AN ENQUIRY CONCERNING HUMAN UNDERSTANDING
SECOND EDITION, 1902
DAVID HUME
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Extracted from:
ENQUIRIES CONCERNING THE HUMAN UNDERSTANDING,
AND CONCERNING THE PRINCIPLES OF MORALS,
BY DAVID HUME. REPRINTED FROM THE POSTHUMOUS
EDITION OF 1777, AND EDITED WITH INTRODUCTION,
COMPARATIVE TABLES OF CONTENTS, AND ANALYTICAL
INDEX BY L. A. SELBY-BIGGE, M. A., LATE FELLOW
OF UNIVERSITY COLLEGE, OXFORD. This eBook is for the use of anyone anywhere
at no cost and with almost no restrictions
whatsoever. You may copy it, give it away
or re-use it under the terms of the Project
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CONTENTS
I. Of the Different Species of Philosophy
II. Of the Origin of Ideas III. Of the Association
of Ideas IV. Sceptical Doubts Concerning
the Operations of the Understanding V. Sceptical
Solution of these Doubts VI. Of Probability
VII. Of the Idea of Necessary Connexion VIII.
Of Liberty and Necessity IX. Of the Reason
of Animals X. Of Miracles XI. Of a Particular
Providence and of a Future State XII. Of
the Academical or Sceptical Philosophy. Footnotes.
Index.
SECTION 1.
OF THE DIFFERENT SPECIES OF PHILOSOPHY.
1. Moral philosophy, or the science of human
nature, may be treated after two different
manners; each of which has its peculiar merit,
and may contribute to the entertainment,
instruction, and reformation of mankind.
The one considers man chiefly as born for
action; and as influenced in his measures
by taste and sentiment; pursuing one object,
and avoiding another, according to the value
which these objects seem to possess, and
according to the light in which they present
themselves. As virtue, of all objects, is
allowed to be the most valuable, this species
of philosophers paint her in the most amiable
colours; borrowing all helps from poetry
and eloquence, and treating their subject
in an easy and obvious manner, and such as
is best fitted to please the imagination,
and engage the affections. They select the
most striking observations and instances
from common life; place opposite characters
in a proper contrast; and alluring us into
the paths of virtue by the views of glory
and happiness, direct our steps in these
paths by the soundest precepts and most illustrious
examples. They make us feel the difference
between vice and virtue; they excite and
regulate our sentiments; and so they can
but bend our hearts to the love of probity
and true honour, they think, that they have
fully attained the end of all their labours.
2. The other species of philosophers consider
man in the light of a reasonable rather than
an active being, and endeavour to form his
understanding more than cultivate his manners.
They regard human nature as a subject of
speculation; and with a narrow scrutiny examine
it, in order to find those principles, which
regulate our understanding, excite our sentiments,
and make us approve or blame any particular
object, action, or behaviour. They think
it a reproach to all literature, that philosophy
should not yet have fixed, beyond controversy,
the foundation of morals, reasoning, and
criticism; and should for ever talk of truth
and falsehood, vice and virtue, beauty and
deformity, without being able to determine
the source of these distinctions. While they
attempt this arduous task, they are deterred
by no difficulties; but proceeding from particular
instances to general principles, they still
push on their enquiries to principles more
general, and rest not satisfied till they
arrive at those original principles, by which,
in every science, all human curiosity must
be bounded. Though their speculations seem
abstract, and even unintelligible to common
readers, they aim at the approbation of the
learned and the wise; and think themselves
sufficiently compensated for the labour of
their whole lives, if they can discover some
hidden truths, which may contribute to the
instruction of posterity.
3. It is certain that the easy and obvious
philosophy will always, with the generality
of mankind, have the preference above the
accurate and abstruse; and by many will be
recommended, not only as more agreeable,
but more useful than the other. It enters
more into common life; moulds the heart and
affections; and, by touching those principles
which actuate men, reforms their conduct,
and brings them nearer to that model of perfection
which it describes. On the contrary, the
abstruse philosophy, being founded on a turn
of mind, which cannot enter into business
and action, vanishes when the philosopher
leaves the shade, and comes into open day;
nor can its principles easily retain any
influence over our conduct and behaviour.
