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

by Steven Pinker

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...