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The book was initially published as a monograph in the International Encyclopedia of Unified Science, then as a book by University of Chicago Press in 1962 (BooksEnthsiast.com). (All page numbers below refer to the third edition of the text, 1996).
Kuhn traced the origin of the book to 1947, when he was a graduate student at Harvard University and had been asked to teach a science class for humanities undergraduates, with the focus being historical case studies. Kuhn later said that, until then, "I'd never read an old document in science." Aristotle's Physics was astonishingly unlike Isaac Newton's work in its concepts of matter and motion. Kuhn concluded that Aristotle's concepts were not "bad Newton" but, rather, simply different.
Kuhn states that the practice of science comes in three phases.
The first phase, which is undergone only once, is the pre-scientific phase, in which there is no consensus on any theory. This phase is characterized by several incompatible and incomplete theories. One theory eventually becomes sufficiently accepted that scientists begin to successfully use it methodically. Other knowledge, such as common terminology, common experimental methods and equipment and, to a greater or lesser degree, a common interpretation of scientific phenomena, develops into a paradigm.
After this occurs, normal science begins. Kuhn explains that normal science is what scientists spend most of their careers doing. It can only be performed under a specific paradigm, and its goal is to explain and expand the paradigm. Kuhn explained normal science as a process of puzzle solving: armed with knowledge provided by a paradigm, scientists can begin to make well-founded and trusted assumptions about what they are studying. This may seem to violate long held ideals about objectivity in science, but it is extremely difficult to study anything without making at least a few basic assumptions (see Naïve empiricism). The challenge of normal science is to see how well one can apply all one's knowledge and assumptions to a certain problem.
It is important to note that there are advantages and disadvantages to using a paradigm to make assumptions about a particular topic. The advantage is that if all scientists are using similar assumptions, then their methods, terminology, and analyses will all be very homogeneous and easily compared. It allows for greater communication and cooperation between people. However, if many scientists use similar assumptions that are not entirely correct, they may be led astray for a very long time before an anomaly occurs which brings attention to the problem. When this happens there is usually a period of disagreement between scientists, and the theory is modified in an ad hoc way to accommodate experimental evidence that might seem to contradict the original theory.
As anomalies — the failures of the current paradigm to take into account observed phenomenon — accumulate, their significance is judged by the practitioners of the discipline. Some may be dismissed as errors in observation, others as only requiring small adjustments to the current paradigm. Eventually, Kuhn claims, the anomalies may become too great for many of the practicing scientists, leading to a loss of faith in the dominant paradigm. This will usher in a crisis of revolutionary science in which new paradigms are explored and axioms are re-examined. Eventually a new paradigm is devised which for some has a greater potential for problem solving than the old. A period follows in which there are adherents to both paradigms. In time, the new paradigm may replace the old, and a paradigm shift has occurred.
One well-known Kuhnian example involves Copernicus' suggestion that the EarthEarth also known as the Earth or Terra is the planet on which we live, the third planet outward from the Sun. It is the largest of the solar system's terrestrial planets, and the only planetary body that modern science confirms as harbouring life. The pla revolves around the SunSee Sun (disambiguation) for other meanings of the word "Sun", and other newspapers known as "The Sun The Sun a daily newspaper published in the United Kingdom, has the highest circulation of any daily English-language newspaper in the world, standing at, rather than the PtolemaicThis article is about the geographer and astronomer Ptolemy. For Alexander the Great's general, see Ptolemy I of Egypt. For others, see Ptolemy (disambiguation). Claudius Ptolemaeus (Greek: Klaudios Ptolemaios; A. circa 85 circa 165), known in English as suggestion that the Sun (and the other planetA planet (from the Greek , planetes or "wanderers") is a body of considerable mass that orbits a star and that produces very little or no energy through nuclear fusion. Prior to the 1990s only nine were known (all of them in our own solar system); as of 3s and starFor alternate meanings see star (disambiguation Hubble Space Telescope of the Sagittarius Star Cloud in the Milky Way Galaxy. A star is any massive gaseous celestial body in outer space. Stars appear as shining points in the nighttime sky that twinkle becs) revolves around the Earth. The Ptolemaic theory used an elaborate set of epicycles (circles on top of circles) which were used to predict the movements of the heavenly bodies. Ptolemy's original epicyclic combinations were, by the Middle Ages, becoming noticeably less adequate, and fixes by later astronomers were more and more elaborate. Copernicus offered a return to an alternative view (suggested by many in antiquity) but with rather better data to support it; this new account decreased the complexity of theory necessary to account for the available observations. Once Copernicus' theory was accepted by other astronomers, it ushered in a new period of normal science. Refinements added by Kepler and Newton adhered to the new paradigm.
Other more recent examples are the acceptance of EinsteinAlbert Einstein ( March 14 1879 April 18 1955) was a theoretical physicist who is widely regarded as the greatest scientist of the 20th century. He proposed the theory of relativity and also made major contributions to the development of quantum mechanics's general relativity to replace Newton's account of gravity in the 1920s and 1930s and of Suess and Wegener's plate tectonics in the 1960s by geologists.
The transition period between paradigms was neither quick nor calm. Because of the subjective nature of deciding which evidence was "significant" and which anomalies could be disregarded, pure logic, Kuhn argued, was never the determiner for the new paradigm. Rather, the usefulness of the new paradigm — whether it gave further work to normal science — and whether it seemed, in the eyes of the practitioners, to be a likely solution, played high. And sometimes, as Max Planck observed, and Kuhn quoted (SSR, p. 151):
According to Kuhn, the scientific paradigms before and after a paradigm shift are so different that their theories are incomparable. The paradigm shift does not just change a single theory, it changes the way that words are defined, the way that the scientists look at their subject and, perhaps most importantly, the questions that are considered valid and the rules used to determine the truth of a particular theory. Kuhn went so far as to say that they were incommensurable — literally, lacking comparison, untranslatable. New theories were not, as they had thought of before, simply extensions of old theories, but radically new worldviews whose basic axioms and first-principles were different from the theories they replaced. This incommensurability applies not just before and after a paradigm shift, but between conflicting paradigms. It is simply not possible, according to Kuhn, to construct an impartial language that can be used to perform a neutral comparison between conflicting paradigms, because the very terms used belong within the paradigm and are therefore different in different paradigms.
This has important implications for other attempts to explain scientific progress. Kuhn (SSR, section XII) points out that the probabilistic tools used by verificationists are in themselves inadequate to the task of deciding between conflicting theories, since they are a component of the very paradigms they seek to compare. Similarly, observations intended to falsify a statement will be part of one of the paradigms they seek to compare, and so inadequate to the task. Advocates of such paradigms are in an insidious position: "Though each may hope to convert the other to his way of seeing science and its problems, neither may hope to prove his case. The competition between paradigms is not the sort of battle that can be resolved by proof." (SSR, p. 148).
Kuhn attributes the success of science to the way in which scientists are able to work within a paradigm, removing the need to repeatedly work from first principles. For Kuhn, it is that scientists work within a particular kind of community that explains the astonishing success of science: "The scientific community is a supremely efficient instrument for maximizing the number and precision of the problem solved through paradigm change." (SSR, p. 169).