“If I have seen a little further it is by standing on the shoulders of Giants.” Isaac Newton’s famous comment to fellow scientist Robert Hooke neatly captures a popular view of the advance of science. Scientific progress is a cumulative process, it is supposed, in which each generation of scientists builds on the discoveries of its predecessors: a collaborative march—gradual, methodical, unstoppable—toward a greater understanding of the natural laws that govern the universe.
A popular and attractive picture, perhaps, but seriously misleading according to the American philosopher and historian Thomas S. Kuhn. In his highly influential 1962 book The Structure of Scientific Revolutions, Kuhn gives a much bumpier, jumpier account of scientific development: a history of fitful and intermittent progress punctuated by revolutionary crises known as “paradigm shifts.”
A central feature of Kuhn’s picture of scientific change is that it is culturally embedded in a whole host of historical and other factors. Though Kuhn himself was keen to distance himself from a relativistic reading of his work, such an account of how science develops casts doubt on the very notion of scientific truth and the idea that the aim of science is to discover objectively true facts about how things are in the world. For what sense does it make to talk of objective truth when each scientific community sets its own goals and standards of evidence and proof; filters everything through a web of existing assumptions and beliefs; makes its own decisions about which questions to ask and what counts as a good answer? The usual view is that the truth of a scientific theory is a matter of how well it stands up alongside neutral and objective observations about the world. But as Kuhn and others have shown, there are no “neutral” facts; there is no neat line between theory and data; every observation is “theory-laden”—covered in a thick mulch of existing belief and theory.
Normal and revolutionary science In a period of so-called “normal science,” according to Kuhn, a community of like-minded scientific workers operate within a conceptual framework or world-view called a “paradigm.” A paradigm is an extensive and flexibly defined assemblage of shared ideas and assumptions: common methods and practices, implicit guidelines on suitable topics for research and experimentation, proven techniques and agreed standards of evidence, largely unquestioned interpretations passed from generation to generation, and more. Scientists working within a paradigm are not concerned to venture outside it or to blaze new trails; instead, they are mainly engaged in resolving puzzles thrown up by the conceptual scheme, ironing out anomalies as they arise, and gradually extending and securing the boundaries of the domain.
A period of normal science may continue for many generations, perhaps for several centuries, but eventually the efforts of those within the community create a mass of problems and anomalies that begin to undermine and challenge the existing paradigm. This finally sparks a crisis that encourages some to look beyond the established framework and to begin devising a new paradigm, whereupon there is a shift or migration of workers—which may take years or decades—from the old paradigm to the new. Kuhn’s own favored example was the traumatic transition from the Ptolemaic Earth-centered world-view to the heliocentric system of Copernicus. Another seismic paradigm shift was the supplanting of Newtonian mechanics by quantum physics and relativistic mechanics in the early decades of the 20th century.
It has long been assumed that science is an essentially unified endeavor. It has seemed reasonable to talk of a “scientific method”—a single, well-defined set of procedures and practices that could in principle be applied to many different scientific disciplines; and to speculate on the prospect of some kind of grand unification of the sciences, in which all laws and principles would somehow collapse into an overarching, exhaustive and internally consistent structure. The key to such a coming-together is supposedly a fully reductive account of the sciences, the usual suggestion being that everything will ultimately be subsumed under physics. Recent work, however, has brought a fuller appreciation of the cultural and social embeddedness of the sciences and a greater emphasis on the essential disunity of science. And with it has come a realization that the search for a single scientific method is probably chimerical.
“I do not doubt, for example, that Newton’s mechanics improves on Aristotle’s and that Einstein’s improves on Newton’s as instruments for puzzle-solving. But I can see in their succession no coherent direction of ontological development.”
Thomas Kuhn, 1962
The exaggerated discontinuities and dislocations supposed by Kuhn’s account have meant that it has remained contentious as a historical thesis, but it has nevertheless proved highly influential among philosophers of science. Of particular interest has been the claim that different paradigms are “incommensurable”—that basic differences in their underlying logic mean that results achieved in one paradigm are effectively incompatible with, or untestable within, another paradigm. For example, while we might expect that the “atoms” of the Greek philosopher Democritus cannot be compared with those split by Ernest Rutherford, incommensurability suggests Rutherford’s atoms are different again from the ones described by modern quantum mechanics. This logical discontinuity within the grand architecture of science ran directly counter to the view that had prevailed before Kuhn’s time. Previously it had been accepted that the edifice of scientific knowledge was built up steadily and rationally on foundations laid by earlier workers. At a stroke, Kuhn had swept away the idea of concerted progress toward a single scientific truth and put in its place a landscape of diverse, locally determined and often conflicting scientific aims and methods.
The term “paradigm shift” is unusual among technical or academic terms in making so effortless a migration to the public domain. The notion of radical change in the way people think and look at things is so suggestive and resonant that the term has found its way into all sorts of other contexts. Thus the invention of gunpowder marks a paradigm shift in military technology; penicillin in medical technology; jet engines in aviation; mobile phones in society; graphite rackets in tennis; and so on. Less creditably, the phrase has even become a stock phrase in the marketeer’s handbook. Ironically, of course, Kuhn’s own work represented a paradigm shift in the way that philosophers looked at the progress of science.
Kelvin balls By their nature paradigm shifts are apt to wrong-foot people. In 1900, in a wondrous moment of hubris, the celebrated British physicist Lord Kelvin declared: “There is nothing new to be discovered in physics now. All that remains is more and more precise measurement.” Only a few years later, Einstein’s theories of special and general relativity and the new quantum theory had effectively usurped the throne occupied by Newtonian mechanics for over two centuries.
the condensed idea
Science—evolution and revolution
| Timeline | |
|---|---|
| c.AD1300 | Occam’s razor |
| 1739 | Science and pseudoscience |
| 1962 | Paradigm shifts |