One might think that success in science requires seeing through your own bullshit as well as the bullshit of others. But in my experience, this quality is quite rare. I’ve met only a few scientists who seem immune to wishful thinking. Francis Crick was one. Steven Weinberg is another.

Weinberg won a Nobel Prize in 1979 for helping to show that electromagnetism and the weak nuclear force are different aspects of an underlying electroweak force. Weinberg is also a graceful writer, with a sophisticated grasp of history and philosophy. In his 1993 book Dreams of a Final Theory, he extolled particle physics as the culmination of “the ancient search for those principles that cannot be explained in terms of deeper principles.” He predicted that “the convergence of explanations down to simpler and simpler principles will eventually come to an end in a final theory.”

I interviewed Weinberg in 1995 at the University of Texas (of all places). In my recently republished book The End of Science, I stated that with his “crabapple cheeks, vaguely Asian eyes and silver hair still tinged with red, Weinberg resembles an elf, a large, dignified elf. He would make an excellent Oberon, King of the Fairies in A Midsummer Night’s Dream.” In the interview, Weinberg was brutally candid, rejecting the idea that a final theory would render reality meaningful or even intelligible to non-scientists. I wrote:

Weinberg had little patience for those who suggest that a final theory will reveal the purpose of the universe, or “the mind of God,” as Stephen Hawking once put it. Quite the contrary: Weinberg hoped that a final theory would eliminate the wishful thinking, mysticism and superstition that pervades much of human thought, and even physics.

“As long as we don’t know the fundamental rules,” he said, “we can hope that we’ll find something like a concern for human beings, say, or some guiding divine plan built into the fundamental rules. But when we find out that the fundamental rules of quantum mechanics and some symmetry principles are very impersonal and cold, then it’ll have a very demystifying effect. At least that’s what I’d like to see.”

His face hardening, Weinberg continued: “I certainly would not disagree with people who say that physics in my style or the Newtonian style has produced a certain disenchantment. But if that’s the way the world is, it’s better we find out. I see it as part of the growing up of our species, just like the child finding out there is no tooth fairy. It’s better to find out there is no tooth fairy, even though a world with tooth fairies in it is somehow more delightful.”

Weinberg just produced his 12th book, To Explain the World. The New York Times calls it “a rich, meaningful tale about the emergence of science,” in which Weinberg chides science historians such as Thomas Kuhn for distrusting “overarching narratives and notions of progress.” After reading the book–a history of scientific discovery by a major discoverer–I reached out to Weinberg with some questions:

Horgan: In 1995 you told me that it’s a “terrible time for particle physics.” Are you feeling any better about your field now? Are there any particular advances that give you hope?

Weinberg: I’m not much more cheerful. The Standard Model is working wonderfully, but still has apparently arbitrary features like mass ratios that we don’t understand. We have several bits of evidence of physics beyond the standard model–neutrino masses, dark matter, dark energy, and the very existence of gravitation–but none of these have provided the clue we need to go beyond the Standard Model.

Horgan: Richard Feynman wrote in 1965: “The age in which we live is the age in which we are discovering the fundamental laws of nature, and that day will never come again.” [See Clarification on date below.] Do you ever think that the golden age of discovery in physics, in which you played a crucial part, is over?

Weinberg: I’m surprised that Feynman would have been so optimistic in 1965. That was pretty much of a low point in particle theory. The great success of Feynman and a few others in applying quantum field theory to electrodynamics had not yet been extended to the weak and strong interactions, and influential theorists were even seriously considering abandoning the search for a field theory of these interactions. Since then we have been in a sort of golden age, and although progress seems to have stalled lately, I can’t imagine that the good times are over yet.

Horgan: Do you still believe in the attainability of a “final theory” of physics, one that ends what you called “the ancient search for those principles that cannot be explained in terms of deeper principles”?

Weinberg: I still expect there to be a final theory, but I’m less confident that humans will discover it in this century.

Horgan: In your new book, To Explain the World, you write that “scientific theories cannot be deduced by purely mathematical reasoning.” Doesn’t that principle apply to string theory? At what point, if ever, should string theory be abandoned as a dead end?

Weinberg: String theory may be inspired by mathematical reasoning, but not deduced, and certainly not confirmed.

Horgan: Do you see any viable alternatives to string theory?

