Degrees of Belief is a strong collection of essays distinguished by its inclusion of an unusually wide array of approaches to understanding its subject. The book consists mainly of recent works (growing out of a 2004 conference at the University of Konstanz) from perspectives as diverse as probabilism (the view that degrees of belief ought to be probabilities), Dempster-Shafer theory, possibility theory, ranking theory, AGM (Alchourron-Gardenfors-Makinson) belief-revision theory, and others. The essays are varied in focus, but many are concerned with outlining formal axiomatizations of degree of belief (variously understood), and several of them are surveys of their respective sub-fields. As one might expect, the discussion is often technical and sometimes dense, and so the book is best suited for formally proficient advanced students (graduate or upper-level undergraduate) or professionals seeking to explore other approaches to degree of belief than the ones in which they currently work. Some recurrent themes in the book include the relation of degree of belief to full belief, how degree of belief ought best to be understood (its purpose and function), and the formal laws (so understood) it ought to obey. There is limited reference in some articles to applications (e.g., in computer science), but the main focus of the book is theoretical. What follows is only a small sample of the rich content contained in the book. After a clear and concise preview of the book’s contents, written by one of the editors (Franz Huber), Part I of the book concentrates on how belief relates to degree of belief. The lottery paradox is key here (and also the related preface paradox), and accordingly, the section begins with one exposition of it, by Richard Foley (a revision of Chapter 4 of Foley 1993). The lottery paradox arises from the so-called Lockean thesis that belief is just sufficiently high degree of belief. For example, if I believe p just in case my degree of belief in it is at least 99%, then I’ll
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