Venn, best known for his diagrams for set theory, primarily studied logic and probability theory. The present book is a study of the principles of logic, with special emphasis on inference and induction.

From the Preface to the First Edition (1889): “As many readers will probably perceive, the main original guiding influence with me—as with most of those of the middle generation, and especially with most of those who approached logic with previous mathematical or scientific training—was that of Mill ... I still continue to regard the general attitude towards phenomena, which Mill took up as a logician, to be the soundest and most useful for scientific study ...”

From the Preface to the Second Edition (1907): “Though thus leaving the main outlines unaltered I have done what I could to improve the work, and to try to bring it up to date ... A number of paragraphs have been altered, others have been re-written, and many hundreds of minor alterations, additions and corrections inserted ...”