One of the most interesting and remarkable phenomena of the history of witchcraft is that of the self-confessed witch, the woman who deliberately and of her own accord gave herself out to be possessed of supernatural powers in spite of the terrible peril incurred by such an announcement. The explanation of this is partly economic—the law of supply and demand operating in the case of the occult arts as a marketable commodity, just as in any other—partly psychological. Particularly when there was such unimpeachable authority for the reality and potency of the black arts, there were always people quite anxious to avail themselves of the means of fore-knowledge of, or avenging an injury, or discomfiting a rival, and to pay handsomely for the privilege. The demand existing, there were not wanting those willing to satisfy it, to accept the risk in view of the generosity of the remuneration. Sometimes the reputed witch succeeded in persuading herself that she was one in very deed. Some curious coincidence, the desired object actually occurring after the utterance of spells and incantations, persuaded the superstitious mind, arguing ‘post hoc ergo propter hoc,’ that the spells and incantations held in them a miraculous power. The wretched woman would then with a vain pride or a trembling apprehensive awe perceive in herself a being supernatural.[219] But clearly the greater proportion of witchcraft lore is founded upon confessions wrung by means of the rack from the supposed culprit when brought before a civil or inquisitorial tribunal.