*The Principles of Science* by economist William Stanley Jevons was originally published in 1873 and provides and extensive overview of and introduction to the principles of logic, reasoning, inference, probability, measurement, experimentation, and classification. The book is separated into detailed sections, chapters, and parts, and includes examples, formulas, and extensive references. *The Principles of Science* is a classic guide to scientific method and inquiry, and was one of the first works that encouraged the use of probability as a scientific tool. This edition contains prefaces to both the first and second editions, and should be considered an essential tool for scientists and researchers. English economist and logician WILLIAM STANLEY JEVONS (1835-1882) was born in Liverpool. He studied chemistry and botany at University College, London, and was later professor of logic and political economy at Owens College, Manchester. He is also the author of *The Theory of Political Economy* (1871) and *The State in Relation to Labour* (1882).