This is the story of two drugs. The first, dexfenfluramine, was the active ingredient in the weight loss drug Redux. Although it was available in the U.S. and Canada for only about 18 months, it killed hundreds of people, and severely injured thousands more. The second is marijuana. Over the past several decades, tens of millions of people across North America have used this drug regularly. It has, as far as anybody knows, killed no one. Anyone interested in the politics of science should study the Food and Drug Administration's treatment of these two drugs. Redux was originally rejected for...