Contrary-to-duty obligations
The authors argue successfully that a distinction must be drawn between contrary-to-duty reasoning and defeasible deontic reasoning. Consider the following three sentences: i) You must come to the faculty meeting. ii) If you are seriously ill, you do not have to attend the faculty meeting. iii) If you do not come the faculty meeting you must inform the dean that you will be absent. ii) defeats i), in the sense that i) does not apply under the circumstances when ii) applies. This is a case of defeasible reasoning. In contrast, i) can coexist with iii), which applies due to violation of i). The authors argue that defeasible deontic reasoning can be modelled in the same way as defeasible non-deontic reasoning, whereas contrary-to-duty reasoning requires a different type of formalization. For both purposes, they employ a similarity relation between worlds, but it is not used in the same way. In defeasible reasoning, one selects among the worlds in which the antecedent is true those that are close enough, or maximally close, to the actual world. In contrary-to-duty reasoning, they say, one should select, also among the worlds in which the antecedent is true, those that are ideal (``best''). The formal properties of these two selection mechanisms do not seem to coincide. The conceptual distinctions are drawn in this paper with unusual clarity, and the formal results, although unsurprising, are competently developed. This is an important contribution to the discussion on contrary-to-duty obligations.
scientific article; zbMATH DE number 929964
scientific article