Sect.
IV. Sceptical
Doubts concerning the Operations of the Understanding
PART I.
20. All the
objects of human
reason or enquiry may naturally be
divided into two kinds, to
wit,
Relations of Ideas, and Matters of
Fact. Of the first kind are
the
sciences of Geometry, Algebra, and
Arithmetic; and in short,
every
affirmation which is either
intuitively or
demonstratively certain.
That the square of the
hypothenuse is equal to the
square
of the two sides, is a
proposition which expresses
a relation
between these figures. That
three times five is equal to
the
half of thirty, expresses a
relation between these
numbers.
Propositions of this kind are
discoverable by the mere
operation
of thought, without dependence on
what is anywhere existent in
the
universe. Though there never were a
circle or triangle in
nature, the
truths demonstrated by Euclid
would for ever retain their
certainty
and evidence.
21. Matters of
fact, which
are the second objects of human reason,
are not ascertained in the
same
manner; nor is our evidence of their
truth, however great, of a
like
nature with the foregoing. The
contrary of every matter of
fact
is still possible; because it can
never imply a contradiction,
and
is conceived by the mind with the
same facility and
distinctness,
as if ever so conformable to
reality. That the sun will
not rise
tomorrow is no less intelligible a
proposition, and implies no
more
contradiction than the affirmation,
that it will rise. We should
in
vain, therefore, attempt to
demonstrate its falsehood.
Were
it demonstratively false, it would
imply a contradiction, and
could
never be distinctly conceived by
the mind.
It may, therefore,
be a subject
worthy of curiosity, to enquire what
is the nature of that
evidence which
assures us of any real
existence and matter of
fact, beyond
the present testimony of our
senses, or the records of
our memory.
This part of philosophy, it is
observable, has been little
cultivated,
either by the ancients or
moderns; and therefore our
doubts
and errors, in the prosecution of so
important an enquiry, may be
the
more excusable; while we march
through such difficult paths
without
any guide or direction. They
may even prove useful, by
exciting
curiosity, and destroying that
implicit faith and security,
which
is the bane of all reasoning and
free enquiry. The discovery
of defects
in the common philosophy, if
any such there be, will not,
I presume,
be a discouragement, but
rather an incitement, as is
usual,
to attempt something more full
and satisfactory than has
yet been
proposed to the public.
22. All reasonings
concerning
matter of fact seem to be founded on
the realtion of Cause and
Effect.
By means of that relation alone we
can go beyond the evidence
of our
memory and senses. If you were to
ask a man, why he believes
any matter
of fact, which is absent; for
instance, that his friend is
in
the country, or in France; he would
give you a reason; and this
reason
would be some other fact; as a
letter received from him, or
the
knowledge of his former resolutions
and promises. A man finding
a watch
or any other machine in a desert
island, would conclude that
there
had once been men in that island.
All our reasonings
concerning fact
are of the same nature. And here it
is constantly supposed that
there
is a connexion between the present
fact and that which is
inferred
from it. Were there nothing to bind
them together, the inference
would
be entirely precarious. The hearing
of an articulate voice and
rational
discourse in the dark assures us
of the presence of some
person:
Why? because these are the effects
of the human make and
fabric, and
closely connected with it. If we
anatomize all the other
reasonings
of this nature, we shall find
that they are founded on the
relation
of cause and effect, and that
this relation is either near
or
remote, direct or collateral. Heat and
light are collateral effects
of
fire, and the one effect may justly be
inferred from the other.
23. If we would
satisfy ourselves,
therefore, concerning the
nature of that evidence,
which assures
us of matters of fact, we
must enquire how we arrive
at the
knowledge of cause and effect.
I shall venture to
affirm,
as a general proposition, which admits of
no exception, that the
knowledge
of this relation is not, in any
instance, attained by
reasonings
a priori; but arises entirely from
experience, when we find
that any
particular objects are constantly
conjoined with each other.
Let an
object be presented to a man of ever
so strong natural reason and
abilities;
if that object be entirely new
to him, he will not be able,
by
the most accurate examination of its
sensible qualities, to
discover
any of its causes or effects. Adam,
though his rational
faculties be
supposed, at the very first, entirely
perfect, could not have
inferred
from the fluidity and transparency of
water that it would
suffocate him,
or from the light and warmth of
fire that it would consume
him.
