ried single idea in his mind, without any
other, for any considerable time together.

14. Proof.

For trial, let him take any figure, any degree of light or whiteness, or
what other he pleases, and he will, I suppose, find it difficult to keep
all other ideas out of his mind; but that some, either of another kind,
or various considerations of that idea, (each of which considerations is
a new idea,) will constantly succeed one another in his thoughts, let
him be as wary as he can.

15. The extent of our power over the succession of our ideas.

All that is in a man's power in this case, I think, is only to mind and
observe what the ideas are that take their turns in his understanding;
or else to direct the sort, and call in such as he hath a desire or use
of: but hinder the constant succession of fresh ones, I think he cannot,
though he may commonly choose whether he will heedfully observe and
consider them.

16. Ideas, however made, include no sense of motion.

Whether these several ideas in a man's mind be made by certain motions,
I will not here dispute; but this I am sure, that they include no idea
of motion in their appearance; and if a man had not the idea of motion
otherwise, I think he would have none at all, which is enough to my
present purpose; and sufficiently shows that the notice we take of the
ideas of our own minds, appearing there one after another, is that which
gives us the idea of succession and duration, without which we should
have no such ideas at all. It is not then MOTION, but the constant train
of IDEAS in our minds whilst we are waking, that furnishes us with the
idea of duration; whereof motion no otherwise gives us any perception
than as it causes in our minds a constant succession of ideas, as I have
before showed: and we have as clear an idea of succession and duration,
by the train of other ideas succeeding one another in our minds,
without the idea of any motion, as by the train of ideas caused by the
uninterrupted sensible change of distance between two bodies, which
we have from motion; and therefore we should as well have the idea of
duration were there no sense of motion at all.

17. Time is Duration set out by Measures.

Having thus got the idea of duration, the next thing natural for the
mind to do, is to get some measure of this common duration, whereby it
might judge of its different lengths, and consider the distinct order
wherein several things exist; without whi