Weinberg: I know of one possible alternative, known as asymptotic safety, according to which although there are an infinite number of interaction types, their interaction strengths are not arbitrary, but fixed by the condition that at very high energy these interaction strengths (suitably defined) all approach finite constants. So far this has passed some mathematical tests, but has not led to any specific theory.

Horgan: Will physics ever explain why there is something rather than nothing? Is it possible that science’s final answer to “Why?” will be “Because”?

Weinberg: First question: No. Second: Maybe.

Horgan: Paul Steinhardt has argued that multiverse theories, because they are not falsifiable, are not scientific. Comment?

Weinberg: I don’t agree. First of all, this business of falsifiability is a silly criterion imposed on physical science by Karl Popper, who was looking for some way of discrediting Marxism and psychoanalysis. Our most important theories, like Newtonian mechanics and quantum mechanics, are not falsifiable, because they do not make predictions by themselves, but provide general frameworks for more specific theories, which do make predictions. Further, if we find some future theory that does make successful predictions about a lot of things, which turn out to be true rather than false, and if that theory also predicts the existence of a multiverse, then we should take that prediction seriously even though it can’t be tested directly.

Horgan: Can you explain to me why anyone takes the anthropic principle seriously?

Weinberg: In a sense, almost everyone takes the anthropic principle seriously. Why is the Earth in the narrow zone of distance from the Sun in which water on its surface is liquid? The answer is that we live in a multiplanet universe, in which there are so many planets that some small fraction (even in a single galaxy) are likely to have liquid water, and it is only on such planets that scientists who worry about such things could have evolved. We don’t know if this sort of reasoning is applicable to the constants of nature, but if we are in a multiverse in which what are now called the constants of nature take different values in different big bangs, then the anthropic principle will be just common sense. If not, not.

Horgan: Will further research help dispel the paradoxes of quantum mechanics, or might reality in some sense always be unintelligible?

Weinberg: I think our best hope is to find some successor theory, to which quantum mechanics as we now know it is only a good approximation.

Horgan: Some physicists, notably Roger Penrose, have proposed that physics might be the key to solving the riddle of consciousness and the mind-body problem. Comment?

Weinberg: I doubt it.

Horgan: Stephen Hawking (in The Grand Design) argues that “free will is an illusion.” Apparently Einstein was also a free will doubter. What about you?

Weinberg: The only meaning I can give to free will is that we sometimes do things because we decide to do them. What difference does it make if those decisions can be traced to processes in the brain of which we are not conscious?

Horgan: You once wrote that “sometimes nature seems more beautiful than strictly necessary.” Do you ever doubt your atheism? Do you sympathize with the aggressive stance that some modern scientists have taken against religion?

Weinberg: I don’t entertain serious doubts about the non-existence of the supernatural. I sympathize and agree with some scientists’ anti-religious stance, but I myself have largely given up on such missionary work.

Horgan: Philosopher John Gray and psychologist Steven Pinker have been arguing in The Guardian about whether humanity has achieved moral progress. What do you think? Science aside, how are you feeling about humanity’s future?

Weinberg: In my lifetime there have been instances of evil that at least equal the worst of former times, but I still think there has been moral progress. For instance, there still exists slavery here and there, but now no one will admit and defend it. About the future, my views are old-fashioned. I think the greatest threat to humanity is the enormous arsenal of nuclear weapons maintained by Russia and the U.S.

Horgan: Have you seen any reasonable plan for ridding the world of nuclear weapons?

Weinberg: Given the possibilities of cheating, I can’t think of any plan for eliminating nuclear weapons altogether. But Russia and the U.S. could certainly agree to reduce their arsenals tenfold without endangering their deterrent capabilities.

Further Reading:

See my Q&As with physicists George Ellis, Carlo Rovelli, Edward Witten, Garrett Lisi, Paul Steinhardt and Lee Smolin.

Was I Wrong about ‘The End of Science’?”

If You Want More Higgs Hype, Don’t Read This Column.”

Cosmic Clowning: Stephen Hawking’s “new” theory of everything is the same old CRAP.”

Is speculation in multiverses as immoral as speculation in subprime mortgages?”

Clarification: Feynman made this remark about the “golden age” in The Character of Physical Law, originally published by the BBC in 1965 and based on lectures that Feynman gave at Cornell in 1964, according to Wikipedia.

Photo credit: Larry D. Moore, via Wikipedia.