ps or
hinders, our power of activity. Thus, in so far as we perceive
that a thing affects us with pleasure or pain, we call it good or
evil; wherefore the knowledge of good and evil is nothing else
but the idea of the pleasure or pain, which necessarily follows
from that pleasurable or painful emotion (II. xxii.). But this
idea is united to the emotion in the same way as mind is united
to body (II. xxi.); that is, there is no real distinction
between this idea and the emotion or idea of the modification of
the body, save in conception only. Therefore the knowledge of
good and evil is nothing else but the emotion, in so far as we
are conscious thereof. Q.E.D.

PROP. IX. An emotion, whereof we conceive the cause to be with
us at the present time, is stronger than if we did not conceive
the cause to be with us.

Proof.--Imagination or conception is the idea, by which the
mind regards a thing as present (II. xvii. note), but which
indicates the disposition of the mind rather than the nature of
the external thing (II. xvi. Coroll. ii.). An emotion is
therefore a conception, in so far as it indicates the disposition
of the body. But a conception (by II. xvii.) is stronger, so
long as we conceive nothing which excludes the present existence
of the external object; wherefore an emotion is also stronger or
more intense, when we conceive the cause to be with us at the
present time, than when we do not conceive the cause to be with
us. Q.E.D.

Note.--When I said above in III. xviii. that we are affected
by the image of what is past or future with the same emotion as
if the thing conceived were present, I expressly stated, that
this is only true in so far as we look solely to the image of the
thing in question itself; for the thing's nature is unchanged,
whether we have conceived it or not; I did not deny that the
image becomes weaker, when we regard as present to us other
things which exclude the present existence of the future object:
I did not expressly call attention to the fact, because I
purposed to treat of the strength of the emotions in this part of
my work.

Corollary.--The image of something past or future, that is, of
a thing which we regard as in relation to time past or time
future, to the exclusion of time present, is, when other
conditions are equal, weaker than the image of something present;
consequently an emotion felt towards what is past or future is
less intense, other conditions being equal,