impression related to it, maybe liable to the following objection, by
reason of a little ambiguity in those words strong and lively. It may be
said, that not only an impression may give rise to reasoning, but that an
idea may also have the same influence; especially upon my principle, that
all our ideas are derived from correspondent impressions. For suppose I
form at present an idea, of which I have forgot the correspondent
impression, I am able to conclude from this idea, that such an impression
did once exist; and as this conclusion is attended with belief, it may be
asked, from whence are the qualities of force and vivacity derived, which
constitute this belief? And to this I answer very readily, from the
present idea. For as this idea is not here considered, as the
representation of any absent object, but as a real perception in the
mind, of which we are intimately conscious, it must be able to bestow on
whatever is related to it the same quality, call it firmness, or
solidity, or force, or vivacity, with which the mind reflects upon it,
and is assured of its present existence. The idea here supplies the place
of an impression, and is entirely the same, so far as regards our present
purpose.

Upon the same principles we need not be surprized to hear of the
remembrance of an idea: that is, of the idea of an idea, and of its force
and vivacity superior to the loose conceptions of the imagination. In
thinking of our past thoughts we not only delineate out the objects, of
which we were thinking, but also conceive the action of the mind in the
meditation, that certain JE-NE-SCAI-QUOI, of which it is impossible to
give any definition or description, but which every one sufficiently
understands. When the memory offers an idea of this, and represents it as
past, it is easily conceived how that idea may have more vigour and
firmness, than when we think of a past thought, of which we have no
remembrance.