A paradigm shift is philosopher Thomas Kuhn’s term for the wholesale replacement of a scientific community’s shared framework, or paradigm, once anomalies it cannot explain build into a crisis. Kuhn argued the change is driven as much by the psychology and sociology of the research community as by rational argument.
Summary
- Thomas Kuhn argued that science does not evolve gradually toward truth.
- Science has a paradigm that remains constant before going through a paradigm shift when current theories can’t explain some phenomenon, and someone proposes a new theory.
- A scientific revolution occurs when a new paradigm solves more of the puzzles a research community cares about than the old one did. The two paradigms are incommensurate, meaning there is no paradigm-neutral standard for judging either one objectively closer to reality.
- For example, Lamarckian evolution was replaced with Darwin’s theory of evolution by natural selection.
Paradigm Shift
Thomas Kuhn attacks “development-by-accumulation” views of science, which hold that science progresses linearly by accumulating theory-independent facts.
Kuhn looked at the history of science and argued that science does not simply progress by stages based upon neutral observations (e.g., Positivism).
For Kuhn, the history of science is characterized by revolutions in scientific outlook. Scientists have a worldview or “paradigm.”
A paradigm is a universally recognizable scientific achievement that, for a time, provides model problems and solutions to a community of practitioners.
A paradigm is a basic framework of assumptions, principles and methods from which the members of the community work.
It is a set of norms that tell scientists how to think and behave. Although rival schools of thought exist in science, there is still a single paradigm that all scientists accept uncritically.
Scientists accept the dominant paradigm until anomalies are thrown up.
Scientists then begin to question the basis of the paradigm itself, new theories emerge which challenge the dominant paradigm. Eventually, one of these new theories becomes accepted as the new paradigm.
During different periods of science, certain perspectives held sway over the thinking of researchers.
A particular work may “define the legitimate problems and methods of a research field for succeeding generations of practitioners.”
What a Paradigm Is Made Of
A paradigm is more than a single theory.
It covers the whole package a research community shares: its theories and general outlook, but also its standard techniques, instruments, and how new members are trained.
Part of that package is what Kuhn called an exemplar: a canonical worked example that trainee scientists learn to recognise and reproduce. A first-year physics student does not learn Newton’s laws mainly by memorising F = ma. The skill is practical.
They learn it by solving the same small set of canonical problems every physics student has solved before: the inclined plane, the pendulum, the orbiting satellite. Eventually they see a new problem as the same kind, and know almost automatically which technique to use. That is the exemplar at work.
Learning to be a researcher, on this view, means developing practical know-how, not memorising theories. Because a paradigm is a whole worldview, scientists cannot hold two at once.
What counts as a relevant “fact” is itself defined from inside the paradigm, a thesis Kuhn called theory-ladenness of observation. Facts, on this view, are never neutral.
Kuhn’s Phases of Science
According to Kuhn, knowledge that does not evolve according to the four main phases may not be considered scientific.
Phase 1: Pre-science
- The pre-paradigmatic state refers to a period before a scientific
consensus has been reached. - Disorganized and diverse activity.
- The constant debate over fundamentals.
- As many theories as there are theorists.
- No commonly accepted observational basis. The conflicting theories are constituted with their own set of theory-dependent observations.
Kuhn’s own example was pre-Newtonian optics. Before one theory of light won out, rival schools held light to be a stream of particles, a wave, or an emanation from the eye. Each school collected different “facts” as relevant.
Phase 2: Normal Science
(most common – science is usually stable)
- A paradigm is established, which lays the foundations for legitimate work within the discipline. Scientific work then consists of the articulation of the paradigm in solving puzzles that it throws up.
- A paradigm is a conventional basis for research; it sets a precedent.
- Puzzles that resist solutions are seen as anomalies.
- Anomalies are tolerated and do not cause the rejection of the theory, as scientists are confident these anomalies can be explained over time.
- Scientists spend much of their time in the Model Drift step, battling anomalies that have appeared. They may or may not know this or acknowledge it.
- It is necessary for normal science to be uncritical. If all scientists were critical of a theory and spent time trying to falsify it, no detailed work would ever get done.
“Normal Science, the activity in which most scientists inevitably spend almost all of their time, is predicated on the assumption that the scientific community knows what the world is like.
Much of the success of the enterprise derives from the community’s willingness to defend that assumption, if necessary, at considerable cost.
Normal Science, for example, often suppresses fundamental novelties because they are necessarily subversive of its basic commitments” (Kuhn, 1996, p. 5).
Phase 3: Crisis
- This is where the paradigm shift occurs.
- Anomalies become serious, and a crisis develops if the anomalies undermine the basic assumptions of the paradigm and attempt to remove them consistently fail.
- Under these circumstances, the rules for applying the paradigm become relaxed. Ideas that challenge the existing paradigm are developed.
- In a crisis, there will be ‘extraordinary science’ where there will be several competing theories.
- If the anomalies can be resolved, the crisis is over, and normal science resumes. If not, there is a scientific revolution that involves a change of paradigm.
Kuhn’s Key Study: The Chemical Revolution
Aim: Kuhn needed proof, not just argument.
