Benedict de Spinoza, THE ETHICS
Page: 19

the external bodies, by which the human body has once been
affected, be no longer in existence, the mind will nevertheless
regard them as present, as often as this action of the body is
repeated. Q.E.D.

*****Note--We thus see how it comes about, as is often the case,
that we regard as present many things which are not. It is
possible that the same result may be brought about by other
causes; but I think it suffices for me here to have indicated one
possible explanation, just as well as if I had pointed out the
true cause. Indeed, I do not think I am very far from the
truth, for all my assumptions are based on postulates, which
rest, almost without exception, on experience, that cannot be
controverted by those who have shown, as we have, that the human
body, as we feel it, exists (Cor. after II. xiii.). Furthermore
(II. vii. Cor., II. xvi. Cor. ii.), we clearly understand what is
the difference between the idea, say, of Peter, which
constitutes the essence of Peter's mind, and the idea of the
said Peter, which is in another man, say, Paul. The former
directly answers to the essence of Peter's own body, and only
implies existence so long as Peter exists; the latter indicates
rather the disposition of Paul's body than the nature of Peter,
and, therefore, while this disposition of Paul's body lasts,
Paul's mind will regard Peter as present to itself, even though
he no longer exists. Further, to retain the usual phraseology,
the modifications of the human body, of which the ideas represent
external bodies as present to us, we will call the images of
things, though they do not recall the figure of things. When
the mind regards bodies in this fashion, we say that it imagines.
I will here draw attention to the fact, in order to indicate
where error lies, that the imaginations of the mind, looked at
in themselves, do not contain error. The mind does not err in
the mere act of imagining, but only in so far as it is regarded
as being without the idea, which excludes the existence of such
things as it imagines to be present to it. If the mind, while
imagining non-existent things as present to it, is at the same