No doubt the subject of many of Abe and Yak’s smoke-filled debates was neither tobacco nor cancer. It was that innocuous word “caused.” It wasn’t the first time that physicians confronted perplexing causal questions: some of the greatest milestones in medical history dealt with identifying causative agents. In the mid-1700s, James Lind had discovered that citrus fruits could prevent scurvy, and in the mid-1800s, John Snow had figured out that water contaminated with fecal matter caused cholera. (Later research identified a more specific causative agent in each case: vitamin C deficiency for
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