The Structure of Scientific Revolutions

Out-of-date theories are not in principle unscientific because they have been discarded. That choice, however, makes it difficult to see scientific development as a process of accretion.

The result of all these doubts and difficulties is a historiographic revolution in the study of science, though one that is still in its early stages.

If these out-of-date beliefs are to be called myths, then myths can be produced by the same sorts of methods and held for the same sorts of reasons that now lead to scientific knowledge. If, on the other hand, they are to be called science, then science has included bodies of belief quite incompatible with the ones we hold today.

This essay attempts to show that we have been misled by them in fundamental ways. Its aim is a sketch of the quite different concept of science that can emerge from the historical record of the research activity itself.

The more carefully they study, say, Aristotelian dynamics, phlogistic chemistry, or caloric thermodynamics, the more certain they feel that those once current views of nature were, as a whole, neither less scientific nor more the product of human idiosyncrasy than those current today.

Since my most fundamental objective is to urge a change in the perception and evaluation of familiar data

Particularly, I was struck by the number and extent of the overt disagreements between social scientists about the nature of legitimate scientific problems and methods. Both history and acquaintance made me doubt that practitioners of the natural sciences possess firmer or more permanent answers to such questions than their colleagues in social science. Yet, somehow, the practice of astronomy, physics, chemistry, or biology normally fails to evoke the controversies over fundamentals that today often seem endemic among, say, psychologists or sociologists. Attempting to discover the source of that difference led me to recognize the role in scientific research of what I have since called “paradigms.” These I take to be universally recognized scientific achievements that for a time provide model problems and solutions to a community of practitioners.

To my complete surprise, that exposure to out-of-date scientific theory and practice radically undermined some of my basic conceptions about the nature of science and the reasons for its special success.

As Peter Galison wrote, there are three parallel but largely independent traditions of research: theoretical, experimental, and instrumental.18 Each is essential to the other two, but they have a good deal of autonomy: Each has a life of its own.

Research problems do not aim to produce real novelty. A single sentence of page 35 sums up Kuhn’s doctrine: “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.” If you look at any research journal, he wrote, you will find three types of problems addressed: (1) determination of significant facts, (2) matching of facts with theory, and (3) articulation of theory. To expand slightly:

1.Theory leaves certain quantities or phenomena inadequately described and only qualitatively tells us what to expect. Measurement and other procedures determine the facts more precisely.

2.Known observations don’t quite tally with theory. What’s wrong? Tidy up the theory or show that the experimental data were defective.

3.The theory may have a solid mathematical formulation, but one is not yet able to comprehend its consequences. Kuhn gives the apt name of articulation to the process of bringing out what is implicit in the theory, often by mathematical analysis.