All the perceptions of the mind are of two kinds, viz. impressions and
ideas, which differ from each other only in their different degrees
of force and vivacity. Our ideas are copyed from our impressions, and
represent them in all their parts. When you would any way vary the idea
of a particular object, you can only encrease or diminish its force and
vivacity. If you make any other change on it, it represents a different
object or impression. The case is the same as in colours. A particular
shade of any colour may acquire a new degree of liveliness or brightness
without any other variation. But when you produce any other variation,
it is no longer the same shade or colour. So that as belief does nothing
but vary the manner, in which we conceive any object, it can only bestow
on our ideas an additional force and vivacity. An opinion, therefore,
or belief may be most accurately defined, a lively idea related to or
associated with a present impression.[6]
[6] We may here take occasion to observe a very remarkable error,
which being frequently inculcated in the schools, has become a kind
of establishd maxim, and is universally received by all logicians.
This error consists in the vulgar division of the acts of the
understanding, into CONCEPTION, JUDGMENT and REASONING, and in the
definitions we give of them. Conception is defind to be the simple
survey of one or more ideas: Judgment to be the separating or
uniting of different ideas: Reasoning to be the separating or
uniting of different ideas by the interposition of others, which
show the relation they bear to each other. But these distinctions
and definitions are faulty in very considerable articles. For
FIRST, it is far from being true, that in every judgment, which we
form, we unite two different ideas; since in that proposition, GOD
IS, or indeed any other, which regards existence, the idea of
existence is no distinct idea, which we unite with that of the
object, and which is capable of forming a compound idea by the
union. SECONDLY, As we can thus form a proposition, which contains
only one idea, so we may exert our reason without employing more
than two ideas, and without having recourse to a third to serve as
a medium betwixt them. We infer a cause immediately from its
effect; and this inference is not only a true species of reasoning,
but the strongest of all others, and more convincing than when we
interpose another idea to connect the two extremes. What we may in
general affirm concerning these three acts of the understanding is,
that taking them in a proper light, they all resolve themselves
into the first, and are nothing but particular ways of conceiving
our objects. Whether we consider a single object, or several;
whether we dwell on these objects, or run from them to others; and
in whatever form or order we survey them, the act of the mind