Plural <Emphasis Type="Italic">Grundgesetze</Emphasis>

PG (Plural Grundgesetze) is a predicative monadic second-order system which exploits the notion of plural quantification and a few Fregean devices, among which a formulation of the infamous Basic Law V. It is shown that second-order Peano arithmetic can be derived in PG. I also investigate the philosophical issue of predicativism connected to PG. In particular, as predicativism about concepts seems rather un-Fregean, I analyse whether there is a way to make predicativism compatible with Frege’s logicism.     

Unrestricted Quantification and the Structure of Type Theory

Semantic theories based on a hierarchy of types have prominently been used to defend the possibility of unrestricted quantification. However, they also pose a prima facie problem for it: each quantifier ranges over at most one level of the hierarchy and is therefore not unrestricted. It is difficult to evaluate this problem without a principled account of what it is for a quantifier to be unrestricted. Drawing on an insight of Russell's about the relationship between quantification and the structure of predication, we offer such an account. We use this account to examine the problem in three different type-theoretic settings, which are increasingly permissive with respect to predication. We conclude that unrestricted quantification is available in all but the most permissive kind of type theory.     

Knowledge of language in action

Knowledge of a language is a kind of knowledge, the possession of which enables a speaker to understand and perform a variety of linguistic actions in that language. In this paper, I pursue an agency-oriented approach to knowledge of language. I begin by examining two major agency-oriented models of knowledge of language: Michael Dummett's Implicit Knowledge Model and Jennifer Hornsby's Practical Knowledge Model. I argue that each of these models is inadequate for different reasons. I present an Acquaintance Knowledge Model, in which a speaker's knowledge of a language is a combination of the speaker's first-order linguistic ability and second-order acquaintance with his ability and actions.     

On the Referential Indeterminacy of Logical and Mathematical Concepts

Hartry Field has recently examined the question whether our logical and mathematical concepts are referentially indeterminate. In his view, (1) certain logical notions, such as second-order quantification, are indeterminate, but (2) important mathematical notions, such as the notion of finiteness, are not (they are determinate). In this paper, I assess Fields analysis, and argue that claims (1) and (2) turn out to be inconsistent. After all, given that the notion of finiteness can only be adequately characterized in pure second-order logic, if Field is right in claiming that second-order quantification is indeterminate (see (1)), it follows that finiteness is also indeterminate (contrary to (2)). After arguing that Field is committed to these claims, I provide a diagnosis of why this inconsistency emerged, and I suggest an alternative, consistent picture of the relationship between logical and mathematical indeterminacy.     

Boolos and the Metamathematics of Quine's Definitions of Logical Truth and Consequence

The paper is concerned with Quine's substitutional account of logical truth. The critique of Quine's definition tends to focus on miscellaneous odds and ends, such as problems with identity. However, in an appendix to his influential article On Second Order Logic, George Boolos offered an ingenious argument that seems to diminish Quine's account of logical truth on a deeper level. In the article he shows that Quine's substitutional account of logical truth cannot be generalized properly to the general concept of logical consequence. The purpose of this paper is threefold: first, to introduce the reader to the metamathematics of Quine's substitutional definition of logical truth; second, to make Boolos' result accessible to a broader audience by giving a detailed and self-contained presentation of his proof; and, finally, to discuss some of the possible implications and how a defender of the Quinean concepts might react to the challenge posed by Boolos' result.     

To Be is to Be the Object of a Possible Act of Choice

Aim of the paper is to revise Boolos’ reinterpretation of second-order monadic logic in terms of plural quantification ([4], [5]) and expand it to full second order logic. Introducing the idealization of plural acts of choice, performed by a suitable team of agents, we will develop a notion of plural reference. Plural quantification will be then explained in terms of plural reference. As an application, we will sketch a structuralist reconstruction of second-order arithmetic based on the axiom of infinite à la Dedekind, as the unique non-logical axiom. We will also sketch a virtual interpretation of the classical continuum involving no other infinite than a countable plurality of individuals.     

Self as a second-order object: Reinterpreting the Jamesian “Me”

Existing definitions of the self can be lumped into three groups: self as self-reflectivity, self as self-concept, and self as the individual. This article traces current disagreements over the definition of the self to a crucial ambiguity in William James's original delineation of the “Me.” Implicit in James's delineation was a distinction between first-order objects and second-order objects: while first-order objects are things as they are, independent of the perception of a knowing subject, second-order objects are things as perceived by a knowing subject. This article makes this distinction explicit and argues that the self is a second-order object associated with the first-person or “emic” perspective. Defined as the empirical existence of the individual (first order) perceived by the individual as “me” or “mine” (second order), the self is distinguished from the “I” which is the mental capacity for self-reflection; the self-concept which is the mental representation of the individual's existence; and the individual which is the empirical referent of the self-concept. As a second-order object, the “Me,” i.e., the self, is the unity of the existence and perception of the individual.     

Modalising Plurals

There has been very little discussion of the appropriate principles to govern a modal logic of plurals. What debate there has been has accepted a principle I call (NecInc); informally if this is one of those then, necessarily: this is one of those. On this basis Williamson has criticised the Boolosian plural interpretation of monadic second-order logic. I argue against (NecInc), noting that it isn’t a theorem of any logic resulting from adding modal axioms to the plural logic PFO+, and showing that the most obvious formal argument in its favour is question begging. I go on to discuss the behaviour of natural language plurals, motivating a case against (NecInc) by developing a case that natural language plural terms are not de jure rigid designators. The paper concludes by developing a model theory for modal PFO+ which does not validate (NecInc). An Appendix discusses (NecInc) in relation to counterpart theory.     

On the Consistency of a Plural Theory of Frege’s <Emphasis Type="Italic">Grundgesetze</Emphasis>

PG (Plural Grundgesetze) is a predicative monadic second-order system which is aimed to derive second-order Peano arithmetic. It exploits the notion of plural quantification and a few Fregean devices, among which the infamous Basic Law V. In this paper, a model-theoretical consistency proof for the system PG is provided.