This paper develops the first deontic logic in the context of paraconsistent logics.

E j lemmon, B a o williams, Bas van fraassen, And ruth marcus have argued on behalf of the existence of moral dilemmas, I.E., Cases where an agent is subject to conflicting absolute moral obligations. The paper criticizes this support and contends that no moral dilemma is possible.

The Right and the Good, a classic of twentieth-century philosophy by the eminent scholar Sir David Ross, is now presented in a new edition with a substantial introduction by Philip Stratton-Lake, a leading expert on Ross. Ross's book is the pinnacle of ethical intuitionism, which was the dominant moral theory in British philosophy for much of the nineteenth and early twentieth century. Intuitionism is now enjoying a considerable revival, and Stratton-Lake provides the context for a proper understanding of Ross's great (...) work today. (shrink)

This is a volume of philosophical studies, centred on problems of personal identity and extending to related topics in the philosophy of mind and moral philosophy.

A strong tradition in philosophy denies the possibility of moral dilemmas. Recently, several philosophers reversed this tradition. In this dissertation, I clarify some fundamental issues in this debate, argue for the possibility of moral dilemmas, and determine some implications of this possibility. ;In chapter I, I define moral dilemmas roughly as situations where an agent morally ought to adopt each of two alternatives but cannot adopt both. Moral dilemmas are resolvable if and only if one of the moral oughts overrides (...) the other. ;In chapter II, I criticize several opponents of moral dilemmas, including utilitarians, Kant, Aquinas, and Ross. My main criticism is that no opponent of moral dilemmas can adequately justify moral residue . ;Chapters III and IV concern the two main arguments against the possibility of moral dilemmas. First, the argument for 'ought' implies 'can' runs as follows. If the agent cannot adopt both, then it is not the case that the agent ought to adopt both. But the agent ought to adopt both, since the agent ought to adopt each . Thus, the defining judgements of a moral dilemma seem to imply a contradiction. In response, I argue that the relation between 'ought' and 'can' is not a logical implication but a conversational implicature. ;Chapter IV concerns the argument from 'ought' implies 'permitted': If the agent ought to adopt one alternative, then the agent is permitted to adopt that alternative, which means that it is not the case that the agent ought not to adopt that alternative. But the agent ought not to adopt that alternative, since the agent ought to adopt the other alternative and cannot adopt both. I respond that 'ought' does not logically imply but conversationally implicates 'permitted'. ;In chapter V, I argue that, despite recent claims, both moral realism and anti-realism are compatible with the possibility of moral dilemmas. Thus, there are several reasons to accept and no reasons to deny the possibility of moral dilemmas. (shrink)

In Contradiction advocates and defends the view that there are true contradictions, a view that flies in the face of orthodoxy in Western philosophy since Aristotle. The book has been at the center of the controversies surrounding dialetheism ever since its first publication in 1987. This second edition of the book substantially expands upon the original in various ways, and also contains the author’s reflections on developments over the last two decades. Further aspects of dialetheism are discussed in the companion (...) volume, Doubt Truth to be a Liar, also published by Oxford University Press in 2006. (shrink)

I explore various ways of integrating the framework for predeterminism, agency, and ability in[P.McNamara, Nordic J. Philos. Logic 5 (2)(2000) 135] with a framework for obligations. However,the agential obligation operator explored here is defined in terms of a non-agential yet personal obligation operator and a non-deontic (and non-normal) agency operator. This is contrary to the main current trend, which assumes statements of personal obligation always take agential complements. Instead, I take the basic form to be an agent’s being obligated to (...) be such that p. I sketch some logics for agential obligation based on personal obligation and agency, first in a fairly familiar context that rules out conflicting personal obligations (and derivatively, conflicting agential obligations), and then in contexts that do allow for conflicts (of both sorts). (shrink)

A moral dilemma is a situation in which an agent ought to do each of two actions, Both of which he cannot do. If there are genuine moral dilemmas, The ethical theorist is presented with a problem: he must reject several very plausible principles of standard deontic logic. The main reasons usually given to show that there are moral dilemmas are examined, And it is argued that they are not sufficient. Several positive arguments are then presented, Arguments which try to (...) show that an adequate moral theory must rule out the possibility of genuine dilemmas. (shrink)

