KEY TO EXERCISES IN LOGIC SCIENTIFIC METHOD BY A. WOLF, M. A., D. LiT. Professor of Logic and Scientific Method in the University of London Fellow of the University of London, University College Formerly Fellow of St. Johrfs College, Cambridge Author of Studies in Logic Essentials of Scientific Method etc. LONDON GEORGE ALLEN UNWIN LTD. RUSKIN HOUSE, 40 MUSEUM STREET, W. C. i First published . 1926 All rights reserved Printed in Great Britain by Unwin Brothers, Ltd., Woking PREFACE THIS little book was written in the first instance for the benefit of those students of Logic and Scientific Method who receive insufficient or no help in the way of oral instruction. But it may be used profitably even by those who enjoy the advantages of the most efficient teaching. The main function of the following pages is to deal with the exercises, as distinguished from the book-questions. So far as the more elementary book-questions are concerned, the books in ordinary use should supply the required answers. In the case of all the more difficult questions, references are given to various works where the necessary material will be found, and other suggestions are made here and there. But the exercises to the number of over four hundred are treated, it is hoped, with sufficient fulness. The range of questions and exercises dealt with in this and its companion volume is so extensive that all sorts and conditions may find some help in them candidates for Honours Degrees and for the Higher Civil Service, as well as absolute beginners. Exercises in Logic and Scientific Method, New Edition KANSAS CITY MO. PUBLIC LIBRARY 6813886 8 KEY TO EXERCISES IN LOGIC The amount of help to be derived from these pages must needs depend on the proper use of the aids they afford. In the study of Logic and Scientific Method, as of everything else, the amount of good to be got out of it depends on the amount of work put into it, and the degree of interest brought to bear upon it. Solutions afford no insight unless the problems are first felt and grappled with. A. WOLF. LONDON, July 1926. CONTENTS PAGE PREFACE 7 GROUP A. SCOPE OF LOGIC II B. TERMS 12 C. PREDICABLES, CATEGORIES, ETC. . . 15 D. LAWS OF THOUGHT 20 E. THEORY OF JUDGMENT AND IMMEDIATE INFERENCE 21 F. EXERCISES IN IMMEDIATE INFERENCE . . 25 G. THEORY OF INFERENCE 49 H. SYLLOGISTIC DOCTRINE SO I. SYLLOGISTIC EXERCISES 57 J. THEORY OF INDUCTION 89 K. EXERCISES IN SCIENTIFIC METHOD , . 92 L. PROBABILITY AND CHANCE . . , , 140 M. MISCELLANEOUS FALLACIES - 144 GROUP A SCOPE OF LOGIC 6. J. S. Mill System of Logic, Introduction. 7. J. Dewey How We Think or W. B, Pillsbury Psychology of Reasoning. 8. W. E. Johnson Logic, Vol. I, Introduction, 9. H. Sidgwick Philosophy, Ch. V. F. H. Bradley Principles of Logic, Vol II, Terminal Essay L 10. B. Bosanquet Implication and Linear In ference, Ch. VII f Some of the more difficult subjects are marked with an asterisk. GROUP B TERMS 4. J. N. Keynes Formal Logic, Ch. II. 7. H. W. B. Joseph Introduction to Logic, Ch. IL 9. Abstract is used here in a wide sense so as to include what is general and concrete as well as what is abstract in th stricter sense of the term. The wider usage was common formerly, on the ground that general terms are obtained by a process of abstraction. n. The question whether a term is used collectively is quite different from the question whether it is collective. Whether a term is collective depends on its definition any name which in the singular denotes some group of similar units as a group not a class or kind is collective. No context is necessary to determine that. But any name whether collective or not can be used in the plural either collectively or distributively, according as what is predicated is applied to the plural subject as one group, or to each separately, How a term is used can only be determined TERMS 13 by reference to the context...