In his classic essay “The Ethics of Belief,” mathematical and philosophical wunderkind W.K. Clifford (1845-1879) famously made rationality a branch of ethics. A belief is rational when we have discharged all of our epistemic duties in forming that belief and are thereby within our epistemic rights in holding it. Your epistemic duty is to carefully examine beliefs to retain only those that pass strict standards of belief-worthiness. It is always and everywhere wrong, Clifford tells us, to hold to a belief that has failed the test. To cling stubbornly to an idée fixe when the evidence is against it is to be derelict in one’s epistemic duties; it is a defiant assertion of irrationality.

Irrational beliefs can have dangerous consequences, and not just for the person who holds them. Clifford illustrates with the story of a ship owner who knows that his ship is old, leaky, and far overdue for overhaul and repairs. Yet he tells himself that the ship has survived many previous voyages and probably will make one more, so he irresponsibly dismisses his worries and books passage for many poor emigrants. In mid-ocean the ship breaks up in a storm and the hapless emigrants drown. The owner collects the insurance and tells no tales. Irrationality is a moral failure as well as an intellectual one.

I agree with Clifford (and Aristotle) that rationality is a branch of ethics. The cultivation and practice of both the intellectual and the social virtues is necessary for human flourishing, and such flourishing is the final telos of moral actions. Human well-being depends just as crucially upon sound thinking and judgment as it does upon such virtues as justice, generosity, courage, and self-control. Therefore, as a personal virtue, we should eschew irrationality, and, further, exercise social responsibility by not tolerating its promulgation by crackpots, fanatics, shills, hucksters, demagogues, conspiracy theorists, and ideologues.

While I agree with Clifford’s approach, I can only sigh wistfully for the heady days of nineteenth century rationalism, when being rational seemed to be basically a matter of sturdy Victorian self-discipline in discharging our epistemic duties. We now know that it is much harder to be rational than Clifford (or Aristotle) could have imagined. It is not merely that we are now on the far side of the historical chasm of the twentieth century when optimism seemed drowned in an ocean of blood, and science generated horrors of mass destruction. (n.b., Steven Pinker eloquently argues in his recent tour de force, Enlightenment Now, that optimism is abundantly justified and that science is the driver of progress). We now know how difficult rationality is because we have learned so much more about ourselves.

As Michael Shermer explains in The Believing Brain, our brains are belief-forming engines. We emphatically do not do as Hume and other philosophers earnestly exhorted. We do not look at the evidence and then proportion our belief to its strength. On the contrary, we leap to conclusions, generating beliefs promiscuously and prolifically, and then look for evidence to support our beliefs while ignoring contrary evidence. In other words, we are all suckers for confirmation bias, and you are only fooling yourself if you say that you are not. Cognitive scientists such as Daniel Kahneman and Amos Tversky have shown the confirmation bias is only the tip of the iceberg when it comes to the ways that we spontaneously fool ourselves, even, perversely, when we think we are being most rational. Further, we are all subject to groupthink and to various belief-shaping emotional and social influences—as indeed Francis Bacon realized long ago with his “idols of the mind.”

Such disturbing findings are reinforced by the research of social psychologists such as Jonathan Haidt, as presented in his eye-opening book The Righteous Mind. Haidt says that reason, far from being an objective arbiter between competing claims, instead serves as our inner lawyer, advocating for beliefs that have been predetermined in ways that are anything but classically “rational.” When NFL players kneel during the national anthem, why do you support or condemn them? Whatever arguments you give for either side, the evidence is clear: Your reaction is not determined by the reasons you give. Quite the reverse. Your reasons are just the brief your inner lawyer uses to justify your spontaneous emotional response. If you say that those other people are being emotional while you are just being logical, then you are fooling yourself once again and thereby compounding the problem.

So, are we condemned to irrationality? Are we inevitably suckers for confirmation bias and the many other cognitive traps and illusions that beset the human mind? Is there no higher function of reason than to invent excuses for the emotions? Actually, things are not quite that bad. Scientific and scholarly methods were devised because people are not rational. The rationality of science is due to the methods of science and to the development of professional communities that enforce a culture of objective practice and collective skepticism. Scientists recognize that the individual scientist is a passionate believer, often with a sizable ego, and just as subject to cognitive bias and the blandishments of ideology and vested interest as anyone else. This is why methods, like the double-blind tests of the efficacy of new drugs, were devised to insulate against bias, wishful thinking, and distortion.

What, though, about questions like theism vs. atheism, that do not seem to be settled by a straightforward application of logic or scientific method? Now, zealots on either side will demur and insist that their position is obviously compelling, and that the other side is plainly sunk in dogma, confusion, and self-delusion. Some fervent atheists hold that all religious believers are gullible or dishonest and that a whiff of science easily disperses the flimsy, antiquated, and superstitious claims of religion. Likewise, hardcore religious apologists have written many books adducing supposedly overwhelming evidence that demands the verdict that their own religion is the true one.* Others, including some who should know better, say that atheists refuse to believe so that they can indulge in sexual sin without guilt.** Such extreme and simplistic views are sad and silly and based on nothing but ignorance and hostility.

As always, the actual situation is much more complex than ax-grinders think. The late, great John Hick, perhaps the foremost recent philosopher of religion, argued that the universe is religiously “ambiguous.” That is, as the universe presents itself to us, we may reasonably construe it as “physics all the way down,” that is, that all things are explicable in terms of physical entities, laws, and forces, and reality contains no transcendent or supernatural aspect. This is the naturalistic view most atheists endorse. On the other hand, says Hick, given the totality of human experience, it is just as reasonable to affirm the existence of a transcendent reality. After all, very many human beings across cultures and across time have had profound and compelling experiences of the sacred or numinous and an undeniable sense of being in the presence of the divine. Hick argues that each interpretation, the naturalistic and the religious, is compatible with the evidence and cannot be condemned as irrational.

Being a rational atheist or believer (or a rational liberal or conservative, for that matter) is not a matter of how you formed that commitment, but how you live it. We have no choice but to judge things as they honestly seem to us, but, informed by studies such as Haidt’s, we know that how things seem to us is not a function of a fictitious ideal rationality. Where rationality comes in is in the self-critical nature of our commitments and in the quality of the arguments and evidence we employ in defense of our positions. To listen seriously and respectfully to the most articulate and intelligent persons on the other side, and to defend your views with the best evidence and most logical arguments you can find is to be as rational an animal as humans can be.

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*I talked to one well-known religious writer that told me he had written eighteen books on the resurrection of Jesus. This was some years ago, and it is probably more now. Wow. Honestly, if I did not feel that I had nailed something down in two or three books I would turn to something else.

**Oh yeah. Nothing appeals to attractive young women more than carrying a copy of Hume’s Dialogues Concerning Natural Religion under your arm. An irresistible pick-up line is, “Hey, babe, wanna come by my place for a heavy discussion of the evidential problem of evil?”