musing is a passion, it is possible to have a passion for musing, and
musing is nothing else than the association of ideas in which the will does
not intervene.

THE PASSIONS.--Coming to the passions strictly speaking, there are
some which are of the soul and only of the soul; the passion for God is a
passion of the soul, the passion for liberty is a passion of the soul; but
there are many more which are the effects of the union of the soul with the
body. These passions are excited in the soul by a state of the body or a
movement of the body or of some part of the body; they are "emotions" of
the soul corresponding to "movements" of the machine. All passions have
relation to the desire for pleasure and the fear of pain, and according as
they relate to the former or the latter are they expansive or oppressive.
There are six principal passions, of which all the rest are only
modifications: admiration, love, desire, joy, having relation to the
appetite of happiness; hatred, sadness, having relation to the fear of
pain. "All the passions are good and may become bad" (Descartes in this
deviates emphatically from Stoicism for which the passions are simply
maladies of the soul). All passions are good in themselves. They are
destined (this is a remarkable theory) to cause the duration of thoughts
which would otherwise pass and be rapidly effaced; by reason of this, they
cause man to act; if he were only directed by his thoughts, unaccompanied
by his passions, he would never act, and if it be recognized that man is
born for action, it will at the same time be recognized that it is
necessary he should have passions.

But, you will say, there can be good passions (of a nature to give force to
just ideas) and evil passions.

No, they are all good, but all also have their bad side, their deviation,