ason from causes and effects; and
it is the same principle, which convinces us of the continued existence
of external objects, when absent from the senses. But though these two
operations be equally natural and necessary in the human mind, yet in
some circumstances they are [Sect. 4.] directly contrary, nor is it
possible for us to reason justly and regularly from causes and effects,
and at the same time believe the continued existence of matter. How
then shall we adjust those principles together? Which of them shall we
prefer? Or in case we prefer neither of them, but successively assent
to both, as is usual among philosophers, with what confidence can we
afterwards usurp that glorious title, when we thus knowingly embrace a
manifest contradiction?

This contradiction [Part III. Sect. 14.] would be more excusable, were
it compensated by any degree of solidity and satisfaction in the other
parts of our reasoning. But the case is quite contrary. When we trace up
the human understanding to its first principles, we find it to lead us
into such sentiments, as seem to turn into ridicule all our past pains
and industry, and to discourage us from future enquiries. Nothing is
more curiously enquired after by the mind of man, than the causes of
every phenomenon; nor are we content with knowing the immediate causes,
but push on our enquiries, till we arrive at the original and ultimate
principle. We would not willingly stop before we are acquainted with
that energy in the cause, by which it operates on its effect; that tie,
which connects them together; and that efficacious quality, on which the
tie depends. This is our aim in all our studies and reflections: And
how must we be disappointed, when we learn, that this connexion, tie, or
energy lies merely in ourselves, and is nothing but that determination
of the mind, which is acquired by custom, and causes us to make
a transition from an object to its usual attendant, and from the
impression of one to the lively idea of the other? Such a discovery not
only cuts off all hope of ever attaining satisfaction, but even prevents
our very wishes; since it appears, that when we say we desire to know
the ultimate and operating principle, as something, which resides in
the external object, we either contradict ourselves, or talk without a
meaning.

This deficiency in our ideas is not, indeed, perceived in common life,
nor are we sensible, that in the most usual conjunctions of cause and