Alexander Pruss's Blog

Unger famously argues that he doesn’t exist, by claiming a contradiction between three claims (I am quoting (1) and (2) verbatim, but simpl...

Suppose the future is open. Then it is not true that tomorrow Jones will freely mow the lawn. Moreover, it is necessarily not true that Jon...

The Barcan formula says: ∀ x □ ϕ  → □∀ x ϕ . The Barcan formula is dubious. Suppose, for instance, that the only things in existence are...

The usual examples of a posteriori necessities are identities between kinds and objects under two descriptions, at least one of which invol...

Van Inwagen’s famous argument against the Principle of Sufficient Reason rests on the principle: A necessary truth cannot explain a contin...

I’ve come to be impressed by the idea that where there is apparent arbitrariness, there is probably contingency in the vicinity. The earth ...

Logical-closure views of modality have this form: There is a collection C of special truths. A proposition is necessary if and only if i...

A family of views of necessity (e.g., Peacocke, Sider, Swinburne, and maybe Chalmers) identifies a family F of special true statements that...

There are many set-theoretic claims that are undecidable from the basic axioms of set theory. Plausibly, the truths of set theory hold of ne...

There is something very unappealing about unexplained, i.e., brute, metaphysical necessities that are “arbitrary”. For instance, suppose tha...

We prefer more elegant theories to uglier ones. Why should we think this preference leads to truth? This is a classic question in the philo...

Consider this argument: Obviously necessarily, if N is a necessary being that exists, it is impossible that N doesn't exist. It is conc...

The Peano Axioms are consistent. If not, mathematics (and the science resting on it) is overthrown. Moreover, it is absurd to suppose that t...

Assume the background here . So, there is a privileged set N of true sentences from some language L , and N includes, among other thin...

The neo-conventionalist account of necessity holds that necessity is just a messy property accidentally created by our conventions. We h...

On standard naturalist views, neither the objective facts of mathematics and morality nor their grounds (e.g., Platonic entities, etc.) ...

A plausible account of necessity is that p is necessary provided that p can be proved in the correct logical system K and p is possi...

Suppose that none of the participants in World War II had ever existed. Then it would have been impossible for World War II to oc...

Start with the idea of grades of necessity . At the bottom, say [note 1] , lie ordinary empirical claims like that I am typing now, which ...

Leibniz famously holds that: God creates the best logically possible world. In order to resist logical fatalism, Leibniz denies...