In this work, we propose a meaningful extension of description logics for non-monotonic reasoning. We introduce \, a logic allowing for the representation of and reasoning about both typical class-membership and typical instances of a relation. We propose a preferential semantics for \ in terms of partially-ordered DL interpretations which intuitively captures the notions of typicality we are interested in. We define a tableau-based algorithm for checking \ knowledge-base consistency that always terminates and we show that it is sound and (...) complete w.r.t. our preferential semantics. The general framework we here propose can serve as the foundation for further exploration of non-monotonic reasoning in description logics and similarly structured logics. (shrink)

In this work we propose an encoding of Reiter’s Situation Calculus solution to the frame problem into the framework of a simple multimodal logic of actions. In particular we present the modal counterpart of the regression technique. This gives us a theorem proving method for a relevant fragment of our modal logic.

Traditionally, consistency is the only criterion for the quality of a theory in logic-based approaches to reasoning about actions. This work goes beyond that and contributes to the metatheory of actions by investigating what other properties a good domain description should have. We state some metatheoretical postulates concerning this sore spot. When all postulates are satisfied we call the action theory modular. Besides being easier to understand and more elaboration tolerant in McCarthy’s sense, modular theories have interesting properties. We point (...) out the problems that arise when the postulates about modularity are violated, and propose algorithmic checks that can help the designer of an action theory to overcome them. (shrink)

We investigate an aspect of defeasibility that has somewhat been overlooked by the non-monotonic reasoning community, namely that of defeasible modes of reasoning. These aim to formalise defeasibility of the traditional notion of necessity in modal logic, in particular of its different readings as action, knowledge and others in specific contexts, rather than defeasibility of conditional forms. Building on an extension of the preferential approach to modal logics, we introduce new modal osperators with which to formalise the notion of defeasible (...) necessity and distinct possibility, and that can be used to represent expected effects, refutable knowledge, and so on. We show how KLM-style conditionals can smoothly be integrated with our richer language. We also propose a tableau calculus which is sound and complete with respect to our modal preferential semantics, and of which the computational complexity remains in the same class as that of the underlying classical modal logic. (shrink)

Modal accounts of normality in non-monotonic reasoning traditionally have an underlying semantics based on a notion of preference amongst worlds. In this paper, we motivate and investigate an alternative semantics, based on ordered accessibility relations in Kripke frames. The underlying intuition is that some world tuples may be seen as more normal, while others may be seen as more exceptional. We show that this delivers an elegant and intuitive semantic construction, which gives a new perspective on defeasible necessity. Technically, the (...) revisited logic does not change the expressive power of our previously defined preferential modalities. This conclusion follows from an analysis of both semantic constructions via a generalisation of bisimulations to the preferential case. Reasoners based on the previous semantics therefore also suffice for reasoning over the new semantics. We complete the picture by investigating different notions of defeasible conditionals in modal logic that can also be captured within our framework. (shrink)

There are various contexts in which it is not pertinent to generate and attend to all the classical consequences of a given premiss—or to trace all the premisses which classically entail a given consequence. Such contexts may involve limited resources of an agent or inferential engine, contextual relevance or irrelevance of certain consequences or premisses, modelling everyday human reasoning, the search for plausible abduced hypotheses or potential causes, etc. In this paper we propose and explicate one formal framework for a (...) whole spectrum of consequence relations, flexible enough to be tailored for choices from a variety of contexts. We do so by investigating semantic constraints on classical entailment which give rise to a family of infra-classical logics with appealing properties. More specifically, our infra-classical reasoning demands (beyond ${\alpha\models\beta}$ ) that Mod(β) does not run wild, but lies within the scope (whatever that may mean in some specific context) of Mod(α), and which can be described by a sentence ${\bullet\alpha}$ with ${\beta\models\bullet\alpha}$ . Besides being infra-classical, the resulting logic is also non-monotonic and allows for non-trivial reasoning in the presence of inconsistencies. (shrink)

