Bernard DeVoto says Joseph Smith was a "paranoid" that experienced hallucinations, says Book of Mormon was influenced by Solomon Spaulding's Manuscript Found and Sidney Rigdon.
Bernard DeVoto, “The Centennial of Mormonism,” American Mercury 19, no. 73 (January 1930): 4–5.
Let us, therefore, look into the matter. Psychiatrists, it appears, recognize a complex mental organization known as the paranoid personality. Its characteristic is the subordination of all ideas and the direction of all efforts to one dominant belief or purpose. When such a personality passes the border-line of sanity, this obsessive idea robs logic of all its validity, inhibits the normal perception of casual relationships, and prevents the victim from perceiving the difference between his imaginative projection of his desires and the world of reality. A common result is the development of a superb self-confidence, a belief in one's cause that nothing can destroy. Such self-confidence may even create a belief that one is omnipotent; and from omnipotence to divinity is an easy step. The paranoid may thus acquire delusions of grandeur.
But, since complete megalomania is uncommon in this disorder, the paranoid usually perceives that his accomplishment here and there falls short of his intention and his power. Clearly, the cause of this failure cannot be in himself; it must life in the machinations of enemies or of the Devil. Consequently, paranoids also exhibit delusions of persecution. Yet a third mark of the type is a craze for authorship—the production of immensely long manuscripts, sometimes logical and intelligible, but sometimes clearly insane. The paranoid, again, is likely to be religious. He may be, finally, a man of great physical energy, and buoyant spirits, with a rare capacity to command the allegiance of others. One psychologist has remarked, indeed, that much of the progress of the human race has been a by-product of paranoia—that paranoids whose obsessions are socially useful are simply called geniuses. That is perhaps true; but the asylums are filled with paranoids who have missed genius, and not every man who has proclaimed himself chosen of God has made the world lovelier.
Unquestionably, Joseph Smith was a paranoid. Intensely religious during adolescence, he began to experience auditory hallucinations. Voices which he identified as Jehovah's, as well as those of prophets and angels, informed him of his divinely appointed mission—to establish the True Church and lead it to domination over the whole world. To these hallucinations were added others to a visual character in which he beheld the holy Personages who talked with him. His religious mission became the obsession to which he related every item of his experience, and as it developed the prophet expanded in grandeur.
He became a despot over his flock; he proclaimed himself indispensable to God; he spouted fiery abuse on all magistrates and rulers; he settled offhand problems of religion, metaphysics and science that forty centuries had found insoluble. When he was killed at last this backwoods Cagliostro was the general of a private militia decorated with uniforms and sabres beyond the invention of Negro burying-societies, and a candidate for the Presidency of the United States, and had established himself not only as a prophet in constant communication with God but also as a presumptive deity himself.
Clearly these were paranoid delusions of grandeur. And, as usual, they carried with them compensatory delusions of persecution. Devils and earthly villains tried to keep Joseph from translating the Golden Plates. Even before the establishment of the church enemies beset him; thereafter the Almighty Himself could not fend them off. Miscreants and monsters of all horrible and revolting sorts did Satan's work. . . .
The paranoid impulse to authorship never left him. In the midst of an incredibly busy life—a life filled with ruling thousands of subjects besides speculating in land and stocks, rearing temples to the Lord, maintaining a huge propaganda, perfecting the organization of the church, and instituting the sacrament of celestial marriage—in the midst of all this, Joseph still had time to emit countless pages of bad prose. The stream never ran dry; to the day of his death he was vilifying his enemies and recording miracles in his autobiography, and setting down fresh gospels and epistles, direct from Jehovah. The paranoid faculty for seizing all the flotsam of human thought and converting it to the support of the dominant obsession appears in everything he wrote.
The same faculty explains the Book of Mormon, the translation from the Golden Plates. Joseph was, as his first title-page announced, the "author and proprietor" of this Testament. Somehow, whether by an actual reading of it or through the reports of Sidney Rigdon, he had become acquainted with Solomon Spaulding's "Manuscript Found," a turgid historical novel, built up out of Elias Boudinot's "Star of the West," other speculations of the same kind, and a prose style as lethal as Joseph's own. It circulated widely in manuscript and could easily have come into his hands, as it certainly came into Rigdon's. The prophet's mind seized on this mass of moony nonsense about the Nephites and Lamanites, and welded to it the doctrinal controversies whose reverberations he had heard since infancy and the polemics that Rigdon carried over from the Disciples of Christ. It was a yeasty fermentation, formless, aimless, and inconceivably absurd—at once a parody of all American religious thought and something more than parody, a disintegration. The œstrus of paranoia projected it into a new Bible .