Logic and Language Workshop

Hannah Clark-Younger (University of Otago), Dr Melissa Fusco (Columbia University), Kai Tanter (The University of Melbourne)

There will be a small workshop on issues related to logic and language with talks by Hannah Clark-Younger (Otago), Melissa Fusco (Columbia), and Kai Tanter (Melbourne).

12-1:15 Melissa Fusco: "Deontic Disjunction: Solving Free Choice Permission and Ross's Puzzle"

1:15-2-30 Kai Tanter: "A joint solution Ross's Paradox & the Problem of Free Choice"

2:30-3 Coffee break

3-4:15 Hannah Clark-Younger: "A Dynamic Logic of Commands and Permissions"  

Abstracts below.

Hannah Clark-Younger: "A Dynamic Logic of Commands and Permissions"

Melissa Fusco: "Deontic Disjunction: Solving Free Choice Permission and Ross's Puzzle"

Abstract: Formal developments of normative theories typically claim the guidance they give is universal: for any agent, and any way the world could be, there is a way she ought (according to that theory) to act.  Yet when we consider an agent facing an open, indeterminate future, cases are possible in which what she ought to do depends on what she actually does.  These situations follow the letter of the law while seeming to violate its spirit.  A famous example, discussed by Gibbard and Harper (1978), comes from Somerset Maugham: while in Damascus, you learn that Death is coming to collect your soul.  Your one option is to flee to Aleppo.  But you are confident that Death never misses her quarry: if you flee to Aleppo, Death will be there.  But if you stay in Damascus, Death will be there too.     If Death is going to Damascus, you ought to go to Aleppo, and if Death is going to Aleppo, you ought to go to Damascus.  So for any way the future could go, there something you ought to do. Yet there is a clear sense in which there is nothing you can do: since Death's destination mirrors yours, no act is such that you ought to have done it, given that you do it.  The norms of rationality in cases of this structure---and cases with the opposite structure, where available acts deontically validate themselves---are the subject of much recent work in ethics, decision theory, and the metaphysics of persons.  I show how a model theory for the natural language modals 'ought' and 'may' can incorporate these nonstandard notions of deontic validation and self-defeat.  This theorizing makes contact with natural language in the form of my solutions to Ross's puzzle (Ross 1941) and free choice permission (Kamp 1973).   

Kai Tanter: "A joint solution Ross's Paradox & the Problem of Free Choice"

Ross's Paradox is the apparent invalidity of the inference from the command 'Write your abstract!' to 'Write your abstract or watch YouTube!', despite it being valid according to many imperative logics. The Problem of Free Choice is the apparent validity of the inference from the permission 'Write your abstract or watch YouTube' to 'Write your abstract' and also 'Watch YouTube', but not the permission 'Write your abstract and watch YouTube'. This is despite normally being able to infer a conjunction whenever both conjuncts are inferable. Elaborating on (Castañeda 1981) I will make three arguments: (1) that Ross's Paradox can only be solved together with the Problem of Free Choice; (2) that we ought to validate the Ross Inference φ ⊢ φ ∨ ψ; and (3) that we ought to invalidate the Free Choice Inferences φ ∨ ψ ⊢ φ and φ ∨ ψ ⊢ ψ. In doing so I will use a framework where an imperative inference is valid when jointly "ruling in" the premise and "ruling out" the conclusion is incoherent. The general argument is however intended to be relatively framework neutral.