But after the Council of Nicaea (325) when the Christian Church had become the official church of the Empire, the supervision of the written word became part of the routine duty of the clergy. Some books were absolutely forbidden. Others were described as “dangerous” and the people were warned that they must read them at their own risk. Until authors found it more convenient to assure themselves of the approval of the authorities before they published their works and made it a rule to send their manuscripts to the local bishops for their approbation. Even then, a writer could not always be sure that his works would be allowed to exist. A book which one Pope had pronounced harmless might be denounced as blasphemous and indecent by his successor. On the whole, however, this method protected the scribes quite effectively against the risk of being burned together with their parchment offspring and the system worked well enough as long as books were copied by hand and it took five whole years to get out an edition of three volumes. All this of course was changed by the famous invention of Johann Gutenberg, alias John Gooseflesh. After the middle of the fifteenth century, an enterprising publisher was able to produce as many as four or five hundred copies in less than two weeks’ time and in the short period between 1453 and 1500 the people of western and southern Europe were presented with not less than forty thousand different editions of books that had thus far been obtainable only in some of the better stocked libraries. The Church regarded this unexpected increase in the number of available books with very serious misgivings. It was difficult enough to catch a single heretic with a single home made copy of the Gospels. What then of twenty million heretics with twenty million copies of cleverly edited volumes? They became a direct menace to all idea of authority and it was deemed necessary to appoint a special tribunal to inspect all forthcoming publications at their source and say which could be published and which must never see the light of day. Out of the different lists of books which from time to time were published by this committee as containing “forbidden knowledge” grew that famous Index which came to enjoy almost as nefarious a reputation as the Inquisition. But it would be unfair to create the impression that such a supervision of the printing-press was something peculiar to the Catholic Church. Many states, frightened by the sudden avalanche of printed material that threatened to upset the peace of the realm, had already forced their local publishers to submit their wares to the public censor and had forbidden them to print anything that did not bear the official mark of approbation.