The main role of ghosts in the literature of the early church was to display the power of the saints. While Augustine was still alive, Sulpitius Severus wrote The Life of St. Martin, in which we find the following tale of Martin confronting and vanquishing the evil ghost of a thief who was being worshiped by mistake:
Not far from the town and very close to the monastery was a place [a village called Calitonnum] which enjoyed a certain sanctity because of the mistaken opinion that martyrs were buried there. Even an altar was maintained, erected there by former bishops.
But Martin was disinclined to believe what was uncertain. He kept asking those who were older, priests and clerics alike, to reveal the name of the martyr and the date of his martyrdom. He felt, he said, considerable scruple in the matter, since nothing certain had been handed down by any reliable report from his predecessors. He himself abstained from visiting the place for a while: he neither disparaged the cult, since his own position was uncertain, nor granted the populace the support of his authority, lest he fortify a superstition.
One day, taking a few of the brothers with him, he went to the place. He stood upon the tomb itself and prayed to the Lord to reveal who was buried there and what his merits were.
He then turned to the left and saw standing near him a grim, unclean spirit. He ordered him to speak out his name and his deserts. The spirit announced his name and confessed his criminal life: formerly a brigand, he had been executed for his crimes and was receiving veneration through the mistaken opinion of the populace; he had nothing in common with the martyrs—heavenly glory was their portion; punishment, his.
Strange wonder: those who were with Martin heard the voice, yet saw no one.
Martin then recounted what he had seen and ordered the altar which had been in that place to be removed. Thus he freed the people from the error of that superstition.
Augustine’s view of ghostly visions—both waking and oneiric—dominated discourse from the 4th century until about the 10th. The unseen world was divided between God, Jesus, the Holy Spirit, angels and saints on the one side and Satan and demons on the other. Between the unseen and material worlds, there was little place for intermediary spirits or ghosts except for those doing work for God or the Devil.
Gradually, however, this bright line between this world and the next began to fade. Hagiography continued to depict saints vanquishing demons and evil spirits, and the niceties that vexed St. Augustine’s subtle mind were gradually cast aside. His concerns about the barrier between the living the dead, the nature of a being that could be perceived after death, the type of vision the witness used to see them: none of these could withstand the vigorous European culture that would see a flowering of creative forces in the Carolingian Renaissance.