No object ever discovers, by the
qualities which appear to
the senses,
either the causes which produced
it, or the effects which
will arise
from it; nor can our reason,
unassisted by experience,
ever draw
any inference concerning real
existence and matter of fact.
24. This
proposition, that
causes and effects are discoverable,
not by reason but by
experience,
will readily be admitted with
regard to such objects, as
we remember
to have once been altogether
unknown to us; since we must
be
conscious of the utter inability,
which we then lay under, of
foretelling
what would arise from them.
Present two smooth pieces of
marble
to a man who has no tincture of
natural philosophy; he will
never
discover that they will adhere
together in such a manner as
to
require great force to separate them
in a direct line, while they
make
so small a resistance to a lateral
pressure. Such events, as
bear little
analogy to the common course
of nature, are also readily
confessed
to be known only by
experience; nor does any man
imagine
that the explosion of
gunpowder, or the attraction
of
a loadstone, could ever be
discovered by arguments a
priori.
In like manner, when an effect is
supposed to depend upon an
intricate
machinery or secret structure
of parts, we make no
difficulty
in attributing all our knowledge of it
to experience. Who will
assert that
he can give the ultimate reason,
why milk or bread is proper
nourishment
for a man, not for a lion or a
tiger?
But the same truth
may not
appear, at first sight, to have the
same evidence with regard to
events,
which have become familiar to
us from our first appearance
in
the world, which bear a close
analogy to the whole course
of nature,
and which are supposed to
depend on the simple
qualities of
objects, without any secret
structure of parts. We are
apt to
imagine that we could discover these
effects by the mere
operation of
our reason, without experience. We
fancy, that were we brought
on a
sudden into this world, we could at
first have inferred that one
billiard-ball
would communicate motion to
another upon impulse; and
that we
needed not to have waited for the
event, in order to pronounce
with
certainty concerning it. Such is the
influence of custom, that,
where
it is strongest, it not only covers
our natural ignorance, but
even
conceals itself, and seems not to take
place, merely because it is
found
in the highest degree.
25. But to
convince us that
all the laws of nature, and all the
operations of bodies without
exception,
are known only by
experience, the following
reflections
may, perhaps, suffice. Were
any object presented to us,
and
were we required to pronounce
concerning the effect, which
will
result from it, without consulting
past observation; after what
manner,
I beseech you, must the mind
proceed in this operation?
It must
invent or imagine some event, which
it ascribes to the object as
its
effect; and it is plain that this
invention must be entirely
arbitrary.
The mind can never possibly find
the effect in the supposed
cause,
by the most accurate scrutiny and
examination. For the effect
is totally
different from the cause, and
consequently can never be
discovered
in it. Motion in the second
billiard-ball is a quite
distinct
event from motion in the first;
nor is there anything in the
one
to suggest the smallest hint of the
other. A stone or piece of
metal
raised into the air, and left without
any support, immediately
falls:
but to consider the matter a priori,
is there anything we
discover in
this situation which can beget the
idea of a downward, rather
than
an upward, or any other motion, in the
stone or metal?
And as the first
imagination
or invention of a particular effect, in
all natural operations, is
arbitrary,
where we consult not experience;
so must we also esteem the
supposed
tie or connexion between the cause
and effect, which binds them
together,
and renders it impossible
that any other effect could
result
from the operation of that cause.
When I see, for instance, a
billiard-ball
moving in a straight line
towards another; even
suppose motion
in the second ball should by
accident be suggested to me,
as
the result of their contact or
impulse; may I not conceive,
that
a hundred different events might
as well follow from that
cause?
May not both these balls remain at
absolute rest? May not the
first
ball return in a straight line, or
leap off from the second in
any
line or direction? All these
suppositions are consistent
and
conceivable. Why then should we give
the preference to one, which
is
no more consistent or conceivable than
the rest? All our reasonings
a priori
will never be able to show us
any foundation for this
preference.
