The Methodology of Modal Logic as Metaphysics

Timothy Williamson’s Modal Logic as Metaphysics is, among much else, a detailed and complex defense of the metaphysical view he calls necessitism, the view that necessarily everything necessarily exists (is something), that although it may be a contingent matter how things are, what things there are is entirely a matter of necessity. The majority of contemporary modal metaphysicians reject this view; they are contingentists. Williamson examines the case for necessitism with great thoroughness, and with a distinctive methodology captured in slogan form by the book’s title. The book is an impressive achievement, and will have an impact on the shape of future debate. Necessitism appears to fly in the face of common opinion. Surely—or so I think—if my parents had never met, then I would not have existed. Surely—or so I think—I could have had a brother (although I actually do not), without it being the case that there (actually) exists something that could have been my brother. Indeed, on the familiar assumption that one’s genetic makeup is part of one’s essence, necessitism leads to an ontological explosion of my possible brothers, all of whom (actually) exist. A common response to necessitism is that the conflict with common opinion is so great that it can be rejected out of hand. Williamson would disagree. A possible person is not a person, not something made of flesh and blood; a possible person is a non-concrete object that is possibly concrete. Common opinion, arguably, does not distinguish between concrete existence and existence tout court. Perhaps the common opinion that I could have failed to exist is respected well enough if I could have failed to be anything concrete.