One of the few points of agreement to be found in mainstream responses to the logical and semantic problems generated by vagueness is the view that if any modification of classical logic and semantics is required at all then it will only be such as to admit underdetermined reference and truth-value gaps. Logics of vagueness including many valued logics, fuzzy logics, and supervaluation logics all provide responses in accord with this view. The thought that an adequate response might require the (...) recognition of cases of overdetermination and truth value gluts has few supporters. This imbalance lacks justification. As it happens, Jaskowski's paraconsistent discussive logic-a logic which admits truth value gluts-can be defended by reflecting on similarities between it and the popular supervaluationist analysis of vagueness already in the philosophical literature. A simple dualisation of supervaluation semantics results in a paraconsistent logic of vagueness based on what has been termed subvaluational semantics. (shrink)

Vagueness, Logic and Ontology explores various responses to the philosophical problems generated by vagueness and its associated paradox - the sorites paradox. Hyde argues that the theoretical space in which vagueness is sometimes ontologically grounded and modelled by a truth-functional logic affords a coherent response to the problems posed by vagueness. Showing how the concept of vagueness can be applied to the world, Hyde's ontological account proposes a substantial revision of orthodox semantics, metaphysics and logic. This book will be of (...) particular interest to readers in philosophy, linguistics, cognitive science and geographic information systems. (shrink)

The sorites paradox is the name given to a class of paradoxical arguments, also known as little by little arguments, which arise as a result of the indeterminacy surrounding limits of application of the predicates involved. For example, the concept of a heap appears to lack sharp boundaries and, as a consequence of the subsequent indeterminacy surrounding the extension of the predicate ‘is a heap’, no one grain of wheat can be identified as making the difference between being a heap (...) and not being a heap. Given then that one grain of wheat does not make a heap, it would seem to follow that two do not, thus three do not, and so on. In the end it would appear that no amount of wheat can make a heap. We are faced with paradox since from apparently true premises by seemingly uncontroversial reasoning we arrive at an apparently false conclusion. (shrink)

Difficulties in arriving at an adequate conception of vagueness have led many writers to describe a phenomenon that has come to be known as "higher-order vagueness". Almost as many have found it to be a problem that needs to be addressed. In what follows I shall argue that, whilst we must acknowledge its presence, it is a pseudo-problem. The crucial point is the vagueness of "vague", which shows the phenomenon to be unproblematic though real enough.

The idea that the phenomenon of vagueness might be modelled by a paraconsistent logic has been little discussed in contemporary work on vagueness, just as the idea that paraconsistent logics might be fruitfully applied to the phenomenon of vagueness has been little discussed in contemporary work on paraconsistency. This is prima facie surprising given that the earliest formalisations of paraconsistent logics presented in Jáskowski and Halldén were presented as logics of vagueness. One possible explanation for this is that, despite initial (...) advocacy by pioneers of paraconsistency, the prospects for a paraconsistent account of vagueness are so poor as to warrant little further consideration. In this paper we look at the reasons that might be offered in defence of this negative claim. As we shall show, they are far from compelling. Paraconsistent accounts of vagueness deserve further attention. (shrink)

Paraconsistent responses to vagueness are often thought to represent a revision of logical theory that is too radical to be defensible. The paracomplete logic of supervaluationism, SpV, is not only taken to be more conservative but is also commonly said to 'preserve classical logic'. This chapter argues that this is wrong on both counts. The paraconsistent logic SbV, or subvaluationism, is no less conservative than SpV nor more so. In the end both logics offer equally compelling theoretical approaches to vagueness. (...) Each approach is also equally objectionable, with neither providing an adequate account of vagueness, but this criticism arises from a feature shared by each approach that is independent of their paracompleteness or paraconsistency per se. For all that has been said, a paraconsistent approach, and the associated recourse to truth-value gluts, remains a contender in accounting for vagueness. (shrink)

