Jared Warren

This paper investigates the determinacy of mathematics. We begin by clarifying how we are understanding the notion of determinacy before turning to the questions of whether and how famous independence results bear on issues of determinacy in mathematics. From there, we pose a metasemantic challenge for those who believe that mathematical language is determinate, motivate two important constraints on attempts to meet our challenge, and then use these constraints to develop an argument against determinacy and discuss a particularly popular approach to resolving indeterminacy, before offering some brief closing reflections. We believe our discussion poses a serious challenge for most philosophical theories of mathematics, since it puts considerable pressure on all views that accept a non-trivial amount of determinacy for even basic arithmetic.

Unrestricted inferentialism holds both that any collection of inference rules can determine a meaning for an expression and meaning constituting rules are automatically valid. Prior's infamous tonk connective refuted unrestricted inferentialism, or so it is universally thought. This paper argues against this consensus. I start by formulating the metasemantic theses of inferentialism with more care than they have hitherto received; I then consider a tonk language — Tonklish — and argue that the unrestricted inferentialist's treatment of this language is only problematic if it is mistakenly assumed that Tonklish can be homophonically translated into English. Next, I discuss the proper, non-homophonic, translation of Tonklish into English, rebut various objections, and consider several variants of Tonklish. The paper closes by highlighting the philosophical advantages that unrestricted inferentialism has over its competitors once the terrors of tonk have been tamed.

Rudolf Carnap famously distinguished between the external meanings that existence questions have when asked by philosophers and the internal meanings they have when asked by non-philosophers. Carnap’s overall position involved various controversial commitments, but relatively uncontroversial interpretative principles also lead to a Carnap-style distinction between internal and external questions. In section 1 of this paper I offer arguments for such a distinction in several particular cases; in section 2 I defend my arguments from numerous objections and motivate them by using points drawn from the general theory of interpretation; and in section 3 I discuss the meanings of external questions, ultimately arguing that they are best understood as involving primitive metaphysical notions, and that when so understood, it is natural to adopt a general error theory about philosophical ontology.

Theodore Sider’s recent book, “Writing the Book of the World”, employs a primitive notion of metaphysical structure in order to make sense of substantive metaphysics. But Sider and others who employ metaphysical primitives face serious epistemological challenges. In the first section I develop a specific form of this challenge for Sider’s own proposed epistemology for structure; the second section develops a general reliability challenge for Sider’s theory; and the third and final section argues for the rejection of Siderean structure in the course of answering a transcendental argument against such rejection.

Conventionalism about mathematics claims that mathematical truths are true by linguistic convention. This is often spelled out by appealing to facts concerning rules of inference and formal systems, but this leads to a problem: since the incompleteness theorems we’ve known that syntactic notions can be expressed using arithmetical sentences. There is serious prima facie tension here: how can mathematics be a matter of convention and syntax a matter of fact given the arithmetization of syntax? This challenge has been pressed in the literature by Hilary Putnam and Peter Koellner. In this paper I sketch a conventionalist theory of mathematics, show that this conventionalist theory can meet the challenge just raised , and clarify the type of mathematical pluralism endorsed by the conventionalist by introducing the notion of a semantic counterpart. The paper’s aim is an improved understanding of conventionalism, pluralism, and the relationship between them.

Recently a number of works in meta-ontology have used a variant of J.H. Harris's collapse argument in the philosophy of logic as an argument against Eli Hirsch's quantifier variance. There have been several responses to the argument in the literature, but none of them have identified the central failing of the argument, viz., the argument has two readings: one on which it is sound but doesn't refute quantifier variance and another on which it is unsound. The central lesson I draw is that arguments against quantifier variance must pay strict attention to issues of translation and interpretation. The paper also has a substantial appendix in which I prove the equivalence of plural mereological nihilism and standard first-order atomistic mereology; results of this kind are often appealed to in the literature on quantifier variance but without many details on the nature or proof of the result.