As in other parts of the Roman world, so too in Spain, heresies were many and varied at this time. One of the most prominent of them, Priscillianism, originated in Spain, taking its name from its propounder, Priscillian. Priscillian was a Galician, who under the influence of native beliefs set forth a new interpretation of Christianity. He denied the mystery of the Trinity; claimed that the world had been created by the Devil and was ruled by him, asserting that this life was a punishment for souls which had sinned; defended the transmigration of souls; held that wine was not necessary in the celebration of the mass; and maintained that any Christian, whether a priest or not, might celebrate religious sacraments. In addition he propounded much else of a theological character which was not in accord with Catholic Christianity. It was to condemn Priscillianism that the Council of Saragossa was called. Nevertheless, this doctrine found favor even among churchmen of high rank, and Priscillian himself became bishop of Ávila. In the end he and his principal followers were put to death, but it was three centuries before Priscillianism was completely stamped out. In addition to this and other heresies the church had to combat the religions which were already in existence when it entered the field, such as Roman paganism and the indigenous faiths. It was eventually successful, although many survivals of old beliefs were long existent in the rural districts. [Sidenote: Economic development and public works.] The Romans continued the economic development of Spain on a greater scale than their predecessors. Regions which the other peoples had not reached were for the first time benefited by contact with a superior civilization, and the materials which Spain was already able to supply were diversified and improved. Although her wealth in agricultural and pastoral products was very great, it was the mines which yielded the richest profits. It is said that there were forty thousand miners at Cartagena alone in the second century B.C. Commerce grew in proportion to the development of wealth, and was facilitated in various ways, one of which deserves special mention, for its effects were far wider than those of mere commercial exchange. This was the building of public works, and especially of roads, which permitted the peoples of Spain to communicate freely with one another as never before. The roads were so extraordinarily well made that some of them are still in use. The majority date from the period of the empire, being built for military reasons as one of the means of preserving peace. They formed a network, crossing the peninsula in different directions, not two or three roads, but many. The Romans also built magnificent bridges, which, like the roads, still remain in whole or in part. Trade was fostered by the checking of fraud and abuses through the application of the Roman laws of property and of contract.