Marcus argues that moral dilemmas are real, but that they are not the result of inconsistent moral principles. Moral principles are consistent just in case there is some world where all principles are 'obeyable.' They are inconsistent just in case there is no world where all are 'obeyable.' What this logical point is meant to show is that moral dilemmas do not make moral codes inconsistent. She also discusses guilt, and argues that guilt is still appropriate even in cases of (...) conflict, even when the agent thinks the right thing to do is clear. (shrink)

This multiplex semantics incorporates multiple relations of deontic accessibility or multiple preference rankings on alternative worlds to represent distinct normative standards. This provides a convenient framework for deontic logic that allows conflicts of obligation, due either to conflicts between normative standards or to incoherence within a single standard. With the multiplex structures, two general senses of "ought" may be distinguished, an indefinite sense under which something is obligatory when it is enjoined by some normative standard and a core sense for (...) when something is enjoined by all normative standards. Multiple normative standards may themselves be given a preferential order; this leads to a concept of ranked obligation. This paper presents the foundations of this multiplex semantics and the propositional deontic logics they define. (shrink)

Lemmon argues that dilemmas occur between classes of 'oughts;' duties, obligations, and moral principles. He claims that there are not conflicts within each class, presumably because he is a utilitarian, and thinks that moral principles will always be univocal.

This paper develops an informal semantics for 'ought to be' and 'ought to be given...' and argues for its plausibility. A feature of the semantics is that it invalidates 'if a entails b, And o(a), Then o(b)' and 'if o(a) & o(b), Then o(a&b)', While validating detachment for conditional obligation.

Let us say that a normative conflict is a situation in which an agent ought to perform an action A, and also ought to perform an action B, but in which it is impossible for the agent to perform both A and B. Not all normative conflicts are moral conflicts, of course. It may be that the agent ought to perform the action A for reasons of personal generosity, but ought to perform the action B for reasons of prudence: perhaps (...) A involves buying a lavish gift for a friend, while B involves depositing a certain amount of money in the bank. In general, our practical deliberation is shaped by a concern with a variety of morally neutral goods—not just generosity and prudence, but any number of others, such as etiquette, aesthetics, fun—many of which are capable of providing conflicting reasons for action. I mention these ancillary values in the present setting, however, only to put them aside. We will be concerned here, not with normative conflicts more generally, but precisely with moral conflicts—situations in which, even when our attention is restricted entirely to moral reasons for action, it is nevertheless true that an agent ought to do A and ought to do B, where it is impossible to do both. (shrink)

From a philosophical standpoint, the work presented here is based on van Fraassen [26]. The bulk of that paper is organized around a series of arguments against the assumption, built into standard deontic logic, that moral dilemmas are impossible; and van Fraassen only briefly sketches his alternative approach. His paper ends with the conclusion that “the problem of possibly irresolvable moral conflict reveals serious flaws in the philosophical and semantic foundations of ‘orthodox’ deontic logic, but also suggests a rich set (...) of new problems and methods for such logic.” My goal has been to suggest that some of these methods might be found in current research on nonmonotonic reasoning, and that some of the problems may have been confronted there as well.I have shown that nonmonotonic logics provide a natural framework for reasoning about moral dilemmas, perhaps even more useful than the ordinary modal framework, and that the issues surrounding the treatment of exceptional information within these logics run parallel to some of the problems posed by conditional oughts. However, there is also another way in which deontic logic might benefit from a connection to nonmonotonic reasoning. A familiar criticism among ethicists of work in deontic logic is that it is too abstract, and too far removed from the kind of problems confronted by real agents in moral deliberation. It must be said that similar criticisms of abstraction and irrelevance are often lodged against work in nonmonotonic reasoning by more practically minded researchers in artificial intelligence; but here, at least, the criticisms are taken seriously. Nonmonotonic logic aims at a qualitative account of commonsense reasoning, which can be used to relate planning and action to defeasible goals and beliefs; and at least some of the theories developed in this area have been tested in realistic situations. By linking the subject of deontic logic to this research, it may be possible also to relate the idealized study of moral reasoning typical of the field to a more robust treatment of practical deliberation. (shrink)

