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Supervaluational theories of vagueness have achieved considerable popularity in the past decades, as seen in eg [5], [12]. This popularity is only natural; supervaluations let us retain much of the power and simplicity of classical logic, while avoiding the commitment to strict bivalence that strikes many as implausible. Like many nonclassical logics, the supervaluationist system SP has a natural dual, the subvaluationist system SB, explored in eg [6], [28].1 As is usual for such dual systems, the classical features of SP (typically viewed as benefits) appear in SB in ‘mirror-image’ form, and the nonclassical features of SP (typically viewed as costs) also appear in SB in ‘mirror-image’ form. Given this circumstance, it can be difficult to decide which of two dual systems is better suited for an approach to vagueness.2 The present paper starts from a consideration of these two approaches— the supervaluational and the subvaluational—and argues that neither of them is well-positioned to give a sensible logic for vague language. §2 presents the systems SP and SB and argues against their usefulness. Even if we suppose that the general picture of vague language they are often taken to embody is accurate, we ought not arrive at systems like SP and SB. Instead, such a picture should lead us to truth-functional systems like strong Kleene logic (K3) or its dual LP. §3 presents these systems, and argues that supervaluationist and subvaluationist understandings of language are better captured there; in particular, that a dialetheic approach to vagueness based on the logic LP is a more sensible approach. §4 goes on to consider the phenomenon of higher-order vagueness within an LP-based approach, and §5 closes with a consideration of the sorites argument itself.

According to one account, vagueness is "metaphysical." The friend of metaphysical vagueness believes that, for some object and some property, there can be no determinate fact of the matter whether that object exemplifies that property. A second account maintains that vagueness is due only to ignorance. According to the epistemic account, vagueness is explained completely by and is nothing over and above our not knowing some relevant fact or facts. These are the minority views. The dominant position maintains that there is a third possible variety of vagueness, linguistic vagueness. And, it goes on to insist, all vagueness is of this third variety. I shall argue, however, that linguistic vagueness is not a third variety of vagueness. Either it is a species of metaphysical vagueness or a kind of ignorance. And this, I argue, makes trouble for the claim that all vagueness is linguistic.

We all know that much in our thought and language, as well as much in the law, is vague. We are also reasonably good at recognizing cases of vagueness, even though most of us would be hard pressed to say exactly what vagueness is. In recent decades, there has been a flowering of work in the philosophy of logic and language attempting to do just that. Much of this work focuses on what it is for a word or phrase to be vague. The aim of this effort is to clarify what it is for a claim, question, command, or promise expressed using such a term to be vague, as well as what it is to reason with such terms. Different logico-linguistic theories have different conceptions of the scope of putative laws of classical logic, including bivalence (which states that every declarative sentence or proposition is either true or false) and excluded middle (which asserts all instances of A or ~A). In addition to this work in philosophical logic, recent decades have seen a growing interest in vagueness among legal scholars and philosophers of law. Here the focus is not so much on what legal vagueness is, which is generally assumed to be readily recognizable. Rather, it is on the extent and sources of vagueness in the law, the implications of vagueness for interpretation and adjudication, the systemic effects of vagueness, and the function – i.e. important positive value – of vagueness in certain areas of the law, as opposed to its disutility in others.1 To date, these two investigations of vagueness – in philosophical logic and the philosophy of law – have been largely independent of one another. This independence gives rise to a natural line of questioning. Can work in one domain contribute to work in..

Higher-order vagueness is widely thought to be a feature of vague predicates that any adequate theory of vagueness must accommodate. It takes a variety of forms. Perhaps the most familiar is the supposed existence, or at least possibility, of higher-order borderline cases—borderline borderline cases, borderline borderline borderline cases, and so forth. A second form of higherorder vagueness, what I will call ‘prescriptive’ higher-order vagueness, is thought to characterize complex predicates constructed from vague predicates by attaching operators having to do with the predicates’ proper application. For example, the predicates ‘mandates application of “old”’ and ‘can competently be called “old”’ are prescriptively higher-order vague. Higher-order vagueness appears in other guises as well,1 but these two have been of particular interest to philosophers and will be my target here. I want to expose some misconceptions about them. If I am right, higher-order vagueness is less prevalent, and less important theoretically, than is usually supposed.2 In what follows I am going to assume that vagueness is a semantic feature of natural language. For the most part I won’t discuss epistemic or pragmatic views, and I will say nothing about so-called metaphysical vagueness.

