perate with it in action, the
better adapted will the mind be for distinctly understanding. We can
thus determine the superiority of one mind to another; we can also see
the reason why we have only a very confused knowledge of our body,
together with many other things which I shall deduce in what follows.

_The Complexity of the Human Mind_

The idea which constitutes the formal Being of the human mind is the
idea of a body which is composed of a number of individuals composite to
a high degree. But an idea of each individual composing the body must
necessarily exist in God; therefore the idea of the human body is
composed of these several ideas of the component parts. The idea which
constitutes the formal Being of the human mind is not simple, but is
composed of a number of ideas.

All ways in which any body is affected follow at the same time from the
nature of the affected body, and from the nature of the affecting body;
therefore the idea of these modifications necessarily involves the
nature of each body, and therefore the idea of each way in which the
human body is affected by an external body involves the nature of the
human body and of the external body.

Hence it follows, in the first place, that the human mind perceives the
nature of many bodies together with that of its own body.

It follows, secondly, that the ideas we have of external bodies indicate
the constitution of our own body rather than the nature of external
bodies.

_Imagination_

If the human body be affected in a way which involves the nature of any
external body, the human mind will contemplate that external body as
actually existing or as present, until the human body be affected by a
mode which excludes the existence or presence of the external body.

When external bodies so determine the fluid parts of the human body that
they often strike upon the softer parts, the fluid parts change the
plane of the soft parts, and thence it happens that the fluid parts are
reflected from the new planes in a direction different from that in
which they used to be reflected, and that also afterwards when they
strike against these new planes by their own spontaneous motion, they
are reflected in the same way as when they were impelled towards those
planes by external bodies. Consequently those fluid bodies produce a
modification in the human body while they keep up this reflex motion
similar to that produced by the presence of an external body. T