Benedict de Spinoza, THE ETHICS
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time conscious that they do not really exist, this power of
imagination must be set down to the efficacy of its nature, and
not to a fault, especially if this faculty of imagination depend
solely on its own nature--that is (I. Def. vii.), if this
faculty of imagination be free.

XVIII. If the human body has once been affected by two or more
bodies at the same time, when the mind afterwards imagines any
of them, it will straightway remember the others also.

>>>>>Proof--The mind (II. xvii. Cor.) imagines any given body,
because the human body is affected and disposed by the
impressions from an external body, in the same manner as it is
affected when certain of its parts are acted on by the said
external body; but (by our hypothesis) the body was then so
disposed, that the mind imagined two bodies at once; therefore,
it will also in the second case imagine two bodies at once, and
the mind, when it imagines one, will straightway remember the
other. Q.E.D.

*****Note--We now clearly see what 'Memory' is. It is simply a
certain association of ideas involving the nature of things
outside the human body, which association arises in the mind
according to the order and association of the modifications
(affectiones) of the human body. I say, first, it is an
association of those ideas only, which involve the nature of
things outside the human body: not of ideas which answer to the
nature of the said things: ideas of the modifications of the
human body are, strictly speaking (II. xvi.), those which
involve the nature both of the human body and of external bodies.
I say, secondly, that this association arises according to the
order and association of the modifications of the human body, in
order to distinguish it from that association of ideas, which
arises from the order of the intellect, whereby the mind
perceives things through their primary causes, and which is in
all men the same. And hence we can further clearly understand,
why the mind from the thought of one thing, should straightway
arrive at the thought of another thing, which has no similarity
with the first; for instance, from the thought of the word