e which renders our experience useful to us, and
makes us expect, for the future, a similar train of events with
those which have appeared in the past."...

"All belief of matter-of-fact or real existence is derived 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."--(IV. pp. 52-56.)

The only comment that appears needful here is, that Hume has attached
somewhat too exclusive a weight to that repetition of experiences to
which alone the term "custom" can be properly applied. The proverb says
that "a burnt child dreads the fire"; and any one who will make the
experiment will find, that one burning is quite sufficient to establish
an indissoluble belief that contact with fire and pain go together.

As a sort of inverted memory, expectation follows the same laws; hence,
while a belief of expectation is, in most cases, as Hume truly says,
established by custom, or the repetition of weak impressions, it may
quite well be based upon a single strong experience. In the absence of
language, a specific memory cannot be strengthened by repetition. It is
obvious that that which has happened cannot happen again, with the same
collateral associations of co-existence and succession. But, memories of
the co-existence and succession of impressions are capable of being
indefinitely strengthened by the recurrence of similar impressions, in
the same order, even though the collateral associations are totally
different; in fact, the ideas of these impressions become generic.

If I recollect that a piece of ice was cold yesterday, nothing c