The feelings of our heart, the agitation
of our passions, the vehemence of our affections,
dissipate all its conclusions, and reduce
the profound philosopher to a mere plebeian.
4. This also must be confessed, that the
most durable, as well as justest fame, has
been acquired by the easy philosophy, and
that abstract reasoners seem hitherto to
have enjoyed only a momentary reputation,
from the caprice or ignorance of their own
age, but have not been able to support their
renown with more equitable posterity. It
is easy for a profound philosopher to commit
a mistake in his subtile reasonings; and
one mistake is the necessary parent of another,
while he pushes on his consequences, and
is not deterred from embracing any conclusion,
by its unusual appearance, or its contradiction
to popular opinion. But a philosopher, who
purposes only to represent the common sense
of mankind in more beautiful and more engaging
colours, if by accident he falls into error,
goes no farther; but renewing his appeal
to common sense, and the natural sentiments
of the mind, returns into the right path,
and secures himself from any dangerous illusions.
The fame of Cicero flourishes at present;
but that of Aristotle is utterly decayed.
La Bruyere passes the seas, and still maintains
his reputation: But the glory of Malebranche
is confined to his own nation, and to his
own age. And Addison, perhaps, will be read
with pleasure, when Locke shall be entirely
forgotten.
The mere philosopher is a character, which
is commonly but little acceptable in the
world, as being supposed to contribute nothing
either to the advantage or pleasure of society;
while he lives remote from communication
with mankind, and is wrapped up in principles
and notions equally remote from their comprehension.
On the other hand, the mere ignorant is still
more despised; nor is any thing deemed a
surer sign of an illiberal genius in an age
and nation where the sciences flourish, than
to be entirely destitute of all relish for
those noble entertainments. The most perfect
character is supposed to lie between those
extremes; retaining an equal ability and
taste for books, company, and business; preserving
in conversation that discernment and delicacy
which arise from polite letters; and in business,
that probity and accuracy which are the natural
result of a just philosophy. In order to
diffuse and cultivate so accomplished a character,
nothing can be more useful than compositions
of the easy style and manner, which draw
not too much from life, require no deep application
or retreat to be comprehended, and send back
the student among mankind full of noble sentiments
and wise precepts, applicable to every exigence
of human life. By means of such compositions,
virtue becomes amiable, science agreeable,
company instructive, and retirement entertaining.
Man is a reasonable being; and as such, receives
from science his proper food and nourishment:
But so narrow are the bounds of human understanding,
that little satisfaction can be hoped for
in this particular, either from the extent
of security or his acquisitions. Man is a
sociable, no less than a reasonable being:
But neither can he always enjoy company agreeable
and amusing, or preserve the proper relish
for them. Man is also an active being; and
from that disposition, as well as from the
various necessities of human life, must submit
to business and occupation: But the mind
requires some relaxation, and cannot always
support its bent to care and industry. It
seems, then, that nature has pointed out
a mixed kind of life as most suitable to
the human race, and secretly admonished them
to allow none of these biasses to draw too
much, so as to incapacitate them for other
occupations and entertainments. Indulge your
passion for science, says she, but let your
science be human, and such as may have a
direct reference to action and society. Abstruse
thought and profound researches I prohibit,
and will severely punish, by the pensive
melancholy which they introduce, by the endless
uncertainty in which they involve you, and
by the cold reception which your pretended
discoveries shall meet with, when communicated.
Be a philosopher; but, amidst all your philosophy,
be still a man.
5. Were the generality of mankind contented
to prefer the easy philosophy to the abstract
and profound, without throwing any blame
or contempt on the latter, it might not be
improper, perhaps, to comply with this general
opinion, and allow every man to enjoy, without
opposition, his own taste and sentiment.
