Benedict de Spinoza, THE ETHICS
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'pomum' (an apple), a Roman would straightway arrive at the
thought of the fruit apple, which has no similitude with the
articulate sound in question, nor anything in common with it,
except that the body of the man has often been affected by these
two things; that is, that the man has often heard the word
'pomum,' while he was looking at the fruit; similarly every man
will go on from one thought to another, according as his habit
has ordered the images of things in his body. For a soldier,
for instance, when he sees the tracks of a horse in sand, will
at once pass from the thought of a horse to the thought of a
horseman, and thence to the thought of war, &c.; while a
countryman will proceed from the thought of a horse to the
thought of a plough, a field, &c. Thus every man will follow
this or that train of thought, according as he has been in the
habit of conjoining and associating the mental images of things
in this or that manner.

XIX. The human mind has no knowledge of the body, and does not
know it to exist, save through the ideas of the modifications
whereby the body is affected.

>>>>>Proof--The human mind is the very idea or knowledge of the
human body (II. xiii.), which (II. ix.) is in God, in so far as
he is regarded as affected by another idea of a particular thing
actually existing: or, inasmuch as (Post. iv.) the human body
stands in need of very many bodies whereby it is, as it were,
continually regenerated; and the order and connection of ideas
is the same as the order and connection of causes (II. vii.);
this idea will therefore be in God, in so far as he is regarded
as affected by the ideas of very many particular things. Thus
God has the idea of the human body, or knows the human body, in
so far as he is affected by very many other ideas, and not in so
far as he constitutes the nature of the human mind; that is (by
II. xi. Cor.), the human mind does not know the human body. But
the ideas of the modifications of body are in God, in so far as
he constitutes the nature of the human mind, or the human mind
perceives those modifications (II. xii.), and consequently (II.