"Father Brown" had first made his appearance in magazines and these detective stories became the most purely popular of Gilbert's books. It was a new genre: detection in which the mind of a man means more than his footprints or cigar ash, even to the detective. The one reproduced in most anthologies--"The Invisible Man"--depends for its solution on the fact that certain people are _morally_ invisible. To the question "Has anyone been here" the answer "No" does not include the milkman or the postman: thus the postman is the morally invisible man who has committed the crime. A thread of this sort runs through all the stories, but they are, like all his romances, full too of escape and peril and wild adventure.
Life on several occasions imitated Gilbert's fancies. Thus the Azeff revelations followed his fantastic idea in _The Man Who Was Thursday_ of the anarchists who turn out to be detectives in disguise. The technique of Father Brown himself was imitated by a man in Detroit who recovered a stolen car by putting himself imaginatively in the thief's place and driving an exactly similar car around likely corners till he came suddenly upon his own, left in a lonely road. He wrote to tell Gilbert of this adventure.
From Chicago came an even odder example. "It is extremely difficult," wrote the _Tribune_, "to determine the proper relationship of the Chiesa-Prudente-Di Cossato duels to Mr. Gilbert K. Chesterton's book, _The Ball and the Cross"_ . . .
The flight in search of a duelling ground; the pursuit by the police; the friendly intervention of the anarchist wineshop-keeper, Volpi; the offer of his backyard for fighting purposes; the unfriendly intervention of the police; the friendly intervention of the reporters; the renewed and insistently unfriendly intervention of the police commissioner; the disgust of the duellists; the extreme disgust of the anarchist; the renewed flight of the fighters, seconds, physicians, reporters, and the anarchist over the back fences--all these and other incidents are essentially Chestertonian.
The Di Cossato affair was carried off with fully as much spirit and dash; with fully as many automobiles, seconds, physicians, reporters and police, all scampering over the country roads until the artistic deputy and the aged veteran of the war of 1859, outdistancing their pursuers, could find opportunity in comparative peace to cut the glorious gashes of satisfied honour in each other's faces.
*