A concise yet rigorous introduction to logic and discrete mathematics. This book features a unique combination of comprehensive coverage of logic with a solid exposition of the most important fields of discrete mathematics, presenting material that has been tested and refined by the authors in university courses taught over more than a decade. The chapters on logic - propositional and first-order - provide a robust toolkit for logical reasoning, emphasizing the conceptual understanding of the language and the semantics of classical (...) logic as well as practical applications through the easy to understand and use deductive systems of Semantic Tableaux and Resolution. The chapters on set theory, number theory, combinatorics and graph theory combine the necessary minimum of theory with numerous examples and selected applications. Written in a clear and reader-friendly style, each section ends with an extensive set of exercises, most of them provided with complete solutions which are available in the accompanying solutions manual. Key Features: Suitable for a variety of courses for students in both Mathematics and Computer Science. Extensive, in-depth coverage of classical logic, combined with a solid exposition of a selection of the most important fields of discrete mathematics Concise, clear and uncluttered presentation with numerous examples. Covers some applications including cryptographic systems, discrete probability and network algorithms. Logic and Discrete Mathematics: A Concise Introduction is aimed mainly at undergraduate courses for students in mathematics and computer science, but the book will also be a valuable resource for graduate modules and for self-study. (shrink)

The first part of the chapter surveys some of the main ways in which the Sorites Paradox has figured in arguments in practical philosophy in recent decades, with special attention to arguments where the paradox is used as a basis for criticism. Not coincidentally, the relevant arguments all involve the transitivity of value in some way. The second part of the chapter is more probative, focusing on two main themes. First, I further address the relationship between the Sorites Paradox and (...) the main arguments discussed in the first part, by elucidating in what sense they rely on (something like) tolerance principles. Second, I briefly discuss the prospect of rejecting the respective principles, aiming to show that we can do so for some of the arguments but not for others. The reason is that in the latter cases the principles do not function as independent premises in the reasoning but, rather, follow from certain fundamental features of the relevant scenarios. I also argue that not even adopting what is arguably the most radical way to block the Sorites Paradox – that of weakening the consequence relation – suffices to invalidate these arguments. (shrink)

Fuzzy logics are many-valued logics that are well suited to reasoning in the context of vagueness. They provide the basis for the wider field of Fuzzy Logic, encompassing diverse areas such as fuzzy control, fuzzy databases, and fuzzy mathematics. This book provides an accessible and up-to-date introduction to this fast-growing and increasingly popular area. It focuses in particular on the development and applications of "proof-theoretic" presentations of fuzzy logics; the result of more than ten years of intensive work by researchers (...) in the area, including the authors. In addition to providing alternative elegant presentations of fuzzy logics, proof-theoretic methods are useful for addressing theoretical problems and developing efficient deduction and decision algorithms. Proof-theoretic presentations also place fuzzy logics in the broader landscape of non-classical logics, revealing deep relations with other logics studied in Computer Science, Mathematics, and Philosophy. The book builds methodically from the semantic origins of fuzzy logics to proof-theoretic presentations such as Hilbert and Gentzen systems, introducing both theoretical and practical applications of these presentations. (shrink)

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. (shrink)

When do claims to be saved of a small or moderate harm aggregate against a competing claim to be saved from an early death? In this short response to Kamm's Bioethical Prescriptions, I argue for the following answer: aggregation of weaker claims against a life is permitted just in case, in a one-to-one contest, a person with a weaker claim would have a personal prerogative to prioritize her claim over a stranger’s competing claim to life.

It is notoriously difficult to find an intuitively satisfactory rule for evaluating populations based on the welfare of the people in them. Standard examples, like total utilitarianism, either entail the Repugnant Conclusion or in some other way contradict common intuitions about the relative value of populations. Several philosophers have presented formal arguments that seem to show that this happens of necessity: our core intuitions stand in contradiction. This paper assesses the state of play, focusing on the most powerful of these (...) ‘impossibility theorems’, as developed by Gustaf Arrhenius. I highlight two ways in which these theorems fall short of their goal: some appeal to a supposedly egalitarian condition which, however, does not properly reflect egalitarian intuitions; the others rely on a background assumption about the structure of welfare which cannot be taken for granted. Nonetheless, the theorems remain important: they give insight into the difficulty, if not perhaps the impossibility, of constructing a satisfactory population axiology. We should aim for reflective equilibrium between intuitions and more theoretical considerations. I conclude by highlighting one possible ingredient in this equilibrium, which, I argue, leaves open a still wider range of acceptable theories: the possibility of vague or otherwise indeterminate value relations. (shrink)

