Manhattan, April 8, 2024. Scientists often use the terms real, reality and realism in tendentious, question-begging ways. When you say, This is real or This is reality, you are implicitly saying, This is what really matters.

Take, for example, What Is Real? The Unfinished Quest for the Meaning of Quantum Physics. The book’s title implies that physics represents knowledge-seeking at its most profound. So does physicists’ ridiculous claim that a unified theory of gravity, electromagnetism and the nuclear forces would be a theory of everything.

Such a theory would have nothing to say about death, love, fear, war, justice, beauty and other deep, defining features of the human condition. Fictions like War and Peace, The Golden Bowl and Ulysses tell us far more about our messy, painful human reality than physics ever will. Theory of everything? Give me a break.

Okay, with that off my chest, I’m ready to make the case for realism. I don’t mean realism in the colloquial sense, meaning hardheadedness. No, I mean realism in the fancy philosophical sense, which equates reality with the material world, objective knowledge of which we can discover through science.

This position is sometimes called scientific realism, or, by smug postmodernists, naïve realism. Philosophers will probably object to my definition of realism, but philosophers object to any definition, that’s what philosophers do. In this column I’ll spell out why, in spite of my habitual doubts about realism, I consider myself a realist.

When you present the realist position to non-philosophers, they often react with some equivalent of: Duh, what idiot doubts that there is a real world out there and that science discovers it? Actually, many people object to realism, and some are quite clever.

Antirealism takes many forms. These include postmodernism, which denies that absolute truth is attainable and brackets “scientific knowledge” in scare quotes; idealism, which says mind is at least as fundamental as matter; and the simulation hypothesis, the idea that we’re living in a virtual reality, like The Matrix. The common thread is that objective, physical “reality” is illusory or unknowable.

My polemic The End of Science has a realist premise: Our modern scientific map of the world is largely true and, given science’s limits, unlikely to undergo significant revisions. We have discovered electrons, protons, elements, DNA, bacteria, viruses, neurons, gravity and galaxies. These things are real, they exist whether or not we believe in them, and only fools, mystics and philosophers like Thomas Kuhn would dare claim otherwise.

My end-of-science prophesy has held up reasonably well. But my recent efforts to learn quantum mechanics with the math have me second-guessing my realism and wondering whether it really is naïve.

In The End of Science, I say particle physics “rests on the firm foundation of quantum mechanics.” Firm foundation? Ha! Experts have been squabbling over what quantum mechanics means for a century now without reaching any agreement.

Some quantum interpretations challenge the bedrock realist assumption that the world is objectively knowable. In his marvelous little book Q Is for Quantum, physicist Terry Rudolph says quantum mechanics makes it hard to sustain the “naïve realistic belief” that the universe “has physical properties of some form independent of my concerns.”

I’ve come to doubt the realist claim that mathematical models mirror nature. I just finished Why Does Math Work If It’s Not Real? by mathematician Dragan Radulovic. He extols the power of mathematics to capture many features of nature, from the orbits of planets to the swerve of an electron. On the other hand, Radulovic acknowledges, mathematics is riddled with paradoxes and contradictions, and the connection between mathematics and reality is mysterious, and tenuous.

The Schrödinger equation employs so-called imaginary numbers, multiples of the square root of –1.  My efforts to understand how imaginary numbers map onto the real world have led me, perversely, in the opposite direction. Instead of imaginary numbers becoming more real, real numbers, which fall on a line extending from positive to negative infinity, seem less real.

In “Confusions Regarding Quantum Mechanics,” physicist Gerard ‘t Hooft calls real numbers “artificial,” manmade” and “arbitrary,” suggesting that they give us a sense of false, unwarranted precision. Physicist Nicolas Gisin, similarly, has suggested that “real number” might be an oxymoron. Maybe we should see mathematical models as calculating devices that predict experimental outcomes but have an obscure relation to reality, whatever that is.

Quantum mechanics also undermines materialism, the notion that matter is the fundamental stuff of reality. Quantum theorist John Wheeler proposes that we live in a “participatory” universe, in which our questions and observations define the universe and even bring it into existence. My psychedelic sojourns make me sympathetic toward this mind-centric, idealist view. One trip left me wondering whether our “reality” is actually virtual, the fever dream of an insane God.

And yet. Although my realism often wobbles, I remain a realist, for several reasons. One is that antirealist conjectures--like the simulation hypothesis and my own psychedelic theology—strike me as immoral. When antirealists suggest that our world is an illusion, they trivialize human suffering and injustice, and they undermine our motives for making the world a better place.

I also get squeamish when postmodernists insist that scientific “knowledge” reflects our subjective fears, desires, biases. Of course, there is some truth to this assertion. Scientists’ lust for fame, glory and money can corrupt them. And as I emphasize in Mind-Body Problems, we can’t escape our subjectivity when we try to understand ourselves.

But taken too far, postmodernism can undercut efforts to analyze and solve all-too-real problems like climate change, economic inequality and war. Even the most radical postmodernists must acknowledge that science works. We might not know what quantum mechanics means, but the theory has spawned countless applications, including, most recently, quantum computers.

So, I keep clinging to my version of realism, which I like to think is practical and ethical rather than naïve. My realism acknowledges science’s fallibility as well as its power. My realism holds that nothing matters more, nothing is more real, than human suffering, which science, in spite of its flaws, can help alleviate.

Like democracy, realism is flawed, but it beats the alternatives.

Further Reading:

I wrestle with realism in my two free, online books Mind-Body Problems and My Quantum Experiment. And here are some columns related to realism:

Is Derealization a Delusion or Insight?

The Weirdness of Weirdness

Conservation of Ignorance: A New Law of Nature

Self-Doubt Is My Superpower

Quantum Mechanics, the Chinese Room and the Limits of Understanding

Self-plagiarism alert: This is an updated, streamlined and vastly improved version of a paywalled column I wrote for ScientificAmerican.com.