Thomas Kuhn's Theory of Scientific Revolutions

Thomas Kuhn, in Structure of Scientific Revolutions (first edition 1962, second edition 1970) argued that scientific revolutions proceeded through the following stages:
  1. "Normal Science", that is to say everyday, bread-and-butter science, is a "puzzle-solving" activity conducted under a reigning "paradigm".

  2. An "anomaly" arises when a puzzle, considered as important or essential in some way, cannot be solved. The anomaly cannot be written off as just an ill-conceived research project; it continues to assert itself as a thorn in the side of the practicing scientists. The anomaly is a novelty that cannot be written off, and which cannot be solved. Examples of anomalies include:

  3. This opens up a period called the "crisis", during which time new methods and approaches are permitted, since the older ones have proved incapable of rising to the task at hand (solving the anomaly). Views and procedures previously considered heretical are temporarily permitted, in the hope of cracking the anomaly.

  4. One of these new approaches is successful, and it becomes the new paradigm through a "paradigm shift". This constitutes the core of the scientific revolution.

  5. The new paradigm is popularized in text-books, which serve as the instruction material for the next generation of scientists, who are brought up with the idea that the paradigm -- once new and revolutionary -- is just the way things are done. The novelty of the scientific revolution recedes and disappears, until the process is begun anew with another anomoly-crisis-paradigm shift.