Thomas Kuhn, born in 1922 and passed away in 1996, got interested about the history of Physics during his Ph.D. studies
He was in charge of a course, for humanities students, that was about the episodes in the history of science . To prepare for his lectures he decided to read the original texts as much has he could. Once he started to read Physics by Aristotle he was totally surprised with the new Universe that unfolded before him: the ideas expressed in that book seemed to come from outer space!
But they just had come from another time and space. Kuhn realized that taking into account the historical context and the remarkable internal consistency of Aristotle's Physics, it wasn't bad Physics: it was just another kind of Physics. From that moment on Kuhn was more and more drawn to reading the original sources while always stressing that original sources need to be read and analyzed in context.
Essential to Kuhn's analysis of science is the notion of paradigm. A paradigm is a highly ample concept in Kuhn's usage: it is simultaneously all of the laws, all of the theories, all methodological rules, all applications and extensions, all the models, metaphysical suppositions, conceptual frameworks and even the vague and imprecise scheme of the way Nature works.
Of course that such a broad concept had to face its fair share of scrutiny. To respond to his critics Kuhn dropped the notion of paradigm and focused on the much less vague notion of "disciplinary matrix". A disciplinary matrix has four subdivisions:
- Symbolic generalizations: laws and definitions of symbols contained in the laws.
- Metaphysical assumptions: shared beliefs of a scientific community during a certain time interval.
- Values: the criteria of simplicity, internal coherence, accuracy, elegance, plausibility shared by the scientific community.
- Exemplars: the designated body of knowledge contained in lab activities, exercises, textbooks, etc, that will help the student acquire his/her scientific formation.
At first we have the period of pre-paradigmatic science, a period of competition between multiple schools of thought where the explanation of certain natural phenomena cause divergences on what is to be studied and how it is to be studied (this occurrence of competing views of Nature is what Kuhn called incommensurability - a rather controversial, bum rapped and poorly understood concept).
After this period a school of thought has won preponderance and one can speak of an existing scientific community. This community has now a set of procedures, problems and a world view that are more or less broadly shared and is engaged in what mostly is puzzle solving activities. This is the period of normal science and as Kuhn rightly pointed out scientists in this stage have a kind of aversion to novelties on their fields of expertise.
Anomalies in the reigning paradigm are seen as minor nuisances that have to be solved in the context of the scientific zeitgeist. If the anomaly resists numerous attempts of a solution for a long enough period of time it will cause an erosion of the rules that are present in normal science and a period of renewed uncertainty about the disciplinary matrix is sure to follow (this convoluted period that has a lot of similarities with the pre-paradigmatic stage of science is sometimes called multi-paradigmatic science).
Following this either a new theory emerges where the discrepancies are mostly taken care of, or the old theory, with some little modifications, is able to accommodate the results that seemed to be out of its range. The first possibility is what is called a scientific revolution and after it a new period of normal science will follow in which the breadth and depth of the new disciplinary matrix will increase.
Two things are worth noticing in order to finish this very short introduction:
- Even though the period of normal science is adverse to scientific novelties it, nevertheless, is a catalyst for them given its constant poking at the limits of its own domains of application.
- On Kuhn's approach to the development of science, progress is achieved not in a cumulative way: science consists of long stretches of time where scientists engage in what Kuhn called normal science that are interrupted whenever a sufficient amount of anomalous results are too big to be ignored. In Kuhn's terminology this sets off a period that is called a crisis. After the resolution of this crisis by means of a scientific revolution a new world view emerges from which the old world view results can be derived (for instance Newtonian Dynamics results can be derived from Special Relativity by formally taking the limit $ {c \rightarrow \infty} $), but the underlying metaphysical assumptions of the two theories are profoundly at odds with each other.