In a word, then,
every effect
is a distinct event from its cause. It
could not, therefore, be
discovered
in the cause, and the first
invention or conception of
it, a
priori, must be entirely arbitrary.
And even after it is
suggested,
the conjunction of it with the cause
must appear equally
arbitrary; since
there are always many other
effects, which, to reason,
must
seem fully as consistent and
natural. In vain, therefore,
should
we pretend to determine any single
event, or infer any cause or
effect,
without the assistance of
observation and experience.
26. Hence we may
discover
the reason why no philosopher, who is
rational and modest, has
ever pretended
to assign the ultimate cause
of any natural operation, or
to
show distinctly the action of that
power, which produces any
single
effect in the universe. It is
confessed, that the utmost
effort
of human reason is to reduce the
principles, productive of
natural
phenomena, to a greater
simplicity, and to resolve
the many
particular effects into a few
general causes, by means of
reasonings
from analogy, experience, and
observation. But as to the
causes
of these general causes, we should
in vain attempt their
discovery;
nor shall we ever be able to
satisfy ourselves, by any
particular
explication of them. These
ultimate springs and
principles
are totally shut up from human
curiosity and enquiry.
Elasticity,
gravity, cohesion of parts,
communication of motion by
impulse;
these are probably the ultimate
causes and principles which
we shall
ever discover in nature; and we
may esteem ourselves
sufficiently
happy, if, by accurate enquiry and
reasoning, we can trace up
the particular
phenomena to, or near to,
these general principles.
The most
perfect philosophy of the natural
kind only staves off our
ignorance
a little longer: as perhaps the
most perfect philosophy of
the moral
or metaphysical kind serves
only to discover larger
portions
of it. Thus the observation of
human blindness and weakness
is
the result of all philosophy, and
meets us at every turn, in
spite
of our endeavours to elude or avoid
it.
27. Nor is
geometry, when
taken into the assistance of natural
philosophy, ever able to
remedy
this defect, or lead us into the
knowledge of ultimate
causes, by
all that accuracy of reasoning for
which it is so justly
celebrated.
Every part of mixed mathematics
proceeds upon the
supposition that
certain laws are established by
nature in her operations;
and abstract
reasonings are employed, either
to assist experience in the
discovery
of these laws, or to determine
their influence in
particular instances,
where it depends upon any
precise degree of distance
and quantity.
Thus, it is a law of
motion, discovered by
experience,
that the moment or force of any body
in motion is in the compound
ratio
or proportion of its solid contents
and its velocity; and
consequently,
that a small force may remove
the greatest obstacle or
raise the
greatest weight, if, by any
contrivance or machinery, we
can
increase the velocity of that
force, so as to make it an
overmatch
for its antagonist. Geometry
assists us in the
application of
this law, by giving us the just
dimensions of all the parts
and
figures which can enter into any
species of machine; but
still the
discovery of the law itself is owing
merely to experience, and
all the
abstract reasonings in the world
could never lead us one step
towards
the knowledge of it. When we
reason a priori, and
consider merely
any object or cause, as it
appears to the mind,
independent
of all observation, it never could
suggest to us the notion of
any
distinct object, such as its effect;
much less, show us the
inseparable
and inviolable connexion between
them. A man must be very
sagacious
who could discover by reasoning
that crystal is the effect
of heat,
and ice of cold, without being
previously acquainted with
the operation
of these qualities.
PART II.
28. But we have
not yet attained
any tolerable satisfaction with
regard to the question first
proposed.
Each solution still gives
rise to a new question as
difficult
as the foregoing, and leads us
on to farther enquiries.
When it
is asked, What is the nature of all
our reasonings concerning
matter
of fact? the proper answer seems to
be, that they are founded on
the
relation of cause and effect. When
again it is asked, What is
the foundation
of all our reasonings and
conclusions concerning that
relation?
it may be replied in one word,
Experience. But if we still
carry
on our sifting humour, and ask, What
is the foundation of all
conclusions
from experience? this implies a
new question, which may be
of more
difficult solution and explication.
