rfect diversity is seen in two or more
objects which are separated by intervals of space and periods of time.
But, in both these cases, there is no sharp line of demarcation between
identity and diversity, and it is impossible to say when an object
ceases to be one and becomes two.

When a sea-anemone multiplies by division, there is a time during which
it is said to be one animal partially divided; but, after a while, it
becomes two animals adherent together, and the limit between these
conditions is purely arbitrary. So in mineralogy, a crystal of a
definite chemical composition may have its substance replaced, particle
by particle, by another chemical compound. When does it lose its
primitive identity and become a new thing?

Again, a plant or an animal, in the course of its existence, from the
condition of an egg or seed to the end of life, remains the same neither
in form, nor in structure, nor in the matter of which it is composed:
every attribute it possesses is constantly changing, and yet we say that
it is always one and the same individual. And if, in this case, we
attribute identity without supposing an indivisible immaterial something
to underlie and condition that identity, why should we need the
supposition in the case of that succession of changeful phenomena we
call the mind?

In fact, we ascribe identity to an individual plant or animal, simply
because there has been no moment of time at which we could observe any
division of it into parts separated by time or space. Every experience
we have of it is as one thing and not as two; and we sum up our
experiences in the ascription of identity, although we know quite well
that, strictly speaking, it has not been the same for any two moments.

So with the mind. Our perceptions flow in even succession; the
impressions of the present moment are inextricably mixed up with the
memories of yesterday and the expectations of to-morrow, and all are
connected by the links of cause and effect.

" ... as the same individual republic may not only change its
members, but also its laws and constitutions; in like manner the
same person may vary his character and disposition, as well as his
impressions and ideas, without losing his identity. Whatever
changes he endures, his several parts are still connected by the
relation of causation. And in this view our identity with regard to
the passions serves to corroborate that with regard to t