lways subject to passions,
and that he follows and obeys the common order of Nature, accommodating
himself to it as far as the nature of things requires. The force and
increase of any passion and its perseverance in existence are not
limited by the power by which we endeavor to persevere in existence, but
by the power of an external cause compared with our own power.

_The Nature of Good and Evil_

We call a thing good which contributes to the preservation of our being,
and we call a thing evil if it is an obstacle to the preservation of our
being; that is to say, a thing is called by us good or evil as it
increases or diminishes, helps or restrains, our power of action. In so
far, therefore, as we perceive that any object affects us with joy or
sorrow do we call it good or evil, and therefore the knowledge of good
or evil is nothing but an idea of joy or sorrow which necessarily
follows from the emotion itself of joy or sorrow. But this idea is
united to the emotion in the same way as the mind is united to the body,
or, in other words, this idea is not actually distinguished from the
emotion itself; that is to say, it is not actually distinguished from
the idea of the modification of the body, unless in conception alone.
This knowledge, therefore, of good and evil is nothing but the emotion
itself of joy and sorrow in so far as we are conscious of it.

_The Control of the Emotions_

An emotion, in so far as it is related to the mind, is an idea by which
the mind affirms a greater or less power of existence for its body than
the body possessed before. Whenever, therefore, the mind is agitated by
any emotion, the body is at the same time affected with a modification
by which its power of action is increased or diminished. Again, this
modification of the body receives from its own cause a power to
persevere in its own being, a power, therefore, which cannot be
restrained nor removed unless by a bodily cause affecting the body with
a modification contrary to the first, and stronger than it. Thus the
mind is affected by the idea of a modification stronger than the former
and contrary to it; that is to say, it will be affected with an emotion
stronger than the former and contrary to it, and this stronger emotion
will exclude the existence of the other or remove it. Thus an emotion
cannot be restrained nor removed unless by an opposed and stronger
emotion.

An emotion, in so far as it is related to the mind, cannot b