John Stuart Mill is often remembered as one of history’s great classical economists and a champion of individual freedom in works like On Liberty. However, a deeper look into his largest and most comprehensive work, Principles of Political Economy, reveals a far more complex and radical social philosopher. Mill was deeply critical of the economic injustices of his day and saw the need for fundamental reform.

This guide explores Mill’s critical perspective on the institution of private property and his surprisingly sympathetic analysis of socialist ideas. Far from dismissing them, Mill believed that the principles behind socialism held the key to understanding the “probable futurity of the labouring classes.” In fact, as the Editor’s Introduction to his work notes, Mill and his intellectual partner, Harriet Taylor, came to identify themselves “under the general designation of Socialists,” a view that challenges the conventional understanding of this pivotal 19th-century thinker.