Enlightenment Now: The Case for Reason, Science, Humanism, and Progress

After a year the average test score at a private high school increased by thirty points. Which explanation for this change is most analogous to Darwin’s explanation for the adaptation of species?

A. The school no longer admitted children of wealthy alumni unless they met the same standards as everyone else.

B. Since the last test, each returning student had grown more knowledgeable.

The correct answers are B and A. The psychologist Andrew Shtulman gave high school and university students a battery of questions like this which probed for a deep understanding of the theory of natural selection, in particular the key idea that evolution consists of changes in the proportion of a population with adaptive traits rather than a transformation of the population so that its traits would be more adaptive. He found no correlation between performance on the test and a belief that natural selection explains the origin of humans. People can believe in evolution without understanding it, and vice versa.¹⁰ In the 1980s several biologists got burned when they accepted invitations to debate creationists who turned out to be not Bible-thumping yokels but well-briefed litigators who cited cutting-edge research to sow uncertainty as to whether the science was complete.

Professing a belief in evolution is not a gift of scientific literacy, but an affirmation of loyalty to a liberal secular subculture as opposed to a conservative religious one. In 2010 the National Science Foundation dropped the following item from its test of scientific literacy: “Human beings, as we know them today, developed from earlier species of animals.” The reason for that change was not, as scientists howled, because the NSF had given in to creationist pressure to bowdlerize evolution from the scientific canon. It was that the correlation between performance on that item and on every other item on the test (such as “An electron is smaller than an atom” and “Antibiotics kill viruses”) was so low that it was taking up space in the test that could go to more diagnostic items. The item, in other words, was effectively a test of religiosity rather than scientific literacy.¹¹ When the item was prefaced with “According to the theory of evolution,” so that scientific understanding was divorced from cultural allegiance, religious and nonreligious test-takers responded the same.¹²

Or consider these questions:

Climate scientists believe that if the North Pole icecap melted as a result of human-caused global warming, global sea levels would rise. True or False?

What gas do most scientists believe causes temperatures in the atmosphere to rise? Is it carbon dioxide, hydrogen, helium, or radon?

Climate scientists believe that human-caused global warming will increase the risk of skin cancer in human beings. True or False?

The answer to the first question is “false”; if it were true, your glass of Coke would overflow as the ice cubes melted. It’s icecaps on land, such as Greenland and Antarctica, that raise sea levels when they melt. Believers in human-made climate change scored no better on tests of climate science, or of science literacy in general, than deniers. Many believers think, for example, that global warming is caused by a hole in the ozone layer and that it can be mitigated by cleaning up toxic waste dumps.¹³ What predicts the denial of human-made climate change is not scientific illiteracy but political ideology. In 2015, 10 percent of conservative Republicans agreed that the Earth is getting warmer because of human activity (57 percent denied that the Earth is getting warmer at all), compared with 36 percent of moderate Republicans, 53 percent of Independents, 63 percent of moderate Democrats, and 78 percent of liberal Democrats.¹⁴

In a revolutionary analysis of reason in the public sphere, the legal scholar Dan Kahan has argued that certain beliefs become symbols of cultural allegiance. People affirm or deny these beliefs to express not what they know but who they are.¹⁵ We all identify with particular tribes or subcultures, each of which embraces a creed on what makes for a good life and how society should run its affairs. These creeds tend to vary along two dimensions. One contrasts a right-wing comfort with natural hierarchy with a left-wing preference for forced egalitarianism (measured by agreement with statements like “We need to dramatically reduce inequalities between the rich and the poor, whites and people of color, and men and women”). The other is a libertarian affinity to individualism versus a communitarian or authoritarian affinity to solidarity (measured by agreement with statements like “Government should put limits on the choices individuals can make so they don’t get in the way of what’s good for society”). A given belief, depending on how it is framed and who endorses it, can become a touchstone, password, motto, shibboleth, sacred value, or oath of allegiance to one of these tribes. As Kahan and his collaborators explain: