Research Seminar in Logic and Language

Due to a general overhaul of Tilburg University's web, the site of the TiLPS Research Seminar in Logic and Language will temporarily be unavailable for update. Until things are back to normal all information on the schedule for the 2010 Fall semester will appear here.

23 September: Room DZ 6
Vague Desire: the Sorites and Money Pump
David Etlin, University of Leuven

14 October: Room DZ 10
The Barcan Formula and Completeness of First-Order Modal Logic
Eric Pacuit, TiLPS

In this talk, we will survey some recent work on completeness of first-order modal logics. In particular we will look at the role that the Barcan formula(s) play in various completeness proofs. We will focus on non-normal systems (cf. "First-Order Classical Modal Logic" by Horacio Arlo-Costa and Eric Pacuit, Studia Logica 84(2), 2006) and general completeness theorems (cf. "A General Semantics for Quantified Modal Logic" by Robert Goldblatt and Edwin Mares, Advances in Modal Logic 6, 2006). Time permitting we will also look at alternative semantics for the first-order modal language.

28 October: Room DZ 8
Agreeing to Disagree in Probabilistic Dynamic Epistemic Logic
Lorenz Demey, University of Leuven, ILLC

In this talk I will discuss Aumann's celebrated agreeing to disagree theorem from the perspective of probabilistic dynamic epistemic logic. I will first introduce Aumann's own formal statement of the theorem, and its intuitive motivation. Next I will introduce probabilistic Kripke models and various ways of updating them. These tools are then used to model several versions of the agreement theorem. I will also introduce sound and complete agreement logics. On the basis of these technical results I will make some philosophical/methodological points about the agreement theorem, in particular about the role of common knowledge and the underlying dynamics. If time permits, I will also compare my approach with another way of modeling the agreement theorem in DEL, which has been developed by Dégremont and Roy.

11 November: Room DZ 6
Adjectives, Scales and Zeros
Galit Weidman Sassoon, ILLC

Degree questions such as "how tall is John?" and equatives such as "John is as tall as Mary" do not imply that John is tall, while their negative counterparts ("how short is John?" and "John is as short as Mary") do imply that John is short. Existing theories attempt to explain this by means of a competition between unmarked (positive) and marked (negative) antonyms, and by means of a null morpheme that introduces a standard-variable into the derivation (in analogy with the standard analysis of the positive form "John is tall/short"; cf. Rett 2007). This talk attempts to present data that challenge these theories, as well as an alternative analysis for the facts based on the existence of an absolute zero or its lack thereof, in the interpretation of, e.g., 'tall' and 'short', respectively. Implications for additional dominant linguistic analyses of scalar adjectives will be discussed, pertaining to differences between absolute and relative adjectives (cf. Winter and Rothstein 2005; Kennedy and McNally 2005; Kennedy 2007).

9 December: Room DZ 6
Sense and Circularity: Recursion in Higher Order Logic
Reinhard Muskens, TiLPS

In this talk I will report on ongoing work with the goal of developing a higher order logic that is not only truly intensional, in the sense that necessarily coextensional objects need not have the same properties, but in which it is also possible to model Fregean senses as algorithms along the lines of Moschovakis [1]. In this influential paper Moschovakis succeeds in combining an account of the procedural character of meaning with an account of circular statements such as the Liar and Truthteller—these circular statements are associated with looping algorithms. Moschovakis [1] uses a first order logic, while higher order logics are more suitable for natural language description. This is remedied in Moschovakis [2] by adding recursors to the simply typed lambda calculus, but while [2] succeeds admirably in modeling the procedural character of language, the possibility of modeling circularity is lost, as an acyclicity requirement is necessary. My aim here is to remedy this situation. I will discuss the idea of taking the intensional logic of [5] ('classical higher order logic minus Extensionality') and partializing it along the lines of [3]. In partial logics some extra connectives become available, but terms in the classical part of the language exhibit monotonicity behaviour with respect to the definedness ordering. I will discuss the possibility of defining a sublanguage which contains the classical fragment but additionally has a simultaneous fixpoint operator similar to Moschovakis' and using it to model procedurality and circularity in ordinary language.

[1] Y. Moschovakis. Sense and Denotation as Algorithm and Value. In Logic Colloquium '90 (Helsinki 1990), volume 2 of Lecture Notes in Logic, pages 210-249. Springer, Berlin, 1994.
[2] Y. Moschovakis. A Logical Calculus of Meaning and Synonymy. Linguistics and Philosophy, 29:27-89, 2006.
[3] R.A. Muskens. Meaning and Partiality. CSLI, Stanford, 1995.
[4] R.A. Muskens. Sense and the Computation of Reference. Linguistics and Philosophy, 28(4):473-504, 2005.
[5] R.A. Muskens. Intensional Models for the Theory of Types. Journal of Symbolic Logic, 72(1):98-118, 2007.