To understand our modern economic world, we must first understand the intellectual drama that gave it shape. In the 19th century, the field of political economy was haunted by the “bleak expectations” of thinkers like Thomas Malthus and David Ricardo. Their work had earned economics its title as the “dismal science,” suggesting that poverty and inequality were governed by laws as “unalterable as the laws of gravitation.” Humanity, it seemed, was trapped in a system where progress for the few meant permanent misery for the many.

It was in this climate that John Stuart Mill undertook his monumental work, Principles of Political Economy. His goal was not merely to update Adam Smith’s The Wealth of Nations, but to rescue economics from this deterministic pessimism. Mill believed economics was not an abstract science of numbers but a “branch of Social Philosophy,” and he sought to prove that humanity was not the subject of its economic destiny, but its author.

To begin this journey with Mill as our guide, we must first define its central subject: Wealth. He offers a definition that cuts through centuries of confusion:

Wealth, then, may be defined as all useful or agreeable things which possess exchangeable value.

This was a vital clarification. For generations, the dominant “Mercantile System” had taught that a nation’s wealth was its hoard of gold and silver. Mill showed that money is merely an instrument for exchanging true wealth—the actual goods and services that satisfy human wants. This distinction was the first step in transforming economics from a study of treasure into a study of human well-being. With this foundational concept established, our journey into Mill’s vision of social and economic history can begin.