The author first finds the theological root of his subject. During the middle ages it was held that all power or force was spiritual, that it came from a spiritual source — from God — and was communicated to the earth by spiritual agents or angels. No inevitable causation was admitted. The laws of nature were the precepts in accordance with which the angels executed the will of God. Sometimes he suspended their agency, acting everywhere himself, or he delegated unusual power to them, when their operations were known as miracles. Hence a knowledge of nature was at this time chiefly a knowledge of the angels. Lucifer, the highest of these angels, rebelled against God. The contest ended with the overthrow of the rebel and his followers; but God, calm in the consciousness of his omnipotence, determined that Lucifer, now changed by his rebellion into a spirit wholly evil, should enjoy liberty of action within certain limits. The activity of the fallen spirit consists henceforth in incessant warfare against God. Man is tempted and falls. The earth is divided into two antagonistic kingdoms, those of good and evil. Over one reigns God and his angels of light, over the other the devil and his minions. Such was the dualistic conception of the middle ages, and to it may be traced the magic of the Church, the astrology, alchemy, and sorcery of the learned, as well as the diabolic forms of witchcraft believed in by the common people.
The Church, exercising its watch-care for man, surrounded him from the cradle to the grave by the safeguards of magic. Thus, soon after the birth of the child the priest must be ready to sprinkle it with holy water, which has been purified from the pollution of demons by prayer and conjuration; and so strong was the impression that the child, begotten in sin and by nature Lucifer's property, would be doomed to the torments of hell without the grace of baptism, that certain conscientious servants of the Church attempted to devise some means by which the saving water might be brought in contact with the child before it saw the light.
Holy water, when drunk by the sick and infirm, healed and strengthened; if sprinkled upon the field it promoted fertility, and given to domestic animals it afforded them protection against witchcraft.
Says Thomas Aquinas: "It is a dogma of faith that the demons can produce wind, storms, and rain of fire from heaven. The atmosphere is a battle-field between angels and devils. The latter work the constant injury of man, the former his melioration; and the consequence is that changeableness of weather which threatens to frustrate the hopes of husbandry. And, when Lucifer is able to bestow even upon man — sorcerers and wizards — the power to destroy the fields, the vineyards, and dwellings of man by rain, hail, and lightning, is it to be wondered at if the Church, which is man's protection against the devil, and whose especial calling it is to fight him, should in this sphere also be his counterpoise, and should seek, from the treasury of its divine