Henry Charles Lea 
History of the Inquisition of the Middle Ages Volume II [EPUB ebook] 

Excerpt: "The men who laid the foundations of the Inquisition in Languedoc had before them an apparently hopeless task. The whole organization and procedure of the institution were to be developed as experience might dictate and without precedents for guidance. Their uncertain and undefined powers were to be exercised under peculiar difficulties. Heresy was everywhere and all-pervading. An unknown but certainly large portion of the population was addicted to Catharism or Waldensianism, while even the orthodox could not, for the most part, be relied upon for sympathy or aid. Practical toleration had existed for so many generations, and so many families had heretic members, that the population at large was yet to be educated in the holy horror of doctrinal aberrations. National feeling, moreover, and the memory of common wrongs suffered during twenty years of bitter contest with invading soldiers of the Cross, during which Catholic and Catharan had stood side by side in defence of the fatherland, had created the strongest bonds of sympathy between the different sects."