In Chapter 4 Sachs discusses five lessons he applied from clinical medicine to economics. According to his five tenets of “clinical economics,” (1) economies are complex systems, like the human body; (2) these systems each require differential diagnosis, as there is no one-size-fits-all approach to economics; (3) economists must consider an economy’s supportive relationships, like trade partners, just as doctors must consult with a patient’s family; (4) economists should monitor and evaluate economies just as physicians monitor their patients; and (5) like doctors, economists should adhere to norms and standards, such as working toward the greater economic good rather than self-interest.

In medicine, differential diagnosis is the process by which doctors identify one disease from others that present with similar symptoms. Sachs applies differential diagnosis to economics in Chapter 4, where he asserts that there is no one-size-fits-all cure for extreme poverty, then builds upon the idea in subsequent chapters. He believes that economists must examine each economy on a case-by-case basis, to identify the specific problems that require attention in a given country.

The Age of Enlightenment was a philosophical movement spanning the 17th and 18th centuries. Enlightenment-era thinkers believed rational thought, republican government, liberty, and science were crucial to social progress.