BOOK I PART II
unchangeable. For it inevitably follows from
thence, that since the idea of duration cannot be
derived from such an object, it can never-in any
propriety or exactness be applied to it, nor can
any thing unchangeable be ever said to have
duration. Ideas always represent the Objects or
impressions, from which they are derived, and
can never without a fiction represent or be ap-
plied to any other. By what fiction we apply
the idea of time, even to what is unchangeable,
and suppose, as is common, that duration is a
measure of rest as well as of motion, we shall
consider (Sect 5.) afterwards.
There is another very decisive argument,
which establishes the present doctrine concern-
ing our ideas of space and time, and is founded
only on that simple principle, that our ideas of
them are compounded of parts, which are in-