In VAGUENESS AND DEGREES OF TRUTH, Nicholas Smith develops a new theory of vagueness: fuzzy plurivaluationism. -/- A predicate is said to be VAGUE if there is no sharply defined boundary between the things to which it applies and the things to which it does not apply. For example, 'heavy' is vague in a way that 'weighs over 20 kilograms' is not. A great many predicates -- both in everyday talk, and in a wide array of theoretical vocabularies, from law (...) to psychology to engineering -- are vague. -/- Smith argues, based on a detailed account of the defining features of vagueness, that an accurate theory of vagueness must involve the idea that truth comes in degrees. The core idea of degrees of truth is that while some sentences are true and some are false, others possess intermediate truth values: they are truer than the false sentences, but not as true as the true ones. Degree-theoretic treatments of vagueness have been proposed in the past, but all have encountered significant objections. In light of these, Smith develops a new type of degree theory. Its innovations include a definition of logical consequence that allows the derivation of a classical consequence relation from the degree-theoretic semantics, a unified account of degrees of belief and their relationships with degrees of truth and subjective probabilities, and the incorporation of semantic indeterminacy -- the view that vague statements need not have unique meanings -- into the degree-theoretic framework. -/- As well as being essential reading for those working on vagueness, Smith's book provides an excellent entry-point for newcomers to the area -- both from elsewhere in philosophy, and from computer science, logic and engineering. It contains a thorough introduction to existing theories of vagueness and to the requisite logical background. (shrink)

From Fine and Kamp in the 70’s—through Osherson and Smith in the 80’s, Williamson, Kamp and Partee in the 90’s and Keefe in the 00’s—up to Sauerland in the present decade, the objection continues to be run that fuzzy logic based theories of vagueness are incompatible with ordinary usage of compound propositions in the presence of borderline cases. These arguments against fuzzy theories have been rebutted several times but evidently not put to rest. I attempt to do so in this (...) paper. (shrink)

There is no large number of very small bads that is worse than a small number of very large bads – or so, some maintain, it seems plausible to say. In this article, I criticize and reject two recently proposed vindications of the above intuition put forth by Dale Dorsey and Alex Voorhoeve. Dorsey advocates for a threshold marked by the interference with a person's global life projects: any bad that interferes with the satisfaction of a life project is worse (...) than any number of bads that don't interfere with such a life project. Such thresholds, I argue, are broadly implausible. Voorhoeve gives a contractualist account for the irrelevance of minor bads. His account, I argue, does not, among other things, provide the right kind of reason in defence of the above intuition. (shrink)

Ethicists and economists commonly assume that if A is all things considered better than B, and B is all things considered better than C, then A is all things considered better than C. Call this principle Transitivity. Although it has great conceptual, intuitive, and empirical appeal, I argue against it. Larry S. Temkin explains how three types of ethical principle, which cannot be dismissed a priori, threaten Transitivity: (a) principles implying that in some cases different factors are relevant to comparing (...) A to C than to comparing A to B or B to C; (b) principles of limited scope; (c) principles implying that morally relevant differences in degree can amount to differences in kind. My counterexamples employ a principle of type (c): pleasures and pains enormously different in intensity differ in kind. Temkin has also endorsed this type of counterexample, using arguments based on earlier drafts of this paper. (shrink)

Axiomatic utility theory plays a foundational role in some accounts of normative principles. In this context, it is sometimes argued that transitivity of “better than” is a logical truth. Larry Temkin and Stuart Rachels use various examples to argue that “better than” is non–transitive, and that transitivity is not a logical truth. These examples typically involve some sort of “discontinuity.” In his discussion of one of these examples, John Broome suggests that we should reject the claim which involves “discontinuity.” We (...) can, I suggest, make sense of the examples which Temkin uses while sacrificing neither transitivity nor “discontinuity.” This response to Temkin's examples involves developing and modifying James Griffin's account of “discontinuity.” If the account of “discontinuity” seems implausible, that is because of a failure to allow for vagueness. A similar argument can be made in the context of the well-known “repugnant conclusion.” Footnotes1 This paper emerged from a discussion in one of John Broome's seminars. I am very grateful to John Broome, Erik Carlson, James Griffin, Wlodek Rabinowicz, Stuart Rachels, and Larry Temkin for allowing me to read various forthcoming manuscripts which are mentioned in the paper. I am also extremely grateful to Gustaf Arrhenius, Walter Bossert, Luc Bovens, John Broome, Richard Cookson, Robin Cubitt, James Griffin, Graham Loomes, Ben McQuillin, Shepley Orr, Wlodek Rabinowicz, Stuart Rachels, Bob Sugden, and two anonymous referees for comments on earlier versions. Any errors or omissions are mine. (shrink)

