This book offers an account of suppositional reasoning relevant to practical deliberation, explanation, prediction and hypothesis testing. In arguing that supposition plays a far greater role in deliberation and decision than it is given credit for, this major study will be required reading for all philosophers and logicians concerned with conditionals, decision theory and inductive inference. It will also interest those in artificial intelligence who work on expert systems, default reasoning, and nonmonotonic reasoning. – Table of contents: Preface. 1. Introduction; 2. Unextended Ramsey tests; 3. Modality without modal ontology; 4. Aspects of conditional logic; 5. Nonmonotonicity in belief change and suppositional reasoning; 6. Inductive expansion; 7. Defaults; 8. Matters of degree; 9. Normality and expectation; 10. Agents and automata. – Notes; Bibliography; Name index; Subject index.