Recently a fascinating debate has been rekindled over whether vagueness is metaphysical or linguistic. That is, is vagueness an objective feature of reality or is it merely an artifact of our language? Bertrand Russell’s contribution to this debate is considered by many to be decisive. Russell suggested that it is a mistake to conclude that the world is vague simply because the language we use to describe it is vague. He argued that to draw such an inference is to commit “the fallacy of verbalism”. I argue that this is only a fallacy if we have no reason to believe that the world is as our language says. Since vagueness is apparently not eliminable from our language---a fact that Russell himself acknowledged---an indispensability argument can be launched for metaphysical vagueness. In this paper I outline such an argument.

In a seminal paper of 1923 on vagueness, Bertrand Russell discussed some of the most important problems concerning the nature of vagueness, its extension within the language, and its relation to truth and logic. The present paper inquires into Russell's theory. The following topics will be analysed and discussed in turn in sections 1?5: Russell's definition of vagueness; his claim that all phrases are vague; his theory of the source of the vagueness in our language; his principles for the transmission of vagueness; and his claim that logic is incompatible with vagueness. This paper is an attempt to give a rational reconstruction of Russell's position as expressed in his paper. Compatible passages in other of his works are also studied.

It is common among philosophers who take an interest in the phenomenon of vagueness in natural language not merely to acknowledge higher-order vagueness but to take its existence as a basic datum— so that views that lack the resources to account for it, or that put obstacles in the way, are regarded as deficient just on that score. My main purpose in what follows is to loosen the hold of this deeply misconceived idea. Higher-order vagueness is no basic datum but an illusion, fostered by misunderstandings of the nature of (ordinary, if you will ‘first-order’) vagueness itself. To see through the illusion is to take a step that is prerequisite for a correct understanding of vagueness, and for any satisfying dissolution of its attendant paradoxes.

The naive theory of vagueness holds that the vagueness of an expression consists in its failure to draw a sharp boundary between positive and negative cases. The naive theory is contrasted with the nowadays dominant approach to vagueness, holding that the vagueness of an expression consists in its presenting borderline cases of application. The two approaches are briefly compared in their respective explanations of a paramount phenomenon of vagueness: our ignorance of any sharp boundary between positive and negative cases. These explanations clearly do not provide any ground for choosing the dominant approach against the naive theory. The decisive advantage of the former over the latter is rather supposed to consist in its immunity to any form of sorites paradox. But another paramount phenomenon of vagueness is higher-order vagueness: the expressions (such as ‘borderline’ and ‘definitely’) introduced in order to express in the object language the vagueness of the object language are themselves vague. Two highly plausible claims about higher-order vagueness are articulated and defended: the existence of “definitely ω ” positive and negative cases and the “radical” character of higher-order vagueness itself. Using very weak logical principles concerning vague expressions and the ‘definitely’-operator, it is then shown that, in the presence of higher-order vagueness as just described, the dominant approach is subject to higher-order sorites paradoxes analogous to the original ones besetting the naive theory, and therefore that, against the communis opinio , it does not fare substantially better with respect to immunity to any form of sorites paradox.

There is now a widespread accord among philosophers that the vagueness of natural language gives rise to some particularly deep and perplexing problems and paradoxes. It was not always so. For most of the first century of analytical philosophy, vagueness was generally regarded as a marginal, slightly irritating phenomenon, —receiving some attention, to be sure, in parts of the Philosophical Investigations and in the amateur linguistics enjoyed by philosophers in Oxford in the 1950s, but best idealised away in any serious theoretical treatment of meaning, understanding and valid inference. Frege, as is well known, had come to be thoroughly mistrustful of vagueness, supposing that a language fit for the purpose of articulating scientific and mathematical knowledge would have to be purified of it. Later trends in philosophical logic and semantics followed his lead, not indeed in setting about the (futile) task of expurgating vagueness from natural language but by largely restricting theoretical attention to artificial languages in whose workings vagueness was assigned no role.

Vagueness provides the first comprehensive examination of a topic of increasing importance in metaphysics and the philosophy of logic and language. Timothy Williamson traces the history of this philosophical problem from discussions of the heap paradox in classical Greece to modern formal approaches such as fuzzy logic. He illustrates the problems with views which have taken the position that standard logic and formal semantics do not apply to vague language, and defends the controversial realistic view that vagueness is a kind of ignorance--that there really is a grain of sand whose removal turns a heap into a non-heap, but we cannot know which one it is.