— 182 —
      §4. That we have our notion of Succession and Duration from this
Original, viz. from Reflection on the train of Ideas, which we find to
appear one after another in our own Minds, seems plain to me, in
that we have no perception of Duration, but by considering the
train of Ideas, that take their turns in our Understandings. When
that succession of Ideas ceases, our perception of Duration ceases
with it; which every one clearly experiments in himself, whilst he
sleeps soundly, whether an hour, or a day; a month, or a year; of
which Duration of things, whilst he sleeps, or thinks not, he has no
perception at all, but it is quite lost to him; and the moment
wherein he leaves off to think, till the moment he begins to think
again, seems to him to have no distance. And so I doubt not but it
would be to a waking Man, if it were possible for him to keep only
one Idea in his Mind, without variation, and the succession of
others: And we see, that one who fixes his Thoughts very intently
on one thing, so as to take but little notice of the succession of Ideas
that pass in his Mind, whilst he is taken up with that earnest
Contemplation, lets slip out of his Account a good part of that
Duration, and thinks that time shorter than it is. But if sleep
commonly unites the distant parts of Duration, it is, because during
that time we have no Succession of Ideas in our Minds. For if a Man,
during his Sleep, dreams, and variety of Ideas make themselves
perceptible in his Mind one after another, he hath then, during such
a dreaming, a Sense of Duration, and of the length of it. By which it is
to me very clear, that Men derive their Ideas of Duration, from their
— 183 —
Reflection on the train of the Ideas, they observe to succeed one
another in their own Understandings, without which Observation
they can have no Notion of Duration, whatever may happen in the
World.
Locke Hum II, 14, §4, pp. 182-183