Larry Temkin famously argues that what he calls spectrum arguments yield strong reason to reject Transitivity, according to which the ‘all-things-considered better than’ relation is transitive. Spectrum arguments do reveal that the conjunctions of independently plausible claims are inconsistent with Transitivity. But I argue that there is very strong independent reason to reject such conjunctions of claims, and thus that the fact that they are inconsistent with Transitivity does not yield strong reason to reject Transitivity.

One of the currently popular dogmata of anti-consequentialism is that consequentialism doesn't respect, recognize, or in some important way account for what is referred to as the The charge is often made, but rarely explained in any detail, much less argued for. In this paper I explain what I take to be the most plausible interpretation of the separateness of persons charge. I argue that the charge itself can be deconstructed into at least two further objections to consequentialist theories. These (...) objections amount to (i) the rejection of axiological aggregation, and (ii) the rejection of deontic aggregation. Of these two objections, I argue that the first one, though often made, is untenable. I also argue that the second objection, in its various forms, relies on distinctions whose moral significance is vigorously denied by almost all consequentialist theorists. I thus argue that the separateness of persons objection poses no special threat to consequentialism. (shrink)

The Rachels–Temkin spectrum arguments against the transitivity of better than involve good or bad experiences, lives, or outcomes that vary along multiple dimensions—e.g., duration and intensity of pleasure or pain. This paper presents variations on these arguments involving combinations of good and bad experiences, which have even more radical implications than the violation of transitivity. These variations force opponents of transitivity to conclude that something good is worse than something that isn’t good, on pain of rejecting the good altogether. That (...) is impossible, so we must reject the spectrum arguments. (shrink)

This paper deals with problems that vagueness raises for choices involving evaluative tradeoffs. I focus on a species of such choices, which I call ‘qualitative barrier cases.’ These are cases in which a qualitatively significant tradeoff in one evaluative dimension for a given improvement in another dimension could not make an option better all things considered, but a merely quantitative tradeoff for the given improvement might. Trouble arises, however, when one of the options constitutes a borderline case of an evaluative (...) kind. I argue that in such cases we can neither affirm nor deny that trading off losses in one evaluative dimension for gains in another yields a better outcome. Theoretically, this result provides a way to defuse an argument that has been presented by both Larry Temkin and Stuart Rachels that purports to show that the ‘better than’ relation is intransitive. Practically, it allows us to undermine the claim that rational agents are better off withholding their contribution to a public good in certain instances of the free-rider problem, and thus to take an important step towards solving these problems. (shrink)

This paper deals with problems that vagueness raises for choices involving evaluative tradeoffs. I focus on a species of such choices, which I call ‘qualitative barrier cases.’ These are cases in which a qualitatively significant tradeoff in one evaluative dimension for a given improvement in another dimension could not make an option better all things considered, but a merely quantitative tradeoff for the given improvement might. Trouble arises, however, when one of the options constitutes a borderline case of an evaluative (...) kind. I argue that in such cases we can neither affirm nor deny that trading off losses in one evaluative dimension for gains in another yields a better outcome. Theoretically, this result provides a way to defuse an argument that has been presented by both Larry Temkin and Stuart Rachels that purports to show that the ‘better than’ relation is intransitive. Practically, it allows us to undermine the claim that rational agents are better off withholding their contribution to a public good in certain instances of the free-rider problem, and thus to take an important step towards solving these problems. (shrink)

Although the thesis that the moral better than relation is transitive seems obviously true, there is a growing literature according to which Parfit’s repugnant conclusion and related puzzles reveal that this thesis is false or problematic. This paper begins by presenting several such puzzles and explaining how they can be used in arguments for the intransitivity of better than. It then proposes and defends a plausible alternative picture of the behavior of better than that both resolves the repugnant conclusion and (...) preserves transitivity. On the threshold-based model of lexicality defended here, hedonic episodes whose intensity is above a certain point are lexically greater than those whose intensity is below it. The final sections argue that this model is independently plausible and can be defended from several important objections. (shrink)

