Among such results is one which has not met with all the attention it deserves. Historians speak at length of the many and wide-spread heresies which infected Europe during the middle ages; but their Eastern origin has not been thoroughly investigated, and we have no doubt that, if it had been, many of them would be found to have come with a returning wave of the Crusades. All these errors bear at the outset a very Oriental appearance. Paulicians, Petrobrusians, Albigensians, and kindred sects, all started from the principle of dualism, and even at the time were openly accused of Manicheistic ideas. They all involved more or less immoral principles, and rejected, or at least strove to weaken, the commonly-received ideas upon which society, civil and religious, is founded. Had they succeeded in spreading their errors through Europe, it is possible that the invasion would have been more fatal in its consequences than that of Islamism itself. And, even in their failure, they left among European societies the germ of secret associations which have existed from that time down, and which in our days have burst forth undisguised to terrify nations, and cause them to dread the coming of the last days. To an attentive observer it is clear that the heresies of the twelfth, thirteenth, and fourteenth centuries resemble more the errors of our days than the Protestantism which intervened. Luther's first principles, if carried to their legitimate conclusion, would have inaugurated the socialism and communism of modern times; but he shrank from the consequences of his own doctrines, and the necessity of his standing well with the German princes caused him, during the War of the Peasants, almost to retract his first utterances and take his stand midway between Catholic principles and the thorough nihilism of later times. It is known that in the after-part of his life he endeavored to repair the ruins of every dogma, social and religious, which he at first had tried to subvert and destroy. The Manicheism of the middle ages was certainly not of so scientific and elaborate a nature as modern socialism; but it would have been productive of like evil results to society had it not been crushed down by the united power of the Church and the state. If it had been successful, it is impossible to imagine what would have become of Europe. Of its Eastern origin historians say little. We know, however, that, after a residence in the East, the most pious Christians grew lukewarm and less firm in their opposition to the dangerous errors then prevalent in Asia. Tournefort remarked this in his own time, during the reign of Louis XIV.