a lively idea related to a present impression; let us now proceed to
examine from what principles it is derived, and what bestows the vivacity
on the idea.

I would willingly establish it as a general maxim in the science of human
nature, that when any impression becomes present to us, it not only
transports the mind to such ideas as are related to it, but likewise
communicates to them a share of its force and vivacity. All the
operations of the mind depend in a great measure on its disposition, when
it performs them; and according as the spirits are more or less elevated,
and the attention more or less fixed, the action will always have more or
less vigour and vivacity. When therefore any object is presented, which
elevates and enlivens the thought, every action, to which the mind
applies itself, will be more strong and vivid, as Tong as that
disposition continues, Now it is evident the continuance of the
disposition depends entirely on the objects, about which the mind is
employed; and that any new object naturally gives a new direction to the
spirits, and changes the disposition; as on the contrary, when the mind
fixes constantly on the same object, or passes easily and insensibly
along related objects, the disposition has a much longer duration. Hence
it happens, that when the mind is once inlivened by a present impression,
it proceeds to form a more lively idea of the related objects, by a
natural transition of the disposition from the one to the other. The
change of the objects is so easy, that the mind is scarce sensible of it,
but applies itself to the conception of the related idea with all the
force and vivacity it acquired from the present impression.

If in considering the nature of relation, and that facility of
transition, which is essential to it, we can satisfy ourselves concerning
the reality of this phaenomenon, it is well: But I must confess I place my