... ordinary mankind. This world itself, travelling blindly and swiftly in overcrowded space, among a million other worlds travelling blindly and swiftly in contrary directions, may very well come by a knock that would set it into explosion like a penny squib. And what, pathologically looked at, is the human body with all its organs, but a mere bagful of petards? The least of these is as dangerous to the whole economy as the ship's powder-magazine to the ship; and with every breath we breathe, and every meal we eat, we are putting one or more of them in peril. If we clung as devotedly ... — Essays of Robert Louis Stevenson • Robert Louis Stevenson