"The confounding Political Economy with the Sciences and Arts to which it is subservient, has been one of the principal obstacles to its improvement"

Nassau William Senior's quote is referring to the confusion between Political Economy and the sciences and arts that it depends on. He thinks that this confusion has actually been a major obstacle to the progress of Political Economy. Political Economy is a social science that studies the production, circulation, and usage of items and services. It is carefully related to other social sciences such as sociology, sociology, and economics. Nevertheless, it is also dependent on other sciences and arts such as mathematics, history, and philosophy. By conflating Political Economy with these other disciplines, it has actually been difficult to make progress in the field. Senior's quote is a reminder that Political Economy ought to be studied on its own terms and not be confused with the other sciences and arts that it relates to.