Mike Follows reviews The Knowledge Machine: How an Unreasonable Idea Created Modern Science by Michael Strevens
Whether or not you know much about the philosophy of science, The Knowledge Machine by Michael Strevens is arguably the most accessible and engaging book on the topic ever written. The author – a philosopher at the University of New York – has produced something that is enthralling, beautiful and persuasive. Reading Strevens’ book is a bit like talking to a critical friend. Indeed, it was such a joy, I read it twice.
The author’s basic premise is that disagreements in science are settled by empirical tests whose results are archived in formal scientific journals. It’s what he calls the “iron rule of explanation”, which also allows theoretical ideas to be published without supporting evidence, provided they are intended for empirical testing. While I don’t agree with everything Strevens has to say, his book certainly helped me clarify my own thinking.
The author starts by discussing the “great method debate”, in which he pitches Karl Popper against Thomas Kuhn. Popper believed that, to qualify as science, a claim must be falsifiable, with scientists accepting the claim only if it cannot be falsified. Kuhn, meanwhile, introduced the concept of “normal science” operating within a settled “paradigm” that only occasionally gets upended. In fact, Strevens calls this “more than an explanatory framework; it is a complete recipe for doing science”.
In presenting these as rival theories, Strevens misrepresents and oversimplifies their ideas. “Do scientists fight to preserve the status quo,” he asks, “as Kuhn’s theory would tend to suggest, or to overthrow it, as Popper would have it?” Surely, though, these philosophies are complementary, with Popper nesting inside Kuhn? After all, scientists who do normal science are trying to replicate published results, which might lead to those ideas being falsified.
Strevens then turns in detail to the expedition carried out in 1919 by the British astronomer Arthur Eddington, who studied that year’s solar eclipse. It was designed to test whether the bending of light from distant stars supported Newton’s law of gravitation or Einstein’s general theory of relativity. Although the results were equivocal, Eddington concluded that they confirmed general relativity, which demonstrates that there is an element of subjectivity in the way scientific claims are interpreted.
This subjectivity is partly because of what’s known as the Duhem–Quine problem, which states that a scientific claim cannot be assessed in isolation because it depends on a retinue of auxiliary or background assumptions. Scientists also engage in what Strevens calls “plausibility rankings” to weigh up the significance of each assumption or to assess conflicting evidence. As Strevens puts it, scientists harbour a variety of “enthusiasms, hopes and fears [that] mould their thinking far below the threshold of awareness”.
Eventually a consensus is reached, just as migrating birds eventually find their destination. Ultimately, science is beautifully self-correcting.
His suggestion is that Eddington was simply beguiled by the beauty of Einstein’s theory and, being a pacifist, accepted it in his eagerness for scientific rapprochement with Germany following the First World War. This, in turn, leads Strevens to concede that “scientists seem scarcely to follow any rules at all”, echoing the Austrian philosopher Paul Feyerabend’s dictum that “anything goes”. As for Strevens’ own philosophical position, that isn’t clear in the book but I suspect he is a “radical subjectivist” of the kind who have superseded Kuhn and Popper.
In discussing how science progresses, Strevens makes clear that different interpretations of the same data are allowed because science does not depend on “the unwavering rationality of any individual scientist” but on a succession of them, all applying the iron rule. “As evidence accumulates, plausibility rankings begin to converge”, which leads to competing theories being whittled down. Eventually a consensus is reached, just as migrating birds eventually find their destination. Ultimately, science is beautifully self-correcting.
Strevens also explains how scientists find inspiration wherever they like. While he doesn’t give examples, consider how Einstein and other physicists made progress via thought experiments or how the chemist August Kekulé day-dreamed his way to establishing the ring-like nature of the benzene molecule. This discussion reminded me of the Nobel-prize-winning biologist François Jacob, who contrasted the reasoning scientists do in their heads (what he called “night science”) with the formal stuff that appears in research papers (“day science”).
Sadly, Strevens’ iron rule stops scientists from supporting their claims with appeals to elegance or anything else that is non-empirical. It’s a prohibition he says is “irrational”. Whereas philosophers take into account all relevant considerations as part of the “principle of total evidence”, scientists wantonly throw away potentially valuable information. According to Strevens, it’s like buying a used car from a dealership but perversely ignoring the garage’s inspection report.
Strevens also focuses on the notion of mathematical beauty, which was held up as a guiding light by the likes of the late Steven Weinberg. So where does that put string theory? It lacks empirical support but has proved to be an elegant and useful framework for half a century. Surely it deserves to be accepted as legitimate science via a logical upgrade to the iron rule? Not so, says Strevens, who urges scientists not to “meddle with the iron rule”.
The Knowledge Machine is required reading for anyone who wants a more authentic picture of how science progresses.
Ironically, this puts him in agreement with Richard Feynman, who saw no place for philosophy in science, famously declaring that “experiment is the sole judge of scientific ‘truth’”. It seems though that Strevens has only a grudging respect for scientists. He laments their narrow focus yet concedes it’s also a necessary virtue. Strangely, he blames scientists for trashing the environment, yet recognizes that science holds the key to solving our environmental problems.
The Knowledge Machine is replete with colourful anecdotes and clever analogies (the author’s description of science as a coral reef is sublime). Strevens is provocative and thought-provoking – and includes more than enough footnotes and references for readers to explore ideas further.
Although a potted history of the philosophy of science might have been helpful for those new to the discipline, The Knowledge Machine is required reading for anyone who wants a more authentic picture of how science progresses. You might not always agree with him, but Strevens challenges you to re-assess your understanding of the history, sociology and philosophy of science.
