A common view is that science progresses by a series of abrupt changes in which new scientific theories replace old ones that are “proven wrong” and never again see the light of day. Unless, as John Horgan has suggested, we have reached the ”end of science,” every theory now in use, such as evolution or gravity, seems destined to be overturned. If this is true, then we cannot interpret any scientific theory as a reliable representation of reality.
While this view of science originated with philosopher Karl Popper, its current widespread acceptance is usually imputed to Thomas Kuhn, whose The Structures of Scientific Revolutions (1962) was the best selling academic book of the twentieth century, and probably also the most cited.
Kuhn alleged that science does not progress gradually but rather through a series of revolutions. He characterized these revolutions with the now famous and overworked term paradigm shifts in which the old problem-solving tools, the “paradigms” of a discipline are replaced by new ones. In between revolutions, not much is supposed to happen. And after the revolution, the old paradigms are largely forgotten.
Being a physicist by training, Kuhn focused mainly on revolutions in physics. One of the most important examples he covered was the transition from classical mechanics to quantum mechanics that occurred in the early 1900s. In quantum mechanics, the physicist calculates probabilities for particles following certain paths, rather than calculating the exact paths themselves as in classical mechanics.
True, this constitutes a different procedure. But has classical mechanics become a forgotten tool, like the slide rule? Hardly. Except for computer chips, lasers, and a few other special devices, most of today’s hightech society is fully explicable with classical physics alone. While quantum mechanics is needed to understand basic chemistry, no special quantum effects are evident in biological mechanisms. Thus, most of what is labeled natural science in today’s world still rests on a foundation of Newtonian physics that has not changed much, in basic principles and methods, for centuries.
Nobel physicist Steven Weinberg, who was a colleague of Kuhn’s at Harvard and originally admired his work, has taken a retrospective look at Structures. In an article on the October 8, 1998, New York Review of Books called “The Revolution That Didn’t Happen,” Weinberg writes:
It is not true that scientists are unable to “switch back and forth between ways of seeing,” and that after a scientific revolution they become incapable of understanding the science that went before it. One of the paradigm shifts to which Kuhn gives much attention in Structures is the replacement at the beginning of this century of Newtonian mechanics by the relativistic mechanics of Einstein. But in fact in educating new physicists the first thing that we teach them is still good old Newtonian mechanics, and they never forget how to think in Newtonian terms, even after they learn about Einstein’s theory of relativity. Kuhn himself as an instructor at Harvard must have taught Newtonian mechanics to undergraduates.
Weinberg maintains that the last “mega-paradigm shift” in physics occurred with the transition from Aristotle to Newton, which actually took several hundred years: “[N]othing that has happened in our understanding of motion since the transition from Newtonian to Einsteinian mechanics, or from classical to quantum physics fits Kuhn’s description of a ‘paradigm shift.’”
While tentative proposals often prove incorrect, I cannot think of a single case in recent times where a major physical theory that for many years has successfully described all the data within a wide domain was later found to be incorrect in the limited circumstances of that domain. Old, standby theories are generally modified, extended, often simplified with excess baggage removed, and always clarified. Rarely, if ever, are such well-established theories shown to be entirely wrong. More often the domain of applicability is refined as we gain greater knowledge or modifications are made that remain consistent with the overall principles.
This is certainly the case with Newtonian physics. The advent of relativity and quantum mechanics in the twentieth century established the precise domain for physics that had been constructed up to that point, but did not dynamite that magnificent edifice. While excess baggage such as the aether and phlogiston was cast off, the old methods still exist as smooth extrapolations of the new ones to the classical domain. The continued success and wide application of Newtonian physics must be viewed as strong evidence that it represents true aspects of reality, that it is not simply a human invention.
Furthermore, the new theories grew naturally from the old. When you look in depth at the history of quantum mechanics, you have to conclude it was not the abrupt transition from classical mechanics usually portrayed. Heisenberg retained the classical equations of motion and simply represented observables by matrices instead of real numbers. Basically, all he did was make a slight modification to the algebraic rules of mechanics by relaxing the commutative law. Quantization then arose from assumed commutation rules that were chosen based on what seemed to work. Similarly, the Schrödinger equation was derived from the classical Hamilton-Jacobi equation of motion. These were certainly major developments, but I maintain they were more evolutionary than revolutionary.
Where else in the history of science to the present can we identify significant paradigm shifts? With Darwin and Mendel, certainly, in biology. But what in biology since then? Discovering the structure of DNA and decoding the genome simply add to the details of the genetic mechanism that are being gradually enlarged without any abrupt change in the basic naturalistic paradigm.
A kind of Darwinian graduated evolution characterizes the development of science and technology. That is not to say that change is slow or uniform, in biological or social systems. The growth of science and technology in recent years has been quick but not instantaneous and still represents a relatively smooth extension of what went before.