Reasoning about Minimal Belief and Negation as Failure

We investigate the problem of reasoning in the propositional fragment of MBNF, the logic of minimal belief and negation as failure introduced by Lifschitz, which can be considered as a unifying framework for several nonmonotonic formalisms, including default logic, autoepistemic logic, circumscription, epistemic queries, and logic programming. We characterize the complexity and provide algorithms for reasoning in propositional MBNF. In particular, we show that entailment in propositional MBNF lies at the third level of the polynomial hierarchy, hence it is harder than reasoning in all the above mentioned propositional formalisms for nonmonotonic reasoning. We also prove the exact correspondence between negation as failure in MBNF and negative introspection in Moore's autoepistemic logic

Propositions

This encyclopedia article explores the basics of what philosophers mean by the word 'proposition.' The term 'proposition' has a broad use in contemporary philosophy. It is used to refer to some or all of the following: the primary bearers of truth-value, the objects of belief and other "propositional attitudes" (i.e., what is believed, doubted, etc.), the referents of that-clauses, and the meanings of sentences

Realism, Truthmakers, and Language: A study in meta-ontology and the relationship between language and metaphysics

Metaphysics has had a long history of debate over its viability, and substantivity. This thesis explores issues connected to the realism question within the domain of metaphysics, ultimately aiming to defend a realist, substantive metaphysics by responding to so-called deflationary approaches, which have become prominent, and well supported within the recent metametaphysical and metaontological literature. To this end, I begin by examining the changing nature of the realism question. I argue that characterising realism and anti-realism through theories of truth unduly places epistemology prior to ontology, and is unwarranted in assuming a non-neutrality between theories of truth and positions within the realism debate. I therefore propose a characterisation of realism and anti-realism understood through truthmaking. This produces a suitable working characterisation of realism that will be used within the remainder of this project. In the second section, I trace the historical influences upon current deflationary approaches to metaphysics, most prominently those of Carnap, and Putnam. I argue that Quine’s supposed attack on Carnap’s anti-metaphysical thought fails, and show how current deflationary thought, most prominently exhibited by Hirsch, came to focus on linguistically derived concerns over the substantivity of metaphysics. In the third section, I outline a number of issues for the deflationist, and defend the coherency and legitimacy of the unrestricted existential quantifier. Focusing on the linguistic aspect of deflationism, I argue that the conception of language that the deflationist relies upon lacks suitable empirical and theoretical support within linguistics and other related domains. Furthermore, I suggest that linguistic analysis in fact supports the claim that the quantifier carries no inherent restrictions. This restores our ability to suitably posit the unrestricted existential quantifier, as a quantifier wherein the domain is only restricted by metaphysically substantive restrictions. Through this, I argue that metaphysics is a substantive domain of discourse. Lastly, I sketch a positive account of how, under an empirically and theoretically justified conception of language, metaphysics can be coherently held to be a realist, substantive enterprise, contra claims that hold that the nature of language inherently prevents metaphysics being considered to be a substantive domain of discourse

Data and Language in Organizations: Epistemological Aspects of Management Support Systems

This book contributes to the literature on management decision support systems (DSS). DSS research is motivated by the observation that much of what managers do involves unstructured problem solving. For the reason, the structured, procedural models implemented in management information systems (MIS) have had little impact on actual managerial practice. Actually, the terms "decision" and "problem solving" over-simplify the image of managerial activity, if what is meant is choosing from a set of well-defined alternatives. Management also includes such aspects as reality testing, problem finding, scenario generation, and just plain muddling through. A broader conception of management cognition -- of which decision making is only a part -- is therefore adopted. The challenge to technology development is to support these unstructured managerial activities. The emphasis is to amplify managerial cognition and to improve decision effectiveness. However, to achieve this we must go beyond platitudes and come to a better understanding of what managers actually do. The activity of managers is almost entirely linguistic. Computers, as symbolic processors, ought to be an effective complement. However, a fundamental problem, stressed repeatedly throughout the book, is semantic change. The context of managers is always changing, whereas computational inference depends on fixed semantics. Herein Lies the basis for a theory of management support systems. The theory takes the form of an applied epistemology: how do managers know their world and detect its changes? Thus, while this book is oriented towards improving information technology, its attention is primarily to the content of management information and only secondarily to technology. Technological innovations abound. What is needed now is a better understanding of what these technologies are to do

Situation semantics and its foundations

The aim of this thesis is to examine several aspects of situation semantics and to evaluate the contribution which the theory makes to our understanding of language, in particular whether it brings us nearer to a solution of some traditional puzzles with attitude reports.The presentation is in three parts. The first part, comprising chapters one and two, consists of a general introduction to the issues involved and tackles the question of where situation semantics places the boundary between semantics and pragmatics. The second and main part, chapters three to six, is devoted to demonstrating the language- dependent status of abstract situations. The interpretations of expressions and the role of the setting in composition are analysed in chapter three. In chapter four I consider Russell's views on propositions and the Russellian semantics Richards has given. Chapter five examines in detail the suggestion of chapter three that the level of abstract situations is not independent of language, recasts situation semantics accordingly as an interpreted language, and lastly considers an extension of situation semantics to include molecular facts. In chapter six situation semantics is related to direct reference semantics. Finally, chapters seven and eight treat attitude reports, analysing firstly the ingredients of Barwise and Perry's approach to the semantics of the attitudes, and secondly setting out some traditional puzzles and considering how situation semantics deals with them.The goal throughout is to clarify and understand what the ideas and insights behind situation semantics are and to determine their importance for semantic theory