"Human science can never be quite certain of things like that," said Father Brown, still looking at the red budding of the branches over his head, "if only because of the difficulty about definition and connotation. What is a weapon? People have been murdered with the mildest domestic comforts; certainly with tea-kettles, probably with tea-cosies. On the other hand, if you showed an Ancient Briton a revolver, I doubt if he would know it was a weapon—until it was fired into him, of course."