If Descartes' motivation is to make God master of the modal economy, then I think we
must conclude that he has failed. For on the account just sketched,
end p.44
there remain metaphysical necessities over which God has no control. On this Cartesian
account it is impossible even for omnipotent God to hold our present cognitive capacities
fixed while enabling us to comprehend what it would be like for 2 + 3 ≠ 5. (An act of
divine revelation could have the effect of warranting a person in believing that the sum of
2 and 3 could have been 7. But unless the revelation somehow enhances the believer's
intellect, the believer is not equipped to know what it would be like for the proposition to
be true.) The Cartesian account has another consequence that may be unsettling for many
theists. If every proposition is metaphysically contingent, then propositions about God's
nature are not exempt. To take examples, the propositions that God is omniscient,
omnipotent (which, keep in mind, plays a central role in the present interpretation of
Descartes' views), perfectly good, or even that God exists are at best contingently true.
But, to anticipate discussion coming later in this essay, it has generally been taken to be a
consequence of God's aseity that God's existence and nature are metaphysically
necessary.
The Cartesian strategy of demoting all necessary truths to contingent truths thus comes
with a cost. Perhaps it is a cost a theist would be willing to pay for securing an especially
strong version of divine sovereignty. Perhaps not. There is another way of approaching
the same issues that has its roots in the thought of Augustine. The Cartesian strategy
appears to be founded on the unlimited power of God's will. What I call the Augustinian
strategy takes as its point of departure the integrity of God's intellect. Plato had said that
the Forms, abstract entities denoted by expressions like Justice, Beauty, and The Good
(or Goodness Itself), are eternal, unchanging, perfect exemplars, which concrete things
only deficiently resemble, and the objects on which objective knowledge depends.
Augustine claimed to be merely following Plato's lead in locating the Forms in the mind
of God (1982, 79–81). Augustine's move is an affirmation of God's sovereignty: if the
Forms are God's thoughts or ideas, then their very existence depends on God's thinking
them.
We can, I believe, embellish the Augustinian strategy by connecting the notion of Forms
as divine thoughts to the notion of necessary truth. If they are to serve the function of
grounding necessary truth, and thereby ensure the possibility of stable, objective
knowledge as opposed to inconstant, wavering belief, the Forms, construed as divine
ideas, must at a minimum be eternal objects of God's thinking. Particular triangles
scrawled in the sand or on the blackboard come and go and may not (cannot?) have the
sum of their interior angles quite equal to 180 degrees. But The Triangle Itself never
ceases to exist or falls short of having its interior angles sum to 180 degrees. (Or at least
this is true of The Euclidean Triangle Itself!) But it is not clear that God's eternally
thinking of The Triangle is sufficient to explain why it is a necessary truth that its interior
angles sum to 180 degrees. Even if we suppose that necessary truths are eternally true, it
need not follow that eternal truths are necessarily true. We should not rule out of court
the view that God knew “from eternity” that Adam would sin at such and such a time, yet
that Adam's sinning was contingent.