Of the Anti-Trinitarian Biography of the Rev. Robert Wallace, or of the previous compilations of Saudius and Bock, I have made but little use. To include the names of all who reject some of the Christian dogmas was quite beside my purpose, though I have included those of early Unitarians and Universalists who, I conceive, exhibited the true spirit of free inquiry in the face of persecution. To the Freydenker Lexikon of J. A. Trinius (1759) my obligations are slight, but should be acknowledged. To Bayle's Dictionary, Hoefer's Nouvelle Biographie Generale, Meyer's Konversations Lexikon, Franck's Dictionnaire des Sciences Philosophiques, and to Larousse's Grand Dictionnaire Universel I must also express my indebtedness. In the case of disputed dates I have usually found Haydn's Dictionary of Biography (1886) most trustworthy, but I have also consulted Oettinger's valuable Moniteur des Dates. The particulars have in all cases been drawn from the best available sources. I have not attempted to give a full view of any of the lives dealt with, but merely sought to give some idea of their services and relation to Freethought. Nor have I enumerated the whole of the works of authors who have often dealt with a variety of subjects. As full a list as is feasible has, however, been given of their distinctive Freethought works; and the book will, I hope, be useful to anyone wishing information as to the bibliography of Freethought. The only work of a bibliographical kind is the Guide du Libre Penseur, by M. Alfred Verlière, but his list is very far from complete even of the French authors, with whom it is almost entirely occupied. I should also mention La Lorgnette Philosophique, by M. Paquet, as giving lively sketches, though not biographies, of some modern French Freethinkers. In the compilation of my list of names I have received assistance from my friends, Mr. G. W. Foote (to whom I am also indebted for the opportunity of publication), Mr. W. J. Birch, Mr. E. Truelove and Mr. F. Malibran. For particulars in regard to some English Freethinkers I am indebted to Mr. Charles Bradlaugh, Mr. George Jacob Holyoake and Mr. E. T. Craig, while Professor Dalla Volta, of Florence, has kindly assisted me with some of the Italian names. I must also express my indebtedness to A. de Gubernatis, whose Dizionario Biografico degli Scrittori Contemporanei I have found of considerable service. My thanks are also due to G. K. Fortescue, Esq., for permission to examine the titles of all Freethought works in the British Museum.