Actualism is the thesis that necessarily everything that there is exists. Serious actualism is the thesis that necessarily no object has a property in a world in which it does not exist. In this paper I present a new argument from actualism to serious actualism.

This chapter critically examines Plantinga’s version of modal actualism, and his arguments against Prior’s version of modal actualism.

In this essay, I consider several objections raised by John Pollock against my account of modality. I define possibilism – i.e., the view that there is a property that does not entail existence, but is entailed by every property – and then give a more adequate definition of actualism based on its disagreement with possibilism. Pollock argues that the property of nonexistence is such that objects exemplify it in worlds in which they do not exist and based on this fact (...) concludes that serious actualism is false. I give an argument that nonexistence is necessarily unexemplified and a separate argument for the conclusion that serious actualism is true. I conclude the essay by arguing that it does make a difference whether we accept existentialism or essentialism. (shrink)

I am going to describe a variant formulation of classical extensional first-order logic and contrast it with the standard formulation. The formulation I will give is in one clear sense equivalent to the standard one, and it is a routine task to show that it is equivalent to it in this sense. So one might regard my formulation as a mere notational variation. But there are also ways in which the two formulations I will contrast are not equivalent, and I (...) will argue that these ways reflect an important conceptual difference between them. The differences become more important as one generalizes or extends classical logic in various ways, but they are there even in the classical systems. (shrink)

Take a formula of first-order logic which is a logical consequence of some other formulae according to model theory, and in all those formulae replace schematic letters with English expressions. Is the argument resulting from the replacement valid in the sense that the premisses could not have been true without the conclusion also being true? Can we reason from the model-theoretic concept of logical consequence to the modal concept of validity? Yes, if the model theory is the standard one for (...) sentential logic; no, if it is the standard one for the predicate calculus; and yes, if it is a certain model theory for free logic. These conclusions rely inter alia on some assumptions about possible worlds, which are mapped into the models of model theory. Plural quantification is used in the last section, while part of the reasoning is relegated to an appendix that includes a proof of completeness for a version of free logic. (shrink)

Yagisawa (2005) considers two old arguments against the existence requirement. Both arguments are significantly less appealing than Yagisawa suggests. In particular, the second argument, first given by Kaplan (1989: 498), simply assumes that existence is contingent (§1). Yagisawa’s ‘new’ argument shares this weakness. It also faces a dilemma. Yagisawa must either treat ‘at @’ as a sentential operator occupying the same grammatical position as ‘∼’ or as supplying an extra argument place. In the former case, Yagisawa’s argument faces precisely the (...) problems he concedes that Kaplan’s argument does (§2). In the latter case, though the argument does not face these problems, it renders the sense in which things exist contingently no threat to (E) properly understood (§3). (shrink)

Actualism is the thesis that necessarily, everything that there is exists. Serious actualism is the thesis that necessarily, no object has a property in a world in which it does not exist. Let's call the claim that actualism entails serious actualism the Entailment Thesis (ET). In this paper I will improve upon a previous argument of mine for (ET). I will then consider the prospects for defending a similar thesis in the temporal realm—the thesis that presentism entails serious presentism.

In this paper, I investigate a system of quantified modal logic, due in many respects to Bressan (see [2]), from several perspectives -- both semantic and proof-theoretic. As Anderson and Belnap note in [1]: "It seems to be generally conceded that formal systems are natural or substantial if they can be looked at from several points of view. We tend to think of systems as artificial or ad hoc if most of their formal properties arise from some one notational system (...) in terms of which they are described." My efforts in this paper will be in part to lend substantiality to the system in question. Several formulation of the system are given and proved equivalent in appropriate senses. Also, some comments are made concerning possible alternative formulations. (shrink)