THE

PRINCIPLES OF LOGIC

BY

HERBERT AUSTIN AIKINS, PH.D.
Leffingwell Professor of Philosophy in the College for Women of
Western Reserve University

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PREFACE TO THE SECOND EDITION.

APART from the Introduction and the Conclusion this book can be divided into four parts. The first deals with the interpretation of language and the blunders that result from a disregard of its exact meaning. The second treats of deduction; showing what inferences can always be safely drawn, without any special knowledge of the world, from one or two supposedly true statements of a given type, and what can not. The third is concerned with induction in the narrower sense of the term, and explains the methods for ascertaining or testing general laws of nature by the observation of particular facts (thus showing how we can justify the universal propositions from which we usually reason in deduction). The fourth shows how these general laws can be used, in turn, for the discovery of new facts.

Into the first part of the book (Chapters II-VII) I have put an extended account of all the "semi-logical" fallacies and of certain others which depend, like them, on the misuse or misunderstanding of language. To understand these fallacies requires absolutely no knowledge of logical forms, and by treating of them at the outset we do away with an unnecessary barrier between the deductive part of the book and the inductive, arouse the student's interest at the very beginning, and make him less likely to take the rigorous accuracy that is necessary in syllogistic reasoning for a useless quibbling and mincing of words.

One cannot go far in the interpretation of language without coming to the categories, so I have treated of them here-briefly, and I hope simply, but as seriously as I could.

Chapter IV (on Division and Classification) does not really belong to the first part of the book at all. I put it where it is because of its intimate relation to definition. But it interrupts the continu

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ity of the discussion, and it would have been better to put the first part of it after Chapter IX and take up the subject of classification in connection with Chapters XXX-XXXII.

In the second part of the book (Chapters IV and VIII-XX) I tried to treat deduction from the objective or realistic standpoint, as already explained in the preface to the first edition, i.e., to tell how things must be related to each other in one respect if they are also related in some other respect, instead of talking about the relations of 'thoughts' or merely giving rules for the arrangement and manipulation of words; and I tried to preserve the distinction between the different categories, instead of making it all a mere question of whether one class does or does not include a part of another. This involved a separate treatment for each of the syllogistic figures. But some of those who have been kind enough to criticise the book think that a shorter treatment along the traditional lines would have been sufficient for the average student and have left him with something more available for instant use. To meet their views I am adding an appendix in which syllogism and its subsidiary processes are treated very briefly in the orthodox way. Those who are pressed for time and are content with a ready rule for testing arguments can use this appendix as a substitute for Chapters IV and VIII-XVI. Others also might do well to learn the appendix first. But if logic is to serve in any way as an introduction to metaphysics the text should not be omitted. For we cannot ask whether or not one class includes part of another without implying the possibility of an answer to the questions there discussed about the identity and qualities of things.

In the chapter on the Ill-conceived Universe I hope I have found an appropriate place for the discussion of certain material fallacies that it is customary for logicians to mention, though they have no special relation to the traditional logical doctrine, and for certain others not usually mentioned at all, although they are very important. The view of inference that I took throughout the whole book enabled me to give them a very definite relation to its pr nciples.

The third part of the book (Chapters XXI-XXXII) covers the familiar ground of induction, with chapters on Averages, Probability, and Statistics. In the fourth part (Chapters XXXIII-XXXV) I have worked together the principles of historical criticism and the legal rules of evidence to cover ground not always included in text

books of logic. And in the Conclusion I have inquired into the ultimate justification for the whole logical process.

Some reviewers have been misled by my use of the borrowed term "material"-I said "objective or 'material""—in the preface to the first edition. I did not mean to say that my standpoint is materialistic, for it is not, as any careful reader can see; but only that it is realistic in the Scottish sense- -that I assume the existence of something more than homeless 'ideas' or 'concepts', and make use of this assumption throughout—even in explaining the Law of Contradiction.

My indebtedness to other authors is apparent. I am no less indebted to individuals-particularly to colleagues in other departments who have given me valuable suggestions on matters related to their special subjects; but most of all to Dr. W. T. Marvin, to whom I read the whole book while it was still in manuscript.

August, 1904.

H. A. A.