we consider； when we say； and ； are
nothing but perceptions in the mind； and fleeting copies or
representations of other existences； which remain uniform
and independent。
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 any thing 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 any
thing 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。
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。
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。
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
； 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
nor ； 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。＇37＇
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 ； as the cause of our perceptions； a
notion so imperfect； that no sceptic will think it worth
while to contend against it。
* * * *
PART II。
I/T may seem a very extravagant attempt of the
sceptics to destroy by argument and ratiocination；
yet is this the grand scope of all their enquiries and
disputes。 They endeavour to find objections； both to our
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 ； 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
； 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。＇38＇ 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 ； this
angle of contact becomes still less； even ；
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； ？ 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。
The absurdity of these bold determinations of the
abstract sciences seems to become； if possible； still more
palpable with regard to time than extension。 An infinite
number of real parts of time； passing in succession； and
exhausted one after another； appears so evident a
contradiction； that no man； one should think； whose
judgement is not corrupted； instead of being improved； by
the sciences； would ever be able to admit of it。
Yet still reason must remain restless； and unquiet；
even with regard to that scepticism； to which she is driven
by these seeming absurdities and contradictions。 How any
clear； distinct idea can contain circumstances；
contradictory to itself； or to any other clear； distinct
idea； is absolutely incomprehensible； and is； perhaps； as
absurd as any proposition； which can be formed。 So that
nothing can be more sceptical； or more full of doubt and
hesitation； than this scepticism itself； which arises from
some of the paradoxical conclusions of geometry or the
science of quantity。＇39＇
The sceptical objections to evidence； or to the
reasonings concerning matter of f