Josiah Davis

Thomas Kuhn on Science


What is the nature of science? Is science fundamentally data and methodology driven or is it based on an particular and unproven view of the world? Originally published in 1962, The Structure of Scientific Revolutions challenges the conventional understanding of science through a deep analysis of historical examples such as the Copernican, Newtonian, and Lavoisierian Revolutions. Thomas Kuhn, a former physicist turned historian argues against a cumulative and deterministic view of science, one where new knowledge is gradually added upon past knowledge through strict following of a “scientific methodology”, which was famously advocated for by Karl Popper. Rather, he stresses the idea of a paradigm, which is an accomplishment that defines “acceptable” problems for normal research but is ultimately based on a particular view of the world which cannot be proved by simple appeals to data and falsified hypotheses. The fact that almost all normal science presupposes these these fundamental paradigms, and that these paradigms can be (and are) completely replaced with new paradigms if (a) they are found to be seriously lacking and (b) an alternative paradigm is supplied, raises the question of what it means to make scientific progress.

Questions and Answers

Q: What is the Structure of Scientific Revolutions?

normal science with a paradigm and a dedication to solving puzzles; followed by serious anomalies, which lead to a crisis; and finally resolution of the crisis by a new paradigm (Introductory Essay by Ian Hacking).

Q: What is Normal Science?

The most striking feature of the normal research problems we have just encountered is how little they aim to produce major novelties, conceptual or phenomenal (Chapter VII, Crisis and the Emergence of Scientific Discoveries).

To scientists, at least, the results gained in normal research are significant because they add to the scope and precision with which the paradigm can be applied (Chapter VII, Crisis and the Emergence of Scientific Discoveries).

Q: How is Normal Science like Puzzle Solving?

It is no criterion of goodness in a puzzle that its outcome be intrinsically interesting or important (Chapter VII, Crisis and the Emergence of Scientific Discoveries).

Though intrinsic value is no criterion for a puzzle, the assured existence of a solution is (Chapter VII, Crisis and the Emergence of Scientific Discoveries).

There must also be rules that limit both the nature of acceptable solutions and the steps by which they are to be obtained. To solve a jigsaw puzzle is not, for example, merely “to make a picture” (Chapter VII, Crisis and the Emergence of Scientific Discoveries).

Q: What is a Paradigm?

An achievement that serves:

for a time implicitly to define the legitimate problems and methods of a research field for succeeding generations of practitioners (Chapter II, The Route to Normal Science).

These achievements possess two critical characteristics:

  1. …sufficiently unprecedented to attract an enduring group of adherents away from competing modes of scientific activity.
  2. … sufficiently open-ended to leave all sorts of problems for the redefined group of practitioners to resolve. (Chapter II, The Route to Normal Science).

Q: What is an Anomaly?

…the recognition that nature has somehow violated the paradigm-induced expectations that govern normal science (Chapter VI, Anomoly and the Emergence of Scientific Discoveries).

Q: What is a Crisis?

[A situation where] the awareness of anomaly had lasted so long and penetrated so deep that one can appropriately describe the fields affected by it as in a state of growing crisis (Chapter VII, Crisis and the Emergence of Scientific Discoveries).

Q: Why is a Revolution Necessary?

… the proponents of competing paradigms practice their trades in different worlds. One contains constrained bodies that fall slowly, the other pendulums that repeat their motions again and again. In one, solutions are compounds, in the other mixtures. One is embedded in a flat, the other in a curved, matrix of space. Practicing in different worlds, the two groups of scientists see different things when they look from the same point in the same direction.

Q: What is an example of a Scientific Revolution?

The Copernican Revolution is one of several examples that he describes in depth:

When its predecessor, the Ptolemaic system, was first developed during the last two centuries before Christ and the first two after, it was admirably successful in predicting the changing positions of both stars and planets. No other ancient system had performed so well; for the stars, Ptolemaic astronomy is still widely used today as an engineering approximation; for the planets, Ptolemy’s predictions were as good as Copernicus’. But to be admirably successful is never, for a scientific theory, to be completely successful. With respect both to planetary position and to precession of the equinoxes, predictions made with Ptolemy’s system never quite conformed with the best available observations. Further reduction of those minor discrepancies constituted many of the principal problems of normal astronomical research for many of Ptolemy’s successors… (Chapter VII, Crisis and the Emergence of Scientific Discoveries)

Given a particular discrepancy, astronomers were invariably able to eliminate it by making some particular adjustment in Ptolemy’s system of compounded circles. But as time went on, a man looking at the net result of the normal research effort of many astronomers could observe that astronomy’s complexity was increasing far more rapidly than its accuracy and that a discrepancy corrected in one place was likely to show up in another (Chapter VII, Crisis and the Emergence of Scientific Discoveries).

In the sixteenth century, Copernicus’ coworker, Domenico da Novara, held that no system so cumbersome and inaccurate as the Ptolemaic had become could possibly be true of nature. And Copernicus himself wrote in the Preface to the De Revolutionibus that the astronomical tradition he inherited had finally created only a monster. By the early sixteenth century an increasing number of Europe’s best astronomers were recognizing that the astronomical paradigm was failing in application to its own traditional problems. That recognition was prerequisite to Copernicus’ rejection of the Ptolemaic paradigm and his search for a new one. His famous preface still provides one of the classic descriptions of a crisis state. (Chapter VII, Crisis and the Emergence of Scientific Discoveries).

Copernicus saw as counterinstances what most of Ptolemy’s other successors had seen as puzzles in the match between observation and theory (Chapter VIII, The Response to Crisis).

Copernicus complained that in his day astronomers were so “inconsistent in these [astronomical] investigations . . . that they cannot even explain or observe the constant length of the seasonal year.” “With them,” he continued, “it is as though an artist were to gather the hands, feet, head and other members for his images from diverse models, each part excellently drawn, but not related to a single body, and since they in no way match each other, the result would be monster rather than man” (Chapter VIII, The Response to Crisis).

Consider, for another example, the men who called Copernicus mad because he proclaimed that the earth moved. They were not either just wrong or quite wrong. Part of what they meant by ‘earth’ was fixed position. Their earth, at least, could not be moved. Correspondingly, Copernicus’ innovation was not simply to move the earth. Rather, it was a whole new way of regarding the problems of physics and astronomy, one that necessarily changed the meaning of both ‘earth’ and ‘motion.’4 Without those changes the concept of a moving earth was mad. (Chapter XII, The Resolution of Revolutions).

Q: Is Kuhn anti-truth?

Unfortunately [Kuhn’s work] was also abused by the wave of skeptical intellectuals who called the very idea of truth in question. Kuhn had no such intention. He was a fact lover and a truth seeker (Introductory Essay by Ian Hacking).

Q: So, what do Scientists do?

The scientific enterprise as a whole does from time to time prove useful, open up new territory, display order, and test long-accepted belief. Nevertheless, the individual engaged on a normal research problem is almost never doing any one of these things. Once engaged, his motivation is of a rather different sort. What then challenges him is the conviction that, if only he is skillful enough, he will succeed in solving a puzzle that no one before has solved or solved so well. Many of the greatest scientific minds have devoted all of their professional attention to demanding puzzles of this sort. On most occasions any particular field of specialization offers nothing else to do, a fact that makes it no less fascinating to the proper sort of addict (Chapter IV, Normal Science as Puzzle Solving).