emphasizes the importance of critical inquiry throughout human history. The opening of the book sets the stage by exploring the origin and meaning of "freethought" and the various terms historically associated with it, such as "deist" and "infidel." Robertson highlights the developments in the English language regarding these concepts, particularly in the late 17th century, and discusses previous historiographical attempts to address freethought, pointing to a lack of comprehensive treatment by freethinkers themselves. Through this groundwork, he prepares readers to understand the psychological and social dynamics behind freethinking—positing that it constitutes a reaction against conventional doctrines and an assertion of intellectual freedom—paving the way for a detailed exploration of freethought's history across different civilizations in subsequent chapters. (This is an automatically generated summary.)