Origin of the general Opinions respecting Demonology among Mankind--The Belief in the Immortality of the Soul is the main inducement to credit its occasional re-appearance--The Philosophical Objections to the Apparition of an Abstract Spirit little understood by the Vulgar and Ignorant--The situations of excited Passion incident to Humanity, which teach Men to wish or apprehend Supernatural Apparitions--They are often presented by the Sleeping Sense--Story of Somnambulism--The Influence of Credulity contagious, so that Individuals will trust the Evidence of others in despite of their own Senses--Examples from the "Historia Verdadera" of Bernal Dias del Castillo, and from the Works of Patrick Walker--The apparent Evidence of Intercourse with the Supernatural World is sometimes owing to a depraved State of the bodily Organs--Difference between this Disorder and Insanity, in which the Organs retain their tone, though that of the Mind is lost--Rebellion of the Senses of a Lunatic against the current of his Reveries--Narratives of a contrary Nature, in which the Evidence of the Eyes overbore the Conviction of the Understanding--Example of a London Man of Pleasure--Of Nicolai, the German Bookseller and Philosopher--Of a Patient of Dr. Gregory--Of an Eminent Scottish Lawyer, deceased--Of this same fallacious Disorder are other instances, which have but sudden and momentary endurance--Apparition of Maupertuis--Of a late illustrious modern Poet--The Cases quoted chiefly relating to false Impressions on the Visual Nerve, those upon the Ear next considered--Delusions of the Touch chiefly experienced in Sleep--Delusions of the Taste--And of the Smelling--Sum of the Argument. You have asked of me, my dear friend, that I should assist the "Family Library" with the history of a dark chapter in human nature, which the increasing civilization of all well-instructed countries has now almost blotted out, though the subject attracted no ordinary degree of consideration in the older times of their history. Among much reading of my earlier days, it is no doubt true that I travelled a good deal in the twilight regions of superstitious disquisitions. Many hours have I lost--"I would their debt were less!"--in examining old as well as more recent narratives of this character, and even in looking into some of the criminal trials so frequent in early days, upon a subject which our fathers considered as a matter of the last importance. And, of late years, the very curious extracts published by Mr. Pitcairn, from the Criminal Records of Scotland, are, besides their historical value, of a nature so much calculated to illustrate the credulity of our ancestors on such subjects, that, by perusing them, I have been induced more recently to recall what I had read and thought upon the subject at a former period.