Formal Philosophy Workshop

The Melbourne-Glasgow Formal Philosophy Workshop will be held on 12-13 June at The University of Melbourne in Arts West 561 North Wing. The schedule and abstracts are below.

12 June   

10-11:30 Greg Restall (Melbourne) -- What proofs are for

11:30-1 Shawn Standefer (Melbourne) -- Hyperintensionality, relevance, and justifications

1-2:30 Lunch

2:30-4 Toby Handfield (Monash) -- Intuitions in decision theory: empirical evidence

4-5:30 Jake Chandler (La Trobe) -- On Strengthening the Logic of Iterated Revision  

13 June  

11-12:30 Adam Rieger (Glasgow) -- How to avoid electing Trump: a plea for cardinal voting

12:30-2 Lunch

2-3:30 Dana Goswick (Melbourne) -- Should We Endorse a Law of Excluded Middle for Property Instantiation?

3:30-5 Berta Grimau (Glasgow) -- Cluster Semantics for Higher-Level Plurals 

Jake Chandler -- On Strengthening the Logic of Iterated Revision

Darwiche and Pearl's seminal 1997 article outlined a number of baseline principles for a logic of iterated belief revision. These principles, the DP postulates, have been supplemented in a number of alternative ways. Most of the suggestions made have resulted in a form of `reductionism' that identifies belief states with orderings of worlds. However this position has  recently been criticised as being unacceptably strong. Other proposals, such as the popular principle (P), aka `Independence', characteristic of `admissible' revision operators, remain commendably more modest. In this paper, we supplement both the DP postulates and (P) with a number of novel conditions. While the DP postulates constrain the relation between a prior and a posterior conditional belief set, our new principles notably govern the relation between two posterior conditional belief sets obtained from a common prior by different revisions. We show that operators from the resulting family, which subsumes both lexicographic and restrained revision, can be represented as relating belief states that are associated with a `proper ordinal interval' (POI) assignment, a structure more fine-grained than a simple ordering of worlds.

Dana Goswick -- Should We Endorse a Law of Excluded Middle for Property Instantiation?

Abstract: Closely related to the Law of the Excluded Middle (LEM) is the question of whether every object is such that, for every property P, the object either instantiates P or fails to instantiate P.  Call this the "Law of Excluded Middle Instantiation" (LEMI).  I examine the costs and benefits of respecting LEMI.  Ultimately I conclude that we should examine philosophical theories on a case-by-case basis and weigh the pros and cons of the theory, rather than summarily dismissing a view simply because it requires LEMI violations

Berta Grimau -- Cluster Semantics for Higher-Level Plurals

Abstract: Higher-Level Plural Logic (HLPL) is an extension of plural logic which has, in addition to plural terms and quantifiers, higher-level plural ones. The idea is that second-level plurals stand to plurals like plurals stand to singulars (analogously for higher levels). For instance, if English allowed composition of the plural suffix on itself, "catses" would be the plural of "cats" and the second-level plural of "cat". Allegedly, HLPL enjoys the expressive power of a type theory while committing us to nothing more than the austere ontology of first-order logic. Were this true, HLPL would be a very valuable tool, with applications in the philosophy of mathematics and in metaphysics, among other areas. However, whereas the notion of plural reference enjoys widespread acceptance today, its higher-level counterpart has been received with apprehension.   Even though I believe that a homophonic semantic approach to HLPL (that is, one which employs metalinguistic higher-level plural terms and quantifiers) is suitable, in this talk I shall present an alternative semantics -- one which makes use only of singular and plural devices. Roughly speaking, the idea is that higher-level plural terms refer to some objects under a certain cluster, where a cluster is a relation which holds of some objects iff they are organized in groups.   In my talk, after introducing the debate around higher-level plurals, I describe my proposal to analyze them in terms of clusters. Next, I show that this semantics offers some advantages over its main rivals. And, finally, I argue that reference under clusters is a species of a much broader phenomenon: restricted reference, a mode of reference which can explain many failures of substitutivity of co-referential terms.  

Toby Handfield -- Intuitions in decision theory: empirical evidence

Abstract: The rivalry between causal decision theory and evidential decision theory is one of the central debates in the field. At least superficially, the discussion has involved heavy reliance on thought experiments and the intuitions generated by those thought experiments. In this talk I present some recent empirical work that attempts to assess whether folk intuitions about these cases are liable to be affected by a number of possible confounds present in the original thought experiments. In particular, we examine the so-called Psychopath Button — a case which involves the option to commit murder — and find evidence that the moral valence of the decision involved has a substantial effect on folk intuitions. We also describe a second experiment (data collection still underway) in which we test for effects of extreme stakes, extreme probabilities, and causal structure on intuitions in Newcomb’s puzzle and related cases. (Work co-authored with Adam Bales (Cambridge) and Josh May (UA–Birmingham))

Greg Restall -- What proofs are for

Abstract: In this short talk, I present a new account of the nature of proof, with the aim of explaining how proof could actually play the role in reasoning that it does, and answering some long-standing puzzles about the nature of proof. Along the way, I’ll explain how Kreisel’s Squeezing argument helps us understand the connection between an informal notion of of validity and the notions formalised in our accounts of proofs and models, and the relationship between proof-theoretic and model-theoretic analyses of logical consequence.

Adam Rieger --  How to avoid electing Trump: a plea for cardinal voting

Abstract:   Suppose a population with diverse opinions is to elect a single winner (for example a President).  How should the winner be chosen?  I will give a brief survey of the terrain, ending by arguing for a novel system based on cardinal scoring of candidates rather than ordinal ranking.

Shawn Standefer -- Hyperintensionality, relevance, and justifications  

Abstract: Relevant logics and justification logics both deal with hyperintensional operators. In this talk, I will motivate their combination and argue that the resulting package preserves most of their appealing features. I will provide models for the combined package, although these models will diverge from the standard evidence-function models used for classical justification logics, and I will suggest a philosophical interpretation for these models.