The Demon-Haunted World: Science as a Candle in the Dark

by Carl Sagan

Argumentation cannot suffice for the discovery of new work, since the subtlety of Nature is greater many times than the subtlety of argument. Control experiments are essential. If, for example, a new medicine is alleged to cure a disease 20 percent of the time, we must make sure that a control population, taking a dummy sugar pill which as far as the subjects know might be the new drug, does not also experience spontaneous remission of the disease 20 percent of the time. Variables must be separated. Suppose you’re seasick, and given both an acupressure bracelet and 50 milligrams of meclizine. You find the unpleasantness vanishes. What did it—the bracelet or the pill? You can tell only if you take the one without the other, next time you’re seasick. Now imagine that you’re not so dedicated to science as to be willing to be seasick. Then you won’t separate the variables. You’ll take both remedies again. You’ve achieved the desired practical result; further knowledge, you might say, is not worth the discomfort of attaining it. Often the experiment must be done “double-blind,” so that those hoping for a certain finding are not in the potentially compromising position of evaluating the results. In testing a new medicine, for example, you might want the physicians who determine which patients’ symptoms are relieved not to know which patients have been given the new drug. The knowledge might influence their decision, even if only unconsciously. Instead the list of those who exper...