Psychologically, Mrs Eddy is at least classified, if not entirely explained, by one word--monoideism. She was a person of one idea. These people, for whom we usually have the simpler term of "crank", are common enough. I have no personal acquaintance with the circle-squaring and perpetual-motion cranks mentioned by De Morgan (_The Budget of Paradoxes_), but I know a "flat-earth" crank, and am well acquainted with a "British-Israelite" crank, who seems to derive unspeakable joy--tempered only by his failure to convert me--from the thought that we Britishers are veritably the descendants of one or more of the Lost Tribes. All these people are conscious of a mission. They have had a revelation, and are anxious to impart it. Their efforts may not be due to the "last infirmity of noble mind", still less to a lower motive. They may just be built that way. The majority of them, like my Lost-Tribes friend, get no hearing because of the inflexible pragmatism of a stiffnecked and utilitarian generation. "What difference does it make whether we are the Tribes or not?" asks the man in the street. And he passes on with a shrug or a grin, according to temperament. This terrible pragmatic test makes short work of many amiable cranks. And it is just here that Christian Science scores its point; for it cures physical disease, thereby becoming intensely practical. Health is the chief "good" of life. Anything that will restore it to an ailing body commands immediate and universal respect. Christian Science therefore appeals, on its practical side, to the deepest thing in us--to the primal instinct of self-preservation. Hence its success. It is possible to blame Mrs Eddy unjustly for her love of power as such. She was not unique in this respect. The difference is that Mrs Eddy succeeded while the others have not, and are consequently not heard of. My Lost-Tribes friend would be as autocratic as anybody if he had the chance; but his motive would not be greed of power, but rather the overmastering desire to push his cause, to proselytise, to promulgate his one idea, almost by force, if such a thing were possible. Most of us know a few fanatics of this kind. The objects of their devotion are varied--one is mad north-north-west, another south-south-east--but all suffer from a lack of balance, a lack of proper distribution of interest. Of course, we may cheerfully admit that we are all more or less specialists in our several departments, and that the line between sanity and insanity is rather arbitrary. We all seem more or less mad to those who do not agree with us.