He picked a well-documented episode that could show the anomaly-crisis-revolution pattern actually happening in a mature science: the 18th-century shift from phlogiston theory to Lavoisier’s oxygen theory of combustion.
Method: Kuhn read 18th-century chemical treatises to trace how phlogiston theorists explained combustion. He showed how increasingly precise balances produced a measurable anomaly, and how the rival camps argued past each other for roughly two decades.
Results: The evidence was simple. Chemists found that some burned metals gained weight instead of losing it, directly contradicting a theory in which a fire-like substance, “phlogiston,” is released during burning.
Phlogiston theorists patched the anomaly for decades, even suggesting phlogiston had “negative weight,” before the chemical community abandoned the theory outright in favour of Lavoisier’s oxygen theory.
Conclusion: Kuhn concluded the shift was not a step-by-step win for a better-confirmed theory. It was a wholesale reorganisation. The vocabulary, the accepted elements, and the decisive experiments all changed together.
It is Kuhn’s strongest single piece of evidence because it is so well documented. But critics note that basing a general theory of scientific change on one historical episode has real limits.
Phase 4: Revolution
- Eventually, a new paradigm will be established, but not because of any logically compelling justification.
- The reasons for the choice of a paradigm are largely psychological and sociological.
- The new paradigm solves the puzzles that made the old one break down. Kuhn denied this proves it is objectively closer to an external reality, since incommensurable paradigms cannot be compared on any neutral, paradigm-free standard.
- Different paradigms are held to be incommensurable — the new paradigm cannot be proven or disproven by the rules of the old paradigm, and vice versa.
- There is no natural measure or scale for ranking different paradigms.
Critical Evaluation
Kuhn’s impact runs deep. It shows up in the vocabulary of the philosophy of science itself. Besides “paradigm shift,” Kuhn raised the word “paradigm” from a specialist term in linguistics to its now-familiar broader meaning.
The idea caught on. The phrase “paradigm shift” is now so widely used that scientists have become more aware of, and often more receptive to, paradigm changes. Kuhn’s analysis of how scientific views evolve has, by itself, shaped that evolution. That shift was real.
For Kuhn, the choice of paradigm was sustained by, but not ultimately determined by, logical processes. Kuhn believed that it represented the consensus of the community of scientists. Acceptance or rejection of some paradigm is, he argued, a social process as much as a logical process.
This means Kuhn has been accused of being a relativist. Maybe all the theories are equally valid?
Why should we believe in today’s science when it might be overturned in the future?
Kuhn resisted this reading, but not by claiming paradigm shifts bring science objectively closer to the truth. Instead, he argued a later paradigm is usually a better instrument for solving the puzzles a community cares about than the one it replaced.
Does science make progress through scientific revolutions? Are later paradigms better than earlier ones? No, Kuhn suggests, they are just different.
The scientific revolutions that supplant one paradigm with another do not take us closer to the truth about how the world is.
Successive paradigms are incommensurable. Kuhn says that a later paradigm may be a better instrument for solving puzzles than an earlier one.
Kuhn compared this to a Gestalt switch, the kind of flip you get with an ambiguous figure like the duck-rabbit illusion. A viewer cannot see both the duck and the rabbit at once; they have to “choose” one, and neither reading is more correct.
His historical example was Galileo’s telescope. Galileo’s opponents refused to accept what they saw through it as evidence about the heavens. On their paradigm, the laws governing the stars were categorically different from those governing earthly objects.
Paradigms define their own puzzles. What counts as a puzzle for one paradigm may be no puzzle at all for another.
So why is it progressive to replace one paradigm with another which solves puzzles that the earlier paradigm does not even recognize?
Kuhn used his incommensurability thesis to disprove the view that paradigm shifts are objective. Truth is relative to the paradigm.
Science does not change its paradigm overnight. Younger scientists take a new paradigm forward.
As Kuhn put it, “a new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.”
Thomas Kuhn showed contemporary philosophers could not ignore the history of science and the social context in which science takes place. Science is a product of the society in which it is practiced.
Contemporary Research
Because Kuhn’s model is a piece of historical and philosophical argument, “contemporary research” here means recent scholarship that tests or applies the Kuhnian framework, not new experiments.
Is psychology unified under one paradigm? Historian of psychology Christopher Green traced the discipline’s actual 140-year institutional history (Green, 2015). He looked at which fields were absorbed into which university departments, which societies merged, and which political disputes shaped what counted as “psychology.”
No unifying theory emerged.
Instead, the topics were yoked together by contingent, opportunistic decisions about which university departments and learned societies to merge. He concluded that psychology is unlikely ever to unify the way physics did under Newton. Its future, he argued, more plausibly involves fragmenting into several large, coherent sub-disciplines.
Does the replication crisis fit Kuhn’s model? Vazire (2018) reframes psychology’s post-2011 replication crisis as a “credibility revolution.”
She argues that four connected reforms, greater transparency, pre-registration, direct replication, and higher evidentiary standards, function together as a genuine shift in what counts as an acceptable scientific claim. Failed replications and inflated effect sizes are the accumulated anomalies driving that shift.
