Probability theory is increasingly important to philosophy. Bayesian probabilistic models offer us ways of getting to grips with fundamental problems about information, coherence, reliability, confirmation, and testimony, and thus show how we can justify beliefs and evaluate theories. Bovens and Hartmann provide a systematic guide to the use of probabilistic methods not just in epistemology, but also in philosophy of science, voting theory, jurisprudence, and cognitive psychology. Luc Bovens is Professor of Philosophy at the London School of Economics and Political Science. Stephan Hartmann is Reader in Philosophy and Director of the Centre for Philosophy of Natural and Social Science at the London School of Economics and Political Science.