The topic of vagueness re-emerged in the twentieth century from relative obscurity. It deals with the phenomenon in natural language that manifests itself in apparent semantic indeterminacy - the indeterminacy, for example, that arises when asked to draw the line between the tall and non-tall, or the drunk and the sober. Vagueness, Logic and Ontology explores various responses to the philosophical problems generated by vagueness and its associated paradox - the sorites paradox. Hyde argues that the theoretical space in which (...) vagueness is sometimes ontologically grounded and modelled by a truth-functional logic affords a coherent response to the problems posed by vagueness. Showing how the concept of vagueness can be applied to the world, Hyde's ontological account proposes a substantial revision of orthodox semantics, metaphysics and logic. (shrink)

It is commonly suggested that vagueness is a purely semantic phenomenon having no metaphysical or ontological implications, requiring no new ontological category for its explanation. It does not entail any revision of the metaphysical view that the world is precise or determinate contra advocates of a vague or fuzzy ontology like Bertil Rolf and Michael Tye. The suggestion is often bolstered by arguments that purport to show that the world is completely describable in a precise language. The precision of the (...) world is then taken to follow from the availability of such a complete precise description thereof. In this sense vague language might be considered superficial. (shrink)

Richard Sylvan (né Routley) was one of Australasia's most prolific and systematic philosophers. Though known for his innovative work in logic and metaphysics, the astonishing breadth of his philosophical endeavours included almost all reaches of philosophy. Taking the view that very basic assumptions of mainstream philosophy were fundamentally mistaken, he sought radical change across a wide range of theories. However, his view of the centrality of logic and recognition of the possibilities opened up by logical innovation in the fundamental areas (...) of metaphysics resulted in his working primarily in these two, closely connected fields. It is this work in logic and metaphysics that is the main focus of what follows. (shrink)

Can identity be vague? More exactly, can there be objects x and y such that it is vague whether x = y, and the vagueness is due to the objects themselves as opposed to vagueness in language used to denote the objects? The question has been extensively discussed since Evans (1978) where it was claimed that an affirmative answer was a necessary condition for the thesis that there could be vague objects. A recent, ingenious argument in Pinillos (2003) seeks to (...) establish the negative and show that it cannot be de re vague whether x = y. The argument depends crucially on count claims concerning objects whose identity conditions are de re vague, and so we must learn how to count such objects — clouds, persons and much else besides. When that has been accomplished we can see a way out of Pinillos’s argument, and claim that de re vague identity remains coherent. (shrink)

Val Plumwood (nee Morrell) is best known in the logic community for her work on relevant logics published jointly with Richard Sylvan. Together, as `"Val and Richard Routley", they worked at the center of the Canberra Logic Group from 1971 to 1981 before they divorced and changed names, whereupon Val shifted her focus to issues in environmental philosophy. Her writing in that latter field drew so much attention, in fact, that most people familiar with her philosophical work know her solely (...) for contributions there and are quite often surprised to hear of her work in non-classical logic. While her ``fame as an environmental philosopher overshadowed her work in logic, this work included significant contributions to the emerging study of non-classical logics and relevant logics in particular. Like Sylvan, she later turned to applications of this non-classical thinking in other areas, eventually in areas traditionally deemed beyond the reach of logical innovation. (shrink)

Conservation biology has amongst its aims the conservation of the biologically valuable. As a consequence, some underlying theory of value is invoked. Clear challenges to orthodox value theory have been on the table for some time now, with some arguing for recognition of intrinsic values in nature, and some conservation biologists subsequently drawing on such a view. However, this development of value theory has recently been criticised for lacking sufficient clarity and failing to serve the needs of decision-making in conservation (...) biology. These criticisms serve to highlight confusion and difficulties in the development of a coherent and efficacious theory of intrinsic value for application in decision-making. They do not, however, count as sufficient grounds for the rejection of such a theory. Sylvan appears to offer a theory that avoids the criticisms made. The debate here is instructive in clearing away some of the misguided claims frequently encountered in this area and in seeing the value in Sylvan’s “deep green theory”. (shrink)