Derek Parfit defends the Imprecise Lexical View as a way to avoid the Repugnant Conclusion. Allowing for ‘imprecise equality’, Parfit argues, makes it possible to avoid some well-known problems for the Lexical View. It is demonstrated that the Lexical View has stronger implications than envisaged by Parfit; moreover, his assumption of Non-diminishing Marginal Value makes the Lexical View collapse into a much stronger view, which lets the two appear incompatible. Introducing imprecise equality does not address the latter problem. But it (...) does makes it possible for the Imprecise Lexical View to soften the discontinuities it would otherwise face, at the cost of blurring the difference between options.However, if Non-diminishing Marginal Value is rejected, the remaining complications for the resulting most plausible version of the Imprecise Lexical View, including a confrontation with Arrhenius’ Non-Elitism Condition, may be within a range where the view largely remains defensible. (shrink)

The spectrum argument purports to show that the better-than relation is not transitive, and consequently that orthodox value theory is built on dubious foundations. The argument works by constructing a sequence of increasingly less painful but more drawn-out experiences, such that each experience in the spectrum is worse than the previous one, yet the final experience is better than the experience with which the spectrum began. Hence the betterness relation admits cycles, threatening either transitivity or asymmetry of the relation. This (...) paper examines recent attempts to block the spectrum argument, using the idea that it is a mistake to affirm that every experience in the spectrum is worse than its predecessor: an alternative hypothesis is that adjacent experiences may be incommensurable in value, or that due to vagueness in the underlying concepts, it is indeterminate which is better. While these attempts formally succeed as responses to the spectrum argument, they have additional, as yet unacknowledged costs that are significant. In order to effectively block the argument in its most typical form, in which the first element is radically inferior to the last, it is necessary to suppose that the incommensurability is particularly acute: what might be called radical incommensurability. We explain these costs, and draw some general lessons about the plausibility of the available options for those who wish to save orthodox axiology from the spectrum argument. (shrink)

This book presents a systematic treatment of deductive aspects and structures of fuzzy logic understood as many valued logic sui generis. It aims to show that fuzzy logic as a logic of imprecise (vague) propositions does have well-developed formal foundations and that most things usually named ‘fuzzy inference’ can be naturally understood as logical deduction. It is for mathematicians, logicians, computer scientists, specialists in artificial intelligence and knowledge engineering, and developers of fuzzy logic.

It is plausible to claim that it is morally worse to kill an innocent person than to give any number of people a mild one‐hour headache. Alaistar Norcross has argued that consequentialists, at least, should reject this claim. According to him, any harm that can befall a person can be morally outweighed by a sufficient number of very small harms. He gives a general argument for this view, and tries to show, by means of an argument from analogy, that it (...) is less counter‐intuitive than it appears. I show that his main argument relies on a false assumption, and argue that the purported analogy is dubious. (shrink)

This article criticises one of Stuart Rachels' and Larry Temkin's arguments against the transitivity of 'better than'. This argument invokes our intuitions about our preferences of different bundles of pleasurable or painful experiences of varying intensity and duration, which, it is argued, will typically be intransitive. This article defends the transitivity of 'better than' by showing that Rachels and Temkin are mistaken to suppose that preferences satisfying their assumptions must be intransitive. It makes cler where the argument goes wrong by (...) showing that it is a version of Zeno's paradox of Achilles and the Tortoise. (shrink)

Suppose that A and B are two kinds of goods such that more of each is better than less. A is strongly superior to B if any amount of A is better than any amount of B. It is weakly superior to B if some amount of A is better than any amount of B. There are many examples of these relations in the literature, sometimes under the labels “higher goods” and “discontinuity.” The chapter gives a precise and generalized statement (...) of Strong and Weak Superiority and discusses different ways in which these relations can be relevant to the aggregation of welfare. It also proves a number of general results. One of the results gives rise to a dilemma: It can be used as an argument against the existence of value superiority or, alternatively, as an argument against the view that superiority entails a radical difference in value. (shrink)

Suppose one sets up a sequence of less and less valuable objects such that each object in the sequence is only marginally worse than its immediate predecessor. Could one in this way arrive at something that is dramatically inferior to the point of departure? It has been claimed that if there is a radical value difference between the objects at each end of the sequence, then at some point there must be a corresponding radical difference between the adjacent elements. The (...) underlying picture seems to be that a radical gap cannot be scaled by a series of steps, if none of the steps itself is radical. We show that this picture is incorrect on a stronger interpretation of value superiority, but correct on a weaker one. Thus, the conclusion we reach is that, in some sense at least, abrupt breaks in such decreasing sequences cannot be avoided, but that such unavoidable breaks are less drastic than has been suggested. In an appendix written by John Broome and Wlodek Rabinowicz, the distinction between two kinds of value superiority is extended from objects to their attributes. (shrink)

