any such impression, you may be certain you are mistaken, when you
imagine you have any such idea.

But though it be impossible to shew the impression, from which the idea of
time without a changeable existence is derived; yet we can easily point
out those appearances, which make us fancy we have that idea. For we may
observe, that there is a continual succession of perceptions in our mind;
so that the idea of time being for ever present with us; when we consider
a stedfast object at five-a-clock, and regard the same at six; we are apt
to apply to it that idea in the same manner as if every moment were
distinguished by a different position, or an alteration of the object.
The first and second appearances of the object, being compared with the
succession of our perceptions, seem equally removed as if the object had
really changed. To which we may add, what experience shews us, that the
object was susceptible of such a number of changes betwixt these
appearances; as also that the unchangeable or rather fictitious duration
has the same effect upon every quality, by encreasing or diminishing it,
as that succession, which is obvious to the senses. From these three
relations we are apt to confound our ideas, and imagine we can form the
idea of a time and duration, without any change or succession.



SECT. VI. OF THE IDEA OF EXISTENCE, AND OF EXTERNAL EXISTENCE.


It may not be amiss, before we leave this subject, to explain the ideas
of existence and of external existence; which have their difficulties, as
well as the ideas of space and time. By this means we shall be the better
prepared for the examination of knowledge and probability, when we