The fragment below belongs to the first part of my book “The Pillars of Philosophy of Economic Behavior”.
In an 1831 letter to the Scottish author John Sterling (1806-1844), John Stuart Mill told him that he was «working out» in political economy, aiming to clear up some points that he thought were dubious and correcting others he considered wrong, “to shew what the science is & how it should be studied.” Mill was concerned with principles. “I am here much more in my element: the only thing that I believe I am really fit for, is the investigation of abstract truth, and the more abstract the better. If there is any science which I am capable of promoting, I think it is the science of science itself, the science of investigation – of method.” For him, there were many differences between the methods that were used at the time and it was necessary to shed light on this issue in order to find a method that expressed political economy as a science. “For Mill, a scientific approach meant the simplicity he found in Newtonian science, that is, the explanation of a mass of facts and details by organizing principle.” The motivation for what Mill stood for resulted in his essay On the Definition of Political Economy, which had the goal of defining scope, laws and methods in order to place political economy in the realm of science.
 Mill, J., «Letters», Collected Works, Vol. XII, 78-79.
 Redman, D., The Rise of Political Economy, 322.