Scientific revolutions are necessary, Kuhn contends, because without them, science would not progress. Normal science, the kind of science that is characterized by rapid, highly specialized, and incremental progression, would not be possible without paradigms. And paradigms, Kuhn believes, only come about out of crisis states, which are produced by irreconcilable anomalies.

Paradigms provide scientists with the confidence and structure to do the kind of everyday work that moves science forward. In turn, this kind of everyday work—normal science—inevitably encounters anomalies that cannot be squared with the existing paradigm, and new paradigms can only be birthed through revolutions. It is these revolutions that continue to set science on the path towards steady progress.

Kuhn tackles the philosophical angle of scientific revolutions, positing that revolutions produce changes in the world view of scientists. Kuhn wavers between describing this shift as a change in world view and as a change in worlds. He suggests scientific revolutions may give rise to an entirely new world, in the sense that scientists who inhabit new paradigms approach, view, and interpret the world differently; they use the same terms to mean entirely different things, transplanting them into different contexts.