Logic is not only an exact science, but is the most simple and elementary of all sciences; it ought therefore undoubtedly to find some place in every course of education. The relations of propositions and the forms of argument present as precise a subject of instruction and as vigorous an exercise of thought, as the properties of geometrical figures, or the rules of Algebra. Yet every school-boy is made to learn mathematical problems which he will never employ in after life, and is left in total ignorance of those simple principles and forms of reasoning which will enter into the thoughts of every hour. Logic should no longer be considered an elegant and learned accomplishment; it should take its place as an indispensable study for every well-informed person. These Lessons I trust will introduce to the science many who have not leisure or inclination to read more elaborate treatises, and many who would not be attracted by the numerous but somewhat dry and brief compendiums published in past years. It is desirable that Lessons in Logic should be made the basis of many exercises, and for this purpose I have supplied abundance of questions and examples at the end of the book, some of which are selected from the examination papers of the Oxford, London, and Edinburgh Universities. In my own classes I have constantly found that the working and solution of logical questions, the examination of arguments and the detection of fallacies, is a not less practicable and useful exercise of mind than is the performance of calculations, and the solution of problems in a mathematical class. Except in a few places, where special notice is given, I have abstained from putting forward any views not commonly accepted by teachers of logic; and I have throughout devoted more attention to describing clearly and simply the doctrines in which logicians generally agree, than discussing the points in which there is a difference of opinion. The recent logical discoveries of Sir W. Hamilton, Archbishop Thomson, Prof. de Morgan, and especially the late Prof. Boole, cannot yet be fully adopted in an elementary work, but I have attempted to give a clear notion of the results to which they inevitably lead. In the latter Lessons which treat of Induction I have generally followed Sir John Herschel, Dr Whewell and Mr J. S. Mill, as the recognised authorities on the subject. These Lessons in fact may be regarded as an easy introduction to some of the most important parts of Mr Mill's treatise on Logic. At the end of almost every Lesson will be found references to the works in which the student will most profitably continue his reading of the subject treated, so that this little volume may serve as a guide to a more extended course of study. The Opposition of Propositions Conversion of Propositions, and Immediate In- |