Chapter 6: “Exchanging” applies Chapter 3’s principles to economics in the same way Chapters 4 and 5 have applied these principles to language and natural science. Foucault argues that our modern analysis of economy—called “political economy”—did not exist in the Classical Age. Instead, they had analysis of wealth, which examined the link between signs of wealth and representation. The chapter is divided into eight parts.

In part one (“The Analysis of Wealth”), Foucault outlines the differences between political economy and analysis of wealth. Production and labor power, the basis of political economy, were not considered important factors to examine in the Classical Age. Instead, it is wealth itself and its symbols (gold, coins, etc.) that needed examining. The ideas of value, price, and how wealth circulated were all far more important than labor and production values.

In part two (“Money and Prices”), Foucault examines the Classical Age’s discourse on money and prices. Analysts of wealth were concerned with finding the best medium to use for money (silver versus gold, for example) and how to set prices in relation to the medium of money. The value of money was based on its ability to represent wealth and rarity.