A Treatise of Human Nature | Page 8

two kinds,
those Of SENSATION and those of REFLEXION. The first kind arises in the soul
originally, from unknown causes. The second is derived in a great measure from our
ideas, and that in the following order. An impression first strikes upon the senses, and

makes us perceive heat or cold, thirst or hunger, pleasure or pain of some kind or other.
Of this impression there is a copy taken by the mind, which remains after the impression
ceases; and this we call an idea. This idea of pleasure or pain, when it returns upon the
soul, produces the new impressions of desire and aversion, hope and fear, which may
properly be called impressions of reflexion, because derived from it. These again are
copied by the memory and imagination, and become ideas; which perhaps in their turn
give rise to other impressions and ideas. So that the impressions of reflexion are only
antecedent to their correspondent ideas; but posterior to those of sensation, and derived
from them. The examination of our sensations belongs more to anatomists and natural
philosophers than to moral; and therefore shall not at present be entered upon. And as the
impressions of reflexion, viz. passions, desires, and emotions, which principally deserve
our attention, arise mostly from ideas, it will be necessary to reverse that method, which
at first sight seems most natural; and in order to explain the nature and principles of the
human mind, give a particular account of ideas, before we proceed to impressions. For
this reason I have here chosen to begin with ideas.

SECT. III. OF THE IDEAS OF THE MEMORY AND IMAGINATION.
We find by experience, that when any impression has been present with the mind, it again
makes its appearance there as an idea; and this it may do after two different ways: either
when in its new appearance it retains a considerable degree of its first vivacity, and is
somewhat intermediate betwixt an impression and an idea: or when it entirely loses that
vivacity, and is a perfect idea. The faculty, by which we repeat our impressions in the
first manner, is called the MEMORY, and the other the IMAGINATION. It is evident at
first sight, that the ideas of the memory are much more lively and strong than those of the
imagination, and that the former faculty paints its objects in more distinct colours, than
any which are employed by the latter. When we remember any past event, the idea of it
flows in upon the mind in a forcible manner; whereas in the imagination the perception is
faint and languid, and cannot without difficulty be preserved by the mind steddy and
uniform for any considerable time. Here then is a sensible difference betwixt one species
of ideas and another. But of this more fully hereafter.[


Part II, Sect. 5.]
There is another difference betwixt these two kinds of ideas, which:-s no less evident,
namely that though neither the ideas, of the memory nor imagination, neither the lively
nor faint ideas can make their appearance 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