Through all ages, among all races, the living have alleged themselves from time to time to have seen the forms and even heard the voices of the dead. Scientific men have been forced by the actual and public exercise of the power under the most crucial tests—for instance, to produce insensibility in surgical operations—to admit that the will of one man can control the brain, the senses, the physical frame of another without material contact, perhaps at a distance. There are narratives of marvels wrought by human will, chiefly in remote, but occasionally in recent times, transcending and even contradicting or overruling the known laws of Nature. All these evidences point to one conclusion; all corroborate and confirm one another. The men of science ridicule them because in so many cases the facts are imperfectly authenticated, and because in others the action of the powers is uncertain, dependent on conditions imperfectly ascertained, and not of that material kind to which material science willingly submits. But if they be facts, if they relate to any element of human nature, all these things can be systematically investigated, the true separated from the false, the proven from the unproven. The powers can be investigated, their conditions of action laid down. Probably they may be so developed as to be exercised with comparative certainty, whether by every one or only by those special constitutions in which they may inhere. Such investigations will at present only enlist the attention and care of a few qualified persons, and, that they may be carried on in peace and safety, should be carried on in secrecy. But upon them may, I hope, be founded a certainty as regards the higher side of man's nature not less complete than that which science, by similar methods, has gradually acquired in regard to its purely physical aspects.'