But as the matter is often carried farther,
even to the absolute rejecting of all profound
reasonings, or what is commonly called metaphysics,
we shall now proceed to consider what can
reasonably be pleaded in their behalf.
We may begin with observing, that one considerable
advantage, which results from the accurate
and abstract philosophy, is, its subserviency
to the easy and humane; which, without the
former, can never attain a sufficient degree
of exactness in its sentiments, precepts,
or reasonings. All polite letters are nothing
but pictures of human life in various attitudes
and situations; and inspire us with different
sentiments, of praise or blame, admiration
or ridicule, according to the qualities of
the object, which they set before us. An
artist must be better qualified to succeed
in this undertaking, who, besides a delicate
taste and a quick apprehension, possesses
an accurate knowledge of the internal fabric,
the operations of the understanding, the
workings of the passions, and the various
species of sentiment which discriminate vice
and virtue. How painful soever this inward
search or enquiry may appear, it becomes,
in some measure, requisite to those, who
would describe with success the obvious and
outward appearances of life and manners.
The anatomist presents to the eye the most
hideous and disagreeable objects; but his
science is useful to the painter in delineating
even a Venus or an Helen. While the latter
employs all the richest colours of his art,
and gives his figures the most graceful and
engaging airs; he must still carry his attention
to the inward structure of the human body,
the position of the muscles, the fabric of
the bones, and the use and figure of every
part or organ. Accuracy is, in every case,
advantageous to beauty, and just reasoning
to delicate sentiment. In vain would we exalt
the one by depreciating the other.
Besides, we may observe, in every art or
profession, even those which most concern
life or action, that a spirit of accuracy,
however acquired, carries all of them nearer
their perfection, and renders them more subservient
to the interests of society. And though a
philosopher may live remote from business,
the genius of philosophy, if carefully cultivated
by several, must gradually diffuse itself
throughout the whole society, and bestow
a similar correctness on every art and calling.
The politician will acquire greater foresight
and subtility, in the subdividing and balancing
of power; the lawyer more method and finer
principles in his reasonings; and the general
more regularity in his discipline, and more
caution in his plans and operations. The
stability of modern governments above the
ancient, and the accuracy of modern philosophy,
have improved, and probably will still improve,
by similar gradations.
6. Were there no advantage to be reaped from
these studies, beyond the gratification of
an innocent curiosity, yet ought not even
this to be despised; as being one accession
to those few safe and harmless pleasures,
which are bestowed on human race. The sweetest
and most inoffensive path of life leads through
the avenues of science and learning; and
whoever can either remove any obstructions
in this way, or open up any new prospect,
ought so far to be esteemed a benefactor
to mankind. And though these researches may
appear painful and fatiguing, it is with
some minds as with some bodies, which being
endowed with vigorous and florid health,
require severe exercise, and reap a pleasure
from what, to the generality of mankind,
may seem burdensome and laborious. Obscurity,
indeed, is painful to the mind as well as
to the eye; but to bring light from obscurity,
by whatever labour, must needs be delightful
and rejoicing.
But this obscurity in the profound and abstract
philosophy, is objected to, not only as painful
and fatiguing, but as the inevitable source
of uncertainty and error. Here indeed lies
the justest and most plausible objection
against a considerable part of metaphysics,
that they are not properly a science; but
arise either from the fruitless efforts of
human vanity, which would penetrate into
subjects utterly inaccessible to the understanding,
or from the craft of popular superstitions,
which, being unable to defend themselves
on fair ground, raise these intangling brambles
to cover and protect their weakness. Chaced
from the open country, these robbers fly
into the forest, and lie in wait to break
in upon every unguarded avenue of the mind,
and overwhelm it with religious fears and
prejudices. The stoutest antagonist, if he
remit his watch a moment, is oppressed. And
many, through cowardice and folly, open the
gates to the enemies, and willingly receive
them with reverence and submission, as their
legal sovereigns.
