Schedule of Talks:
Friday, 13 April
9:00 Kai Wehmeier, University of California Irvine: "Actuality and Subjunctivity"
After a brief and selective discussion of the early history of the subject, I will survey results obtained and systems developed in the subjunctivity project, including subjunctive modal logic and its application to Kripke's modal argument against description theories of proper names, the logic of cross-world predication, and the analysis of subjunctive conditionals. I will close with some remarks on the relation between the subjunctive languages and the actuality languages, as well as some methodological considerations pertaining to the philosophy of logic and language.
10:30 Jordan Stein, New York City College of Technology: "Is Every Truth A Priori Equivalent to a Necessary Truth?”
Tharp proves the following ‘theorems of metaphysics’ in the context of ordinary modal predicate logic: every truth is a priori equivalent to a necessary truth, every truth is necessarily equivalent to an a priori truth, and every truth is a priori equivalent to a contingent truth. Humberstone shows that versions of Tharp’s theorems hold for the modal system S5A. In this talk I show that Tharp’s theorems do not hold for Subjunctive Modal Logic (SML) and suggest that their failure provides SML with a leg up when it comes to the formal representation of our concepts of metaphysical possibility and necessity. Along the way I revisit an earlier result which shows that for SML there is no distinction between truth at all worlds w and truth at all worlds w from the point of view of w as actual.
1:00 Allen Hazen, University of Alberta: "Variations on two themes"
In the simplest case, (propositional) modal logic with an actuality operator and with a subjunctive operator produce languages of equal expressive power. I explore (in a preliminary way) extensions of the two approaches to more expressive languages, without finding decisive advantages for either...
2:30 Rohan French, Monash University: "In the Mood for S4: The Expressive Power of the Subjunctive Modal language in Weak Background Logics
We show that over background modal logics weaker than S5 SML is expressively weaker than the logic of ‘actually’ (AML). This complicates arguments which have been given in favour of SML over AML, seemingly making much of the attractiveness of the former dependent upon the correctness of S5 as the logic of metaphysical modality. We conclude by mentioning some methodological issues this raises for the proponent of SML in general.
4:30 John Mackay, University of Wisconsin-Madison: "Subjunctivity and Semantics"
According to the standard picture in natural language semantics, a sentence in the indicative mood usually receives a semantic value that varies in truth-value across possible worlds. I will argue, however, that the behavior of indicative mood sentences embedded in modal environments shows that this is a mistake; indicative mood sentences should receive semantic values that are fixed in truth-value across possible worlds, just as sentences with the actuality operator receive on the more traditional picture. The behavior of indicative mood therefore supports a position articulated by David Lewis in "Index, Context, and Content" that the semantic values of sentences need to be distinguished from the propositions that are the objects of speech acts such as assertion, at least if the latter do vary in truth-value across possible worlds.
Saturday, 14 April
10:00 Helge Rückert, Mannheim University: "Extending Wehmeier’s Modal Logic with Subjunctive Markers: Nested Modals, and Systems other than S5"
Almost ten years ago, Wehmeier presented his subjunctive marker approach to modal logic in order to give an adequate analysis of the distinction between the indicative mood and the subjunctive mood in natural language (in subsequent papers he applied this framework also to transworld predications and to counterfactuals). In my talk, I will show how this approach can be straightforwardly extended in two ways, while staying fully within the spirit of its initial ideas and motivations: 1) Whereas Wehmeier introduced only one subjunctive marker, using several subjunctive markers allows for an adequate treatment of nested modal expressions. 2) Whereas Wehmeier focused on the modal system S5, using indicative and subjunctive versions of the modal expressions themselves allows adequately to formulate other modal systems like T, B or S4
11:30 Richard Mendelsohn, CUNY Graduate Center: "What Did He Actually Say? The Gettier Fallacy"
 F is in many instances ambiguous as between a de dicto and a de re reading. If one regards the  as attached to a sentence F on each reading, then since the  is not de dicto/de re ambiguous, the sentence F itself must be. The failure to recognize the ambiguity can result in an argumentative fallacy. In my talk, I show that Edmund Gettier commits a form of this fallacy in each of his two famous cases against the justified true belief account of knowledge. Gettier equivocates between two modal readings of A is justifiied in believing that F, and in doing so engenders the illusion of a true proposition that A is justified in believing, but which he does not know.
Attendance is free, but RSVPs are encouraged prior to April 2nd. Please contact Patty
Jones, LPS Department Manager, email@example.com
Hosted by: Professor Kai Wehmeier, with the Department of Logic and Philosophy of Science, History and Philosophy of Science (Interdisciplinary Program), and the School of Social Sciences