It is very difficult for us who live in a tolerant age to understand the universal and deep-rooted horror of heresy which prevailed not only in the twelfth and thirteenth centuries, but also down at least to the eighteenth. Too much stress cannot be laid upon the fact that heresy was considered treason against an institution which practically all, both the learned and the unlearned, agreed was not only essential to salvation but was necessary also to order and civilization. Frank criticism of the evil lives of the clergy, not excluding the pope himself, was common enough. But this did not constitute heresy. One might believe that the pope and half the bishops were bad men, and yet in no way question the necessity for the Church's existence or the truth of every one of its dogmas; just as nowadays we might call particular rulers and government officials fools or knaves, without being suspected of repudiating government altogether. The heretic was the anarchist of the Middle Ages. He did not simply denounce the immorality of the officers of the Church; he claimed that the Church was worse than useless. He sought to lead people to throw off their allegiance to it and to disregard its laws and commands. The Church and the civil government consequently proceeded against him as against an enemy of society and order. Heresy was, moreover, a contagious disease, and spread rapidly and unobserved, so that to the rulers of the times even the harshest measures appeared justifiable in order to prevent its dissemination. [Sidenote: Different methods of opposing heresy.] [Sidenote: Internal reform.] 87. There were several ways of opposing heresy. First, a reform of the character of the clergy and a suppression of the abuses in the Church would have removed a great cause of that discontent to which the writers of the time attributed the rapid growth of heresy. The attempt of Innocent III to improve the conditions in the Church by summoning a great council at Rome in 1215 failed, however, and, according to his successor, matters grew worse rather than better. [Sidenote: Extermination by the sword.] A second plan was to organize an expedition against the rebels and annihilate them by the sword. This policy was only possible if a large number of heretics could be found in a single district. In southern France there were many adherents of both the Albigenses and the Waldensians, especially in the county of Toulouse. At the beginning of the thirteenth century there was in this region an open contempt for the Church and a bold defense of heretical teachings even among the higher classes. [Sidenote: Albigensian crusade.]