Can Kuhn’s model diagnose a single subfield? Pearson et al. (2023) apply Kuhn’s vocabulary to psychiatry, arguing the dominant biological paradigm of psychosis, built around genetic and pharmacological explanation, is itself now in crisis.
They point to anomalies it struggles to absorb, including the meaningful, life-historical content of hallucinations and delusions that a purely biological model tends to treat as noise.
Weighed together, Green’s systematic institutional analysis carries the most evidential weight, while Vazire’s and Pearson et al.’s narrower claims remain live possibilities rather than settled findings.
Discussion Question: Is psychology a pre-science?
Was there a cognitive revolution from behaviorism that changed methodology and assumptions? Is cognitive psychology a new paradigm? Hints: It’s still reductionist; input – the output still uses the experimental method.
Does Psychology Have a Paradigm?
Kuhn argued a field only counts as a mature science once most of its researchers share one paradigm.
Applying this test to psychology remains genuinely contested. Historians and psychologists split into three broad positions:
- Preparadigmatic: psychology has never had one shared paradigm and remains a patchwork of competing schools.
- Sequential paradigm: psychology already went through one Kuhnian revolution, from behaviorism to cognitive psychology.
- Multiple paradigms: psychology houses several genuine, coexisting paradigms side by side.
Preparadigmatic View
Joynson (1980) and Boden (1980) argue psychology has never developed a genuine paradigm. On Kuhn’s own strict criterion, they say, the field remains preparadigmatic: a set of competing schools rather than one shared framework.
Kline (1988) reaches a similar conclusion from a different angle. He reads psychology’s major approaches, behaviorist, psychodynamic, cognitive, and humanistic, as rival, incommensurable “paradigms” that have never converged on shared assumptions or methods.
Each camp still disputes basic questions the others consider settled: what counts as evidence, which methods are legitimate, even what psychology is fundamentally about. The disagreement runs deep.
That is exactly the preparadigmatic pattern Kuhn described in early chemistry and pre-Newtonian physics. Many theories, no consensus, and no agreed way to settle the argument between them.
Sequential-Paradigm View
Valentine (1982) takes the opposite view: psychology has already had one genuine Kuhnian revolution. She argues behaviorism, at its peak, came closer than anything else in psychology’s history to a real paradigm.
Behaviorism had a clearly bounded subject matter, observable stimulus–response relationships. It had shared methods, the controlled laboratory experiment, and a training regime built on canonical exemplars like Pavlov’s dogs and Skinner’s operant chamber.
The mid-twentieth-century “cognitive revolution,” on this reading, was a genuine paradigm shift. The core commitment flipped.
Cognitive psychologists rejected behaviorism’s ban on studying unobservable mental states, rather than refining it.
They reintroduced concepts like memory stores and mental representations that behaviorism had ruled out of bounds.
Whether the shift had Kuhn’s full, all-or-nothing character is disputed. Plenty of behaviorist methodology, the controlled experiment, operational definitions, carried straight over into cognitive psychology, which looks more gradual than a clean Gestalt switch.
Multiple-Paradigm View
Smith et al. (1998) reject a two-way split altogether. They argue psychology simultaneously houses several genuine paradigms side by side, psychoanalysis, behaviorism, sociobiology, information-processing and cognitive approaches, and cognitive-developmental psychology.
None of these has driven the others to extinction. That sits in real tension with Kuhn’s own claim that mature paradigms succeed one another rather than coexisting.
Part of the problem is that “paradigm” itself is slippery. Masterman’s (1970) close reading of Kuhn’s book found the word used in more than twenty distinguishable senses, from a single worked example to an entire worldview.
If “paradigm” keeps shifting meaning, it becomes harder to say whether any given subfield genuinely has one, or several, or none at all.
There is no agreed resolution among the three positions.
References
Boden, M. A. (1980). Artificial intelligence and intellectual imperialism. In A. J. Chapman & D. M. Jones (Eds.), Models of man. British Psychological Society.
Green, C. D. (2015). Why psychology isn’t unified, and probably never will be. Review of General Psychology, 19(3), 207–214. https://doi.org/10.1037/gpr0000051
Joynson, R. B. (1980). Models of man: 1879–1979. In A. J. Chapman & D. M. Jones (Eds.), Models of man (pp. 1–14). British Psychological Society.
Kline, P. (1988). Psychology exposed, or the emperor’s new clothes. Routledge.
Kuhn, T. S. (1962). The structure of scientific revolutions. University of Chicago Press.
Pearson, M., Egglestone, S. R., & Winship, G. (2023). The biological paradigm of psychosis in crisis: A Kuhnian analysis. Nursing Philosophy, 24(4), e12418. https://doi.org/10.1111/nup.12418
Smith, P. K., Cowie, H., & Blades, M. (1998). Understanding children’s development (3rd ed.). Blackwell.
Valentine, E. R. (1982). Conceptual issues in psychology. Routledge.
Vazire, S. (2018). Implications of the credibility revolution for productivity, creativity, and progress. Perspectives on Psychological Science, 13(4), 411–417. https://doi.org/10.1177/1745691617751884
