One undeniable resemblance of the two phenomena is the relative infrequency of their occurrence and their divergence from the majority of mankind. Of old there was a tendency to ascribe everything that was uncommon and unaccountable to the influence of a supernatural force. Accordingly, it was believed that famous minds, as well as those that were darkened with madness, stood under a direct divine influence, or even formed, themselves, a part of the Godhead. In the Middle Ages the crazy were held to be bewitched, or possessed of the devil, while the greatest minds were honoured as graced by the Holy Spirit. Not infrequently the crazy, too, if their delusions or hallucinations were of a religious cast, were considered as saints in direct communion with the Deity. At the same time, eminent men of science, persecuted by ignorance and superstition, were abhorred as tools of the devil or burnt as heretics. At all events, genius and insanity—two inexplicable phenomena and vaguely defined—have been confounded together in various ages of the world, according to the ideas of those times.

After modern science had got rid of the dross of superstition and had taken its stand upon skeptical and objective observation, a revolution of opinion took place. Anciently an unbounded freedom had been attributed to the play of Nature. This far surpassed those limits within which rigid laws of Nature allow any such play. That was supernatural. But in modern times the tendency has been to confine the action of Nature within much too restricted bounds. All phenomena must now be brought under a schema artificially erected. Everything must have just such a measure and just such a weight, and every action of Nature is regarded as subject to a numerical rule. This method of investigation may have had beneficial results in physics, chemistry, and the other sciences that have flourished under it, but such a method of violent formularization must prove out of place for a science like psychology, in which we must always be limited to purely empirical facts, so that our investigations can only be analytical, and can never proceed synthetically.