I am also greatly indebted to the Rev. J. Estlin Carpenter, Principal of Manchester College, for having aided me with the parts of this book touching Christian theology; to Mr. R. I. Best, M.R.I.A., Assistant Librarian, National Library, Dublin, for having aided me with the parts devoted to Irish mythology and literature; and to Mr. William McDougall, Wilde Reader in Mental Philosophy in the University of Oxford, for a similar service with respect to Section IV, entitled 'Science and Fairies'. And to these and to all the other scholars whose names appear in this preface, my heartiest thanks are due for the assistance which they have so kindly rendered in reading different parts of the _Fairy-Faith_ when in proof. With the deep spirit of reverence which a student feels towards his preceptors, I acknowledge a still greater debt to those among my friends and helpers who have been my Celtic guides and teachers. Here in Oxford University I have run up a long account with the Right Hon. Sir John Rhŷs, the Professor of Celtic, who has introduced me to the study of Modern Irish, and of Arthurian romance and mythology, and has guided me both during the year 1907-8 and ever since in Celtic folk-lore generally. To Mr. Andrew Lang, I am likewise a debtor, more especially in view of the important suggestions which he has given me during the past two years with respect to anthropology and to psychical research. In my relation to the Faculty of Letters of the University of Rennes, I shall always remember the friendly individual assistance offered to me there during the year 1908-9 by Professor Joseph Loth, then Dean in that University, but now of the College of France, in Paris, particularly with respect to Brythonic mythology, philology, and archaeology; by Professor Georges Dottin, particularly with respect to Gaelic matters; and by Professor Anatole Le Braz, whose continual good wishes towards my work have been a constant source of inspiration since our first meeting during March 1908, especially in my investigation of _La Légende de la Mort_, and of the related traditions and living folk-beliefs in Brittany--Brittany with its haunted ground of Carnac, home of the ancient Brythonic Mysteries. W. Y. E. W. JESUS COLLEGE, OXFORD. _All Saints' Day_, 1911. 'There, neither turmoil nor silence.... 'Though fair the sight of Erin's plains, hardly will they seem so after you have known the Great Plain.... 'A wonder of a land the land of which I speak; no youth there grows to old age.... 'We behold and are not beheld.'--The God Midir, in _Tochmarc Etaine_. INTRODUCTION 'I have told what I have seen, what I have thought, and what I have learned by inquiry.'--HERODOTUS. I. THE RELIGIOUS NATURE OF THE FAIRY-FAITH