7. But is this a sufficient reason, why philosophers
should desist from such researches, and leave
superstition still in possession of her retreat?
Is it not proper to draw an opposite conclusion,
and perceive the necessity of carrying the
war into the most secret recesses of the
enemy? In vain do we hope, that men, from
frequent disappointment, will at last abandon
such airy sciences, and discover the proper
province of human reason. For, besides, that
many persons find too sensible an interest
in perpetually recalling such topics; besides
this, I say, the motive of blind despair
can never reasonably have place in the sciences;
since, however unsuccessful former attempts
may have proved, there is still room to hope,
that the industry, good fortune, or improved
sagacity of succeeding generations may reach
discoveries unknown to former ages. Each
adventurous genius will still leap at the
arduous prize, and find himself stimulated,
rather that discouraged, by the failures
of his predecessors; while he hopes that
the glory of achieving so hard an adventure
is reserved for him alone. The only method
of freeing learning, at once, from these
abstruse questions, is to enquire seriously
into the nature of human understanding, and
show, from an exact analysis of its powers
and capacity, that it is by no means fitted
for such remote and abstruse subjects. We
must submit to this fatigue, in order to
live at ease ever after: And must cultivate
true metaphysics with some care, in order
to destroy the false and adulterate. Indolence,
which, to some persons, affords a safeguard
against this deceitful philosophy, is, with
others, overbalanced by curiosity; and despair,
which, at some moments, prevails, may give
place afterwards to sanguine hopes and expectations.
Accurate and just reasoning is the only catholic
remedy, fitted for all persons and all dispositions;
and is alone able to subvert that abstruse
philosophy and metaphysical jargon, which,
being mixed up with popular superstition,
renders it in a manner impenetrable to careless
reasoners, and gives it the air of science
and wisdom.
8. Besides this advantage of rejecting, after
deliberate enquiry, the most uncertain and
disagreeable part of learning, there are
many positive advantages, which result from
an accurate scrutiny into the powers and
faculties of human nature. It is remarkable
concerning the operations of the mind, that,
though most intimately present to us, yet,
whenever they become the object of reflexion,
they seem involved in obscurity; nor can
the eye readily find those lines and boundaries,
which discriminate and distinguish them.
The objects are too fine to remain long in
the same aspect or situation; and must be
apprehended in an instant, by a superior
penetration, derived from nature, and improved
by habit and reflexion. It becomes, therefore,
no inconsiderable part of science barely
to know the different operations of the mind,
to separate them from each other, to class
them under their proper heads, and to correct
all that seeming disorder, in which they
lie involved, when made the object of reflexion
and enquiry. This talk of ordering and distinguishing,
which has no merit, when performed with regard
to external bodies, the objects of our senses,
rises in its value, when directed towards
the operations of the mind, in proportion
to the difficulty and labour, which we meet
with in performing it. And if we can go no
farther than this mental geography, or delineation
of the distinct parts and powers of the mind,
it is at least a satisfaction to go so far;
and the more obvious this science may appear
(and it is by no means obvious) the more
contemptible still must the ignorance of
it be esteemed, in all pretenders to learning
and philosophy.
Nor can there remain any suspicion, that
this science is uncertain and chimerical;
unless we should entertain such a scepticism
as is entirely subversive of all speculation,
and even action. It cannot be doubted, that
the mind is endowed with several powers and
faculties, that these powers are distinct
from each other, that what is really distinct
to the immediate perception may be distinguished
by reflexion; and consequently, that there
is a truth and falsehood in all propositions
on this subject, and a truth and falsehood,
which lie not beyond the compass of human
understanding. There are many obvious distinctions
of this kind, such as those between the will
and understanding, the imagination and passions,
which fall within the comprehension of every
human creature; and the finer and more philosophical
distinctions are no less real and certain,
though more difficult to be comprehended.
