s
from joy must be limited by human power, together with the power of an
external cause, while that which springs from sorrow must be limited by
human power alone. The latter is, therefore, weaker than the former.

_How the Strength of the Emotions Varies_

I

The imagination is an idea by which the mind contemplates an object as
present, an idea which nevertheless indicates the constitution of the
human body rather than the nature of the external object. Imagination,
therefore, is an emotion in so far as it indicates the constitution of
the body. But the imagination increases in intensity in proportion as we
imagine nothing which excludes the present existence of the external
object. If, therefore, we imagine the cause of an emotion to be actually
present with us, that emotion will be intenser or stronger than if we
imagined the cause not to be present.

When I said that we are affected by the image of an object in the future
or the past with the same emotion with which we should be affected if
the object we imagined were actually present, I was careful to warn the
reader that this was true in so far only as we attend to the image alone
of the object itself, for the image is of the same nature whether we
have imagined the object or not; but I have not denied that the image
becomes weaker when we contemplate as present other objects which
exclude the present existence of the future object.

The image of a past or future object, that is to say, of an object which
we contemplate in relation to the past or future to the exclusion of the
present, other things being equal, is weaker than the image of a present
object, and consequently the emotion towards a future or past object,
other things being equal, is weaker then than the emotion towards a
present object.

The desire which springs from a knowledge of good and evil can be easily
extinguished or restrained, in so far as this knowledge is connected
with the future, by the desire of things which in the present are sweet.

II

In so far as we imagine any object to be necessary do we affirm its
existence, and, on the other hand, we deny its existence in so far as we
imagine it to be not necessary and therefore the emotion towards an
object which we imagine as necessary, other things being equal, is
stronger than that towards an object that is possible, contingent, or
not necessary.

In so far as we imagine an object as contingent, we are not affected by
the i