Any contumacy in reference to their judgments was punished by exclusion from the sacrifices. This sentence of excommunication was the severest punishment among the Gauls. The men so punished were treated as outlaws, and cut off from all human society, with its rights and privileges. Over these Druids there was one head, who wielded the highest influence among them. On his death the nearest of the others in dignity succeeded him, or, if several were equal, the election of a successor was made by the vote of the Druids. Sometimes the primacy was not decided without the arbitrament of arms. The Druids met at a fixed time of the year in a consecrated spot in the territory of the Carnutes, the district which was regarded as being in the centre of the whole of Gaul. This assembly of Druids formed a court for the decision of cases brought to them from everywhere around. It was thought, Caesar says, that the doctrine of the Druids was discovered in Britain and thence carried over into Gaul. At that time, too, those who wanted to make a profounder study of it resorted thither for their training. The Druids had immunity from military service and from the payment of tribute. These privileges drew many into training for the profession, some of their own accord, others at the instance of parents and relatives. While in training they were said to learn by heart a large number of verses, and some went so far as to spend twenty years in their course of preparation. The Druids held it wrong to put their religious teaching in writing, though, in almost everything else, whether public or private affairs, they made use of Greek letters. Caesar thought that they discouraged writing on the one hand, lest their teaching should become public property; on the other, lest reliance upon writing should lessen the cultivation of the memory. To this risk Caesar could testify from his own knowledge. Their cardinal doctrine was that souls did not perish, but that after death they passed from one person to another; and this they regarded as a supreme incentive to valour, since, with the prospect of immortality, the fear of death counted for nothing. They carried on, moreover, many discussions about the stars and their motion, the greatness of the universe and the lands, the nature of things, the strength and power of the immortal gods, and communicated their knowledge to their pupils. In another passage Caesar says that the Gauls as a people were extremely devoted to religious ideas and practices. Men who were seriously ill, who were engaged in war, or who stood in any peril, offered, or promised to offer, human sacrifices, and made use of the Druids as their agents for such sacrifices. Their theory was, that the immortal gods could not be appeased unless a human life were given for a human life. In addition to these private sacrifices, they had also similar human sacrifices of a public character. Caesar further contrasts