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.*

  * 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 ancient or modern
philosophers, 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