Benedict de Spinoza, THE ETHICS
Page: 11

said occurrence. That is, if the object of the idea constituting
the human mind be a body, nothing can take place in that body
without being perceived by the mind.

>>>>>Proof--Whatsoever comes to pass in the object of any idea,
the knowledge thereof is necessarily in God (II. ix. Cor.), in
so far as he is considered as affected by the idea of the said
object, that is (II. xi.), in so far as he constitutes the mind
of anything. Therefore, whatsoever takes place in the object
constituting the idea of the human mind, the knowledge thereof
is necessarily in God, in so far as he constitutes the essence of
the human mind; that is (by II. xi. Cor.) the knowledge of the
said thing will necessarily be in the mind, in other words the
mind perceives it.

*****Note--This proposition is also evident, and is more clearly
to be understood from II. vii., which see.

XIII. The object of the idea constituting the human mind is the
body, in other words a certain mode of extension which actually
exists, and nothing else.

>>>>>Proof--If indeed the body were not the object of the human
mind, the ideas of the modifications of the body would not be in
God (II. ix. Cor.) in virtue of his constituting our mind, but
in virtue of his constituting the mind of something else; that is
(II. xi. Cor.) the ideas of the modifications of the body would
not be in our mind: now (by II. Ax. iv.) we do possess the idea
of the modifications of the body. Therefore the object of the
idea constituting the human mind is the body, and the body as it
actually exists (II. xi.). Further, if there were any other
object of the idea constituting the mind besides body, then, as
nothing can exist from which some effect does not follow (I.
xxxvi.) there would necessarily have to be in our mind an idea,
which would be the effect of that other object (II. xi.); but
(I. Ax. v.) there is no such idea. Wherefore the object of our
mind is the body as it exists, and nothing else. Q.E.D.

*****Note--We thus comprehend, not only that the human mind is
united to the body, but also the nature of the union between
mind and body. However, no one will be able to grasp this