 Fortunately for the world, but unfortunately for economic theorists of the mid 19th century, the data consistently contradicted the trends the theory predicted (de Marchi 1970). Yet the theory continued to hold sway for more than half a century, and the consistently unfavorable data were explained away as due to various “disturbing causes.” It is consequently not surprising that Senior’s and Mill’s accounts of the method of economics emphasize the relative autonomy of theory.