rsy concerning identity is not merely a dispute of
words. For when we attribute identity, in an improper sense, to variable
or interrupted objects, our mistake is not confined to the expression,
but is commonly attended with a fiction, either of something invariable
and uninterrupted, or of something mysterious and inexplicable, or at
least with a propensity to such fictions. What will suffice to prove
this hypothesis to the satisfaction of every fair enquirer, is to shew
from daily experience and observation, that the objects, which are
variable or interrupted, and yet are supposed to continue the same, are
such only as consist of a succession of parts, connected together by
resemblance, contiguity, or causation. For as such a succession answers
evidently to our notion of diversity, it can only be by mistake we
ascribe to it an identity; and as the relation of parts, which leads us
into this mistake, is really nothing but a quality, which produces an
association of ideas, and an easy transition of the imagination from one
to another, it can only be from the resemblance, which this act of the
mind bears to that, by which we contemplate one continued object, that
the error arises. Our chief business, then, must be to prove, that
all objects, to which we ascribe identity, without observing their
invariableness and uninterruptedness, are such as consist of a
succession of related objects.

In order to this, suppose any mass of matter, of which the parts are
contiguous and connected, to be placed before us; it is plain we must
attribute a perfect identity to this mass, provided all the parts
continue uninterruptedly and invariably the same, whatever motion or
change of place we may observe either in the whole or in any of the
parts. But supposing some very small or inconsiderable part to be added
to the mass, or subtracted from it; though this absolutely destroys
the identity of the whole, strictly speaking; yet as we seldom think so
accurately, we scruple not to pronounce a mass of matter the same, where
we find so trivial an alteration. The passage of the thought from the
object before the change to the object after it, is so smooth and easy,
that we scarce perceive the transition, and are apt to imagine, that it
is nothing but a continued survey of the same object.

There is a very remarkable circumstance, that attends this experiment;
which is, that though the change of any considerable part in a mass
of matter destroy