In the production of this state of mind a factor as yet unmentioned plays a leading rôle, the power of mental contagion. Error, like truth, flourishes in crowds. At the hearth of sympathy each finds a home. The fanatical lead, the saner follow. When a person of nervous temperament, not strongly independent in thought and action, enters a spiritualistic circle, where he is constantly surrounded by confident believers, all eager to have him share their sacred visions and profound revelations, where the atmosphere is replete with miracles, and every chair and table may at any instant be transformed into a proof of the supernatural, is it strange that he soon becomes affected by the contagion of belief that surrounds him? He succumbs to its influence imperceptibly and hesitatingly at first, and perhaps yet restorable to his former modes of thought by the fresh air of another and more steadfast mental intercourse, but more and more certainly and ardently convinced the longer he breathes the séance atmosphere. No form of contagion is so insidious in its onset, so difficult to check in its advance, so certain to leave germs that may at any moment reveal their pernicious power, as a mental contagion--the contagion of fear, of panic, of fanaticism, of lawlessness, of superstition, of error. The story of the witchcraft persecutions, were there no similar records to deface the pages of history, would suffice as a standing illustration of the overwhelming power of psychic contagion. To illustrate with any completeness its importance in the production of deception or in the dissemination of error, would carry us beyond the proper limits of the present discussion. It enters at every stage of the process and in every type of illusion. Although it has least effect when deception is carried on by external arrangements, by skilful counterfeits of logical inferences, yet even then it enters into the distinction between a critical, skeptical, and irresponsive body of spectators, and one that is sympathetic, acquiescent, and cordial; it renders it easier to effect bold and striking impressions with a larger audience than with a smaller one; its power is greatest, however, where the subjective factor in deception is greatest, more particularly in such forms of deception as have been last described.