Dr. Ferriar, whom, to mention otherwise than as a man of genius, of learning, and of taste, would be unjust; has adopted the generally accepted division of Insanity, into Mania and Melancholy. In Mania, he conceives "false perception, and consequently confusion of ideas, to be a leading circumstance." The latter, he supposes to consist "in intensity of idea, which is a contrary state to false perception." From the observations I have been able to make respecting Mania, I have by no means been led to conclude, that false perception, is a leading circumstance in this disorder, and still less, that confusion of ideas must be the necessary consequence of false perception.
By perception, I understand, with Mr. Locke, the apprehension of sensations; and after a very diligent enquiry of patients who have recovered from the disease, and from an attentive observation of those labouring under it, I have not frequently found, that insane people perceive falsely, the objects which have been presented to them. It is true, that they all have false ideas, but this by no means infers, a defect of the power by which sensations are apprehended in the mind.
We find madmen equally deranged upon those ideas, which they have been long in the possession of, and on which the perception has not been recently exercised, as respecting those, which they have lately received: and we frequently find those who become suddenly mad, talk incoherently upon every subject, and consequently, upon many, on which the perception has not been exercised for a considerable time.
It is well known, that maniacs often suppose they have seen, and heard those things, which really did not exist at the time; but even this I should not explain by any disability, or error of the perception, since it is by no means the province of the perception to represent unreal existences to the mind. It must therefore be sought elsewhere, probably in the senses, or in the imagination.
I have known eight cases of patients, who insisted that they had seen the devil. It might be urged, that in these instances, the perception was vitiated; but it must be observed, that there could be no perception of that, which was not present and existing at the time. Upon desiring these patients to describe what they had seen, they all represented him as a big, black man, with a long tail, cloven feet, and sharp talons, such as is seen pictured in books. A proof that the idea was revived in the mind from some former impressions. One of these patients however carried the matter a little further, as she solemnly declared, she heard him break the iron chain with which God had confined him, and saw him pass fleetly by her window, with a truss of straw upon his shoulder.