Such persons are more likely to be brought in close contact with their pastors and other clergymen and with religious Superiors of various kinds than even normal individuals. They often put their confessors, particularly, in serious quandaries in the matter of spiritual advice. A review, then, of the accepted ideas of experts with regard to such people is likely to be of special service to those who would understand these cases as well as possible, though the present state of medical knowledge, here as elsewhere, leaves much to be desired. A distinguished authority in mental diseases once said, half in jest though he meant it to be taken at least half in earnest, that a great many more of us are cracked than are usually thought to be, only that most of us succeed in concealing the crack quite well. The frequency of the crank adds to the {283} interest of his study, which is by no means a department of medical science of recent growth. While interest in this class of persons has become much more intense in recent years, eccentric individuals have been an object of close observation and of serious study almost as far back as history goes. When Quintilian said that genius was not far separated from insanity, he meant to record the conclusion of his time, that men of genius are apt to seem inexplicable in their ways to those who come closely in contact with them. Eccentric persons, however, are by no means always undesirable members of a generation. It has been noted by historians in all ages that to the refusal of eccentric individuals,--often thought at the beginning, particularly, to be little better than insane--to accept the traditions of the past, we owe many of the privileges which we enjoy at the present time. Their refusal to think along old lines of thought often makes them valuable pioneers in progress. Definite knowledge with regard to the pathological basis of crankism, or eccentricities, has not yet been obtained. What has been learned, however, has enabled the neurologist to distinguish various forms of mental perturbation, to recognise the probable influence of certain conditions and environments on the future action of eccentric individuals, and to foretell the probable outcome of the cases. All of this information is of very practical importance to religious Superiors and others in positions of religious confidence, who are sure to be brought, even more than the rest of the community, in contact with the eccentric class. It has seemed advisable, then, to condense some of the recent knowledge on this subject into popular form for the use of confessors, spiritual directors, and those in religious authority.