Logic is essential to correct reasoning and also has important theoretical applications in philosophy, computer science, linguistics, and mathematics. This book provides an exceptionally clear introduction to classical logic, with a unique approach that emphasizes both the hows and whys of logic. Here Nicholas Smith thoroughly covers the formal tools and techniques of logic while also imparting a deeper understanding of their underlying rationales and broader philosophical significance. In addition, this is the only introduction to logic available today that presents all the major forms of proof--trees, natural deduction in all its major variants, axiomatic proofs, and sequent calculus. The book also features numerous exercises, with solutions available on an accompanying website. Logic is the ideal textbook for undergraduates and graduate students seeking a comprehensive and accessible introduction to the subject. * Provides an essential introduction to classical logic * Emphasizes the how and why of logic * Covers both formal and philosophical issues * Presents all the major forms of proof--from trees to sequent calculus * Features numerous exercises, with solutions available at http://www-personal.usyd.edu.au/~njjsmith/lawsoftruth * The ideal textbook for undergraduates and graduate students

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, on the basis of 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 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 era - 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.

Nicholas J. J. Smith argues that an adequate account of vagueness must involve degrees of truth. The basic 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. This idea is immediately appealing in the context of vagueness-yet it has fallen on hard times in the philosophical literature, with existing degree-theoretic treatments of vagueness facing apparently insuperable objections. Smith seeks to turn the tide in favour of a degree-theoretic treatment of vagueness, by motivating and defending the basic idea that truth can come in degrees. He argues that no theory of vagueness that does not countenance degrees of truth can be correct, and develops a new degree-theoretic treatment of vagueness-fuzzy plurivaluationism-that solves the problems plaguing earlier degree theories.