Medieval Europe was a hotbed of revolt against religious dogma. Particularly offensive to the established church were the views of the Cathars, whose dualist beliefs Rome condemned as heretical.

Through a variety of literary works, this book explores the dualist religious movement which developed as a culture of the masses and took place in Europe between the 12th and 17th centuries. It examines the strong parallels between the Bogomils and Cathars and the religious practices of the British Lollards, extrapolating Lollardy's spread from eastern to western Europe. Providing numerous text comparisons, the work focuses on a number of authors including John Wycliffe, William Tynsdale, William Langland and John Milton, whose works exhibit the dualist philosophy.