Chapter V of Kuhn, Structure of scientific revolutions
If normal science is so rigid and if scientific communities are so close-knit as the preceding discussion has implied, how can a change of paradigm ever affect only a small subgroup? What has been said so far may have seemed to imply that normal science is a single monolithic and unified enterprise that must stand or fall with any one of its paradigms as well as with all of them together. But science is obviously seldom or never like that … (p. 49)
Kuhn-on-normal-science emphasizes that normal science is rigid and rule-governed, that scientific communities are tight-knit and that the paradigm restricts what scientists do. This implies that normal science is a big, unified system where a change in one paradigm would shake the whole enterprise at once. However, scientific fields often look fragmented from each other, with some fields undergo revolutions while others carry on unaffected.
Kuhn acknowledges the tension: if normal science is rigid, how can only small subgroups experience a scientific-revolution? Kuhn’s answer is that the rigidity of normal science is within specialties, not across all of science.
This is what distinguishes paradigm from rules. If science were governed mainly by shared rules, we’d expect strong coherence across fields. By saying that science is governed by paradigms allows diversity, for different fields to have different paradigms and for subfields to diverge with their own paradigms as they specialize.
e.g. quantum physics scientists all begin with the initial paradigm but as they focus on different techniques, problem sets, exemplars, they effectively acquire distinct paradigms. So, there can be several traditions of normal science without being coextensive and a revolution produced in one subsection will not necessarily extend to the others (p. 50)