merely from some object, present to the memory or senses, and a
customary conjunction between that and some other object. Or in other
words; having found, in many instances, that any two kinds of
objects--flame and heat, snow and cold--have always been conjoined
together; if flame or snow be presented anew to the senses, the mind is
carried by custom to expect heat or cold, and to _believe_ that such a
quality does exist, and will discover itself upon a nearer approach.
This belief is the necessary result of placing the mind in such
circumstances. It is an operation of the soul, when we are so situated,
as unavoidable as to feel the passion of love, when we receive benefits;
or hatred, when we meet with injuries. All these operations are a
species of natural instincts, which no reasoning or process of the
thought and understanding is able either to produce or to prevent.

At this point, it would be very allowable for us to stop our
philosophical researches. In most questions we can never make a single
step farther; and in all questions we must terminate here at last, after
our most restless and curious enquiries. But still our curiosity will be
pardonable, perhaps commendable, if it carry us on to still farther
researches, and make us examine more accurately the nature of this
_belief_, and of the _customary conjunction_, whence it is derived. By
this means we may meet with some explications and analogies that will
give satisfaction; at least to such as love the abstract sciences, and
can be entertained with speculations, which, however accurate, may still
retain a degree of doubt and uncertainty. As to readers of a different
taste; the remaining part of this section is not calculated for them,
and the following enquiries may well be understood, though it be
neglected.