Suppose one sets up a sequence of less and less valuable objects such that each object in the sequence is only marginally worse than its immediate predecessor. Could one in this way arrive at something that is dramatically inferior to the point of departure? It has been claimed that if there is a radical value difference between the objects at each end of the sequence, then at some point there must be a corresponding radical difference between the adjacent elements. The (...) underlying picture seems to be that a radical gap cannot be scaled by a series of steps, if none of the steps itself is radical. We show that this picture is incorrect on a stronger interpretation of value superiority, but correct on a weaker one. Thus, the conclusion we reach is that, in some sense at least, abrupt breaks in such decreasing sequences cannot be avoided, but that such unavoidable breaks are less drastic than has been suggested. In an appendix written by John Broome and Wlodek Rabinowicz, the distinction between two kinds of value superiority is extended from objects to their attributes. (shrink)

In this work, Jamie Mayerfeld undertakes a careful inquiry into the meaning and moral significance of suffering. Understanding suffering in hedonistic terms as an affliction of feeling, he claims that it is an objective psychological condition, amenable to measurement and interpersonal comparison, although its accurate assessment is never easy. Mayerfeld goes on to examine the content of the duty to prevent suffering and the weight it has relative to other moral considerations. He argues that the prevention of suffering is morally (...) more important than the promotion of happiness, and that the duty to relieve suffering is much stronger than most of us acknowledge. (shrink)

A many-valued (aka multiple- or multi-valued) semantics, in the strict sense, is one which employs more than two truth values; in the loose sense it is one which countenances more than two truth statuses. So if, for example, we say that there are only two truth values—True and False—but allow that as well as possessing the value True and possessing the value False, propositions may also have a third truth status—possessing neither truth value—then we have a many-valued semantics in the (...) loose but not the strict sense. A many-valued logic is one which arises from a many-valued semantics and does not also arise from any two-valued semantics [Malinowski, 1993, 30]. By a ‘logic’ here we mean either a set of tautologies, or a consequence relation. We can best explain these ideas by considering the case of classical propositional logic. The language contains the usual basic symbols (propositional constants p, q, r, . . .; connectives ¬, ∧, ∨, →, ↔; and parentheses) and well-formed formulas are defined in the standard way. With the language thus specified—as a set of well-formed formulas—its semantics is then given in three parts. (i) A model of a logical language consists in a free assignment of semantic values to basic items of the non-logical vocabulary. Here the basic items of the non-logical vocabulary are the propositional constants. The appropriate kind of semantic value for a proposition is a truth value, and so a model of the language consists in a free assignment of truth values to basic propositions. Two truth values are countenanced: 1 (representing truth) and 0 (representing falsity). (ii) Rules are presented which determine a truth value for every proposition of the language, given a model. The most common way of presenting these rules is via truth tables (Figure 1). Another way of stating such rules—which will be useful below—is first to introduce functions on the truth values themselves: a unary function ¬ and four binary functions ∧, ∨, → and ↔ (Figure 2).. (shrink)

A growing interest in many-valued logic has developed which to a large extent is based on applications, intended as well as already realised ones. These applications range from the field of computer science, e.g. in the areas of automated theorem proving, approximate reasoning, multi-agent systems, switching theory, and program verification, through the field of pure mathematics, e.g. in independence of consistency proofs, in generalized set theories, or in the theory of particular algebraic structures, into the fields of humanities, linguistics and (...) philosophy. (shrink)

Temkin's book is a very original and deeply unsettling work of skeptical philosophy that mounts an important new challenge to contemporary ethics.

Professor Merrie Bergmann presents an accessible introduction to the subject of many-valued and fuzzy logic designed for use on undergraduate and graduate courses in non-classical logic. Bergmann discusses the philosophical issues that give rise to fuzzy logic - problems arising from vague language - and returns to those issues as logical systems are presented. For historical and pedagogical reasons, three-valued logical systems are presented as useful intermediate systems for studying the principles and theory behind fuzzy logic. The major fuzzy logical (...) systems - Lukasiewicz, Gödel, and product logics - are then presented as generalisations of three-valued systems that successfully address the problems of vagueness. A clear presentation of technical concepts, this book includes exercises throughout the text that pose straightforward problems, that ask students to continue proofs begun in the text, and that engage students in the comparison of logical systems. (shrink)