Philosophers, that give
themselves
airs of superior wisdom and
sufficiency, have a hard
task when
they encounter persons of
inquisitive dispositions,
who push
them from every corner to which
they retreat, and who are
sure at
last to bring them to some dangerous
dilemma. The best expedient
to prevent
this confusion, is to be modest
in our pretensions; and even
to
discover the difficulty ourselves
before it is objected to us.
By
this means, we may make a kind of
merit of our very ignorance.
I shall content
myself, in
this section, with an easy task, and
shall pretend only to give a
negative
answer to the question here
proposed. I say then, that,
even
after we have experience of the
operations of cause and
effect,
our conclusions from that experience
are not founded on
reasoning, or
any process of the understanding.
This answer we must
endeavour both
to explain and to defend.
29. It must
certainly be allowed,
that nature has kept us at a great
distance from all her
secrets, and
has afforded us only the
knowledge of a few
superficial qualities
of objects; while she
conceals from us those
powers and
principles on which the influence of
those objects entirely
depends.
Our senses inform us of the colour,
weight, and consistence of
bread;
but neither sense nor reason can
ever inform us of those
qualities
which fit it for the nourishment and
support of a human body.
Sight or
feeling conveys an idea of the
actual motion of bodies; but
as
to that wonderful force or power,
which would carry on a
moving body
for ever in a continued change of
place, and which bodies
never lose
but by communicating it to
others; of this we cannot
form the
most distant conception. But
notwithstanding this
ignorance of
natural powers* and principles, we
always presume, when we see
like
sensible qualities, that they have
like secret powers, and
expect that
effects, similar to those which we
have experienced, will
follow from
them. If a body of like colour
and consistence with that
bread,
which we have formerly eat, be
presented to us, we make no
scruple
of repeating the experiment, and
foresee, with certainty,
like nourishment
and support. Now this is a
process of the mind or
thought,
of which I would willingly know the
foundation. It is allowed on
all
hands that there is no known
connexion between the
sensible qualities
and the secret powers; and
consequently, that the mind
is not
led to form such a conclusion
concerning their constant
and regular
conjunction, by anything which
it knows of their nature. As
to
past Experience, it can be allowed
to give direct and certain
information
of those precise objects
only, and that precise
period of
time, which fell under its
cognizance: but why this
experience
should be extended to future
times, and to other objects,
which
for aught we know, may be only in
appearance similar; this is
the
main question on which I would insist.
The bread, which I formerly
eat,
nourished me; that is, a body of such
sensible qualities was, at
that
time, endued with such secret
powers: but does it follow,
that
other bread must also nourish me at
another time, and that like
sensible
qualities must always be attended
with like secret powers? The
consequence
seems nowise necessary. At
least, it must be
acknowledged that
there is here a consequence
drawn by the mind; that
there is
a certain step taken; a process of
thought, and an inference,
which
wants to be explained. These two
propositions are far from
being
the same, I have found that such an
object has always been
attended
with such an effect, and I foresee,
that other objects, which
are, in
appearance, similar, will be
attended with similar
effects. I
shall allow, if you please, that
the one proposition may
justly be
inferred from the other: I know,
in fact, that it always is
inferred.
But if you insist that the
inference is made by a chain
of
reasoning, I desire you to produce
that reasoning. The
connexion between
these propositions is not
intuitive. There is required
a medium,
which may enable the mind to
draw such an inference, if
indeed
it be drawn by reasoning and
argument. What that medium
is, I
must confess, passes my
comprehension; and it is
incumbent
on those to produce it, who
assert that it really
exists, and
is the origin of all our conclusions
concerning matter of fact.
* The word, Power,
is here
used in a loose and popular sense. The
more accurate explication of
it
would give additional evidence to this
argument. See Sect. 7.
30. This negative
argument
must certainly, in process of time,
become altogether
convincing, if
many penetrating and able
philosophers shall turn
their enquiries
this way and no one be ever
able to discover any
connecting
proposition or intermediate step,
which supports the
understanding
in this conclusion. But as the
question is yet new, every
reader
may not trust so far to his own
penetration, as to conclude,
because
an argument escapes his
enquiry, that therefore it
does
not really exist. For this reason it
may be requisite to venture
upon
a more difficult task; and
enumerating all the branches
of
human knowledge, endeavour to show
that none of them can afford
such
an argument.