Some instances, especially late ones, of
success in these enquiries, may give us a
juster notion of the certainty and solidity
of this branch of learning. And shall we
esteem it worthy the labour of a philosopher
to give us a true system of the planets,
and adjust the position and order of those
remote bodies; while we affect to overlook
those, who, with so much success, delineate
the parts of the mind, in which we are so
intimately concerned?
9. But may we not hope, that philosophy,
if cultivated with care, and encouraged by
the attention of the public, may carry its
researches still farther, and discover, at
least in some degree, the secret springs
and principles, by which the human mind is
actuated in its operations? Astronomers had
long contented themselves with proving, from
the phaenomena, the true motions, order,
and magnitude of the heavenly bodies: Till
a philosopher, at last, arose, who seems,
from the happiest reasoning, to have also
determined the laws and forces, by which
the revolutions of the planets are governed
and directed. The like has been performed
with regard to other parts of nature. And
there is no reason to despair of equal success
in our enquiries concerning the mental powers
and economy, if prosecuted with equal capacity
and caution. It is probable, that one operation
and principle of the mind depends on another;
which, again, may be resolved into one more
general and universal: And how far these
researches may possibly be carried, it will
be difficult for us, before, or even after,
a careful trial, exactly to determine. This
is certain, that attempts of this kind are
every day made even by those who philosophize
the most negligently: And nothing can be
more requisite than to enter upon the enterprize
with thorough care and attention; that, if
it lie within the compass of human understanding,
it may at last be happily achieved; if not,
it may, however, be rejected with some confidence
and security. This last conclusion, surely,
is not desirable; nor ought it to be embraced
too rashly. For how much must we diminish
from the beauty and value of this species
of philosophy, upon such a supposition? Moralists
have hitherto been accustomed, when they
considered the vast multitude and diversity
of those actions that excite our approbation
or dislike, to search for some common principle,
on which this variety of sentiments might
depend. And though they have sometimes carried
the matter too far, by their passion for
some one general principle; it must, however,
be confessed, that they are excusable in
expecting to find some general principles,
into which all the vices and virtues were
justly to be resolved. The like has been
the endeavour of critics, logicians, and
even politicians: Nor have their attempts
been wholly unsuccessful; though perhaps
longer time, greater accuracy, and more ardent
application may bring these sciences still
nearer their perfection. To throw up at once
all pretensions of this kind may justly be
deemed more rash, precipitate, and dogmatical,
than even the boldest and most affirmative
philosophy, that has ever attempted to impose
its crude dictates and principles on mankind.
10. What though these reasonings concerning
human nature seem abstract, and of difficult
comprehension? This affords no presumption
of their falsehood. On the contrary, it seems
impossible, that what has hitherto escaped
so many wise and profound philosophers can
be very obvious and easy. And whatever pains
these researches may cost us, we may think
ourselves sufficiently rewarded, not only
in point of profit but of pleasure, if, by
that means, we can make any addition to our
stock of knowledge, in subjects of such unspeakable
importance.
But as, after all, the abstractedness of
these speculations is no recommendation,
but rather a disadvantage to them, and as
this difficulty may perhaps be surmounted
by care and art, and the avoiding of all
unnecessary detail, we have, in the following
enquiry, attempted to throw some light upon
subjects, from which uncertainty has hitherto
deterred the wise, and obscurity the ignorant.
Happy, if we can unite the boundaries of
the different species of philosophy, by reconciling
profound enquiry with clearness, and truth
with novelty! And still more happy, if, reasoning
in this easy manner, we can undermine the
foundations of an abstruse philosophy, which
seems to have hitherto served only as a shelter
to superstition, and a cover to absurdity
and error!
SECTION II
OF THE ORIGIN OF IDEAS.
11. Every one will readily allow, that there
is a considerable difference between the
perceptions of the mind, when a man feels
the pain of excessive heat, or the pleasure
of moderate warmth, and when he afterwards
recalls to his memory this sensation, or
anticipates it by his imagination. These
faculties may mimic or copy the perceptions
of the senses; but they never can entirely
reach the force and vivacity of the original
sentiment. The utmost we say of them, even
when they operate with greatest vigour, is,
that they represent their object in so lively
a manner, that we could almost say we feel
or see it: But, except the mind be disordered
by disease or madness, they never can arrive
at such a pitch of vivacity, as to render
these perceptions altogether undistinguishable.
