LOOKING back at the strange and erroneous notions which were formerly entertained of the nature and causes of insanity, and considering what little observation was made of its manifold varieties, we cannot wonder that its jurisprudence was in a very defective state. At first two kinds of insanity only seem to have been recognized by English law—idiocy and lunacy: the idiot who, from his nativity, by a perpetual infirmity is non compos, and the lunatic, who hath some-times his understanding, and sometimes not, aliquando gaudet lucidis intervallis, and therefore is non compos mentis, so long as he hath not understanding. But as time went on a partial insanity was recognized as distinct from total insanity, although this partial insanity was declared not to absolve a person from responsibility for his criminal acts. "There is," says Lord Hale, "a partial insanity, and a total insanity. The former is either in respect to things, quoad hoc vel illud insanire. Some persons that have a competent use of reason in respect of some subjects, are yet under a particular dementia in respect of some particular discourses, subjects, or applications; or else it is partial in respect of degrees; and this is the condition of very many, especially melancholy persons, who for the most part discover their defect in excessive fears and griefs, and yet are not wholly destitute of the use of reason; and this partial insanity seems not to excuse them in the committing of any offense for its matter capital; for, doubtless, most persons that are felons of themselves and others are under a degree of partial insanity when they commit these offenses. It is very difficult to define the invisible line that divides perfect and partial insanity; but it must rest upon circumstances duly to be weighed by judge and jury, lest, on the one side, there be a kind of inhumanity toward the defects of human nature; or, on the other side, too great an indulgence given to great crimes." The invisible line which it was so difficult to define was not, let it be noted, between sanity and insanity, but between perfect and partial insanity. It was thought no inhumanity toward the defects of human nature to punish as a fully responsible agent a person who was suffering from partial insanity, whatever influence the disease might have had upon his unlawful act.
The principle thus laid down by Lord Hale was subsequently acted upon in English courts. Thus, in the trial of Arnold, an undoubted lunatic, for shooting at Lord Onslow, in 1723, Mr. Justice Tracy said: "It is not every kind of frantic humor, or something unaccountable in a man's actions, that points him out to be such a madman as is ex-
- From advance sheets of "Responsibility in Mental Disease," No. 9 of the "International Scientific Series."