Explain Kuhn's account of paradigms, normal and revolutionary science, and incommensurability, and assess what it implies for scientific objectivity and progress

What this dot point is asking

SEAB wants you to explain Thomas Kuhn's account of how science actually develops, through paradigms, normal science, crises and revolutions, and to assess what it implies for the objectivity and progress of science. Kuhn's view is the great rival to Popper's: where Popper offers a logic of how science ought to proceed, Kuhn offers a history of how it does. Your task is to set out his key concepts and weigh the worry that they make science less objective than we assumed.

The answer

Paradigms

A paradigm, in Kuhn's sense, is the constellation of shared commitments that defines a mature scientific community: a dominant theory, accepted methods and instruments, standards for what counts as a legitimate problem and an acceptable solution, and, importantly, concrete exemplary achievements (exemplars) that serve as models for future research. A paradigm is more than a theory; it is a whole way of seeing and working that scientists absorb through training, largely by solving standard problems.

Normal science

Most science, for Kuhn, is normal science: the patient activity that a paradigm makes possible. Normal scientists do not test the paradigm; they work within it, solving puzzles such as measuring constants more precisely, extending the theory to new cases, and articulating its consequences. The paradigm is assumed to be broadly correct, so when a puzzle resists solution, the failure is usually blamed on the scientist rather than the paradigm. This is why paradigms are highly stable and productive.

Anomalies, crisis and revolution

Over time, anomalies, results the paradigm cannot accommodate, accumulate. A few are tolerated, but when they grow serious and persistent, the community enters a crisis: confidence in the paradigm weakens and alternatives are entertained. A scientific revolution occurs when a new paradigm replaces the old one. After the revolution, normal science resumes under the new framework. Science thus develops not by smooth accumulation but by long stable periods punctuated by occasional upheavals.

Incommensurability

Kuhn's most controversial claim is that successive paradigms are incommensurable: they differ so deeply in concepts, problems and standards that there is no neutral, paradigm-independent measure by which to compare them point for point. Terms shift meaning across the divide, the two paradigms partly disagree about what the facts even are (because observation is theory-laden), and they may not agree on what counts as a good solution. Choosing between paradigms is therefore not a simple matter of reading off which fits the neutral evidence better.

The challenge to objectivity and progress

Incommensurability raises a worry. If paradigm choice is not decided by a shared, theory-neutral standard, theory change can look more like a conversion or a sociological shift than a purely rational, evidence-driven decision. This seems to threaten the idea that science is fully objective and that it progresses toward truth. Kuhn softens this: he holds that trans-paradigm values, accuracy, scope, simplicity, fruitfulness and consistency, guide the choice, so it is not arbitrary. But because scientists weigh these values differently, judgement enters, and there is no algorithm. The defensible reading is that Kuhn shows scientific objectivity to be more value-laden and judgement-dependent than the cumulative picture allowed, without licensing the claim that anything goes.

Examples in context

Example 1. The shift in our model of the cosmos. The move from an Earth-centred to a Sun-centred model of the heavens was not just the addition of a fact; it reorganised what counted as a problem, what the central concepts meant, and what observations were salient. Defenders of each system could often accommodate the same data differently. The episode illustrates a Kuhnian revolution and the incommensurability of frameworks that partly disagree about how to read the evidence.

Example 2. Anomaly tolerated then decisive. A small, persistent discrepancy in a planet's orbit was, for a long time, treated as an unsolved puzzle within the reigning framework rather than a refutation of it. Only in the context of a new framework did the same discrepancy become a telling point in favour of the rival. This shows the Kuhnian claim that whether an anomaly counts as a refutation depends on the paradigm, contrary to naive falsificationism.

Try this

Q1. Define a paradigm and explain what normal science is. [6 marks]

• Cue. A paradigm is a framework of shared theory, methods, standards and exemplary solutions defining a community; normal science is the puzzle-solving done within it, assuming the paradigm is broadly correct rather than testing it.

Q2. Explain Kuhn's notion of incommensurability and why it matters for objectivity. [8 marks]

• Cue. Rival paradigms lack a common neutral standard because concepts, problems, standards and even facts differ; this makes paradigm choice judgement-laden rather than a neutral calculation, challenging a fully objective, cumulative picture of science.

Q3. Explain one way Kuhn's view differs from Popper's. [6 marks]

• Cue. Popper says a refuted theory should be rejected; Kuhn observes scientists retain a paradigm despite anomalies until a better one appears, and he describes how science develops rather than prescribing a logic of testing.