An Introduction to
Thomas S. Kuhn's
The Structure of Scientific Revolutions (originally
published in 1962)
Thomas Kuhn is an historican
of science, originally trained as a physicist, who published a short book
in 1962 on how science progresses. It has had an impact far beyond anything
he originally envisioned. Translated into sixteen languages and selling
over one million copies, Kuhn's book has reshaped how we think about science
and remains hotly debated today. Anyone interested in science as a form
of social activity should be familiar with Kuhn's book.
Kuhn's scientific interests
have focused exclusively on the natural sciences, particularly physics
and chemistry. He has never claimed to have anything to say directly about
the social sciences; in fact, he has expressed skepticism about whether
his ideas are applicable to the social sciences. Still, his work has been
enthusiastically received by sociologists and other social scientists,
for essentially two reasons:
1) First, Kuhn provides a highly sociological
view of what science is and how it progresses. Disputing the sense
of almost inevitable, linear progress suggested by science textbooks,
Kuhn's view of science emphasizes communities of real people, held
together by shared beliefs and periodically split apart by conflict.
Kuhn was certainly not the first to recognize that the science shares
many characteristics with other social activities, but he provides
a model of what this involves that has been particularly compelling
to many social scientists.
2) Second, many sociologists have found
Kuhn's model of how a scientific field emerges and changes to be very
suggestive about sociology's claim to be a science. Not all sociologists
have drawn the same conclusions from Kuhn, but his ideas and vocabulary
have come to frame much of their discussion. It is almost impossible
to make sense of many theoretical debates within sociology without
familiarity with Kuhn's basic concepts.
Despite its relative
brevity (just over 200 pages), Kuhn's book is a demanding one, presupposing
familiarity with the history and philosophy of science. Accordingly, what
I shall try to do in this handout is to introduce you to the main points
relevant to this course. Inevitably in this process I shall leave out
Kuhn's rich historical detail. I will rely on direct quotations from Kuhn
as much as possible, however, in order to let him speak for himself and
for you to get a flavor of his writing. The true measure of the success
of this introduction to Kuhn's work is if it convinces you someday to
search out the book and read it yourself, for this introduction barely
skims the surface of a complex and fascinating book.
In his Preface, Kuhn
notes that a year he spent among social scientists at the Center for Advanced
Study in the Behavioral Sciences confronted him
with unanticipated problems about the
differences between such communities [of social scientists] and those
of the natural scientists among whom I had been trained. Particularly,
I was struck by the number and extent of the overt disagreements between
social scientists about the nature of legitimate scientific problems
and methods. Both history and acquaintance made me doubt that practitioners
of the natural science possess firmer or more permanent answers to
such questions than their colleagues in social science. Yet, somehow,
the practice of astronomy, physics, chemistry, or biology normally
fails to evoke the controversies over fundamentals that today often
seem endemic among, say, psychologists or sociologists. Attempting
to discover the source of that difference led me to recognize the
role in scientific research of what I have since called "paradigms."
These I take to be universally recognized scientific achievements
that for a time provide model problems and solutions to a community
of practitioners. Once that piece of my puzzle fell into place, a
draft of this essay emerged rapidly. (p. viii)
Note that in this passage Kuhn gives an
early and preliminary definition of one of his key concepts: paradigm.
But Kuhn's concepts are complex, and he reworks his definitions as he
approaches them from different angles. So pay attention to how he recasts
the meaning of "paradigm" later on.
One reason why Kuhn's
book was so important and controversial was that it challenged the prevailing
positivistic concept of science as a unitary and unidirectional
process of accumulating facts about the world. [As you may recall from
class discussion, positivism generally stresses the radical difference
between science and other forms of human understanding and sees no essential
difference between the goals and methods of natural and social sciences.]
For Kuhn, the textbooks by which each scientific generation learns its
craft convey a very misleading concept of what science is and how it develops.
He summarizes the textbook view of science as follows:
If science is the constellation of facts,
theories, and methods collected in current texts, then scientists
are the men who, successfully or not, have striven to contribute one
or another element to that particular constellation. Scientific development
becomes [in such a view] the piecemeal process by which these items
have been added, singly and in combination, to the ever growing stockpile
that constitutes scientific technique and knowledge. And history of
science becomes the discipline that chronicles both these successive
increments and the obstacles that have inhibited their accumulation.
(pp. 1-2)
The rest of Kuhn's book is an attack on
this texbook notion of science as incremental, evolutionary, cumulative,
and based on a single scientific method.
Kuhn's alternative to
this textbook view is organized around four key concepts: paradigm, normal
science, anomaly, and scientific revolution. For Kuhn, the development
of science is a discontinuous process, punctuated periodically by scientific
revolutions.
