Past Event

On the role of “similarity” in evaluating duties

Dr. Ana Arregui
Assistant Professor (Linguistics)
(University of Ottawa)

In this talk I will investigate some aspects of the interpretation of deontic statements (statements of obligation and permission), being primarily interested in similarities between deontic statements and counterfactuals. I will explore the interaction between primary and secondary duties against the background of ‘contrary to duty imperatives’ (CTDs). I will appeal to our intuitions regarding this interaction to argue for a semantics of deontic statements that tracks counterfactual-style revision.

An example of a CTD is provided in (1):

(1)       

a. The children should not be cycling on the street. (primary duty)

b. If the children are cycling on the street, they should be cycling on the left side of the street. (CTD) (from Prakken and Sergot 1996)

CTDs are conditionals that spell out the ‘best option’ in the event that a primary duty fails.  There is a vast literature on CTD puzzles (for an overview, see Aqvist 2002, Carmo and Jones 2002). The problem I will investigate in this talk is how to understand when we are happy to fall back on the secondary duty. At times, our intuitions clearly insist on the primary duty, and at other times we are willing to fall back on the ‘second choice’ option.

Consider the CTD in (2):

(2)      

a. You should be wearing your winter coat.

b. If you are not wearing your winter coat, you should be wearing your raincoat (it blocks the wind).

Imagine now that a friend sees you at the bus stop, wearing only a shirt and a thin cardigan, shivering:

(3)      

Your friend: You should be wearing your winter coat.

You: I know, but I left it behind at my sister’s house.

Your friend: Well, you should be wearing your raincoat (then).

(4)       

Your friend: You should be wearing your winter coat.

You: I know, but I was late this morning and just ran out of the house without my winter coat.

Your friend: #Well, you should be wearing your raincoat (then).

Although the conditions for the CTD are satisfied in both cases, we are happy to fall back on the secondary duty in (3), but not in (4). I will show that our intuitions regarding when to fall back on secondary duties follow from a semantics for deontic modals that appeals to a revision process that patterns with revision in counterfactuals. This means that the notion of similarity relevant to the evaluation of counterfactuals is also at play in the semantics of deontic modals, supporting the view that our reasoning in the evaluation of deontic claims has much in common with other types of modal reasoning.