Thomas Kuhn (1922–1996) was a historian and philosopher of science who sought to describe how science has progressed in history. His theory has been very influential; the phrase “paradigm shift”, now a well-known adage, was popularized from Kuhn’s work.[1]
According to Kuhn, science progresses relatively slowly and incrementally, expanding and testing the prevailing theories. He called this “normal science.” But every now and then, new data come to light that do not fit current theories. Generally, the scientific establishment of the day will attempt to fit this anomalous data into existing theories by incorporating a new aspect to the original. If this does not work, the existing theory is called into question, setting the stage for a paradigm shift. A new theory may be proposed which, by successfully modeling all relevant data, starts to gain ascendancy in the scientific community. Simultaneously, the older theory loses credibility, particularly as the generation schooled in the old paradigm is replaced. It is sometimes said that a paradigm shift progresses one funeral at a time.[2]
There have been several notable paradigm shifts in scientific history. The Copernican revolution, which we considered briefly in Chapter 3, was a historically significant paradigm shift. Prior to Copernicus, astronomers based their work on ancient Greek models, particularly that of Ptolemy. This model envisaged Earth at the center of the universe, and the sun, moon and other stars travelling around the earth in “epicycles”. Ptolemy’s model was complex but correlated well with the astronomical knowledge of the time.
Ptolemy’s model gradually fell out of favor as a paradigm shift, which we now refer to as the Copernican revolution, unfolded over almost two centuries. Copernicus realized that a heliocentric model, that is, one in which the Sun, not the earth, occupies the central position, with the planets orbiting around it, fit the observations better and was simpler. Initially the Copernican-era astronomers believed that the orbits of the planets were circular, but later measurements and theories suggested elliptical orbits. This model soon gained widespread support. Many of the scientists involved are household names today: Copernicus, Galileo, Kepler, and Newton. The paradigm shift was a slow process. It took 183 years from Copernicus’ publishing his heliocentric concept in 1543, to the finishing touches added by the English polymath Isaac Newton in the third edition of his Principia in 1726.
But from 1905, with the publication of Einstein’s theory of relativity, several of Newton’s signature theories were themselves on the receiving end of a paradigm shift. Scientists realized to their shock that Newton’s theory was not “true”. As a model it was—and remains—good enough for astronauts to chart a course to the moon and back, and to make many other accurate predictions, but it is not “true”. This was another major paradigm shift; the Einsteinian era of physics had overtaken the Newtonian era. As we shall see later, this paradigm shift has a direct bearing on the origins debate.
Another relevant paradigm shift concerns Darwin’s theory of evolution. After Darwin proposed his theory in 1859, the work of Gregor Mendel (1822–1884) won wide acceptance. Over time, scientists realized that Darwin’s original theory, which did not incorporate Mendel’s ideas, was inadequate. A new evolutionary synthesis, known as Neo-Darwinism, or the Modern Synthesis, was devised to incorporate the latest relevant scientific discoveries. Neo-Darwinism drew from a range of disciplines[3] and emphasized mutations as the origin of the genetic novelty on which natural selection worked. The synthesis utilized statistical concepts concerning changes of gene expression in populations. This expansion is probably an example of the process of normal science, but the Neo-Darwinian synthesis itself is breaking down because of new discoveries in the fields of information science and genetics. We may yet see a paradigm shift away from Neo-Darwinian evolution among the secular humanist scientific community, as the modern synthesis is recognized by some scientists to have crumbled beyond repair.[4]
In the origins debate, we saw earlier that philosopher Thomas Nagel had labelled the Neo-Darwinian cause as “ripe for displacement”. What Nagel is saying is that the Neo-Darwinian approach is no longer tenable; a paradigm shift is needed as no amount of add-on tweaks can save it. Of course, Nagel received substantial criticism for this,[5] and this collective defense mechanism of the established scientific community brings us to our fourth philosophical approach to science.
[1] As an aside, it was Kuhn’s seminal 1962 book, The Structure of Scientific Revolutions, (Kuhn, 2012) that provided the final nail in the coffin of logical positivism.
[2] Attributed to German physicist Max Planck.
[3] For example, paleontology, genetics, ecology, mathematical analysis and cytology (Huxley, 1942, p. 8).
[4] For example, Eugene Koonin stated “… the Modern Synthesis is gone. What’s next?” (Koonin, 2009).
[5] For example, refer article “Do you only have a brain? On Thomas Nagel: a philosopher’s broadside against Darwinism and materialism is mostly an instrument of mischief” (Leiter & Weisberg, 2012).