the first. For example, from thinking of the word “pomum” [apple] a Roman will
straightway fall to thinking of the fruit, which has no likeness to that articulated sound
nor anything in common with it other than that the man’s body has often been affected
by them both; that is, the man has often heard the word “pomum” while seeing the fruit.
So everyone will pass on from one thought to another according as habit in each case
has arranged the images in his body. A soldier, for example, seeing the tracks of a horse
in the sand will straightway pass on from thinking of the horse to thinking of the rider,
and then thinking of war, and so on. But a peasant, from thinking of a horse, will pass
on to thinking of a plough, and of a field, and so on. So every person will pass on from
thinking of one thing to thinking of another according as he is in the habit of joining
together and linking the images of things in various ways.
PROPOSITION 19:The human mind has no knowledge of the body, nor does it know it
to exist, except through ideas of the affections by which the body is affected.
Proof: The human mind is the very idea or knowledge of the human body
(Pr. 13, II), and this idea is in God (Pr. 9, II) insofar as he is considered as affected
by another idea of a particular thing; or, since (Post. 4) the human body needs very
many other bodies by which it is continually regenerated, and the order and connec-
tion of ideas is the same (Pr. 7, II) as the order and connection of causes, this idea is
in God insofar as he is considered as affected by the ideas of numerous particular
things. Therefore, God has the idea of the human body, or knows the human body,
insofar as he is affected by numerous other ideas, and not insofar as he constitutes
the nature of the human mind; that is (Cor. Pr. 11, II), the human mind does not know
the human body. But the ideas of the affections of the body are in God insofar as he
does constitute the nature of human mind; i.e., the human mind perceives these
affections (Pr. 12, II) and consequently perceives the human body (Pr. 16, II), and
perceives it as actually existing (Pr. 17, II). Therefore, it is only to that extent that the
human mind perceives the human body.
PROPOSITION 20:There is also in God the idea or knowledge of the human mind, and
this follows in God and is related to God in the same way as the idea or knowledge of
the human body.
Proof: Thought is an attribute of God (Pr. 1, II), and so (Pr. 3, II) the idea of both
Thought and its affections—and consequently of the human mind as well—must neces-
sarily be in God. Now this idea or knowledge of the mind does not follow in God insofar
as he is infinite, but insofar as he is affected by another idea of a particular thing (Pr. 9, II).
But the order and connection of ideas is the same as the order and connection of causes
(Pr. 7, II). Therefore, the idea or knowledge of the mind follows in God and is related to
God in the same way as the idea or knowledge of the body.
PROPOSITION 21:This idea of the mind is united to the mind in the same way as the
mind is united to the body.
Proof: That the mind is united to the body we have shown from the fact that the
body is the object of the mind (Prs. 12 and 13, II), and so by the same reasoning the idea
of the mind must be united to its object—that is, to the mind itself—in the same way as
the mind is united to the body.
Scholium: This proposition is understood far more clearly from Sch. Pr. 7, II.
There we showed that the idea of the body and the body itself—that is (Pr. 13, II), mind
and body—are one and the same individual thing, conceived now under the attribute of