and imagine that any form might be changed into any other. So,
also, those who confuse the two natures, divine and human,
readily attribute human passions to the deity, especially so long
as they do not know how passions originate in the mind. But, if
people would consider the nature of substance, they would have no
doubt about the truth of Prop. vii. In fact, this proposition
would be a universal axiom, and accounted a truism. For, by
substance, would be understood that which is in itself, and is
conceived through itself-that is, something of which the
conception requires not the conception of anything else ; whereas
modifications exist in something external to themselves, and a
conception of them is formed by means of a conception of the
thing in which they exist. Therefore, we may have true ideas of
non-existent modifications ; for, although they may have no
actual existence apart from the conceiving intellect, yet their
essence is so involved in something external to themselves that
they may through it be conceived. Whereas the only truth
substances can have, external to the intellect, must consist in
their existence, because they are conceived through themselves.
Therefore, for a person to say that he has a clear and
distinct-that is, a true-idea of a substance, but that he is not
sure whether such substance exists, would be the same as if he
said that he had a true idea, but was not sure whether or no it
was false (a little consideration will make this plain) ; or if
anyone affirmed that substance is created, it would be the same
as saying that a false idea was true-in short, the height of
absurdity. It must, then, necessarily be admitted that the
existence of substance as its essence is an eternal truth. And
we can hence conclude by another process of reasoning-that there
is but one such substance. I think that this may profitably be