certain passages in his _Meditations_. The soul thinks and has
passions. There are three kinds of ideas, the factitious, the adventitious,
and the innate; the factitious ideas are those which the imagination forms;
the adventitious ideas are those suggested by the external world through
the intermediary of the senses; the innate ideas are those constituting the
mind itself, the conditions under which it thinks and apart from which it
cannot think: we cannot conceive an object not extended, nor an object
apart from time, nor anything without a cause; the ideas of time, space,
and cause are innate ideas; we cannot conceive ourselves as other than
free; the idea of liberty is an innate idea.

The soul has passions; it is therein that, without dependence on the body,
it has intimate relations with and is modified by it, not radically, but in
its daily life. There are operations of the soul which cannot strictly be
termed passions, and yet which are directed or at least _influenced_
by the body. Memory is passive, and consequently memory is a species of
passion. The lively sensations which the body transmits to the brain leave
impressions (Malebranche would say "traces"), and according to these
impressions the soul is moved a second or a third time, and that is what is
called memory. "The impressions of the brain render it suitable to stir
the soul in the same way as it has been stirred before, and also to make it
recollect something, just as the folds in a piece of paper or linen make it
more suitable to be folded anew as it was before than if it had never been
thus folded." Similarly, the association of ideas is passive, and in
consequence is a kind of passion. The association of ideas is the fact that
thought passes along the same path it has already traversed, and follows in
its labyrinth the thread which interlinks its thoughts, and this thread is
the traces which thoughts have left in the brain. In abandoning ourselves
to the association of ideas, we are passive and we yield ourselves freely
to a passion. That is so true that current speech itself recognizes this: