses, in a great variety of circum-
stances, without the possibility of a previous
concert, the evidence may he equal to that
of demonstration. [693]

A second kind of probable evidence, is
the authority of those who are good judges
of the point in question. The supreme
court of judicature of the British nation, is
often determined by the opinion of lawyers
in a point of law, of physicians in a point of
. medicine, and of other artists, in what re-
lates to their several professions. And, in
the common affairs of life, we frequently
rely upon the judgment of others, in points
of which we are not proper judges our-

A third kind of probable evidence, is that
by which we recognise the identity of things
and persons of our acquaintance. That two
swords, two horses, or two persons, may be
so perfectly alike as not to be distinguish-
able by those to whom they are best known,
cannot be shewn to be impossible. But we
learn either from nature, or from experience,
that it never happens ; or so very rarely,
that a person or thing, well known to us, is
immediately recognised without any doubt,
when we perceive the marks or signs by
which we were in use to distinguish it from
all other individuals of the kind.

This evidence we rely upon in the most
important affairs of life ; and, by this evi-
dence, the identity, both of things and of
persons, is determined in courts of judica-

A fourth kind of probable evidence, is
that which we have of men's future actions
and conduct, from the general principles of
action in man, or from our knowledge of the

Notwithstanding the folly and vice that
are to be found among men, there is a certain
degree of prudence and probity which we
rely upon in every man that is not insane.
If it were not so, no man would be safe in
the company of another, and there could be

no society among mankind. If men were
as much disposed to hurt as to do good, to
lie as to speak truth, they could not live to-
gether ; they would keep at as great dis-
tance from one another as possible, and the
race would soon perish. [694]

We expect that men will take some care
of themselves, of their family, friends, and
reputation ; that they will not injure others
without some temptation ; that they will
have some gratitude for good offices, and
some resentment of injuries.

Such maxims with regard to human con-

Online LibraryThomas ReidThe works of Thomas Reid, D.D.; now fully collected, with selections from his umpublished letters → online text (page 108 of 114)