we can in some sense distinguish different ideas in the mind of God but the
distinctions we draw are mere distinctions of reason, and the ideas thereby distin-
guished are mere beings of reason. (Or, to use the terminology of chapter 6, mere
beings by courtesy.) One might think that if the ontic grounds of true essentialist
claims are mere beings of reason, then strict essence is not a metaphysically ground-
floor notion: what undergirds strict essences are entities that exist only in a non-
fundamental sense. The general principle I am appealing to is this. Suppose that any
proposition containing a constituentβnecessarily has an ontic ground for its truth.
Suppose also that, necessarily, the ultimate ontic grounds for the truth of any
proposition containing a constituentβdo not fundamentally exist. Thenβis not
metaphysically fundamental.
One could resist the conclusion of this argument, however, by denying that ideas
in the mind of God are theultimateontic essences of things. Instead, God is the
ultimate ontic essence of things. And so there is no threat to the metaphysical
fundamentality of strict essence. If God is the ultimate ontic essence of all things
that have a strict essence, then, unless all things that have strict essences exist
necessarily, the truth of a given propositional essence of a thing needn’t imply the
existence of that thing.
Alternatively, one could accept an alternative conception of God that embraces
mereological simplicity without embracing complete metaphysical simplicity.
Though God has no proper parts, nonetheless God has many genuinely non-identical
features. Among these features are various numerically distinct divine ideas, each of
which could serve as the ontic ground of a true essentialist claim without comprom-
ising the metaphysical fundamentality of strict essence, provided that these features
enjoy a perfectly natural mode of existence. It is unclear whether ideas in the mind of
God must be necessary beings, and hence it is unclear whether one’s essence is
modally more robust than one’s existence.
Finally, let us turn to a discussion of the view that essences aresui generisentities.
Perhaps little positively favors this view—this is the view to embrace when other
alternatives fail. And because essences aresui generisentities, we are more in the dark
about whether they in some way depend on those things of which they are essences.
What it is for essences to be asui generisentities is for them to form their own
ontological category, which, as defended in section 4.4, is for them to share a
distinctive mode of being. Perhaps this view can be motivated by the concerns
about the grounds of essential facts we discussed earlier. Perhaps those sympathetic
to the idea that facts about essences are not apt to be grounded should seriously
consider instead taking essences themselves to besui generisentities.
Descartes’identification of God’s will with God’s understanding. See also Kaufman (2003) for a discussion
of both Aquinas’s and Descartes’theories of divine simplicity, as well as how Descartes’views on divine
simplicity connect up with his doctrine that God freely creates“the eternal truths.”