The Believing Brain - Michael Shermer [183]
When both the Haitians and Dominicans gained their independence in the nineteenth century, another comparative difference unfolded. Haitian slave revolts were violent and Napoléon’s intervention to try to restore order resulted in the Haitians’ deep distrust of Europeans. They wanted nothing to do with future trade and investments, imports and exports, or immigration and emigration, and so they did not benefit economically from these and other factors. By contrast, Dominican independence was relatively nonviolent, and it shuttled back and forth for decades between independence and control by Spain, which in 1865 decided that it did not want the territory. Throughout this period the Dominicans spoke Spanish, developed exports, traded with European countries, and attracted European investors and a diverse immigrant population of Germans, Italians, Lebanese, and Austrians, who helped build a vibrant economy. Both countries succumbed to the power of evil dictators in the mid-twentieth century. Rafael Trujillo’s control of the Dominican Republic involved considerable economic growth because of his desire to personally enrich himself, and this led to a vibrant export industry (most of which he owned); scientists and foresters were imported to help preserve the forests for Trujillo’s personal use and profiteering through his logging companies. Haiti’s dictator François “Papa Doc” Duvalier did none of this and instead further isolated the Haitians from the rest of the world.
Employing the comparison method with such natural experiments of history is no different from what sociologists and economists do in comparing natural experiments of society today. We cannot intentionally impoverish one group of people and then observe if their health, education, and crime rates change. But we can look around and find pockets of impoverished people in inner cities and then measure various factors and compare those to other socioeconomic classes. The process is as rigorous a scientific methodology as any to be found in the experimental sciences. Once an inferential or historical science is well established through the accumulation of positive evidence, it becomes a testable science.
Science and the Principle of Positive Evidence
The convergence of evidence method and the comparison method are routinely used by paleontologists and evolutionary biologists to test hypotheses about evolution, and the results accumulate in the form of positive evidence in support of the theory of evolution. For creationists to disprove evolution, they would need to unravel all these independent lines of evidence as well as construct a rival theory that can explain them better than the theory of evolution. They haven’t, and instead employ only negative evidence in the form of “if evolutionary biologists cannot present a natural explanation of X, then a supernatural explanation of X must be true.” Not so. The principle of positive evidence states that you must have positive evidence in favor of your theory and not just negative evidence against rival theories.
The principle of positive evidence applies to all claims. Skeptics are like people from Missouri, the Show-Me state. Show me positive evidence for your claim. Show me a Sasquatch body. Show me the archaeological artifacts from Atlantis. Show me a Ouija board that spells words with securely blindfolded participants. Show me a Nostradamus quatrain that predicted World War II or 9/11 before (not after) the fact (postdictions don’t count in science because of the hindsight bias). Show me the evidence that alternative medicines work better