Sutton, Fleck's work made me realize that perhaps these ideas need to be set in the sociology of the scientific community. Conant, then president of Harvard University, who first introduced me to the history of science and thus initiated the transformation in my perception of scientific progress.
I NTRODUCTION : A R OLE FOR H ISTORY
Which of the many conceivable experiments relevant to the new field does he prefer to perform first. This extended conception of the nature of scientific revolutions is the one outlined in the pages that follow.
T HE R OUTE TO N ORMAL S CIENCE
Acquiring a paradigm and the more esoteric kind of research it makes possible is a sign of maturity in the development of any scientific field. This is the situation that creates the schools that characterize the early stages of the development of a science.
T HE N ATURE OF N ORMAL S CIENCE
First is that class of facts which the paradigm has shown to reveal especially the nature of things. In the more mathematical sciences, some of the experiments directed at articulation are directed at the determination of physical constants.
N ORMAL S CIENCE AS P UZZLE - SOLVING
The terms "puzzle" and "puzzle solver" highlight several themes that have become increasingly prominent in the preceding pages. Now turn to another, more difficult and more revealing aspect of the parallelism between the puzzles and problems of ordinary science.
T HE P RIORITY OF P ARADIGMS
Something similar may very well apply to the various research problems and techniques that appear within a single normal scientific tradition. Some related questions are discussed in his paper, "The Vernacular of the Laboratory," Philosophy of Science, XXV.
A NOMALY AND THE E MERGENCE OF S CIENTIFIC D ISCOVERIES 52
The first of the claimants to prepare a relatively pure sample of the gas was the Swedish pharmacist C. Note, however, as it will be important later, that the discovery of oxygen in itself was not the cause of the change in chemical theory . Long before he played any role in the discovery of the new gas, Lavoisier was convinced that there was something wrong with the phlogiston theory and that burning bodies absorbed part of the atmosphere.
It told him one thing he was already prepared to discover—the nature of the substance that combustion removes from the atmosphere. Alarmed by inexplicably fogged photographic plates, Sir William Crookes was also on the trail of the discovery. The discovery of the Leyden jar shows all these features as well as the others we have observed before.
That error is the source of several of the anomalies that provide background for the discovery of the Leyden jar. On the other hand, within the areas to which the paradigm directs attention.
C RISIS AND THE E MERGENCE OF S CIENTIFIC T HEORIES 66
This recognition was a prerequisite for Copernicus' rejection of the Ptolemaic paradigm and his search for a new one. If this much is clear in the case of the Copernican revolution, let us turn from it to a second and quite different example, the crisis which preceded the emergence of Lavoisier's theory of oxygen combustion. The history of the former begins in the seventeenth century with the development of the air pump and its use in chemical experimentation.
By the time Lavoisier began his experiments on air in the early 1770s there were almost as many versions of the phlogiston theory as there were pneumatic chemists.8 This. These conclusions did not lead to the rejection of the phlogiston theory, as this theory could be adapted in several ways. Each of these articulations assumed that the moving body dragged along a particle of ether.
The situation changed again only with the gradual acceptance of Maxwell's electromagnetic theory in the last two decades of the nineteenth century. Under these circumstances, one of the factors that led astronomers to Copernicus (and one that could not have led them to Aristarchus) was the acknowledged crisis that was responsible for innovation in the first place.
T HE R ESPONSE TO C RISIS
Lavoisier saw as a counterexample what Priestley had seen as a successfully solved puzzle in the articulation of the phlogiston theory. Instead, by proliferating versions of the paradigm, the crisis loosens the rules of normal puzzle solving in ways that ultimately allow a new paradigm to emerge. More and more attention is being given to it by more and more of the most eminent men in the field.
All crises begin with the blurring of a paradigm and the resulting relaxation of the rules of normal inquiry. We have already explored some of the problems raised by saying that Priestley saw oxygen as dephlogized air. And in this last effort, more than in any other part of the post-paradigm development of science, he will almost resemble our most common image of the scientist.
Or again, new optical discoveries accumulated rapidly just before and during the rise of the wave theory of light. Sometimes the form of the new paradigm is foreshadowed in the structure that extraordinary research has given to the anomaly.
