So far we have met with such sensations only as they take their rise in
an antecedent operation of the understanding; but we have now to deal
with sensations in which the understanding bears no part. These
sensations, if they are not exactly the expression of the present state
of our organs, mark it out specifically, or, better, accompany it. These
sensations have quickly and forcibly to determine the will to aversion or
desire; but, on the other hand, they are ever to float on the surface of
the soul, and never to extend to the province of the reason. The part,
accordingly, played by thought, in the case of a mental perception, is
here taken up by that modification in the animal parts of us which either
threatens the destruction of the sensation or insures its duration: that
is, an eternal law of wisdom has combined with that condition of the
machine which confirms its welfare, a pleasant emotion of the soul; and,
on the other hand, with that condition which undermines it and threatens
ruin, an unpleasant emotion is connected; and this in such a manner that
the sensation itself has not the faintest resemblance to the state of the
organs of which it is the mark. Animal sensations have, on this showing,
a double origin: (1) in the present state of the machine; (2) in the
capacity or faculty (of sensation).

We are now able to understand how it is that the animal sensations have
the power to drive the soul with an irresistible tyranny in the direction
of passionate action, and not seldom gain the upper hand in a struggle
with those sensations which are most purely intellectual. For these last
the soul has produced by means of thought, and therefore they can by
thought be solved or even destroyed. Abstraction and philosophy have
this power over the passions, over opinions--in short, over all the
situations of life; but the animal sensations are forced upon the soul by
a blind necessity, by a stern mechanical law. The understanding, which