— 636 —
Past Existence is known by Memory.
      §11. As when our Senses are actually employ’d about any
Object, we do know that it does exist; so by our Memory we may
be assured, that heretofore Things, that affected our Senses, have
existed. And thus we have knowledge of the past Existence of several
Things, whereof our Senses having informed us, our Memories
still retain the Ideas; and of this we are past all doubt, so long as we
remember well. But this Knowledge also reaches no farther than
our Senses have formerly assured us. Thus seeing Water at this
instant, ’tis an unquestionable Truth to me, that Water doth exist:
and remembring that I saw it yesterday, it will also be always true;
and as long as my Memory retains it, always an undoubted Proposi-
tion to me, that Water did exist 10th. July, 1688. as it will also be
equally true, that a certain number of very fine Colours did exist,
which, at the same time, I saw upon a Bubble of that Water: But
being now quite out of the sight both of the Water and Bubbles too,
it is no more certainly known to me, that the Water doth now exist,
— 637 —
than that the Bubbles or Colours therein do so; it being no more
necessary that Water should exist to day, because it existed yester-
day, than that the Colours or Bubbles exist to day, because they
existed yesterday, though it be exceedingly much more probable,
because Water hath been observed to continue long in Existence,
but Bubbles, and the Colours on them quickly cease to be.
Locke Hum IV, 11, §11, pp. 636-637