In “The Strcuture of Scientific Revolutions,” Thomas Khun describes the history of science as a discontinuous process, that is, not gradually cumulative. Revolutionary events would impose ruptures with the course of all previous scientific research.
The concept of paradigm developed by Thomas Khun is not unique. In his first work, he defines them as “universally recognized achievements that, for some time, provide models of problems and solutions to a scientific community” Khun (1962). According to this first approach to the concept, a paradigm includes:
1.Laws, theories and applications
2.Instruments that scientists use at that time
According to Khun, the early stages of the development of a science tend to show the coexistence of competing schools, resulting in the absence of a homogeneous scientific community. But when a paradigm emerges, a genuine research community is consolidated around it, and the discipline can be considered to have reached its maturity.
During their maturity of a science, under the rule of an established paradigm, scientists deal with the same type of problems (this is what Khun calls “normal science”). These problems or “riddles”, as Khun calls them, have the particularity of having a guaranteed solution. The possible solutions to the enigma and pass them that must be given to obtain them are conditioned by the same rules of each paradigm.
The notion of paradigm was strongly criticized as Khun failed to define it precisely, and on the other hand, the idea of “normal science” reflected dogmatic scientists, victims of indoctrination processes. On the other hand, it will also be said that this model clearly conforms to astronomy and the scientific revolution of the 15th to 16th centuries, but it would not apply so clearly to the path travelled by the biological sciences, for example from Darwin to Pasteur.
These criticisms forced Khun to revise his paradigm definition. In this regard he will say that there are two different senses for the concept:
1.Broaden: The paradigm encompasses all the commitments shared by a group of scientists.
The broad sense corresponds to a disciplinary matrix that includes four types of elements:
a. Symbolic generalizations: That is, those formal or formalizable components either expressed in symbolic notation or in natural language.b. Models: These provide acceptable analogies which have an impact on the search for solutions to unsolved puzzles. They also entail the conditions that must be met by the explanations proposed.
c. Values: play an important role in the cohesion of the scientific community. Some of a general nature refer to the function of science, and others point out the characteristics that theories must have or that indicate the conditions that scientific predictions must meet.
d. Metaphysics: A scientific community shares beliefs that play a leading role in the direction of research.
2. Specifically: The paradigm encompasses a kind of narrower commitments that forms a subset of the paradigm in the broad sense. That is, solutions to specific problems that the scientific community accepts as models.
Feyerabend, had already suggested difficulties in comparing scientific approaches from different paradigmatic frameworks. This idea of incommisurability, also developed by Khun, has some analogy the theory of perception of the gestalt, indeed, a paradigm, replacing the previous one assumes a change in the perceived structure. Thus, when a period of “normal science” is altered, the scientist's perception of his environment requires a new learning that allows him to understand the new gestalt. Because in the new paradigm, old terms, concepts and experiments vary their relationships and establish new ones, previously non-existent.
The idea of Uncommesurability implies:
1.That competing schools have difficulty understanding each other
2.That paradigms would be incompatible, probably as incomparable
This notion of uncommissibility was vulnerable to various criticisms, which is why Khun would review it years later.
Leave Lakatos will say that from Khun's approach, the scientific revolution is irrational, something like a problem of “mass psychology,” in fact Lakatos will consider that the importance given by Khun to sociological and psychological factors blur the explanation of scientific change. Khun will defend himself by saying that he was not properly understood, and will say that while the decisions made by scientists when choosing between one theory and the other are due to socio-psychological reasons, he would admit certain criteria that would allow for interparadigmatic comparison, going to say that the idea of imcommissibility is a metaphor, which does not prevent comparison. It will then establish a difference between translation and interpretation through which it will try to give greater consistency to the idea. In this way, insurmountable impediment to communication would not be an insurmountable impediment. Even if they could not be fully translated, it would be possible to understand the language of a previous time.
If paradigms cannot be compared with each other, there are no objective criteria to decide when one paradigm is “better” than another... then why do scientists abandon one paradigm for another? If rational issues remain on the sidelines and objective criteria are absent, then the epistemological conception seems to deny the idea of progress. However, Khun himself will postulate that progress is not only manifested during periods of “normal science”, but also through revolutions. However, this does not imply that the success of science can be measured against a previously determined goal. Here comes the concept of “evolution” as opposed to “revolution”, which would explain the success of science.
What is progress for Khun then? It is therefore the ability to solve problems. When you lose confidence in a paradigm as long as it does not solve some enigmas. However, many scientists will be reluctant to adopt a new paradigm to me that:
The new paradigm offers the unique possibility of solving an extraordinary and universally recognized problem.
The new paradigm also allows to solve the riddles that the previous paradigm solved.
“ After a scientific revolution, many ancient measurements and manipulations lose their importance or are replaced by others. (...) Whatever the scientist can see after a revolution, he's still looking at the same world. In addition, even if you have been able to use them differently, much of your vocabulary and laboratory instruments will still be the same as before. As a result, post-revolution science includes many of the same manipulations carried out with the same instruments and described in the same terms as its predecessors of the pre-revolution era.” Khun (1962 )
The preceding statement may be contradictory, however, Khun emphasizes the defense of metaphysical realism (since reality exists and is unique) and gnoseological idealism (whereas the subject's idea of the latter is a subjective construction). This implies that research is possible only within a given context, which conditions the knowledge that can be produced by members of a given scientific community.
Thus Khun rejects the possibility of access to things as they are in themselves, therefore, such an objective has no place. Hence, scientific theories are neither true nor false, while truth cannot be found independently of the paradigm, since it determines the methodology of empirical contrast.
This idea sustained by Khun is not, in fact, original. He recalls Kant's transcendental idealism, as he would later recognize. Kant discriminated between phenomenal reality (the perceived world) and nouménic reality (the reality itself). The novelty is that while for Kant, perception of reality is conditioned by universal parameters (which are common to all human beings as they possess the same cognitive apparatus) for Khun, as far as science is concerned, these parameters would change when one paradigm is replaced by another. This relativistic position will unleash criticism of which he will defend himself by saying that he considers himself a believer in scientific progress and that the superiority of a theory over the previous one is a problem independent of the metaphysical question, since superiority is evidenced in the ability of a theory to solve the puzzles.