All the colours of poetry, however splendid,
can never paint natural objects in such a
manner as to make the description be taken
for a real landskip. The most lively thought
is still inferior to the dullest sensation.
We may observe a like distinction to run
through all the other perceptions of the
mind. A man in a fit of anger, is actuated
in a very different manner from one who only
thinks of that emotion. If you tell me, that
any person is in love, I easily understand
your meaning, and form a just conception
of his situation; but never can mistake that
conception for the real disorders and agitations
of the passion. When we reflect on our past
sentiments and affections, our thought is
a faithful mirror, and copies its objects
truly; but the colours which it employs are
faint and dull, in comparison of those in
which our original perceptions were clothed.
It requires no nice discernment or metaphysical
head to mark the distinction between them.
12. Here therefore we may divide all the
perceptions of the mind into two classes
or species, which are distinguished by their
different degrees of force and vivacity.
The less forcible and lively are commonly
denominated Thoughts or Ideas. The other
species want a name in our language, and
in most others; I suppose, because it was
not requisite for any, but philosophical
purposes, to rank them under a general term
or appellation. Let us, therefore, use a
little freedom, and call them Impressions;
employing that word in a sense somewhat different
from the usual. By the term impression, then,
I mean all our more lively perceptions, when
we hear, or see, or feel, or love, or hate,
or desire, or will. And impressions are distinguished
from ideas, which are the less lively perceptions,
of which we are conscious, when we reflect
on any of those sensations or movements above
mentioned.
13. Nothing, at first view, may seem more
unbounded than the thought of man, which
not only escapes all human power and authority,
but is not even restrained within the limits
of nature and reality. To form monsters,
and join incongruous shapes and appearances,
costs the imagination no more trouble than
to conceive the most natural and familiar
objects. And while the body is confined to
one planet, along which it creeps with pain
and difficulty; the thought can in an instant
transport us into the most distant regions
of the universe; or even beyond the universe,
into the unbounded chaos, where nature is
supposed to lie in total confusion. What
never was seen, or heard of, may yet be conceived;
nor is any thing beyond the power of thought,
except what implies an absolute contradiction.
But though our thought seems to possess this
unbounded liberty, we shall find, upon a
nearer examination, that it is really confined
within very narrow limits, and that all this
creative power of the mind amounts to no
more than the faculty of compounding, transposing,
augmenting, or diminishing the materials
afforded us by the senses and experience.
When we think of a golden mountain, we only
join two consistent ideas, gold, and mountain,
with which we were formerly acquainted. A
virtuous horse we can conceive; because,
from our own feeling, we can conceive virtue;
and this we may unite to the figure and shape
of a horse, which is an animal familiar to
us. In short, all the materials of thinking
are derived either from our outward or inward
sentiment: the mixture and composition of
these belongs alone to the mind and will.
Or, to express myself in philosophical language,
all our ideas or more feeble perceptions
are copies of our impressions or more lively
ones.
14. To prove this, the two following arguments
will, I hope, be sufficient. First, when
we analyze our thoughts or ideas, however
compounded or sublime, we always find that
they resolve themselves into such simple
ideas as were copied from a precedent feeling
or sentiment. Even those ideas, which, at
first view, seem the most wide of this origin,
are found, upon a nearer scrutiny, to be
derived from it. The idea of God, as meaning
an infinitely intelligent, wise, and good
Being, arises from reflecting on the operations
of our own mind, and augmenting, without
limit, those qualities of goodness and wisdom.
