No questions which can become the subject of judicial examination are more delicate and difficult than those which depend upon a man’s mental sanity, whether the case be of a civil or a criminal nature; whether it regard his competence to manage his own affairs, or his possession of that moral feeling of right and wrong in the absence of which he cannot be justly punished as a responsible agent. In the first instance, daily experience shows us that general eccentricity, and even delusion upon particular subjects, may exist in union with the most acute perception of personal interests; in the second, it is equally clear that the moral sense may be perverted upon one or more points without being destroyed, and indeed without any other indication of mental disease. We may take as an example of this the burning of York Cathedral some years ago. Martin believed this to be morally a meritorious act, and herein lay his madness: on a case of murder, robbery, or any other infraction of the laws, he would have judged aright. But though he believed it to be meritorious, he knew it to be illegal; he knew that he was subject to punishment, and fled from it accordingly: and upon this ground the question might be raised, whether his madness should have protected him from the penalty affixed to his act. But exclusively of those more strongly marked cases, which alone are likely to become subjects of judicial inquiry, no man can converse extensively with the living, or, through the medium of books, with the dead, without continually asking himself whether the eccentricity, perverseness, intemperance, and extravagance which he sees on all sides are compatible with a perfectly sound state of mind. Mental as well as bodily illness may assume all shapes, and be of all degrees: and both reflection and observation lead us to conclude that excessive indulgence of the passions will impair the understanding, as surely as sensual intemperance injures the constitution. It would not be difficult to enumerate a long list of causes tending more or less to unsettle the reason; indeed, no pursuit, however unexciting it may seem, can be exclusively followed without risk of this result. Science has its dangers as well as love: the philosopher’s stone and the quadrature of the circle have probably turned as many heads as has female ingratitude, from the time of Orlando Furioso downwards. At present, however, we mean to confine ourselves to one particular manifestation of insanity, or something nearly allied to it, with the view of illustrating, in some degree, that large portion of history which is occupied by the crimes and follies of absolute monarchs.