Crisis and the Emergence of Scientific Theories.
As is the case with discovery, a change in an existing theory that results in the invention of a new theory is also brought about by the awareness of anomaly. The emergence of a new theory is generated by the persistent failure of the puzzles of normal science to be solved as they should. Failure of existing rules is the prelude to a search for new ones. These failures can be brought about by observed discrepancies between theory and fact or changes in social/cultural climates Such failures are generally long recognised, which is why crises are seldom surprising. Neither problems nor puzzles yield often to the first attack . Recall that paradigm and theory resist change and are extremely resilient. Philosophers of science have repeatedly demonstrated that more than one theoretical construction can always be placed upon a given collection of data . In early stages of a paradigm, such theoretical alternatives are easily invented. Once a paradigm is entrenched (and the tools of the paradigm prove useful to solve the problems the paradigm defines), theoretical alternatives are strongly resisted. As in manufacture so in science--retooling is an extravagance to be reserved for the occasion that demands it. Crises provide the opportunity to retool.