Excellent Summary on Thomas Kuhn and his 'paradigms':
http://www.emory.edu/EDUCATION/mfp/Kuhnsnap.html
Key Ideas from the Summary:
paradigm normal science anomaly crises scientific revolution (evolution)
Paradigm- a collection of beliefs shared by scientists, a set of agreements about how problems are to be understood
"no natural history can be interpreted in the absence of at least some implicit body of intertwined theoretical and methodological belief that permits selection, evaluation, and criticism."
A fundamental theme of Kuhn's argument is that the typical developmental pattern of a mature science is the successive transition from one paradigm to another through a process of revolution. When a paradigm shift takes place, "a scientist's world is qualitatively transformed [and] quantitatively enriched by fundamental novelties of either fact or theory."
Normal science- "means research firmly based upon one or more past scientific achievements, achievements that some particular scientific community acknowledges for a time as supplying the foundation for its further practice".
"Paradigm changes can result from discovery brought about by encounters with anomaly."
On periods of 'normal science' and on 'times of crisis':
During periods of normal science, the primary task of scientists is to bring the accepted theory and fact into closer agreement. As a consequence, scientists tend to ignore research findings that might threaten the existing paradigm and trigger the development of a new and competing paradigm. For example, Ptolemy popularized the notion that the sun revolves around the earth, and this view was defended for centuries even in the face of conflicting evidence. In the pursuit of science, Kuhn observed, "novelty emerges only with difficulty, manifested by resistance, against a background provided by expectation."
And yet, young scientists who are not so deeply indoctrinated into accepted theories - a Newton, Lavoisier, or Einstein - can manage to sweep an old paradigm away. Such scientific revolutions come only after long periods of tradition-bound normal science, for "frameworks must be lived with and explored before they can be broken." However, crisis is always implicit in research because every problem that normal science sees as a puzzle can be seen, from another perspective, as a counter instance and thus as a source of crisis. This is the "essential tension" in scientific research.
Crises are triggered when scientists acknowledge the discovered counter instance as an anomaly in fit between the existing theory and nature. All crises are resolved in one of three ways. Normal science can prove capable of handing the crisis-provoking problem, in which case all returns to "normal." Alternatively, the problem resists and is labeled, but it is perceived 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 generation with more developed tools. In a few cases, a new candidate for paradigm emerges, and a battle over its acceptance ensues - these are the paradigm wars.
In the face of these arguments, how and why does science progress, and what is the nature of its progress?
Kuhn argued that normal science progresses because members of a mature scientific community work from a single paradigm or from a closely related set and because different scientific communities seldom investigate the same problems. The result of successful creative work addressing the problems posed by the paradigm is progress.
Paradigms can 'bring to light' certain problems and hide others.
Paradigms evolve (Darwinian idea). Not necessarily towards a true objective truth (of nature), but are building on primitive foundations.
As to whether progress consists in science discovering ultimate truths, Kuhn observed that "we may have to relinquish the notion, explicit or implicit, that changes of paradigm carry scientists and those who learn from them closer and closer to the truth." Instead, the developmental process of science is one of evolution from primitive beginnings through successive stages that are characterized by an increasingly detailed and refined understanding of nature. Kuhn argued that this is not a process of evolution toward anything, and he questioned whether it really helps to imagine that there is one, full, objective, true account of nature. He likened his conception of the evolution of scientific ideas to Darwin's conception of the evolution of organisms.
From http://www.emory.edu/EDUCATION/mfp/kuhnsyn.html:
Why a shift occurs:
Why does a shift in view occur? Genius? Flashes of intuition? Sure. Because different scientists interpret their observations differently? No. Observations are themselves nearly always different. Observations are conducted within a paradigmatic framework, so the interpretative enterprise can only articulate a paradigm, not correct it. Because of factors embedded in the nature of human perception and retinal impression? No doubt, but our knowledge is simply not yet advanced enough on this matter. Changes in definitional conventions? No. Because the existing paradigm fails to fit? Always. Because of a change in the relation between the scientist's manipulations and the paradigm or between the manipulations and their concrete results? You bet. It is hard to make nature fit a paradigm.
How a shift occurs:
What is the process by which a new candidate for paradigm replaces its predecessor? At the start, a new candidate for paradigm may have few supporters (and the motives of the supporters may be suspect). If the supporters are competent, they will improve the paradigm, explore its possibilities, and show what it would be like to belong to the community guided by it. For the paradigm destined to win, the number and strength of the persuasive arguments in its favour will increase. As more and more scientists are converted, exploration increases. The number of experiments, instruments, articles, and books based on the paradigm will multiply. More scientists, convinced of the new view's fruitfulness, will adopt the new mode of practising normal science, until only a few elderly hold-outs remain. And we cannot say that they are (or were) wrong. Perhaps the scientist who continues to resist after the whole profession has been converted has ipso facto ceased to be a scientist.
Outline of 'Structure of Scientific Revolutions':
http://www.emory.edu/EDUCATION/mfp/Kuhn.html