The Mathers gave still further proof of faith unshaken by discovering an afflicted damsel in Boston, whom they visited and prayed with, and of whose case Cotton Mather wrote an account circulated in manuscript. This damsel, however, had the discretion to accuse nobody, the spectres that beset her being all veiled. Reason and common-sense at last found an advocate in Robert Calef, a citizen of Boston, sneered at by Cotton Mather as "a weaver who pretended to be a merchant." And afterward, when he grew more angry, as "a coal sent from hell" to blacken his character--a man, however, of sound intelligence and courageous spirit. Calef wrote an account, also handed about in manuscript, of what had been said and done during a visitation of the Mathers to this afflicted damsel, an exposure of her imposture and their credulity, which so nettled Cotton Mather that he commenced a prosecution for slander against Calef, which, however, he soon saw reason to drop. Calef then addressed a series of letters to Mather and the other Boston ministers, in which he denied and ridiculed the reality of any such compacts with the devil as were commonly believed in under the name of witchcraft. The witchcraft spoken of in the Bible meant no more, he maintained, than "hatred or opposition to the word and worship of God, and seeking to seduce therefrom by some sign"--a definition which he had found in some English writer on the subject, and which he fortified by divers texts. It was, perhaps, to furnish materials for a reply to Calef that a circular from Harvard College, signed by Increase Mather as president, and by all the neighboring ministers as fellows, invited reports of "apparitions, possessions, enchantments, and all extraordinary things, wherein the existence and agency of the invisible world is more sensibly demonstrated," to be used "as some fit assembly of ministers might direct." But the "invisible world" was fast ceasing to be visible, and Cotton Mather laments that in ten years scarce five returns were received to this circular.