An Enquiry Concerning Human Understanding - David Hume (free ereaders .txt) 📗
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depended on; but that we must correct their evidence by reason, and by
considerations, derived from the nature of the medium, the distance of
the object, and the disposition of the organ, in order to render them,
within their sphere, the proper criteria of truth and falsehood. There
are other more profound arguments against the senses, which admit not of
so easy a solution.
118. It seems evident, that men are carried, by a natural instinct or
prepossession, to repose faith in their senses; and that, without any
reasoning, or even almost before the use of reason, we always suppose an
external universe, which depends not on our perception, but would exist,
though we and every sensible creature were absent or annihilated. Even
the animal creation are governed by a like opinion, and preserve this
belief of external objects, in all their thoughts, designs, and actions.
It seems also evident, that, when men follow this blind and powerful
instinct of nature, they always suppose the very images, presented by
the senses, to be the external objects, and never entertain any
suspicion, that the one are nothing but representations of the other.
This very table, which we see white, and which we feel hard, is believed
to exist, independent of our perception, and to be something external
to our mind, which perceives it. Our presence bestows not being on it:
our absence does not annihilate it. It preserves its existence uniform
and entire, independent of the situation of intelligent beings, who
perceive or contemplate it.
But this universal and primary opinion of all men is soon destroyed by
the slightest philosophy, which teaches us, that nothing can ever be
present to the mind but an image or perception, and that the senses are
only the inlets, through which these images are conveyed, without being
able to produce any immediate intercourse between the mind and the
object. The table, which we see, seems to diminish, as we remove farther
from it: but the real table, which exists independent of us, suffers no
alteration: it was, therefore, nothing but its image, which was present
to the mind. These are the obvious dictates of reason; and no man, who
reflects, ever doubted, that the existences, which we consider, when we
say, this house and that tree, are nothing but perceptions in the
mind, and fleeting copies or representations of other existences, which
remain uniform and independent.
119. So far, then, are we necessitated by reasoning to contradict or
depart from the primary instincts of nature, and to embrace a new system
with regard to the evidence of our senses. But here philosophy finds
herself extremely embarrassed, when she would justify this new system,
and obviate the cavils and objections of the sceptics. She can no longer
plead the infallible and irresistible instinct of nature: for that led
us to a quite different system, which is acknowledged fallible and even
erroneous. And to justify this pretended philosophical system, by a
chain of clear and convincing argument, or even any appearance of
argument, exceeds the power of all human capacity.
By what argument can it be proved, that the perceptions of the mind
must be caused by external objects, entirely different from them, though
resembling them (if that be possible) and could not arise either from
the energy of the mind itself, or from the suggestion of some invisible
and unknown spirit, or from some other cause still more unknown to us?
It is acknowledged, that, in fact, many of these perceptions arise not
from anything external, as in dreams, madness, and other diseases. And
nothing can be more inexplicable than the manner, in which body should
so operate upon mind as ever to convey an image of itself to a
substance, supposed of so different, and even contrary a nature.
It is a question of fact, whether the perceptions of the senses be
produced by external objects, resembling them: how shall this question
be determined? By experience surely; as all other questions of a like
nature. But here experience is, and must be entirely silent. The mind
has never anything present to it but the perceptions, and cannot
possibly reach any experience of their connexion with objects. The
supposition of such a connexion is, therefore, without any foundation in
reasoning.
120. To have recourse to the veracity of the supreme Being, in order to
prove the veracity of our senses, is surely making a very unexpected
circuit. If his veracity were at all concerned in this matter, our
senses would be entirely infallible; because it is not possible that he
can ever deceive. Not to mention, that, if the external world be once
called in question, we shall be at a loss to find arguments, by which we
may prove the existence of that Being or any of his attributes.
121. This is a topic, therefore, in which the profounder and more
philosophical sceptics will always triumph, when they endeavour to
introduce an universal doubt into all subjects of human knowledge and
enquiry. Do you follow the instincts and propensities of nature, may
they say, in assenting to the veracity of sense? But these lead you to
believe that the very perception or sensible image is the external
object. Do you disclaim this principle, in order to embrace a more
rational opinion, that the perceptions are only representations of
something external? You here depart from your natural propensities and
more obvious sentiments; and yet are not able to satisfy your reason,
which can never find any convincing argument from experience to prove,
that the perceptions are connected with any external objects.
