The Structure of Scientific Revolutions
by Thomas S. Kuhn

VIII - The to Crisis.

The and that a crisis exists loosens stereotypes and provides the incremental necessary for a shift. science does and must continually strive to bring and fact into closer agreement. The recognition and of anomalies result in crises that are a necessary precondition for the of novel and for change. Crisis is the essential in scientific . There is no such thing as without counterinstances. These counterinstances tension and crisis. Crisis is always in because every problem that science sees as a puzzle can be seen, from another viewpoint, as a counterinstance and thus as a of crisis.

In to these crises, scientists generally do not renounce the that has led them into crisis. Rather, they usually devise numerous articulations and ad hoc of their in order to any . Some, unable to tolerate the crisis, leave the profession. As a rule, and recognised anomaly does not crisis . Failure to the expected solution to a puzzle discredits only the scientist and not the . To evoke a crisis, an anomaly must usually be more than just an anomaly. Scientists who paused and examined every anomaly would not get much accomplished. An anomaly must come to be seen as more than just another puzzle of science.

All crises begin with the blurring of a and the loosening of the rules for . As this develops, the anomaly comes to be more generally recognised as such, more attention is to it by more of the field's eminent . The field begins to look quite different: scientists express discontent, competing articulations of the proliferate and scholars view a as the subject matter of their discipline. To this end, they first the anomaly more and give it . They push the rules of science harder than ever to see, in the of difficulty, just where and how far they can be made to work.

All crises close in one of three ways. (i) science proves able to handle the crisis-provoking problem and all returns to "." (ii) The problem resists and is , but it is as resulting from the field's failure to possess the necessary tools with which to solve it, and so scientists set it aside for a future with more developed tools. (iii) A new candidate for , and a battle over its acceptance ensues. Once it has the of , a paradigm is declared invalid only if an candidate is to take its place. Because there is no such thing as in the absence of a , to reject one without simultaneously another is to science itself. To declare a invalid will more than the falsification of the by direct comparison with nature. The judgement leading to this decision the comparison of the existing with nature and with the candidate. from a in crisis to a new one from which a new of science can is not a cumulative . It is a of the field from new . This changes some of the field's generalisations. It changes and applications. It the rules.

How do new ? Some all at once, sometimes in the middle of the night, in the mind of a man deeply immersed in crisis. Those who inventions of a new have generally been either very young or very new to the field whose they changed. Much of this is inscrutable and may be permanently so.

(A Synopsis from the orginal by Professor Frank Pajares, Emory University)