Physics, Earth & Space Icon Physics, Earth & Space

Question for Multiverse Theorists: To What Can Science Appeal if Not Evidence?

Denyse O'Leary

multiverse

Philosopher of religion Mary-Jane Rubenstein asks at Nautilus, “Why is the universe so well suited to our existence?” She answers herself:

The weakest answer is that it’s just a brute fact. If the constants of nature were any different, then we wouldn’t be here to ask why we’re here. The strongest answer verges on theism: The cosmological constant is so improbably small that a godlike fine-tuner must have fashioned it into existence.

She doesn’t like that  “strongest answer” at all. She suggests cosmic pantheism intertwined with the multiverse instead.

When evidence points people away from what they want to believe, they often respond by undermining the evidence. That strategy is particularly difficult in science. Readers may remember the slogan popularized nearly half a century ago by Carl Sagan, to discredit miracles: “Extraordinary claims require extraordinary evidence.” But that won’t work here. As David Deming writes at Philosophia, “Extraordinary evidence is not a separate category or type of evidence — it is an extraordinarily large number of observations.” Fine-tuning of our universe for life easily meets that standard.

Twelve hallmarks of good science theories, noted in Michael Keas’s recent summation at Synthese, are “evidential accuracy, causal adequacy, explanatory depth, internal consistency, internal coherence, universal coherence, beauty, simplicity, unification, durability, fruitfulness, and applicability… ”

The multiverse meets causal adequacy only by sacrificing evidential accuracy (voiding the significance of evidence altogether). It offers explanatory depth by voiding the value of consistency or coherence. It offers unification by voiding the meaning of applicability (the entities to which the concepts are to be applied may or may not exist and it does not matter whether they do). Multiverse theory is perhaps best seen as a bid for an alternative science. Its theories display quite different hallmarks from those of traditional good theories and it can only succeed by undermining those hallmarks.

The multiverse advocates’ project is not to undermine the evidence base as such. There just isn’t any evidence for a multiverse. Their project is rather to undermine the idea that evidence, as used in normal science, should matter in cosmology. String theory, we are told, is useful even if unconfirmed (Quanta). Supersymmetry is beautiful, lacking only supporting evidence (The Economist). The multiverse is a done deal anyway (ScienceBlogs).

It bears repeating: Advocates do not merely propose that we accept faulty evidence. They want us to abandon evidence as a key criterion for acceptance of their theory. Here are some strategies we encounter.

Questioning the importance of testability. Philosopher of science Massimo Pigliucci puts the question squarely at Aeon: Must science be testable, as it has been since the time of Galileo? “Are we on the verge of developing a whole new science, or is this going to be regarded by future historians as a temporary stalling of scientific progress?” Whatever, many now prefer  “non-empirical science.” If the new approach takes hold, the stall will hardly be temporary. For one thing, as Natalie Wolchover and Peter Byrne explain at Quanta, “Testing the multiverse hypothesis requires measuring whether our universe is statistically typical among the infinite variety of universes. But infinity does a number on statistics.” One outcome is that, even though string theory has routinely failed empirical tests, it remains a major branch of cosmology because its “mathematical insights continue to have an alluring pull” that might “unify physics.” But it does not appear set to unify physics around evidence.

Eliminating falsifiability as a criterion. Falsifiability, a principle developed by philosopher of science Karl Popper (1902–1994), offers this test: A theory is scientific if evidence could disprove it. If a theory is so general as to be consistent with any state of evidence or is constantly undergoing revision to deal with contrary evidence, it is not scientific. Popper was impressed by Einstein’s theories because evidence could disprove them, but didn’t. In 2014, cosmologists George Ellis and Joe Silk warned, citing Popper, that some of their colleagues have begun to argue explicitly that “if a theory is sufficiently elegant and explanatory, it need not be tested experimentally, breaking with centuries of philosophical tradition of defining scientific knowledge as empirical” (Nature). Theoretical physicist Carlo Rovelli agrees. When science writer John Horgan asked him, “Do multiverse theories and quantum gravity theories deserve to be taken seriously if they cannot be falsified?” he replied, “No” (Scientific American). But it is becoming clear that Popper defenders like Ellis, Silk, Horgan, and Rovelli are gradually being sidelined (along with Peter Woit and Sabine Hossenfelder) as questionable “Popperazi,” and even “falsifiability police,” on account of their concern that colleagues are succumbing to “wishful thinking.” Indeed, take away traditional science criteria and how do we even distinguish between wishful thinking and raw demands for public assent?

To accomplish the revolution, the new cosmologists must uproot longstanding principles like Occam’s razor. Scholastic philosopher William of Ockham (1285–1347/49) popularized the idea that elements that are not material to an explanation can be discarded. Jason Rosenhouse’s “done deal” multiverse, noted above, relies on an attack on the razor: “It is the people who claim there is only one universe who have some explaining to do. Multiverse proponents are simply saying that whatever created our universe, a quantum fluctuation or whatever, created other universes as well.” But that is like saying that whatever created horses created unicorns as well.

