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

The first is that the world is intelligible. The phenomena we experience may be explained by principles that are deeper than the phenomena themselves. That’s why scientists laugh at the Theory of the Brontosaurus from the dinosaur expert on Monty Python’s Flying Circus: “All brontosauruses are thin at one end, much much thicker in the middle, and then thin again at the far end”—the “theory” is just a description of how things are, not an explanation of why they are the way they are. The principles making up an explanation may in turn be explained by still deeper principles, and so on. (As David Deutsch put it, “We are always at the beginning of infinity.”) In making sense of our world, there should be few occasions on which we are forced to concede, “It just is” or “It’s magic” or “Because I said so.” The commitment to intelligibility is not a matter of raw faith, but progressively validates itself as more of the world becomes explicable in scientific terms. The processes of life, for example, used to be attributed to a mysterious élan vital; now we know they are powered by chemical and physical reactions among complex molecules.

Demonizers of scientism often confuse intelligibility with a sin called reductionism, the analysis of a complex system into simpler elements, or, according to the accusation, nothing but simpler elements. In fact, to explain a complex happening in terms of deeper principles is not to discard its richness. Patterns emerge at one level of analysis that are not reducible to their components at a lower level. Though World War I consisted of matter in motion, no one would try to explain World War I in the language of physics, chemistry, and biology as opposed to the more perspicuous language of the perceptions and goals of leaders in 1914 Europe. At the same time, a curious person can legitimately ask why human minds are apt to have such perceptions and goals, including the tribalism, overconfidence, mutual fear, and culture of honor that fell into a deadly combination at that historical moment.

The second ideal is that we must allow the world to tell us whether our ideas about it are correct. The traditional causes of belief—faith, revelation, dogma, authority, charisma, conventional wisdom, hermeneutic parsing of texts, the glow of subjective certainty—are generators of error, and should be dismissed as sources of knowledge. Instead our beliefs about empirical propositions should be calibrated by their fit to the world. When scientists are pressed to explain how they do this, they usually reach for Karl Popper’s model of conjecture and refutation, in which a scientific theory may be falsified by empirical tests but is never confirmed. In reality, science doesn’t much look like skeet shooting, with a succession of hypotheses launched into the air like clay pigeons and shot to smithereens. It looks more like Bayesian reasoning (the logic used by the superforecasters we met in the preceding chapter). A theory is granted a prior degree of credence, based on its consistency with everything else we know. That level of credence is then incremented or decremented according to how likely an empirical observation would be if the theory is true, compared with how likely it would be if the theory is false.¹⁹ Regardless of whether Popper or Bayes has the better account, a scientist’s degree of belief in a theory depends on its consistency with empirical evidence. Any movement that calls itself “scientific” but fails to nurture opportunities for the testing of its own beliefs (most obviously when it murders or imprisons the people who disagree with it) is not a scientific movement.

Many people are willing to credit science with giving us handy drugs and gadgets and even with explaining how physical stuff works. But they draw the line at what truly matters to us as human beings: the deep questions about who we are, where we came from, and how we define the meaning and purpose of our lives. That is the traditional territory of religion, and its defenders tend to be the most excitable critics of scientism. They are apt to endorse the partition plan proposed by the paleontologist and science writer Stephen Jay Gould in his book Rocks of Ages, according to which the proper concerns of science and religion belong to “non-overlapping magisteria.” Science gets the empirical universe; religion gets the questions of morality, meaning, and value.

But this entente unravels as soon as you begin to examine it. The moral worldview of any scientifically literate person—one who is not blinkered by fundamentalism—requires a clean break from religious conceptions of meaning and value.