Diamond's 'Hamlet Test' Falters: A Flawed Study of Individual Impact

Jared Diamond, the author of Guns, Germs and Steel, has built a career on sweeping historical arguments. His new book introduces what he calls the "Hamlet test"—a framework for determining whether famous individuals truly shaped history or whether others could have done the same work just as well. The test is simple enough: if you can identify contemporaries who produced inferior work, then the original figure must have been uniquely irreplaceable. Shakespeare, Diamond argues, passes this test decisively. His Elizabethan rivals—Ben Jonson, Christopher Marlowe, John Webster—wrote competent plays, but nothing approaching the genius of Hamlet or King Lear. Therefore, Diamond concludes with confidence, no other Elizabethan could have written a masterpiece like Hamlet if Shakespeare had not.

There is a substantial problem with this reasoning, one that literary scholars have long understood. Christopher Marlowe was stabbed to death in a Deptford pub in 1593 at age twenty-nine. By that point, he had already written Doctor Faustus and Tamburlaine—works of genuine power—and had likely collaborated with the younger Shakespeare on the Henry VI plays. Shakespeare did not begin composing his major tragedies, including Hamlet, until a decade after Marlowe's death. The historical record suggests that had Marlowe lived another ten years, he might well have matched or surpassed Shakespeare's achievements. Scholars of literature widely agree that Shakespeare's masterpieces were themselves shaped by Marlowe's outsized influence on the theatrical world. Diamond, however, shows little interest in what literary scholars actually think. He is confident in his intellectual novelty and proceeds as though the question of individual impact has never been rigorously examined before.

The book does offer some persuasive examples. Seretse Khama, the first president of independent Botswana, appears to pass the Hamlet test: he secured democracy by stripping power from traditional chiefs, and only he could have done so because he was the most powerful chief himself. Later, Diamond notes that only wealthy Californians with substantial capital could have built the pomegranate-juice industry—a lesson that amounts to observing that expensive ventures require money. The reader will find moments of genuine insight scattered throughout, but also moments of obvious observation dressed up as discovery.

The book's real methodological strength lies in its use of "natural experiments"—statistical comparisons of similar historical events that allow researchers to isolate individual impact. Diamond draws on work by economists David Card and Alan Krueger, who studied fast-food restaurants on either side of a state line where New Jersey had raised its minimum wage while Pennsylvania had not. Their papers demonstrated that the wage increase led to higher employment, contradicting conventional economic theory. Similar analyses suggest that CEOs account for between six and twenty-nine percent of variation in company earnings, while sports coaches influence at most about thirty percent of a team's performance.

But natural experiments work best when measuring quantifiable outcomes—money, wins and losses. As Diamond moves into murkier territory, the method strains. One study he cites uses parking fines incurred by UN staff in New York as a proxy for their countries' political corruption. Another uses cousin marriage as a proxy for inbreeding-related lower intelligence, then correlates this with the territorial expansion of European monarchs over four centuries. The logical leaps multiply. Diamond also misrepresents evidence when it suits him. He cites a 2009 paper by Benjamin F. Jones and Benjamin A. Olken on assassinations and war to argue that the killing of Franz Ferdinand did not cause World War I. But the paper itself explicitly warns against that conclusion: Ferdinand was not included in their data because he was not technically the leader of the Austro-Hungarian empire. The paper's actual finding—that assassination can facilitate democratic transition in autocracies—goes unmentioned.

The book concludes by suggesting that quantitative social science methods alone can answer fundamental questions about historical causation. One question it raises is when military leaders most influence outcomes. Diamond might have consulted a military historian—Lawrence Freedman's Command, for instance—but he does not. From his vantage point, subject-matter experts in military affairs, literary history, and other specialized fields are simply invisible. The Hamlet test, meant to be a tool for rigorous thinking, instead becomes a way of dismissing expertise across multiple disciplines in favor of a single quantitative lens. The result is a book that mistakes novelty for insight and confidence for evidence.