Bucknill describes insanity, in his Sugden prize essay, as “a condition of the mind in which a false action of conception or judgment, a defective power of the will, or an uncontrollable violence of the emotions and instincts has been separately or conjointly produced by disease.” Maudsley's definition is, “Insanity is, in fact, disorder of brain producing disorder of mind; or, to define its nature in greater detail, it is a disorder of the supreme nerve-centres of the brain—the special organs of mind—producing derangement of thought, feeling, and action, together or separately, of such degree or kind as to incapacitate the individual for the relations of life.... Mind may be defined physiologically as a general term denoting the sum-total of those functions of the brain which are known as thought, feeling, and will. By disorder of the mind is meant disorder of those functions.”
Bucknill considers insanity a disease of the brain affecting the integrity of the mind. Maudsley calls it a disorder of the mind of such a degree as to incapacitate one for the ordinary relations of life, implying that there may be certain deviations from the condition of sound mind which do not constitute insanity. Tuke's definition is that “insanity consists in morbid conditions of the brain, the result of defective formation or altered nutrition of its substance, induced by local or general morbid processes, and characterized especially by non-development, obliteration, impairment, or perversion of one or more of its psychical functions.” Instead of itself being a disease, insanity, properly speaking, is a symptom of diseases which under varying manifestations probably affect different functions of the brain—at least they affect the brain in different ways.
As Krafft-Ebing says, “It is a logical, self-evident proposition that the organ whose function under normal conditions is to bring about all mental processes must be the seat of changes when these functions are disturbed;” and Schüle adds, “The study of disturbances of the mind involves the changes of the normal mental functions produced by disease.... Mental diseases are brain diseases, but they are more than that.” The normal action of the mind is a strange combination of reason and impulse, varying greatly in different persons, and in the same person at different times and under varying influences. The relations of the one to the other, and their influence on action, often change, under varying conditions and circumstances, in sane persons, but still more in the insane.
Lord Bramwell once said that insanity is strong but not conclusive evidence of innocence; and Lord Blackburn has stated that the jury must decide in each individual case whether the disease of the mind or the criminal will was the cause of the crime. The position of Sir James Stephen in his History of the Criminal Law in England best states the most recent views of irresponsibility—namely, that “no act is a crime if the person who does it is, at the time when it is done, prevented either by defective mental power or by any disease affecting his mind from controlling his own conduct, unless the loss of the power of control has been produced by his own default.” He says that a man laboring under such a defect of reason that he does not know that he is doing what is wrong may be defined as one deprived, by disease affecting the mind, of the power of passing a rational judgment on the moral character of the act which he meant to do. There are persons too insane to make a valid will by virtue of a single delusion, whose right to vote, under the law prohibiting the insane from voting, would not be questioned. Another might not be held responsible for crime, and still make a contract involving the rights of others besides himself that would hold in law.
Bucknill's recent medico-legal definition of insanity is, incapacitating weakness or derangement of mind produced by disease; meaning, in criminal cases, inability of abstaining from the criminal act, which would be expressed by Lord Bramwell's test, Could he help it? Bucknill suggests as an amendment to the law of England that no act is a crime if the person who does it is at the time incapable of not doing it by reason of idiocy or of disease affecting the mind.
Any definition of insanity would be incomplete without the statement of Hughlings Jackson's view, that disease only produces negative mental symptoms answering to dissolution, and that all elaborate positive mental symptoms (illusions, hallucinations, delusions, and extravagant conduct) are the outcome of activity of nervous elements untouched by any pathological process; that they arise during activity on the lower level of evolution remaining; that the insane man's illusions, etc. are not caused by disease, but that they are the outcome of activity of what is left of him (of what disease has spared), of all there then is of him. His illusions, etc. are his mind.
THE CLASSIFICATION OF MENTAL DISEASES.—There is no universally accepted classification of mental diseases, and the same terms even are used by different writers to convey entirely different meanings. The classification according to the causes of insanity was suggested by Morel of Paris, and fully elaborated by Skae of Edinburgh, as follows: (1) Moral idiocy; (2) intellectual idiocy; (3) moral imbecility; (4) intellectual imbecility; (5) epileptic insanity; (6) insanity of masturbation; (7) insanity of pubescence; (8) hysterical mania; (9) amenorrhœal mania; (10) post-connubial mania; (11) puerperal mania; (12) mania of pregnancy; (13) mania of lactation; (14) climacteric mania; (15) ovario- and uteromania; (16) senile mania; (17) phthisical mania; (18) metastatic mania; (19) traumatic mania; (20) syphilitic mania; (21) delirium tremens; (22) dipsomania; (23) mania of alcoholism; (24) post-febrile mania; (25) mania of oxaluria and phosphaturia; (26) general paralysis; (27) epidemic mania; (28) idiopathic sthenic mania; (29) idiopathic asthenic mania.
In a large proportion of cases the causes of insanity are so many and so complex that it is not within human power to say which of a number has been the most important, or the assigned and classified cause may be only an accidental complication or the most striking, but by no means most potent, cause.
The classification, according to the functions interfered with, is that adopted by Maudsley and by Bucknill. According to Bucknill, we have
(1) Insanity of the intellect or ideas: Idiocy, imbecility, dementia, delusional insanity, monomania, mania.