After the seminal work of Kraus, Lehmann and Magidor (formally known as the KLM approach) on conditionals and preferential models, many aspects of defeasibility in more complex formalisms have been studied in recent years. Examples of these aspects are the notion of typicality in description logic and defeasible necessity in modal logic. We discuss a new aspect of defeasibility that can be expressed in the case of temporal logic, which is the normality in an execution. In this contribution, we take (...) Linear Temporal Logic (LTL) as case study for this defeasible aspect. LTL has found extensive applications in Computer Science and Artificial Intelligence, notably as a formal framework for representing and verifying computer systems that vary over time. However, some systems may presents exceptions at some innocuous time points where they can be tolerated, or conversely, exceptions at other crucial time points where they need to be addressed. In order to ensure the reliability of such systems, we study a preferential extension of LTL, called defeasible linear temporal logic (LTL ~ ). In the first part of this paper, we show how semantics of KLM's preferential models can be integrated with LTL. We also discuss the addition of non-monotonic temporal operators as a way to formalise defeasible properties of these systems. The second part of this paper is a study of the satisfiability problem of LTL ~ sentences. Based on Sistla and Clarke's work on the complexity of the classical LTL language, we show the bounded-model property of two fragments of LTL ~ language. Moreover, we provide a procedure to check the satisfiability of sentences in both of these fragments. (shrink)

This chapter contains section titled: Personhood: A Start Are Dolphins Persons? Language and the Hand Personhood Redefined Conclusion: What Kind of Beings Are Dolphins?

The newly updated Right and Wrong 2nd Edition is an accessible introduction to the major traditions in western philosophical ethics, written in a lively and engaging style. It is designed for entry-level ethics courses and includes real-life ethical scenarios chosen to appeal directly to students. Greatly expanded and improved, this successful text introduces students to the major ethical traditions, and provides a simple methodology for resolving ethical dilemmas Treats teleological and deontological approaches to ethics as the two most important traditions, (...) but now includes chapters on virtue ethics and the ethics of care The very accessible writing style speaks directly to students’ own experience Draws examples from three types of real-life ethical scenarios submitted by students: academic dishonesty, partying, and personal relationships Provides a concise treatment of this notoriously complex subject, perfect for entry-level ethics and applied ethics courses. (shrink)

This chapter contains section titled: Human Adaptations to the Water: An Exercise in Imagination Life in the ocean: the importance of other people Dolphin Intelligence in the Wild Dolphin Communication Social Intelligence and Group Cohesion Dolphins and Sex The Cognitive and Affective Skills Involved in Group Living Conclusion: Dolphin Intelligence.

This chapter contains section titled: “Human” Versus “Person” Human, Person and Ethics Philosophical Ethics Ethics and Nonhumans “Alien Intelligence” Two Questions.

This chapter contains section titled: “Interspecies ethics” The Dolphin/Tuna Controversy Dolphins in Captivity So What Do We Do? The Ethics of Human/Dolphin Contact: Two Final Thoughts.

For courses in Business Ethics A fresh approach to the assumptions that underlie business practices Two recent events — the 2008 economic meltdown and the ongoing concentration of the nation's wealth in the hands of a very small percentage of the population — have led many people to question a number of basic assumptions about business, corporations, and the workings of contemporary free-market capitalism in a global economy. Written as a dialogue between Socrates and a hypothetical contemporary CEO,Socrates Comes to (...) Wall Street leads students to think critically about perspectives and practices that are taken as “givens” in most American business schools and corporations. Employing this original and provocative approach, author Thomas White seeks to encourage the next generation of business leaders to be more astute about the implications of their actions, and to act more prudently and more fairly than we have seen in the recent past. (shrink)

The theory is presented that the sexual process is a repair mechanism which maintains redundancy within the sub-structure of hierarchical, self-reproducing organisms. In order to keep the problems within mathematically tractable limits , a simple model is introduced: a wheel with 6 spokes, 3 of them vital and 3 redundant, symbolizes the individual . Random accidents destroy spokes; the wheels replicate at regular cycles and engage periodically in pairing and repair phases during which missing spokes are copy-reproduced along the intact (...) spokes of the partner wheel.The hierarchical structure of such a system is analysed and an ‘autonomous unit’ is defined: this is the unit of minimal hierarchical complexity which is capable of perpetuating autonomously all higher and all lower levels of the hierarchy; this is the central unit of selection.Four basic, physical parameters are isolated which determine the essential features of any eucaryotic life cycle: 1. The number of levels of the hierarchy ; 2. the relation between the phases of replication and repair ; 3. the duration of potential repair ; 4. the position of the sexual partners within the hierarchy .The evaluation of fitness components is considered in relation to trends of reproductive patterns in evolution. (shrink)

Islamic ethics in the light of Koranic teachings.