in the mind, unless their correspondent impressions have gone before to
prepare the way for them, yet the imagination is not restrained to the
same order and form with the original impressions; while the memory is in
a manner tied down in that respect, without any power of variation.

It is evident, that the memory preserves the original form, in which its
objects were presented, and that where-ever we depart from it in
recollecting any thing, it proceeds from some defect or imperfection in
that faculty. An historian may, perhaps, for the more convenient Carrying
on of his narration, relate an event before another, to which it was in
fact posterior; but then he takes notice of this disorder, if he be
exact; and by that means replaces the idea in its due position. It is the
same case in our recollection of those places and persons, with which we
were formerly acquainted. The chief exercise of the memory is not to
preserve the simple ideas, but their order and position. In short, this
principle is supported by such a number of common and vulgar phaenomena,
that we may spare ourselves the trouble of insisting on it any farther.

The same evidence follows us in our second principle, OF THE LIBERTY OF
THE IMAGINATION TO TRANSPOSE AND CHANGE ITS IDEAS. The fables we meet
with in poems and romances put this entirely out of the question. Nature
there is totally confounded, and nothing mentioned but winged horses,
fiery dragons, and monstrous giants. Nor will this liberty of the fancy
appear strange, when we consider, that all our ideas are copyed from our
impressions, and that there are not any two impressions which are
perfectly inseparable. Not to mention, that this is an evident
consequence of the division of ideas into simple and complex. Where-ever
the imagination perceives a difference among ideas, it can easily produce
a separation.