John Stuart Mill in his "Autobiography" declares with truth that "the world would be astonished if it knew how great a proportion of its brightest ornaments, of those most distinguished even in popular estimation for wisdom and virtue are complete sceptics in religion." Many of these, as Mill points out, refrain from various motives from speaking out. The work I have undertaken will, I trust, do something to show how many of the world's worthiest men and women have been Freethinkers. My Dictionary does not pretend to be a complete list of those who have rendered services to Freethought. To form such a compilation would rather be the task of an international society than of an individual. Moreover details concerning many worthy workers are now inaccessible. Freethought boasts its noble army of martyrs of whom the world was not worthy, and who paid the penalty of their freedom in prison or at the stake. Some of the names of these are only known by the vituperation of their adversaries. I have done my best to preserve some trustworthy record of as many as possible.