In the summer of 2020, “public-health experts” decided that racism is a public-health crisis comparable to the coronavirus pandemic. It was therefore, they claimed, within their purview to express public support for the Black Lives Matter protests following the murder of George Floyd and to argue that the benefits of such protests outweighed the increased risk of spreading the disease. Those supposed experts actually knew nothing about the likely effects of the protests. They made no concrete predictions about whether they would in any way ameliorate racism in America, just as Nature can make no concrete predictions about whether its political endorsements will actually help a preferred candidate without jeopardizing its other important goals. The political action was expressive, not evidence-based...