J. S. Mill's 4th Proposition on Capital Should Be Understood as a Continuation of the General Glut Debate

John Stuart Mill’s Fourth Fundamental Proposition Respecting Capital, first stated in 1848, had become an enigma well before the nineteenth century had come to an end. Never challenged in Mill’s own lifetime and described in 1876 as “the best test of a sound economist,” it has become a statement that not only fails to find others in agreement, but fails even to find an internally consistent interpretation that would make clear why Mill found it of such fundamental importance. Yet the fourth proposition should be easily understood as a continuation of the general glut debate. Economists led by Malthus had argued that demand deficiency was the cause of recession and a body of unproductive consumers was needed to raise the level of demand if everyone who wished to work was to find employment. Mill’s answer was that to buy goods and services would not increase employment, or, in Mill’s own words, “demand for commodities is not demand for labour.”

—Steven Kates, “Mill's Fourth Fundamental Proposition on Capital: A Paradox Explained,” abstract, Journal of the History of Economic Thought 37, no. 1 (March 2015): 39.