Paradigms
Paradigms, Kuhn suggests, are the basis
of all science. Indeed, what we mean by science are the activities of
a group of people ("practitioners") who share a paradigm. Critics
have pointed out that Kuhn uses the term "paradigm" rather loosely,
but basically all paradigm share "two essential characteristics":
Their achievement was sufficiently unprecedented
to attract an enduring group of adherents away from competing modes
of scientific activity. Simultaneously, it was sufficiently open-ended
to leave all sorts of problems for the redefined group of practitioners
to resolve....By choosing [the term paradigm], I mean to suggest that
some accepted examples of scientific practice--examples which include
law, theory, application, and instrumentation together--provide models
from which spring particular coherent traditions of scientific research....Men
whose research is based on shared paradigms are committed to the same
rules and standards for scientific practice. That commitment and the
apparent consensus it provides are prerequisites for normal science,
i.e., for the genesis and continuation of a particular research tradition.
(p. 10)
Before a shared paradigm
exists, Kuhn points out, there is no agreement about what is important
and how scientists should proceed:
In the absence of a paradigm or some
candidate for paradigm, all of the facts that could possibly pertain
to the development of a given science are likely to seem equally relevant.
As a result, early fact-gathering is a far more nearly random activity
than the one that subsequent scientific development makes familiar.
(p. 15)
The thrust of Kuhn's
argument up to this point can be summed up in his chapter heading, "the
priority of paradigms." Paradigms are not so much the outcome of
science as its very basis. It is when a community of practitioners comes
to share a paradigm that a science (say, electrical engineering--or maybe
sociology?) comes into existence. Indeed, scientific "facts"
only acquire their meaning and significance on the basis of a pre-existing
paradigm. Paradigms make scientific work possible--and such work is in
most instances what Kuhn calls "normal science."
Normal Science
What most scientists do most of the time,
Kuhn says, is normal science. What makes a paradigm attractive is its
promise of success, and normal science is the process of actualizing the
promise of a paradigm. As Kuhn puts it:
The success of a paradigm....is at the
start largely a promise of success discoverable in selected and still
incomplete examples. Normal science consists in the actualization
of that promise, an actualization achieved by extending the knowledge
of those facts that the paradigm displays as particularly revealing,
by increasing the extent of the match between those facts and the
paradigm's predictions, and by further articulation of the paradigm
itself. (pp. 23-24)
New paradigms by their nature leave a lot
of loose ends to be taken care of; Kuhn at first refers to this work as
"mop-up work" and notes: "Mopping-up operations are what
engage most scientists throughout their careers. They constitute what
I am here calling normal science." (p. 24) This work is "mopping-up"
in the sense that the basic direction of the enterprise has been set by
the paradigm. But perhaps a better phrase is the other one Kuhn employs:
"puzzle-solving." What mopping-up practically consists of is
solving puzzles that are posed by the paradigm but not yet answered.
Bringing a normal research problem to
a conclusion is achieving the anticipated in a new way, and it requires
the solution of all sorts of complex instrumental, conceptual, and
mathematical puzzles. The man who succeeds proves himself an expert
puzzle-solver, and the challenge of the puzzle is an important part
of what usually drives him on. (p. 36)
The life of a paradigm,
then, is found in the normal science it generates. A paradigm without
normal science would be lifeless and uninteresting. Still, for all the
ingenuity and effort that goes into normal science, it is a basically
conservative process. What Kuhn means by this is that normal science is
never designed to produce fundamental novelty--that is, to challenge the
paradigm within which normal science takes place. The validity of the
paradigm is simply assumed. In this sense, Kuhn refers good-naturedly
at one point to normal science as "a strenuous and devoted attempt
to force nature into the conceptual boxes supplied by professional education."
(p.5) This is so taken for granted by normal scientists most of the time
they don't even think about it.
Normal science is an
inherently limited enterprise, and interestingly, Kuhn argues, the limitations
paradigms place on normal science research are keys to its success:
We have already seen, however, that
one of the things a scientific community acquires with a paradigm
is a criterion for choosing problems that, while the paradigm is taken
for granted, can be assumed to have solutions. To a great extent these
are the only problems that the community will admit as scientific
or encourage its members to undertake. Other problems, including many
that had previously been standard, are rejected as metaphysical, as
the concern of another discipline, or sometimes as just too problematic
to be worth the time. A paradigm can, for that matter, even insulate
the community from those socially important problems that are not
reducible to the puzzle form, because they cannot be stated in terms
of the conceptual and instrumental tools the pradigm supplies.....One
of the reasons why normal science seems to progress so rapidly is
that its practitioners concentrate on problems that only their own
lack of ingenuity should keep them from solving. (p. 37)
Anomalies and Extraordinary Science
Despite its conservative
character, normal science in the long run inevitably produces novelty--which
it experiences as anomalies--results and findings which do not fit the
expectations of the paradigm. In doing so, normal science sometimes unleashes
a process that ends in scientific revolution. Kuhn states:
....the very nature of normal science
research ensures that novelty shall not be suppressed for very long.
