The second possibility is that none of the forms individually is the ontic ground of
her essences, but collectively they all are.^64 Both are worth exploring.
If the substantial form of an object is the ultimate ontic essence of that object, does
the substantial form in turn have a distinct ultimate ontic essence? Probably the
Aristotelian will say“no.”Every substantial form is its own ultimate ontic essence.
Hence, one thing can be the ontic ground of two (or more) distinct essences, if forms
are universal.
Let us consider the third candidate, according to which the ontic ground of the
total propositional essence of David Lewis just is the set of properties that propos-
itional essence attributes to David Lewis. On the face of it, this candidate is not
promising: this set of properties corresponds to the total propositional essence of
David Lewisbecausethis total propositional essence is true andnot becausethis set is
its ontic ground. (Similar remarks apply to the idea that the properties collectively are
the ontic essence of David Lewis.) Nonetheless, let us note that if properties in general
are necessary beings and sets of properties in general are the ontic grounds of true
essentialist claims, then true essentialist claims are necessarily true.^65 If there are
some creatures that both contingently exist but have strict essences, then the total
propositional essence ofxcan sometimes be true even whenxdoes not exist.^66
We turn next to a discussion of the fourth candidate: the ontic ground of David
Lewis’s propositional essence is an idea in the mind of God.^67 This view also has
traditional defenders who think that the mode of being of essences is“existing
objectively in the mind of God”rather than a distinctive and more independent
mode. This might be the view of Henry of Ghent, but it is arguably Leibniz’s view as
well.^68 On this view, essences either just are ideas in the mind of God or they are
entities that are ontologically parasitic on ideas in the mind of God.
This view is plausible only if there is a God, but let’s go with theflow, since views
about the nature of God have interesting consequences worth drawing out. Suppose
that God is absolutely simple: not only does God lack proper parts, but also there is
no genuine distinction between God’s (intrinsic) features and God.^69 On this view,
(^64) Pasnau (2011: 577) suggests a view on which a substantial form is posited for“each essential
attribute,”which suggests the second sort of view here. Frost (2010: 202) claims that defenders of a
plurality of substantial forms in a single creature hold that the“composition”of these forms is the ground
of what I call the total propositional essence of that creature. 65
66 Assuming that ifxgroundsy, then necessarily, ifxobtains,yobtains.
A related possibility, one that might be attractive for certain fans of truth-making theories, is that the
ultimate ontic ground for a propositional essence is the fact that the object has that propositional essence.
Thanks to Hao Hong for suggesting this candidate. 67
68 Gilson (1952: 84–5) suggests that Scotus holds this.
Wippel (2000: 403–4) suggests that, for Henry of Ghent, the being of essences consists in being
objects of God’s knowledge. Frost (2010) explains why Aquinas rejects this view. Recall that I suggested
that, for Leibniz, complete concepts are good candidates for being ontic essences. Complete concepts are
ideas in the mind of God. 69
This view was attributed to Aquinas in the introduction to this book. It is also the view of Descartes
(1992: 128–9). Cunning (2014) notes some problems for Descartes’modal metaphysics that stem from