A System of Logic, Ratiocinative and Inductive is a book by English philosopher John Stuart Mill. In this work, he formulated the five principles of inductive reasoning that are known as Mill's methods. This work is important insofar as it outlines the empirical principles Mill would use to justify his moral and political philosophies. An article in "Philosophy of Recent Times" has described this book as an "attempt to expound a psychological system of logic within empiricist principles." This work was important to the history of science, being a strong influence on scientists such as Dirac.