I. By an 'adequate' cause, I mean a cause through which
its effect can be clearly and distinctly perceived. By an
'inadequate' or partial cause, I mean a cause through which,
by itself, its effect cannot be understood.
II. I say that we 'act' when anything takes place, either
within us or externally to us, whereof we are the adequate
cause; that is (by the foregoing definition) when through
our nature something takes place within us or externally
to us, which can through our nature alone be clearly and
distinctly understood. On the other hand, I say that we
are passive as regards something when that something
takes place within us, or follows from our nature externally,
we being only the partial cause.
III. By 'emotion' I mean the modifications of the body,
whereby the active power of the said body is increased
or diminished, aided or constrained, and also the ideas
of such modifications.
N.B. If we can be the adequate cause of any of these
modifications, I then call the emotion an activity,
otherwise I call it a passion, or state wherein the mind
is passive.