Date of Degree


Document Type


Degree Name





Graham Priest

Committee Members

Michael Devitt

Melvin Fitting

Kit Fine

David Papineau

Subject Categories

Epistemology | Logic and Foundations of Mathematics | Metaphysics | Philosophy | Philosophy of Language | Philosophy of Mind | Philosophy of Science


Necessity, Essence, Analyticity, Explanation, Definition, Identity


Some truths could not have failed to hold. Such are called metaphysically necessary truths. As Michael Dummett once aptly formulated, the philosophical problem about necessity is twofold: what makes necessary truths necessarily true and how do we recognize them as such? This dissertation aims to address these questions by developing and defending a novel account of necessity, which has the following three main theses: (1) the necessity of a statement about an entity is established as a consequence of a general principle implying that if the entity is a certain way then it is necessarily that way and the fact that the entity is indeed that way; (2) the general principle is analytic in the sense that it is derivable from analysis of relevant concepts; and hence (3) the necessity of the statement can be known by investigating what the entity is in fact like and by conceptual analysis. I call this new account of necessity analytic essentialism.

The two main questions about necessity are given both logical and philosophical treatments. A logical analysis of modal statements is given from the perspective of truthmaker semantics. The analysis is developed into a formal truthmaker semantics for modal statements, and the soundness and completeness results for a well-known family of systems of normal propositional modal logic are established. On the basis of this formal analysis, paradigmatic examples of necessary statements are examined to address the substantive question of how exactly their necessity is established and known. Along the way, the present dissertation brings together a set of recent insights from philosophical logic, the philosophy of language, the philosophy of mind and the philosophy of science to shed new light on certain under-appreciated connections among necessity, identity, definition and explanation.