All reasonings may
be divided
into two kinds, namely,
demonstrative reasoning, or
that
concerning relations of ideas, and
moral reasoning, or that
concerning
matter of fact and existence. That
there are no demonstrative
arguments
in the case seems evident;
since it implies no
contradiction
that the course of nature may
change, and that an object,
seemingly
like those which we have
experienced, may be attended
with
different or contrary effects. May I
not clearly and distinctly
conceive
that a body, falling from the
clouds, and which, in all
other
respects, resembles snow, has yet
the taste of salt or feeling
of
fire? Is there any more intelligible
proposition than to affirm,
that
all the trees will flourish in
December and January, and
decay
in May and June? Now whatever is
intelligible, and can be
distinctly
conceived, implies no
contradiction, and can never
be
proved false by any demonstrative
argument or abstract
reasoning a
priori.
If we be,
therefore, engaged
by arguments to put trust in past
experience, and make it the
standard
of our future judgement, these
arguments must be probable
only,
or such as regard matter of fact
and real existence,
according to
the division above mentioned. But
that there is no argument of
this
kind, must appear, if our
explication of that species
of reasoning
be admitted as solid and
satisfactory. We have said
that
all arguments concerning existence are
founded on the relation of
cause
and effect; that our knowledge of
that relation is derived
entirely
from experience; and that all our
experimental conclusions
proceed
upon the supposition that the
future will be conformable
to the
past. To endeavour, therefore, the
proof of this last
supposition by
probable arguments, or arguments
regarding existence, must be
evidently
going in a circle, and taking
that for granted, which is
the very
point in question.
31. In reality,
all arguments
from experience are founded on the
similarity which we discover
among
natural objects, and by which we
are induced to expect
effects similar
to those which we have found
to follow from such objects.
And
though none but a fool or madman will
ever pretend to dispute the
authority
of experience, or to reject that
great guide of human life,
it may
surely be allowed a philosopher to
have so much curiosity at
least
as to examine the principle of human
nature, which gives this
mighty
authority to experience, and makes
us draw advantage from that
similarity
which nature has placed among
different objects. From
causes which
appear similar we expect
similar effects. This is the
sum
of all our experimental
conclusions. Now it seems
evident
that, if this conclusion were formed
by reason, it would be as
perfect
at first, and upon one instance,
as after ever so long a
course of
experience. But the case is far
otherwise. Nothing so like
as eggs;
yet no one, on account of this
appearing similarity,
expects the
same taste and relish in all of
them. It is only after a
long course
of uniform experiments in any
kind, that we attain a firm
reliance
and security with regard to a
particular event. Now where
is that
process of reasoning which, from
one instance, draws a
conclusion,
so different from that which it
infers from a hundred
instances
that are nowise different from that
single one? This question I
propose
as much for the sake of
information, as with an
intention
of raising difficulties. I cannot
find, I cannot imagine any
such
reasoning. But I keep my mind still
open to instruction, if any
one
will vouchsafe to bestow it on me.
32. Should it be
said that,
from a number of uniform experiments, we
infer a connexion between
the sensible
qualities and the secret
powers; this, I must
confess, seems
the same difficulty, couched in
different terms. The
question still
recurs, on what process of
argument this inference is
founded?
Where is the medium, the
interposing ideas, which
join propositions
so very wide of each other?
It is confessed that the
colour,
consistence, and other sensible
qualities of bread appear
not, of
themselves, to have any connexion
with the secret powers of
nourishment
and support. For otherwise we
could infer these secret
powers
from the first appearance of these
sensible qualities, without
the
aid of experience; contrary to the
sentiment of all
philosophers, and
contrary to plain matter of fact.
Here, then, is our natural
state
of ignorance with regard to the
powers and influence of all
objects.
How is this remedied by
experience? It only shows us
a number
of uniform effects, resulting
from certain objects, and
teaches
us that those particular objects, at
that particular time, were
endowed
with such powers and forces. When a
new object, endowed with
similar
sensible qualities, is produced, we
expect similar powers and
forces,
and look for a like effect. From a
body of like colour and
consistence
with bread we expect like
nourishment and support. But
this
surely is a step or progress of
the mind, which wants to be
explained.