122. There is another sceptical topic of a like nature, derived from the
most profound philosophy; which might merit our attention, were it
requisite to dive so deep, in order to discover arguments and
reasonings, which can so little serve to any serious purpose. It is
universally allowed by modern enquirers, that all the sensible qualities
of objects, such as hard, soft, hot, cold, white, black, &c. are merely
secondary, and exist not in the objects themselves, but are perceptions
of the mind, without any external archetype or model, which they
represent. If this be allowed, with regard to secondary qualities, it
must also follow, with regard to the supposed primary qualities of
extension and solidity; nor can the latter be any more entitled to that
denomination than the former. The idea of extension is entirely acquired
from the senses of sight and feeling; and if all the qualities,
perceived by the senses, be in the mind, not in the object, the same
conclusion must reach the idea of extension, which is wholly dependent
on the sensible ideas or the ideas of secondary qualities. Nothing can
save us from this conclusion, but the asserting, that the ideas of those
primary qualities are attained by Abstraction, an opinion, which, if
we examine it accurately, we shall find to be unintelligible, and even
absurd. An extension, that is neither tangible nor visible, cannot
possibly be conceived: and a tangible or visible extension, which is
neither hard nor soft, black nor white, is equally beyond the reach of
human conception. Let any man try to conceive a triangle in general,
which is neither Isosceles nor Scalenum, nor has any particular
length or proportion of sides; and he will soon perceive the absurdity
of all the scholastic notions with regard to abstraction and
general ideas[31]
[31] This argument is drawn from Dr. Berkeley; and indeed most
of the writings of that very ingenious author form the best
lessons of scepticism, which are to be found either among the
the ancient or modern philosopher, Bayle not excepted. He
professes, however, in his title-page (and undoubtedly with
great truth) to have composed his book against the sceptics as
well as against the atheists and free-thinkers. But that all
his arguments, though otherwise intended, are, in reality,
merely sceptical, appears from this, _that they admit of no
answer and produce no conviction_. Their only effect is to
cause that momentary amazement and irresolution and confusion,
which is the result of scepticism.
123. Thus the first philosophical objection to the evidence of sense or
to the opinion of external existence consists in this, that such an
opinion, if rested on natural instinct, is contrary to reason, and if
referred to reason, is contrary to natural instinct, and at the same
time carries no rational evidence with it, to convince an impartial
enquirer. The second objection goes farther, and represents this opinion
as contrary to reason: at least, if it be a principle of reason, that
all sensible qualities are in the mind, not in the object. Bereave
matter of all its intelligible qualities, both primary and secondary,
you in a manner annihilate it, and leave only a certain unknown,
inexplicable something, as the cause of our perceptions; a notion so
imperfect, that no sceptic will think it worth while to contend
against it.
PART II.
124. It may seem a very extravagant attempt of the sceptics to destroy
reason by argument and ratiocination; yet is this the grand scope of
all their enquiries and disputes. They endeavour to find objections,
both to our abstract reasonings, and to those which regard matter of
fact and existence.
The chief objection against all abstract reasonings is derived from
the ideas of space and time; ideas, which, in common life and to a
careless view, are very clear and intelligible, but when they pass
through the scrutiny of the profound sciences (and they are the chief
object of these sciences) afford principles, which seem full of
absurdity and contradiction. No priestly dogmas, invented on purpose
to tame and subdue the rebellious reason of mankind, ever shocked common
sense more than the doctrine of the infinitive divisibility of
extension, with its consequences; as they are pompously displayed by all
geometricians and metaphysicians, with a kind of triumph and exultation.
A real quantity, infinitely less than any finite quantity, containing
quantities infinitely less than itself, and so on in infinitum; this
is an edifice so bold and prodigious, that it is too weighty for any
pretended demonstration to support, because it shocks the clearest and
most natural principles of human reason.[32] But what renders the matter
more extraordinary, is, that these seemingly absurd opinions are
supported by a chain of reasoning, the clearest and most natural; nor is
it possible for us to allow the premises without admitting the
consequences. Nothing can be more convincing and satisfactory than all
the conclusions concerning the properties of circles and triangles; and
yet, when these are once received, how can we deny, that the angle of
contact between a circle and its tangent is infinitely less than any
rectilineal angle, that as you may increase the diameter of the circle
in infinitum, this angle of contact becomes still less, even _in
infinitum_, and that the angle of contact between other curves and their
tangents may be infinitely less than those between any circle and its
tangent, and so on, in infinitum? The demonstration of these
principles seems as unexceptionable as that which proves the three
angles of a triangle to be equal to two right ones, though the latter
opinion be natural and easy, and the former big with contradiction and
absurdity. Reason here seems to be thrown into a kind of amazement and
suspence, which, without the suggestions of any sceptic, gives her a
diffidence of herself, and of the ground on which she treads. She sees a
full light, which illuminates certain places; but that light borders
upon the most profound darkness. And between these she is so dazzled and
confounded, that she scarcely can pronounce with certainty and assurance
concerning any one object.
[32] Whatever disputes there may be about
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