INSTINCTS OF THE HERD IN PEACE AND WAR BY W. TROTTER T. FISHER UNWIN LTD LONDON: ADELPHI TERRACE _First Published_ _February, 1916_ _Second Impression_ _March, 1917_ _Third Impression_ _July, 1917_ _Second Edition_ _November, 1919_ _Fifth Impression_ _March, 1920_ _Sixth Impression_ _February, 1921_ (_All rights reserved_) {5} PREFACE The first two essays in this book were written some ten years ago and published in the _Sociological Review_ in 1908 and 1909. They had formed a single paper, but it was found necessary to publish in two instalments at an interval of six months, and to cut down to a considerable extent the total bulk. It was lately suggested to me that as the numbers of the review in which the two essays appeared were out of print, the fact that the subject concerned was not without some current interest might justify a republication. It was not possible to do this without trying to embody such fruits as there might be of ten years’ further speculation and some attempt to apply to present affairs the principles which had been sketched out. The new comment very soon surpassed by far in bulk the original text, and constitutes, in fact, all but a comparatively few pages of this book. This rather minute record is made here not because it has any interest of its own, but especially to point out that I have been engaged in trying to apply to the affairs of to-day principles which had taken shape ten years ago. I point this out not in order {6} to claim any gift of foresight in having suggested so long ago reasons for regarding the stability of civilization as unsuspectedly slight, but because it is notorious that the atmosphere of a great war is unfavourable to free speculation. If the principles upon which my argument is based had been evolved during the present times, the reader would have had special reason to suspect their validity, however plausible they might seem in the refracting air of national emergency. The general purpose of this book is to suggest that the science of psychology is not the mass of dreary and indefinite generalities of which it sometimes perhaps seems to be made up; to suggest that, especially when studied in relation to other branches of biology, it is capable of becoming a guide in the actual affairs of life and of giving an understanding of the human mind such as may enable us in a practical and useful way to foretell some of the course of human behaviour. The present state of public affairs gives an excellent chance for testing the truth of this suggestion, and adds to the interest of the experiment the strong incentive of an urgent national peril.