Thomas Kuhn, the twentieth-century physicist and philosopher whose ideas are the main subject of this essay, has been generally categorized under the school of analytic philosophy. But the only reason for this categorization is his American nationality; other than that, there is nothing about the actual content of his philosophy that makes him similar to the analytic philosophers, as he was critical of both logical positivism and the general beliefs about science attached to analytic philosophy. His ideas, as shall be seen, were much closer to those of continental philosophers like Michel Foucault, who did not agree with the traditional view of the development of scientific knowledge.
Paradigm Shift and Phases of Science
It is a quite commonly accepted belief in the general public, with which analytic philosophers including Karl Popper agree too, that scientists are highly critical in their research and they do not take anything for granted; instead, they accept something as a “fact” only based on cold, hard evidence and a rational thought process. But, according to Kuhn, this couldn’t be more incorrect: most of the time, scientists, at least the natural scientists, aren’t critical at all in their work because they accept the given “paradigm” of their discipline without questioning it. Kuhn defines the paradigm of a scientific discipline as the collection of facts, theories, concepts, methods of instrumentation, etc. that are taken for granted in that discipline. A paradigm is a whole worldview that determines how a scientific discipline views reality and also sets the standards for what is “good science” or “bad science”.
Given the vast nature of reality, both natural and social, the paradigm provides the scientist with a map, not only for what to believe in but also for what problems to look for and where to look. Following this, Kuhn says that scientists in a given historical epoch accepting the paradigm without challenging it is actually a good thing most of the time. The reason for this is rather simple: if scientists constantly kept questioning the fundamental concepts and realities of their discipline and did not take the existing paradigm for granted, progress in the sciences would be impossible.
"A paradigm provides a map whose details are elucidated by mature scientific research. And since nature is too complex and varied to be explored at random, that map is as essential as observation and experiment to science’s continuing development. Through the theories they embody, paradigms prove to be constitutive of the research activity."
~ Thomas Kuhn, The Structure of Scientific Revolutions
Based on his concept of the paradigm, Kuhn proposes that any science goes through four different phases:
Pre-paradigmatic
Normal
Crisis
Revolutionary/Extraordinary
A science only goes through the first phase once, but the next three phases are in constant repetition, with the normal phase being the most stable and lasting one; that is, the phases of crisis and scientific revolution eventually return to the normal phase.
The pre-paradigmatic phase of a science is when it's still in an immature state and has not developed a solid foundation and paradigm to work with. The normal phase of a science is the one where scientists have a paradigm to work with; the map that provides them with what to believe in and what to look for has been developed. Scientists in the normal phase simply build upon the existing knowledge of the paradigm. The phase of crisis begins when such a problem, or multiple of them, arises that does not seem to be solved with the accepted paradigm of the discipline. In such a case, two possibilities arise: either with minor changes, like using more precise instrumentation or slight alterations in the methods of the paradigm, the problem is solved and science, with the existing paradigm, returns to its normal phase; but if that doesn’t happen, a revolutionary phase of science begins in which most of the existing methods and knowledge of the old paradigm have to be discarded and scientists have to critically analyze the foundations of their discipline. In such a case, a scientific revolution takes place and a completely new paradigm is developed in order to solve the problem: a “paradigm shift” takes place in science. After the new paradigm is largely accepted, science becomes stable and again enters its normal phase. These cycles of paradigm shifts constantly take place in science and are essential to its development. The Copernican revolution, the general theory of relativity discarding Newton’s gravitational law, and quantum field theory replacing classical field theory are all examples of paradigm shifts in physics, for instance.
Kuhn compares scientific practice with puzzle-solving: normal science is just the normal game of puzzle-solving. One has a given set of rules and pieces that the player has to fit—the paradigm. But a time eventually comes when the pieces just don’t fit, and that’s when the entire rules of the game have to be deconstructed and reformulated in order to solve the puzzle. In his magnum opus, The Structure of Scientific Revolutions, Kuhn writes the following on the transition from normal to extraordinary or revolutionary phase of science:
"When an anomaly comes to seem more than just another puzzle of normal science, the transition to crisis and to extraordinary science has begun. The anomaly itself now comes to be more generally recognized as such by the profession. More and more attention is devoted to it by more and more of the field’s most eminent men... The proliferation of competing articulations, the willingness to try anything, the expression of explicit discontent, the recourse to philosophy and to debate over fundamentals, all these are symptoms of a transition from normal to extraordinary research."
Comparison with Traditional History of Science
From the above discussion, it is not difficult to see how Kuhn disagrees with the traditional analytic view of the history of science, which views scientific knowledge as something cumulative and continuous, without breaks. Instead, Kuhn would agree more with continental philosophers like Michel Foucault, according to whom science is not cumulative but develops by constantly discarding existing truths and knowledge. In analytic philosophy and also in the traditional history of science, it is believed that great men were born and, with their individual creativity, which is taken to be inherent or genetic to them, discovered the truth already engraved into things, nature, and the world around us, and that these truths were not discovered by anyone before them. The core belief that lies in this type of view is that truth is already there to be known, found, or discovered, and due to a number of obstacles, the human mind has not yet seen the truth; a number of individuals come and gradually uncover this truth in parts as a continuous process; the function of the natural scientist then becomes to work towards finding an ultimate truth, the theory of everything as it is called today. This view can easily be falsified by observing the nature of scientific revolutions as described by Kuhn. Whenever a great scientific transformation takes place, new knowledge isn’t simply added to science; a great deal of old, already existing knowledge, things that were seen as objective truths, etc., is also discarded. So, scientific knowledge isn’t cumulative because it isn’t simply about building on existing knowledge but also about discarding existing truths and knowledge—paradigm shifts, as Kuhn terms it.
Incommensurability and Scientific Progress
Kuhn recognized the fact that if one accepts his theory of paradigm shifts, it would have many radical consequences on the way one views scientific progress. As described earlier, the paradigm sets the standards for what is “good science” and “bad science”. For instance, Galilean and Newtonian physics would be considered “good science” by Isaac Newton as he was working in that paradigm, but it would be considered “bad science” by someone like Neils Bohr or Aristotle as they were working under different paradigms. With this in mind, Kuhn suggests that there is no neutral and objective standard to compare scientific theories of different time periods. If one says that current science is better than past science, which standards is one using to make that claim? If one is using the standards of the current scientific paradigm, then surely they would find current science better than past science because it obviously fits the current paradigm. But if one uses an older paradigm, current science would be considered “bad science”. This phenomenon of being fundamentally unable to objectively compare and rank different paradigms is what Kuhn calls “incommensurability”.
It is quite simple to understand, then, how Kuhn’s ideas of paradigm shifts and incommensurability would affect one’s view of “progress” in science. As described earlier, the traditional history of science views scientific knowledge as a sort of building that is constantly being built and increasing in height. But, according to Kuhn, the very foundations of this building of science are demolished during a scientific revolution: most of the knowledge of the past is discarded, and a shift in paradigm takes place. Combining this with the idea of incommensurability—that no scientific paradigm is better than the other—Kuhn concludes that there is no reason to claim that any real scientific progress takes place during a phase of scientific revolution. The only period in which scientific progress can be said to happen is during the normal phases of science because that is when scientists are actually building on the existing structure, but during the revolutionary phase of science, as the very foundations of that structure are destroyed, nothing is being built upon, so it would be incorrect to claim that scientific revolutions bring scientific progress—they only bring changes in paradigms.
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