There is no need to quote more of this class of cases, at least for the present. Their name is legion. One could, in fact, construct an ascending series of cases, all agreeing in their symptom, and differing only in the explanation offered. The series would commence with the explanation of a possessing spirit, and end with that of a deranged nervous system. Ignorant of the nature, or even of the existence, of a nervous system, primitive man explains abnormal mental states as due to a malignant spirit. Martin Luther, George Fox, or John Bunyan, living at a time when the activity of evil spirits was a firmly held doctrine, attribute their infirmities to satanic influence. We are in the true line of descent. To-day we have with us every one of the phenomena on which the satanic theory rested, but they are described, and prescribed for, in medical works instead of manuals of exorcism. The supernaturalist theory gives way to that of the expert neurologist. The exorcist is replaced by the physician. Instead of expelling an intruding demon, we have to repair a deranged system. We cannot argue that while these affections remain constant in character their causes may have been different in other ages from what they are now. That is pure absurdity. To claim that the religious mystic is in moments of exaltation brought into contact with a "deeper reality" is to invite the retort that one might make a similar claim on behalf of the inmates of a lunatic asylum. We cannot, with any pretence to rationality, accept the verdicts of both the neurologist and the exorcist. If we agree that certain states of mind to-day have their origin in neural disorder, on what ground can we believe that similar mental states occurring a thousand or two thousand years ago were due to supernatural stimulation? We may be told that there are more things in heaven and earth than are dreamed of in our philosophy. This may be true, and while it is an observation that would not occur to a fool, it needs no supreme wisdom for its excogitation, and as generally used it is an excuse for idle speculation and grotesque theory. Far more useful is the lesson, sadly needed, that there are few things in heaven or earth that will not yield their secret to a method of investigation that is sanely conceived and diligently employed.