Author's School

Graduate School of Arts & Sciences

Author's Department/Program



English (en)

Date of Award

Winter 1-1-2012

Degree Type


Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Thomas B Sattig


This dissertation provides an account of essentiality that satisfies two main desiderata:

(1) The account should offer an explanation as to why the following two intuitions are true:

(i) It is essential to the set {Socrates} to have Socrates as a member.

(ii) It is not essential to Socrates to be a member of that set.

(2) The account should do justice to the sense of philosophical significance that has traditionally been attached to the notion of essence.

The two intuitions mentioned in: 1) together form what I call `Fine's asymmetry', after Kit Fine, whose paper `Essence and Modality' has persuasively undermined the traditional modal account of essentiality by pointing out: among other worries) that this account cannot plausibly accommodate both of those intuitions.

The account of essentiality proposed in this dissertation offers an alternative to the modal account. It is reductive, in the sense that it provides truth-conditions for essentialist claims without in turn relying on any fundamental notions of an entity's `nature' or `identity'; nor does it rely on any concepts of metaphysical modality. Instead, it is based on a framework of sets, attributes, and states of affairs, which is introduced in chapters 2 and 3. The account itself is then developed in chapters 4 to 7. The first major step in this direction is the introduction, in chapter 4, of the concept of an individuational ontology, which results from a generalization and modification of Peter Aczel's approach to the theory of non-well-founded sets. On this basis, chapter 5 introduces relativized concepts of essence and essentiality, where the relativization in question is to individuational ontologies.

The question of what conditions an individuational ontology O has to satisfy in order for essences-relative-to-O to count as essences simpliciter is the topic of chapters 6 and 7. Chapter 6 sets out to develop a fairly straightforward approach, but this is quickly seen to face apparently insuperable difficulties. Chapter 7 develops a fundamentally different approach, which turns out to be more successful. In chapter 8, it is shown how the resulting account of essentiality manages to accommodate Fine's asymmetry, and in the final chapter, the account is applied to an elucidation of de re modal discourse.


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