It was not until the thirteenth century that the Church had to face that spirit of scepticism or anti-religious feeling which is the chief bug-bear of modern Christianity. Her elaborate organisation and the gradual development of her own dogmatic position enabled her to deal with individual writers of a speculative turn like Berengar or Abailard. Nor were these in any sense anti-Christian. But they were the inciters to heresy; and a real danger to the Church lay in the filtering down of intellectual speculations to ignorant classes, by whom they would be transformed into weapons against the fundamental doctrines of the Christian faith. Indeed, from the eleventh century onward the Church was constantly threatened by heresy of a popular kind, which tended to develop into schism. And for this she had to thank not only the growing materialisation of her doctrine, but even more the worldly life of her ministers. Unpalatable doctrines may commend themselves by the pure lives which profess to be founded on them; but evil doing carries no persuasion to others.
It is a real difficulty that our sources of information of all the heretics of these centuries are chiefly the writings of their successful opponents--the defenders of the orthodox faith. But much information remains to us from the admissions of her supporters as to the depraved condition of the Church at this period; so that we need not believe the allegations or their opponents that a chief inducement to join heretical sects lay in the greater scope for the indulgence of sin. Charges of immorality against opponents were the stock-in-trade of the controversialist, while the greatest authorities in the Church allow that heresy lived upon the scandals and negligences of the Church. Moreover, based as they were upon opposition to the existing organisation, the doctrines of the various sects had much in common. The Church did not distinguish between them, but excommunicated them all alike. If, however, we would understand the developments of opinion in the succeeding centuries, it is important to discriminate; and a clear distinction can be made between those opponents of the Church whose views were aimed against the development of an extreme sacerdotalism within the Church, and those who, going beyond this negative position, reproduced the Manichæan theories of an early age and threatened to raise a rival organisation to that of the Christian Church.