We may prosecute this enquiry to what length
we please; where we shall always find, that
every idea which we examine is copied from
a similar impression. Those who would assert
that this position is not universally true
nor without exception, have only one, and
that an easy method of refuting it; by producing
that idea, which, in their opinion, is not
derived from this source. It will then be
incumbent on us, if we would maintain our
doctrine, to produce the impression, or lively
perception, which corresponds to it.
15. Secondly. If it happen, from a defect
of the organ, that a man is not susceptible
of any species of sensation, we always find
that he is as little susceptible of the correspondent
ideas. A blind man can form no notion of
colours; a deaf man of sounds. Restore either
of them that sense in which he is deficient;
by opening this new inlet for his sensations,
you also open an inlet for the ideas; and
he finds no difficulty in conceiving these
objects. The case is the same, if the object,
proper for exciting any sensation, has never
been applied to the organ. A Laplander or
Negro has no notion of the relish of wine.
And though there are few or no instances
of a like deficiency in the mind, where a
person has never felt or is wholly incapable
of a sentiment or passion that belongs to
his species; yet we find the same observation
to take place in a less degree. A man of
mild manners can form no idea of inveterate
revenge or cruelty; nor can a selfish heart
easily conceive the heights of friendship
and generosity. It is readily allowed, that
other beings may possess many senses of which
we can have no conception; because the ideas
of them have never been introduced to us
in the only manner by which an idea can have
access to the mind, to wit, by the actual
feeling and sensation.
16. There is, however, one contradictory
phenomenon, which may prove that it is not
absolutely impossible for ideas to arise,
independent of their correspondent impressions.
I believe it will readily be allowed, that
the several distinct ideas of colour, which
enter by the eye, or those of sound, which
are conveyed by the ear, are really different
from each other; though, at the same time,
resembling. Now if this be true of different
colours, it must be no less so of the different
shades of the same colour; and each shade
produces a distinct idea, independent of
the rest. For if this should be denied, it
is possible, by the continual gradation of
shades, to run a colour insensibly into what
is most remote from it; and if you will not
allow any of the means to be different, you
cannot, without absurdity, deny the extremes
to be the same. Suppose, therefore, a person
to have enjoyed his sight for thirty years,
and to have become perfectly acquainted with
colours of all kinds except one particular
shade of blue, for instance, which it never
has been his fortune to meet with. Let all
the different shades of that colour, except
that single one, be placed before him, descending
gradually from the deepest to the lightest;
it is plain that he will perceive a blank,
where that shade is wanting, and will be
sensible that there is a greater distance
in that place between the contiguous colours
than in any other. Now I ask, whether it
be possible for him, from his own imagination,
to supply this deficiency, and raise up to
himself the idea of that particular shade,
though it had never been conveyed to him
by his senses? I believe there are few but
will be of opinion that he can: and this
may serve as a proof that the simple ideas
are not always, in every instance, derived
from the correspondent impressions; though
this instance is so singular, that it is
scarcely worth our observing, and does not
merit that for it alone we should alter our
general maxim.
17. Here, therefore, is a proposition, which
not only seems, in itself, simple and intelligible;
but, if a proper use were made of it, might
render every dispute equally intelligible,
and banish all that jargon, which has so
long taken possession of metaphysical reasonings,
and drawn disgrace upon them. All ideas,
especially abstract ones, are naturally faint
and obscure: the mind has but a slender hold
of them: they are apt to be confounded with
other resembling ideas; and when we have
often employed any term, though without a
distinct meaning, we are apt to imagine it
has a determinate idea annexed to it. On
the contrary, all impressions, that is, all
sensations, either outward or inward, are
strong and vivid: the limits between them
are more exactly determined: nor is it easy
to fall into any error or mistake with regard
to them. When we entertain, therefore, any
suspicion that a philosophical term is employed
without any meaning or idea (as is but too
frequent), we need but enquire, from what
impression is that supposed idea derived?
And if it be impossible to assign any, this
will serve to confirm our suspicion. By bringing
ideas into so clear a light we may reasonably
hope to remove all dispute, which may arise,
concerning their nature and reality. 1
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