actions depend
upon their will, these are words to which no idea is attached. What the
will is, and in what manner it moves the body, every one is ignorant,
for those who pretend otherwise, and devise seats and dwelling-places of
the soul, usually excite our laughter or disgust. Just in the same
manner, when we look at the sun, we imagine its distance from us to be
about 200 feet; the error not consisting solely in the imagination, but
arising from our not knowing what the true distance is when we imagine,
and what are the causes of our imagination. For although we may
afterwards know that the sun is more than 600 diameters of the earth
distant from us, we still imagine it near us, since we imagine it to be
so near, not because we are ignorant of its true distance, but because a
modification of our body involves the essence of the sun, in so far as
our body itself is affected by it.

_The Origin and Nature of Confused Ideas_

The ideas of the modifications of the human body involve the nature both
of external bodies and of the human body itself and must involve the
nature not only of the human body, but of its parts, for the
modifications are ways in which the parts of the human body, and
consequently the whole body, are affected. But an adequate knowledge of
external bodies and of the parts composing the human body does not exist
in God in so far as He is considered as affected by the human mind, but
in so far as He is affected by other ideas. These ideas of
modifications, therefore, in so far as they are related to the human
mind alone, are like conclusions without premises, that is to say, as is
self-evident, they are confused ideas.

The idea which forms the nature of the mind is demonstrated in the same
way not to be clear and distinct when considered in itself. So also with
the idea of the human mind, and the ideas of the ideas of the
modifications of the human body, in so far as they are related to the
mind alone, as every one may easily see.

All ideas are in God and in so far as they are related to God are true
and adequate. No ideas, therefore, are inadequate or confused unless in
so far as they are related to the individual mind of some person. All
ideas, therefore, both adequate and inadequate, follow by the same
necessity.

_The Origin and Nature of Adequate Ideas_

Let there be something, _A_, which is common to all bodies, and which is
equally in the part of each body and in the whole. I say th