Sometimes a normal problem, one that ought to be solvable by known
rules and procedures, resists the reiterated onslaught of the ablest
members of the group within whose competence it falls. On other occasions
a piece of equipment designed and constructed for the purpose of normal
research fails to perform in the anticipated manner, revealing an
anomaly that cannot, despite repeated effort, be aligned with professional
expectation. In these and other ways besides, normal science repeatedly
goes astray. And when it does--when, that is, the profession can no
longer evade anomalies that subvert the existing tradition of scientific
practice--then begin the extraordinary investigations that lead the
profession at last to a new set of commitments, a new basis for the
practice of science. The extraordinary episodes in which that shift
of professional commitments occurs are the ones known in this essay
as scientific revolutions. They are the tradition-shattering complements
to the tradition-bound activity of normal science. (pp. 5-6)
Anomalies create a sense
of crisis if they persist, for their existence casts doubt on the "truth"
of the paradigm. The failure of the existing paradigm to explain anomalies
leads to a crisis characterized by the breakdown and proliferation of
theories and methods. "The proliferation of competing articulations,
the willingness to try anything, the expression of explicit discontent,
the recourse to philosophy and to debate over fundamentals, all these
are symptoms of a transition from normal to extraordinary research."
(p. 91) The crisis is resolved in one of three ways:
Sometimes normal
science ultimately proves able to handle the crisis-provoking problem
despite the despair of those who have seen it as the end of an existing
paradigm. On other occasions the problem resists even apparently radical
new approaches. Then scientists may conclude that no solution will
be forthcoming in the present state of their field. The problem is
labelled and set aside for a future generation with more developed
tools. Or, finally, ...... a crisis may end with the emergence of
a new candidate for paradigm and with the ensuing battle over its
acceptance. (p. 84)
Scientific Revolutions
Scientific revolutions,
then, are the culmination of a recurrent process in the history of science,
according to Kuhn. Paradigms give rise to normal science. At some point
normal science gives rise to anomalies, which in turn give rise to a period
of extraordinary science. If the outcome of this process is that a new
paradigm replaces the old one, a scientific revolution is said to have
occurred.
Kuhn is not taking a
relativist position in this--for example, that there is no difference
in the two paradigms except that one is new. He clearly believes that
science progresses in this process, that the new paradigm marks an advance
on the old. There are good reasons why the scientific community makes
the switch. Still, he does emphasize that the decision to replace one
paradigm with another is partly based on faith.
The man who embraces a new paradigm
at an early stage must often do so in defiance of the evidence provided
by problem-solving. He must, that is, have faith that the new paradigm
will succeed with the many large problems that confront it, knowing
only that the older paradigm has failed with a few. A decision of
that kind can only be made on faith. (p. 158)
Because of this role of "faith,"
scientific revolutions share a number of characteristics with social and
political revolutions, Kuhn suggests:
Political revolutions aim to change
political institutions in ways those institutions themselves prohibit.
Their success therefore necessitates the partial relinquishment of
one set of institutions in favor of another, and in the interim, society
is not fully governed by institutions at all. Initially it is crisis
alone that attenuates the role of political institutions as we have
already seen it attenuate the role of paradigms. In increasing numbers
individuals become increasingly estranged from political life and
behave more and more eccentrically within it. Then, as the crisis
deepens, many of these individuals commit themselves to some concrete
proposal for the reconstruction of society in a new institutional
framework. At that point the society is divided into competing camps
or parties, one seeking to defend the old institutional constellation,
the others seeking to institute some new one. And once that polarization
has occurred, political recourse fails. Because they differ
about the institutional matrix within which political change is to
be achieved and evaluated, because they acknowledge no supra-institutional
framework for the adjudication of revolutionary difference, the parties
to a revolutionary conflict must finally resort to the techniques
of mass persuasion, often including force. Though revolutions have
had a vital role in the evolution of political institutions, that
role depends upon their being partially extrapolitical or extrainstitutional
events.
The remainder of this essay aims to
demonstrate that the historical study of paradigm changes reveals
very similar characteristics in the evolution of the sciences. Like
the choice between competing institutions, that between competing
paradigms proves to be a choice between incompatible modes of community
life. Because it has that character, the choice is not and cannot
be determined merely by the evaluative procedures characteristic of
normal science, for these depend in part upon a particular paradigm,
and that paradigm is at issue. When paradigms enter, as they must,
into a debate about paradigm choice, their role is necessarily circular.
Each group uses its own paradigm to argue in that paradigm's defense.
(pp. 93-94)
As this analogy suggests,
no paradigm is ever rejected just because it has problems. Science is
based on paradigms, and so the rejection of one paradigm has to be at
the same time the acceptance of another. As Kuhn puts it: "To reject
one paradigm without simultaneously substituting another is to reject
science itself." (p. 79) Yet just as monarchies like to pretend they
date back practically forever, so the victorious paradigm gives rise to
textbooks that reinterpret scientific history as a mix of past error and
incomplete steps towards the reigning paradigm. Past scientific revolutions
thereby become invisible, and textbook notions of the evolutionary stockpiling
of scientific knowledge become "common sense." Kuhn seeks to
recover this history of science and in the process generate a better understanding
of what science is and how it progresses.
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