Time to go back to Julian Baggini’s book, The Edge of Reason: A Rational Skeptic in an Irrational World, which I have began discussing last month. While the first chapter was about God and the rationality (or lack thereof) of arguments pro and against, the second one is about science and why it is far less rational that we are led to believe (especially by scientists).
The chapter opens with the observation that science is not an objective “view from nowhere” thing, but a sophisticated, yet fallible, human enterprise, fundamentally dependent on human judgment. As in the case of a poll Baggini cites from 1999: when 90 leading physicists were asked which interpretation of quantum mechanics they thought was best, 4 voted for Copenhagen, 30 for Many Worlds, and 50 said either none of the above or undecided. Clearly, which available model is preferable is a question of subjective judgment, not empirical fact (as the very word “interpretation” strongly suggests…).
The point Julian is making throughout the chapter is simple, yet controversial: “My aim is to show how accepting the role of judgement in science in no way undermines it, but it does require us to rethink how we assume reason works.”
One of his best examples comes again from quantum physics, when he notices that Schrödinger’s and Heisenberg’s competing theories were not only equally compatible with the empirical data, but in fact had been shown to be mathematically equivalent. They were, therefore, both empirical and mathematically underdetermined. Which one you preferred came down to subjective judgments having to do with beauty, simplicity, or even, possibly, whether you personally liked one physicist better than the other.
The general idea that theories are never, by themselves, uniquely determined by the evidence is known today as the Duhem-Quine theses, but Baggini points out that the concept goes back at least to John Stuart Mill, who wrote in A System of Logic that a hypothesis “is not to be received as probably true because it accounts for all the known phenomena, since this is a condition sometimes fulfilled tolerably well by two conflicting hypotheses.” Mill thought that this was commonly accepted by “thinkers of any degree of sobriety” (I love the turn of phrase!).
As Julian observes, scientists are often dismissive of the Duhem-Quine theses, charging that it is difficult enough to come up with one reasonable theory to explain the data, let alone dream up multiple alternatives. But “this misses the point. The value of the underdetermination thesis is not to make us seriously consider all alternatives to the most powerful and tested scientific explanations. Its value is that it makes it clear that even when the evidence appears overwhelmingly to support one theory rather than another, there is always a gap, however small, between what the evidence requires we conclude and what we actually conclude.”
Another factor that conjures in hiding the role of human judgment in science is the fiction that there is such thing as a quasi algorithm-like thing called “the scientific method.” While philosophers of the early part of the 20th century kept searching for it, the consensus nowadays is that it doesn’t exist. Yet scientists themselves help perpetuate the myth, both in references to the phantomatic method in introductory textbooks, and also by creating “the false impression of a regular, orderly method by writing up their findings in ways which gloss over the real messiness of discovery.”
Indeed, as Baggini stresses, if one looks at how science is actually done — rather than described in simplistic idealizations — it is a highly messy activity where “quirks and deviations” from the official picture of rigorous experiments and straightforward deduction are not exceptions, but rather the norm.
There are many documented cases in the history of science when a scientist persisted out of sheer obstinate conviction of being right, an attitude we associate instead with pseudoscience. My favorite example among those cited by Julian is Boyle, who was “persistent in holding to his theory when observation refused to confirm it. On 49 occasions he tested his hypothesis that smooth bodies that stuck together in air would come apart in a vacuum, without success, yet succeeded on the 50th attempt.”
What, then, distinguishes a brilliant scientist like Boyle from a crank? Good judgment of his intuitions, arising from experience as well as brilliance. Not much else, really.
Moreover, scientists — especially physicists — tend to rely on theory more than empirical evidence, even when the empirical evidence appears to contradict the theory. Eddington, the astronomer that confirmed Einstein’s theory of relativity in 1919, famously declared that “It is a good rule not to put overmuch confidence in the observational results that are put forward until they have been confirmed by theory,” a striking reversal of the usual idea of how science works.
The temperament and gut feelings of scientists play a major role early on during discovery and initial verification, notable cases include Einstein’s suspicion of quantum mechanics (“God doesn’t play dice”) and Heisenberg finding Schrödinger’s theory “repulsive.”
Here is one gem from the chapter: “Another of Einstein’s remarks is extremely revealing. He once said, ‘I find the idea quite intolerable that an electron exposed to radiation should choose of its own free will, not only its moment to jump off, but also its direction. In that case, I would rather be a cobbler, or even an employee in a gaming-house, than a physicist.'” This is an expression of a strongly emotionally held aesthetic judgment. Nothing to do with physics or mathematics as ordinarily understood, or the quest for truth, for that matter.
And of course beauty and aesthetics are not, in fact, guarantors of truth: “As George Ellis and Joe Silk point out, ‘Experiments have proved many beautiful and simple theories wrong, from the steady-state theory of cosmology to the SU(5) Grand Unified Theory of particle physics, which aimed to unify the electroweak force and the strong force.'”
Scientists — below the surface, mostly in private or informal exchanges — even disagree on major issues of epistemology and metaphysics. For instance, “Bohr … completely rejected scientific realism. ‘There is no quantum world. There is only an abstract quantum mechanical description,’ he said. ‘It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature.'” Needless to say, a number of his colleagues disagreed vehemently, thus unwittingly engaging in philosophical debates about the nature and scope of their discipline.
By the end of the chapter, Baggini concludes: “The success of science should not lead us to believe that it provides the model for all reasoning; rather that the domain of science is one which is especially conducive to the use of reason. … We need a more expansive notion of what it means to be rational, one which includes all the elements that are left out when we focus only on the strictly formal and empirical ones. At the heart of this notion we need to place judgement.” Indeed.