T HE N ATURE AND N ECESSITY OF S CIENTIFIC R EVOLUTIONS 92
The remainder of this essay seeks to show that the historical study of paradigm shifts reveals very similar features in the development of science. Nevertheless, regardless of its strength, the status of the circular argument is only persuasive. Although logical inclusiveness remains a permissible view of the relationship between successive scientific theories, it is historically implausible.
Although N1 are a special case of the laws of relativistic mechanics, they are not Newton's laws. Unless we change the variable definitions in N1, the statements we have derived are not Newtonian. An argument of the same kind is used to justify the surveyors' teaching of earth-centered astronomy.
Because in the transition to the border it is not only the forms of the laws that have changed. And the transformation is one that can only be undertaken with the benefits of hindsight, the explicit guidance of more recent theory.
R EVOLUTIONS AS C HANGES OF W ORLD V IEW
But while psychological experiments are suggestive, given the nature of the case they cannot be more than that. The same kinds of problems would arise if the scientist could switch back and forth, such as the subject of the Gestalt experiments. We have already noted some similar transformations of vision that can be deduced from the history of chemistry.
It could only—and by a different route it did—lead to the series of crises from which Galileo's view of the swinging stone emerged. As a result, post-revolutionary science always includes many of the same manipulations, carried out with the same instruments and described in the same terms, as its pre-revolutionary predecessor. Thus a nugget of silver held together because of the forces of affinity between silver bodies (until after Lavoisier these bodies were themselves thought of as composed of even more elementary particles).
Meldrum, "The Development of the Atomic Theory: (1) Berthollet's Doctrine of Variable Proportions," Manchester Memoirs, LIV. Meldrum, “The Development of the Atomic Theory: (6) The Acceptance of the Theory Advocated by Dalton,” Manchester Memoirs, LV.
T HE I NVISIBILITY OF R EVOLUTIONS
And the philosophy of science, especially that of the English-speaking world, analyzes the logical structure of the same complete body of scientific knowledge. Or again, Newton wrote that Galileo had discovered that constant gravity causes motion proportional to the square of time. But that completion involves more than a multiplication of the historical misconstructions illustrated above.
From the beginning of the scientific enterprise, a textbook presentation implies that scientists have striven for the particular goals embodied in today's paradigms. Many of the puzzles of modern normal science did not exist until after the last scientific revolution. A final example may clarify this account of the impact of textbook presentation on our image of scientific development.
As part of the pedagogical arsenal that turns a person into a scientist, attribution is enormously successful. 4 Marie Boas, in her Robert Boyle and Seventeenth-Century Chemistry (Cambridge, 1958), discusses Boyle's positive contributions to the evolution of the concept of a chemical element in many places.
T HE R ESOLUTION OF R EVOLUTIONS
Instead, testing occurs as part of the competition between two competing paradigms for the allegiance of the scientific community. Most likely, this points to one of the directions in which future discussions of verification should go. These examples point to the third and most fundamental aspect of the incomparability of competing paradigms.
These are the arguments, rarely made fully explicit, that appeal to the individual sense of the right or the aesthetic – such would be the new theory. For Einstein's response to the theory's precise agreement with the observed motion of Mercury's perihelion, see the letter quoted in P. By the time their full aesthetic appeal can be developed, most of the community has been convinced in other ways .
Men have been converted by them at times when most of the articulable technical arguments pointed the other way. More scientists will then be converted and the exploration of the new paradigm will continue.
P ROGRESS THROUGH R EVOLUTIONS
With respect to normal science, part of the answer to the problem of progress is simply in the eye of the beholder. However, that is only part of the answer and certainly not the most important part. All this, however, only points to the second main part of the problem of progress in the sciences.
These last paragraphs indicate the directions in which I believe a more refined solution of the problem of progress in the sciences must be sought. One of these is the description of the role of Newton's Principia in the development of eighteenth-century mechanics on p. I have already pointed out that membership in the community of chemists during the first half of the nineteenth century did not require a belief in atoms.
First, shared values can be important determinants of group behavior, although not all group members use them in the same way. Cases will therefore require more attention than other types of disciplinary matrix components.