Some pretend not to understand (or perhaps genuinely do not understand) what Occam’s razor means. Harvard physics post-grad Tom Rudelius informs us at the Harvard Ichthus that Occam’s razor cannot shave off the multiverse because it “does not say that the simplest idea is usually the right one — it says that the simplest explanation is usually the right one.” Barry Arrington responds at Uncommon Descent:

Yes, the razor is often shaved down to the “simplest explanation is usually the right one,” but that is not the classical formulation, which speaks of multiplying  “entities” beyond necessity.

Now I ask you, is there any greater multiplication of entities than the multiverse?  If “infinite universes” does not multiply entities beyond necessity, it is hard to imagine what would.

Still, the idea is catching on. Recently, we learned that physicists can now explain quantum theory by discarding Occam’s razor. One struggles to think of anything that could not be explained that way.

Meanwhile, widespread questionable beliefs enable cosmology’s war on evidence by preventing sober evaluation of the issues, for example.

Theory in science arises from masses of evidence. The National Academy of Sciences says that the term “theory” “refers to a comprehensive explanation of some aspect of nature that is supported by a vast body of evidence.” If only that were true. String theory and the multiverse do not rely on evidence at all.

The Academy had directed its collective statement about “theory” noted above to evolution. Acceptance of specifically Darwinian evolution, promoted and defended as an article of faith, probably softened up the public to accept other science claims for which zeal has long since outrun evidence. The very language of Darwinism finds its way into undemonstrable cosmology. We are told that a “cosmic version of Darwinian natural selection could apply, in which the most common universes will be those most suitable for producing black holes” (Science Focus.) Elsewhere we learn that we need not consider such a multiverse if we will accept that the laws of nature evolve (Guardian). It’s challenging to contemplate the damage that would be done to our concept of the laws of nature if they were assumed to evolve, but never mind. We also hear that “’Survival of the fittest’ is bigger than just evolutionary biology,” it embraces quantum mechanics (Inverse Science). There is at least some evidence that explanatory value is becoming more valued in biology these days than defending Darwinism. In that case, Darwinian theorists may find current multiverse cosmology a more natural home. It feels right.

Science is inherently self-correcting. A more honest appraisal can be had from Douglas Allchin at the Minnesota Center for the Philosophy of Science:

First, some errors persist for decades, wholly undetected. Second, many errors seem corrected by independent happenstance, not by any methodical appraisal. Third, some errors have been “corrected” in a cascade of successive errors that did not effectively remedy the ultimate source of the error. Fourth, some errors have fostered further serious errors without the first error being noticed. Finally, some corrections to erroneous theories have themselves been rejected when initially presented. In all these cases, scientists failed to identify and correct the errors in a timely manner, or according to any uniform self-correcting mechanism. These historical perspectives underscore that error correction in science requires epistemic work. We need deeper understanding of errors, through the emerging field of error analytics.

Self-correction is essentially a human moral choice; it is not inherent in any enterprise in principle. If scientist have decided on the multiverse for non-evidence-based philosophical reasons, we need not anticipate self-corrections.

Consensus in science should be accepted because it is based on shared knowledge. This approach appeals to people who want to avoid a troublesome issue. Consensus  can certainly be based on shared knowledge but it can also be based on shared ignorance or shared self-interest. Boaz Miller has noted in Synthese:

The existence of agreement in a community of researchers is a contingent fact, and researchers may reach a consensus for all kinds of reasons, such as fighting a common foe or sharing a common bias. Scientific consensus, by itself, does not necessarily indicate the existence of shared knowledge among the members of the consensus community.

The word “consensus,” after all, only means “shared.” The messages from group members, however prominent or eminent, will sound the same to the uninitiated, irrespective of what mainly holds the group together.

Post-modern science is not a blip. It’s part of a general trend toward de-emphasizing fact, evidence, and truth in favor of narrative, spin, and talking points.  Plus, proponents have a weapon that defeats all objections: Human beings did not evolve so as to perceive reality correctly anyway. Astrophysicist Adam Frank explains at NPR that he finds that logic, as advanced by cognitive scientist Donald Hoffman, “exciting and potentially appealing” though probably “wrong.”

But wait! Why must Hoffman’s logic be wrong? If naturalists are right about the nature of our universe, the logic can be neither right nor wrong. We are all animals, and animals are never wrong. Or even absurd. As Cathal O’Connell says, citing David Wallace’s The Emergent Multiverse, “our sense of absurdity evolved to help us scratch a living on the savannahs of Africa. ‘The Universe is not obliged to conform to it’” (Cosmos). Which leads us to examine the parallel developments in the study of human consciousness.

Image: Monoceros (“Unicorn”) constellation, by Sidney Hall [Public domain], via Wikimedia Commons.