ude
only the possibility of existence, necessary existence is inseparable from
the concept of the most perfect being. God cannot be thought apart from
existence; he has the ground of his existence in himself; he is _a se_
or _causa sui_. Finally, Descartes adds a third argument. The idea of
perfections which I do not possess can only have been imparted to me by a
more perfect being than I, which has bestowed on me all that I am and
all that I am capable of becoming. If I had created myself, I would have
bestowed upon myself these absent perfections also. And the existence of a
plurality of causes is negatived by the supreme perfection which I conceive
in the idea of God, the indivisible unity of his attributes. Among the
attributes of God his veracity is of special importance. It is impossible
that he should will to deceive us; that he should be the cause of our
errors. God would be a deceiver, if he had endowed us with a reason to
which error should appear true, even when it uses all its foresight in
avoiding it and assents only to that which it clearly and distinctly
perceives. Error is man's own fault; he falls into it only when he misuses
the divine gift of knowledge, which includes its own standard. Thus
Descartes finds new confirmation for his test of truth in the _veracitas
dei_. Erdmann has given a better defense of Descartes than the philosopher
himself against the charge that this is arguing in a circle, inasmuch as
the existence of God is proved by the criterion of truth, and then the
latter by the former: The criterion of certitude is the _ratio cognoscendi_
of God's existence; God is the _ratio essendi_ of the criterion of
certitude. In the order of existence God is first, he creates the reason
together with its criterion; in the order of knowledge the criterion
precedes, and God's existence follows from it. Descartes himself endeavors
to avoid the circle by making _intuitive_ knowledge self-evident, and by
not bringing in the appeal to God's veracity in _demonstrative_ knowledge
until, in reflective thought, we no longer have each separate link in the
chain of proof present to our minds with full intuitive certainty, but only
remember that we have previously understood the matter with clearness and
distinctness.

Our ideas represent in part things, in part qualities. Substance is defined
by the concept of independence as _res quae ita existit, ut nulla alia re
indigeat ad existendum_; a pregnant definition