We shall afterwards see many instances of this tendency of relation to
make us ascribe an identity to different objects; but shall here confine
ourselves to the present subject. We find by experience, that there is
such a constancy in almost all the impressions of the senses, that their
interruption produces no alteration on them, and hinders them not from
returning the same in appearance and in situation as at their first
existence. I survey the furniture of my chamber; I shut my eyes, and
afterwards open them; and find the new perceptions to resemble perfectly
those, which formerly struck my senses. This resemblance is observed in
a thousand instances, and naturally connects together our ideas of these
interrupted perceptions by the strongest relation, and conveys the
mind with an easy transition from one to another. An easy transition
or passage of the imagination, along the ideas of these different and
interrupted perceptions, is almost the same disposition of mind with
that in which we consider one constant and uninterrupted perception. It
is therefore very natural for us to mistake the one for the other.[5]
This reasoning, it must be confest, is somewhat abstruse, and
difficult to be comprehended; but it is remarkable, that this very
difficulty may be converted into a proof of the reasoning. We may
observe, that there are two relations, and both of them
resemblances, which contribute to our mistaking the succession of
our interrupted perceptions for an identical object. The first is,
the resemblance of the perceptions: The second is the resemblance,
which the act of the mind in surveying a succession of resembling
objects bears to that in surveying an identical object. Now these
resemblances we are apt to confound with each other; and it is
natural we shoud, according to this very reasoning. But let us keep
them distinct, and we shall find no difficulty in conceiving the
precedent argument.