The chief pretenders to the possession of wizardry and powers of divination in Ireland were the Druids,[66] who correspond, but not in all respects, to the Druids of Gaul. They joined to their supernatural lore innocent secular learning, skill in poetry, and knowledge of the laws and history of their country. They gave the kings advice and educated their children. The high value which was attached to their counsels rested naturally on their prophetic powers. They practised divination in various forms, with inscribed rods of yew, for instance, or by means of magic wheels.[67] They could raise the winds, cover the plains with darkness, create envelopes of vapour,[68] which rendered those who moved therein invisible. Though learned in things divine, they did not form a sacerdotal class; and in their religious functions they might be compared rather to augurs than to priests. It was their habit to shave their heads in front from ear to ear and to wear white garments. It was inevitable that these men should be unfriendly to the introduction of new beliefs which threatened their own position, since it condemned the practice of divination and those kindred arts on which their eminent power was based. But their opposition could not be effective, because they had no organisation. The fact, then, that the Christian Church, by its recognition of demons as an actual power with which it had to cope, stood in this respect on the same intellectual plane as the heathen, was an advantage in the task of diffusing the religion. The belief in demons as a foe with which the Church had to deal was expressed officially in the institution of a clerical order called exorcists, whose duty it was, by means of formulae, to exorcise devils at baptism.[69] Patrick had exorcists in his train, and it was not unimportant that the Christian, going forth to persuade the heathen, had such equipments of superstition. He was able to meet the heathen sorcerer on common ground because he believed in the sorceries which he condemned.[70] He was as fully convinced as the pagan that the powers of magicians were real, but he knew that those powers were strictly limited, whereas the power of his own God was limitless. Patrick could never have said to an Irish wizard, as children of enlightenment would now say, “Your magic is imposture; your spells cannot really raise spirits or control the forces of nature; you cannot foretell what is to come.” He would have said, “Yes, you can do such miracles by the aid of evil powers, but those powers are subject to a good power whose religion I preach, and are impotent except through his permission.” This point of mental agreement between the Christian priest and the heathen whom he regarded as benighted, their common belief in the efficacy of sorcery, though they put different interpretations on its conditions,[71] was probably not an insignificant aid in the propagation of the Christian religion.