sure steps, to review frequently our conclusions, and examine accurately
all their consequences; though by these means we shall make both a slow
and a short progress in our systems; are the only methods, by which we
can ever hope to reach truth, and attain a proper stability and
certainty in our determinations.

117. There is another species of scepticism, _consequent_ to science and
enquiry, when men are supposed to have discovered, either the absolute
fallaciousness of their mental faculties, or their unfitness to reach
any fixed determination in all those curious subjects of speculation,
about which they are commonly employed. Even our very senses are brought
into dispute, by a certain species of philosophers; and the maxims of
common life are subjected to the same doubt as the most profound
principles or conclusions of metaphysics and theology. As these
paradoxical tenets (if they may be called tenets) are to be met with in
some philosophers, and the refutation of them in several, they naturally
excite our curiosity, and make us enquire into the arguments, on which
they may be founded.

I need not insist upon the more trite topics, employed by the sceptics
in all ages, against the evidence of _sense_; such as those which are
derived from the imperfection and fallaciousness of our organs, on
numberless occasions; the crooked appearance of an oar in water; the
various aspects of objects, according to their different distances; the
double images which arise from the pressing one eye; with many other
appearances of a like nature. These sceptical topics, indeed, are only
sufficient to prove, that the senses alone are not implicitly to be
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,