John Horty effectively develops deontic logic (the logic of ethical concepts like obligation and permission) against the background of a formal theory of agency. He incorporates certain elements of decision theory to set out a new deontic account of what agents ought to do under various conditions over extended periods of time. Offering a conceptual rather than technical emphasis, Horty's framework allows a number of recent issues from moral theory to be set out clearly and discussed from a uniform point (...) of view. (shrink)

In a recent paper, Sven Danielsson argued that the ‘original paradoxes' of deontic logic, in particular Ross's paradox and Prior's paradox of derived obligation, can be solved by restricting the modal inheritance rule. I argue that this does not solve the paradoxes.

A new possible world semantics for deontic logic is proposed. Its intuitive basis is that prohibitive predicates (such as "wrong" and "prohibited") have the property of negativity, i.e. that what is worse than something wrong is itself wrong. The logic of prohibitive predicates is built on this property and on preference logic. Prescriptive predicates are defined in terms of prohibitive predicates, according to the wellknown formula "ought" = "wrong that not". In this preference-based deontic logic (PDL), those theorems that give (...) rise to the paradoxes of standard deontic logic (SDL) are not obtained. (E.g., O(p & q) → Op & Oq and Op → O(p v q)) are theorems of SDL but not of PDL.) The more plausible theorems of SDL, however, can be derived in PDL. (shrink)

Deontic logic ought to be fundamental to ethical theory and the theory of practical reasoning, but, for various reasons, it hasn’t been. James Forrester faults the standard systems themselves; so, in place of standard deontic logic, he proposes a new deontic logic that should, he thinks, serve moral philosophy more adequately.

Forrester eloquently argues his new system of deontic logic (a special branch of logic involved with obligation and permission) pitting it against standard systems and fitting it into a general logic of practical reasoning. He manages all this with a comprehensive discussion of the general principles of deontics, the semantics of "should" and "ought to do" in standard deontic logic, and a map of what he thinks the logic ought to do to achieve moral realism. Paper edition (unseen), $24.95. Annotation (...) copyright by Book News, Inc., Portland, OR. (shrink)

The essays in this volume illuminate a central topic in ethical theory: moral dilemmas. Some contemporary philosophers dispute the traditional view that a true moral dilemma -- a situation in which a person has two irreconcilable moral duties -- cannot exist. This collection provides the historical background to the ongoing debate with selections from Kant, Mill, Bradley, and Ross. The best recent work on the question is represented in essays by Donagan, Foot, Hare, Marcus, Nagel, van Fraassen, Williams, and others.

This collection of previously unpublished essays addresses a number of issues arising out of philosophical controversies over the possibility of genuine moral dilemmas. Issues addressed include the form of a moral dilemma; the paradoxes a moral dilemma is said to entail; the question of whether a moral dilemma must exhibit inconsistency; the role of intractable circumstances in occasioning moral dilemmas; and the plausibility of supposing that there might be rational ways of addressing moral dilemmas in practice. The contributors, writing from (...) a number of widely differing points of view, include Simon Blackburn, Ruth Barcan Marcus, Alan Donagan, Terrance McConnell, Walter Sinnott-Armstrong, Mary Mothersill, Norman Dahl, David Brink, Peter Railton, Thomas E. Hill, Jr., Christopher Gowans, and H.E. Mason. (shrink)

A textbook on modal logic, intended for readers already acquainted with the elements of formal logic, containing nearly 500 exercises. Brian F. Chellas provides a systematic introduction to the principal ideas and results in contemporary treatments of modality, including theorems on completeness and decidability. Illustrative chapters focus on deontic logic and conditionality. Modality is a rapidly expanding branch of logic, and familiarity with the subject is now regarded as a necessary part of every philosopher's technical equipment. Chellas here offers an (...) up-to-date and reliable guide essential for the student. (shrink)