The paper discusses ten philosophical problems in deontic logic: how to formally represent norms, when a set of norms may be termed ‘coherent’, how to deal with normative conflicts, how contraryto-duty obligations can be appropriately modeled, how dyadic deontic operators may be redefined to relate to sets of norms instead of preference relations between possible worlds, how various concepts of permission can be accommodated, how meaning postulates and counts-as conditionals can be taken into account, and how sets of norms may (...) be revised and merged. The problems are discussed from the viewpoint of input/output logic as developed by van der Torre & Makinson. We argue that norms, not ideality, should take the central position in deontic semantics, and that a semantics that represents norms, as input/output logic does, provides helpful tools for analyzing, clarifying and solving the problems of deontic logic. (shrink)

Moral obligation and permissibility are usually thought to be interdefinable. Following the pattern of the duality definitions of necessity and possibility, we have that something’s being permissible could be defined as its not being obligatory to not do it. And that something’s being obligatory could be defined as its not being permissible to not do it. In this paper, I argue that neither direction of this alleged interdefinability works. Roughly, the problem is that a claim that some act is obligatory (...) or permissible entails that there is a moral law, whereas a negative claim that some act is not obligatory or not permissible does not. Nevertheless, one direction of the interdefinability can potentially be salvaged. I argue that, if we do not require the conceptual possibility of moral dilemmas, then there is a way to plausibly define obligation in terms of permissibility. I conclude that permissibility is the only feasible deontic primitive. (shrink)

According to typical ought-implies-can principles, if you have an obligation to vaccinate me tomorrow, then you can vaccinate me tomorrow. Such principles are uninformative about conditional obligations: what if you only have an obligation to vaccinate me tomorrow if you synthesize a vaccine today? Then maybe you cannot vaccinate me tomorrow ; what you can do instead, I propose, is make it the case that the conditional obligation is not violated. More generally, I propose the ought-implies-can-obey principle: an agent has (...) an obligation only at times at which the agent can obey the obligation. I also propose another principle, which captures the idea that ‘ought’ implies ‘can avoid’. I defend both principles mainly by arguing that they help explain why agents lose obligations, including conditional ones. (shrink)

In his last papers about deontic logic, von Wright sustained that there is no genuine logic of norms. We argue in this paper that this striking statement by the father of deontic logic should not be understood as a death sentence to the subject. Rather, it indicates a profound change in von Wright's understanding about the epistemic and ontological role of logic in the field of norms. Instead of a logical constructivism of deontic systems revealing a necessary structure of prescriptive (...) discourse, which marked his earlier efforts, he adopted the view that such systems should be seem as mere objects of comparison, i.e. as providing practical standards of rationality for normgiving activity. Within such view he proposed an interpretation of standard deontic logic in such a way to free deontic logicians from the philosophical difficulties related to the so-called Jørgensen's dilemma and deontic paradoxes. This effort, as we claim in the present paper, is an application of Wittgenstein's therapeutic method to dissolve philosophical difficulties caused by the use of logical tools to model relations between norms. (shrink)

On the face of it, normative conflicts are commonplace. Yet standard deontic logic declares them to be logically impossible. That prompts the question, What are the proper principles of normative reasoning if such conflicts are possible? This paper examines several alternatives that have been proposed for a logic of 'ought' that can accommodate normative conflicts, and finds all of them unsatisfactory as measured against three criteria of adequacy. It then introduces a new logic that does meet all three criteria, and (...) so allows for the possibility of genuine normative conflicts. (shrink)

Philosophers like G.H. von Wright and D. Makinson have pointed to serious challenges regarding the foundations of deontic logic. In this paper, I suggest that to deal successfully with these challenges a reconsideration of the research program of the discipline is useful. Some problems that have troubled this particular field of logical study for decades may disappear or appear more tractable if we view them from the perspective of a language game introduced by D. Lewis involving three characters: the Master, (...) the Slave and the Kibitzer. The adoption of this perspective opens a natural approach to a new layout of the domain of deontic studies. I propose dividing deontic logic into six sub-areas which are distinguished by their focus on the different idioms typical of the individual players, by conceiving the language game as either being static or as dynamic and by the aims of the logical inquiry. What kind of insights the proposed perspective provides is illustrated by an analysis of the so-called Ross paradox—a problem that has troubled deontic logic since its origins and, though it was many times pronounced solved, still keeps coming back ‘alive and kicking’. (shrink)