For much of human history, we relied on authority figures to tell us what is true and just, based on the presumed wisdom of the leaders of our tribe, government, church, etc. The break from this authoritarian and anti-progressive tradition began with the boldness of ancient philosophers such as Aristotle, but truly accelerated in the 16th and 17th centuries with revolutionary thinkers such as Francis Bacon, Galileo Galilei, and Isaac Newton. These leaders helped shape the “Enlightenment,” an intellectual movement that advocated for individual liberty, religious tolerance, and a rebellion against authority with regard to knowledge.

What emerged was an enduring tradition of criticism and of seeking good explanations in an attempt to understand the world—a tradition we call science, which has lead us to remarkable progress in the last ~400 years.

The best method of criticism

Thanks to the brilliant yet underappreciated 20th-century philosopher Karl Popper, we have a full-fledged theory of knowledge creation—the theory of critical rationalism. We do not obtain knowledge by the charity of some authoritative source passing the “truth” down to us. In fact, there is no such authoritative source. All knowledge is fallible.

Instead, we create knowledge through an iterative process of trial-and-error. First, we conjecture (guess) tentative solutions to our problems. Then, we criticize those theories, attempting to disprove them. We discard theories that are refuted and try to improve on them. If we’re able to replace a refuted theory with a better one, then we can tentatively deem our efforts to have made progress.¹

“What we should do, I suggest, is to give up the idea of ultimate sources of knowledge, and admit that all knowledge is human; that it is mixed with our errors, our prejudices, our dreams, and our hopes; that all we can do is grope for the truth even though it may be beyond our reach.”

Karl Popper, Conjectures and Refutations (1963, pg. 39)

Criticism is the step in this process that helps us root out wrongness. The characteristic (though not the only) method of criticizing candidate theories is through experimental testing—through the scientific method.

After we postulate a theory, we perform a crucial experiment, one for which the old theory predicts one observable outcome and the new theory another. We eliminate the theory whose predictions turn out to be false.²

For instance, our “new” theory could be that a particular dieting method is effective for losing weight. Our “old” theory could be that the dieting method does nothing (the dreaded “null hypothesis”). We would run an experiment and compare the results of a randomly selected group who used the method to a randomly selected “control” group who didn’t. If the treatment group’s results aren’t sufficiently better than the control group’s, then we reject the theory that the dieting method is effective.

The scientific method embraces objectivity, curiosity, careful observation, fierce skepticism, analytical rigor, and continuous improvement.

Good vs. bad explanations

Critically, our scientific theories (guesses) must meet two key criteria. First of all, they must be falsifiable (or testable)—that is, they must be capable of conflicting with possible observations. If no conceivable event would contradict the theory, it cannot be scientific.³

As an example, consider the hypothesis “Scorpios are creative and loyal.” Would a single uncreative, untrustworthy person born between October 23 and November 21 refute the theory? Would 1,000? How uncreative or untrustworthy would they have to be, and how would we know? Unfortunately, the conditions under which these kinds of astrological predictions would be false are never mentioned; therefore, they cannot be scientific (sorry, astrologers…).

Second, our scientific theories must be what physicist David Deutsch calls “good explanations,” those that are hard to vary while still accounting for what they purport to account for. When we can easily tweak our theories without changing their predictions, then testing them is almost useless for correcting their errors. We can toss these out immediately without experiment.⁴ Examples of easily variable explanations include assertions such as “The gods did it,” or “It appeared out of thin air,” or “Because I said so” (sorry, parents…). These kinds of claims are easily varied to explain, well, anything.

Why the world speaks English

Historians have long debated why the “scientific revolution” originated in the West, given that many technological and political innovations originated in the Indian, Islam, and (especially) Chinese empires. For centuries, the Chinese outperformed the Europeans in applying natural knowledge to solve human problems. But it was the emergence and proliferation of the scientific method across Western Europe in the 17th century that sparked the tradition of criticism and wave of innovation that has revolutionized human society. Why?

Our best theory attributes the West’s scientific supremacy to the structure of its knowledge creation practice—that is, to the scientific method. Despite enormous creativity in China, political battles and the Song emperors’ personal interests smothered the work of the early innovators. By contrast, in 1660, the English established the Royal Society of London, which openly shunned authority and embraced science as a path toward prosperity. The Royal Society inspired a generation of new scientists (including Isaac Newton) who would ultimately propel the English to a commanding lead in the scientific race.

“Nullius in verba” (Latin for “take nobody’s word for it”)

Royal Society of London motto (1660)

If the Chinese emperors had embraced a tradition of criticism, the scientific revolution might have occurred 500 years sooner. And the world might be speaking Chinese, instead of English.⁵

***

All knowledge is fallible. We have no authoritative source of “absolute truths.” But that is not what science is about. The real key to science is that our explanatory theories can be improved, both through the creation of new theories, and through criticism and testing of our existing theories—that is, through the scientific method.

The quest for good explanations, guided by a tradition of criticism and a rejection of authority over knowledge, is the source of all progress. It embodies the spirit of science and of the Enlightenment.⁶ For me, there is perhaps no more worthy calling!

1. Popper, K. (1963). Conjectures and Refutations. Routledge & Kegan Paul. 69-71.
2. Deutsch, D. (1997). The Fabric of Reality. Penguin Books. 6-7.
3. Popper, K. (1963). 48-51.
4. Deutsch, D. (2011). The Beginning of Infinity. Penguin Books. 22-26.
5. Bahcall, S. (2019). Loonshots. St. Martin’s Press. 248-257.
6. Deutsch, D. (2011). 8-9.