[Drugmachine]

II.

In 1962, a Berkeley professor named Thomas Kuhn published a book called The Structure of Scientific Revolutions, which went on to become the most influential academic book of the last half century, selling over a million copies in a dozen languages. Kuhn’s book dropped a depth charge under the foundations of academic thinking about the way we search for truth, and about the way we come to believe the things we believe. And although the subject of the book is the way the search for truth works in the physical sciences, it has implications well beyond the sciences.

In The Structure of Scientific Revolutions, Kuhn argues that the traditional picture of science—in which scientists conduct universally replicable experiments to accumulate verified facts, which together make up the body of scientific truths—is without basis in the actual history of science. Instead, scientists are trained to see the world in terms of a certain framework of interrelated concepts, which Kuhn calls a paradigm. In the overwhelming majority of cases, the paradigm not only determines the interpretation that a scientist gives the facts, but even what facts there are to be interpreted: The “facts” that scientists consider admissible for discussion are those that easily conform to the dominant paradigm, or that can be made to conform to it by extending the paradigm or introducing minor repairs into it. Those facts that can’t be made to conform to the reigning paradigm are overlooked entirely or dismissed as unimportant.

Kuhn was famous, of course, for pointing out that things don’t go on like this forever. The history of science is punctuated by shifts in the dominant paradigm, as when Aristotelian physics gave way to Newtonian physics, or when Newton’s science was displaced by Einstein’s. Kuhn calls these shifts in paradigm scientific revolutions, and in the book he discusses tens of such shifts from the history of the physical sciences. Kuhn concludes that while most scientists are reasonable people, what we would usually consider reasonable discussion and argument only takes place among scientists who subscribe to the same paradigm. Nothing like a normal process of persuasion is involved in battles between competing paradigms. Indeed, when scientists representing competing paradigms argue, there is often no way at all that either one will be able to prove his case to the other:The proponents of competing paradigms are always at least slightly at cross-purposes. Neither side will grant all the non-empirical assumptions that the other needs in order to make its case…. [Thus while] each may hope to convert the other to his way of seeing…, neither may hope to prove his case. The competition between paradigms is not the sort of battle that can be resolved by proofs.[1]
As Kuhn points out, even a mountain of facts will not change the mind of a scientist who has been trained in a different paradigm, because the fundamental framework from which he views the world is different: The facts themselves mean something completely different to him. In fact, very few scientific paradigms, including the most famous and most successful, are able to provide the kind of decisive experimental evidence that can force scientists to give up the old paradigm.

How, then, do scientists come to change their minds? Kuhn says that in many cases, they never change their minds—and that an entire generation has to pass before the scientific community enters a new paradigm:
How, then, are scientists brought to make this transposition? Part of the answer is that they are very often not. Copernicanism made very few converts for almost a century after Copernicus’ death. Newton’s work was not generally accepted, particularly on the Continent, for more than half a century after the Principia appeared. Priestley never accepted the oxygen theory, nor Lord Kelvin the electromagnetic theory, and so on…. And Max Planck, surveying his own career in his Scientific Autobiography, sadly remarked that “a new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.” [2]
Kuhn doesn’t go quite as far as endorsing Planck’s claim that paradigms change only when the supporters of the old paradigm die off and a younger generation takes their place. But he comes close, approvingly quoting a passage from The Origin of Species in which Darwin suggests that even the most brilliant scientists will likely be unable to adjust to his theory of natural selection. The prejudices run too deep, Darwin writes, and it will take new generation of scientists to be able to consider the new theory fairly. As he writes:
Although I am fully convinced of the truth of the views given in this volume…, I by no means expect to convince experienced naturalists whose minds are stocked with a multitude of facts all viewed, during a long course of years, from a point of view directly opposite mine…. [B]ut I look with confidence to the future—to young and rising naturalists, who will be able to view both sides of the question with impartiality.[3]