When a man says, I have
found, in all past
instances, such
sensible qualities conjoined with
such secret powers; And when
he
says, Similar sensible qualities
will always be conjoined
with similar
secret powers, he is not
guilty of a tautology, nor
are these
propositions in any respect the
same. You say that the one
proposition
is an inference from the other.
But you must confess that
the inference
is not intuitive; neither is
it demonstrative: Of what
nature
is it, then? To say it is
experimental, is begging the
question.
For all inferences from
experience suppose, as their
foundation,
that the future will resemble
the past, and that similar
powers
will be conjoined with similar
sensible qualities. If there
be
any suspicion that the course of
nature may change, and that
the
past may be no rule for the future,
all experience becomes
useless,
and can give rise to no inference or
conclusion. It is
impossible, therefore,
that any arguments from
experience can prove this
resemblance
of the past to the future; since
all these arguments are
founded
on the supposition of that
resemblance. Let the course
of things
be allowed hitherto ever so
regular; that alone, without
some
new argument or inference, proves
not that, for the future, it
will
continue so. In vain do you
pretend to have learned the
nature
of bodies from your past
experience. Their secret
nature,
and consequently all their effects
and influence, may change,
without
any change in their sensible
qualities. This happens
sometimes,
and with regard to some objects:
Why may it not happen
always, and
with regard to all objects? What
logic, what process of
argument
secures you against this
supposition? My practice,
you say,
refutes my doubts. But you
mistake the purport of my
question.
As an agent, I am quite
satisfied in the point; but
as a
philosopher, who has some share of
curiosity, I will not say
scepticism,
I want to learn the foundation
of this inference. No
reading, no
enquiry has yet been able to
remove my difficulty, or
give me
satisfaction in a matter of such
importance. Can I do better
than
propose the difficulty to the public,
even though, perhaps, I have
small
hopes of obtaining a solution? We
shall at least, by this
means, be
sensible of our ignorance, if we
do not augment our knowledge.
33. I must confess
that a
man is guilty of unpardonable arrogance
who concludes, because an
argument
has escaped his own
investigation, that
therefore it
does not really exist. I must also
confess that, though all the
learned,
for several ages, should have
employed themselves in
fruitless
search upon any subject, it may
still, perhaps, be rash to
conclude
positively that the subject
must, therefore, pass all
human
comprehension. Even though we
examine all the sources of
our knowledge,
and conclude them unfit
for such a subject, there
may still
remain a suspicion, that the
enumeration is not complete,
or
the examination not accurate. But with
regard to the present
subject, there
are some considerations which
seem to remove all this
accusation
of arrogance or suspicion of
mistake.
It is certain that
the most
ignorant and stupid peasants- nay
infants, nay even brute
beasts-
improve by experience, and learn the
qualities of natural
objects, by
observing the effects which result
from them. When a child has
felt
the sensation of pain from touching
the flame of a candle, he
will be
careful not to put his hand near any
candle; but will expect a
similar
effect from a cause which is similar
in its sensible qualities
and appearance.
If you assert, therefore,
that the understanding of
the child
is led into this conclusion by any
process of argument or
ratiocination,
I may justly require you to
produce that argument; nor
have
you any pretence to refuse so
equitable a demand. You
cannot say
that the argument is abstruse,
and may possibly escape your
enquiry;
since you confess that it is
obvious to the capacity of a
mere
infant. If you hesitate,
therefore, a moment, or if,
after
reflection, you produce any
intricate or profound
argument,
you, in a manner, give up the
question, and confess that
it is
not reasoning which engages us to
suppose the past resembling
the
future, and to expect similar
effects from causes which
are, to
appearance, similar. This is the
proposition which I intended
to
enforce in the present section. If I
be right, I pretend not to
have
made any mighty discovery. And if I be
wrong, I must acknowledge
myself
to be indeed a very backward scholar;
since I cannot now discover
an argument
which, it seems, was perfectly
familiar to me long before I
was
out of my cradle.
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