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Kuhn on the Structure of
Scientific Revolutions
The Structure of Scientific Revolutions is a small monograph of less
than one hundred seventy-five pages written in a
fluent colloquial style that makes it easily
accessible to the average reader. It is the most renown of Kuhn’s works; indeed,
it was a succes
de scandale in the academic philosophy
community. It is strategically without any of the
mathematical equations that have enabled the modern
natural sciences since the historic Scientific
Revolution, and is mercifully without any of the
pretentious symbolic-logic chicken tracks that
retarded the examination of the same modern sciences
by the Logical Positivists and their like-minded
pedantics. It
was also a very timely presentation of the ascending
Pragmatist philosophy of science illustrated with a
plethora of apparently exemplifying cases from the
history of science, which seemed conclusively to
document the book's thesis.
Although many tenants of his 1962 book were
previously published by Kuhn in his "The
Essential Tension" in 1959, later reprinted in
a book of the same name in 1977, the 1962 book was
probably the most popular book pertaining to
philosophy and history of science published in the
1960's and for many years afterwards.
It was reported in Kuhn’s New
York Times obituary to have sold about one
million copies and to have been published in sixteen
languages by the time of his death.
It was widely read outside the relatively
small circle of professional philosophers and
historians of science.
In "Reflections on My Critics" in Criticism
and the Growth of Knowledge (ed. Lakatos and
Musgrave, 1970) Kuhn offers some personal insights.
He states that in his work as a historian of
science, he discovered that much scientific behavior
including that of the greatest scientists
persistently violated accepted methodological
canons, and that he wondered why these apparent
failures to conform to the canons did not at all
seem to inhibit the success of the scientific
enterprise. The
accepted methodological canons that Kuhn has in mind
are not only those of the Positivists but also
Popper's falsificationist thesis.
He states that his altered view of the nature
of science transforms what had previously seemed
aberrant behavior into an essential part of an
explanation for science's success, and that his
criterion for emphasizing any particular aspect of
scientific behavior is not simply that it occurs, or
merely that it occurs frequently, but rather that it
fits a theory of scientific knowledge, a theory
which he says may have normative as well as
descriptive value.
The seemingly aberrant behavior is what he
had previously called the problem of scientific
belief, the practice of ignoring anomalies.
The thesis of the book offers a coherent
description of the historical development in what he
calls the mature natural sciences.
Kuhn portrays the developmental procession as
an alternation between two phases, which he calls
"normal science" and "revolutionary
science", with each phase containing the seeds
for the emergence of the other.
In the normal science phase the phenomenon
that Conant called "prejudice" and that in
1957 Kuhn called the "problem of scientific
belief", reappears as "paradigm
consensus" in his 1962 book, where it assumes a
positive function without the ambivalence that it
formerly had in Kuhn's and Conant's minds.
In an article remarkably titled "The
Function of Dogma in Scientific Research" in Scientific Change (ed. Crombie, 1963) Kuhn maintains that advance
from one exclusive paradigm to another rather than
the continuing competition between recognized
classics, is a functional as well as a factual
characteristic of mature scientific development. In the revolutionary science phase the old paradigm around
which a consensus had been formed is replaced by a
new one, which is incommensurable with the old one.
Thus Kuhn’s work gives new and systematic meaning
to the already conventional metaphor, scientific
revolutions.
Kuhn's thesis is not just an eclectic
combination of philosophical and historical ideas. His concepts of normal and revolutionary science are aspects
of his distinctive sociological thesis, in which the
concept of science as a social institution is
fundamental. To
sociologists and cultural anthropologists the
concept of social institution means a set of beliefs
and values shared among the members of a group or
community, and internalized by each individual
member of the community.
The shared beliefs control the individual's
understanding of the world in which he lives, and
the shared value system regulates his voluntary
behavior including his interaction with others.
It is in these sociological terms that Kuhn
advances his startling new concept of the aim of
science. In
the normal science phase the consensus paradigm by
virtue of its consensus status assumes institutional
status in its scientific specialty, and the aim of
normal science is the further articulation of the
paradigm by a puzzle-solving type of research
uncritical of the paradigm.
The paradigm is the scientist's view of the
domain of his science, and the institutional
valuation that consensus associates with the
paradigm makes conformity with it the criterion for
scientific criticism.
Thus what Kuhn previously called the
"problem of scientific belief" is no
longer problematic; the belief status of the
paradigm is explained by its institutional status.
This status effectively makes it what Conant
called a "creed".
Research producing scientific change in the
normal science phase is controlled by belief in the
consensus paradigm, and the resulting scientific
change is always a change within the institutional
framework defined by the paradigm.
In striking contrast the revolutionary
science phase is not a change within the
institutional framework defined by the paradigm, but
rather is a change to another paradigm. It is therefore an institutional change in the sense of a
change of institutions.
Kuhn maintains that the new and old paradigms
involved in such an institutional change are
semantically and ontologically incommensurable, such
that there can be no shared higher framework to
control the revolutionary transition.
The term “revolution” in Kuhn’s thesis
is therefore not a metaphor.
Scientific revolutions are no less
revolutionary in the literal sense than are
political revolutions, because in neither case are
there laws to govern them.
With his sociological thesis in mind, Kuhn's
own dynamic view of science may be described as a
sequence of five phases, which follows closely the
sequence of several of the chapter headings in his
book:
(1) Consensus Phase.
Mature sciences are distinguished by normal
science, a type of research that is firmly based in
some past scientific achievement, and that the
members of the scientific specialty view as
supplying the foundations for research.
Unlike early science there are normally no
competing schools and perpetual quarrels over
foundations in a mature science.
The achievements that guide normal science
research are called paradigms, which consist of
accepted examples that provide models from which
spring particular traditions of scientific research.
A paradigm is an object for further
articulation and specification under new and more
stringent conditions, and it includes not only
articulate rules and theory, but also the tacit
knowledge and pre-articulate skills acquired by the
scientist. No
part of the aim of normal science is to call forth
new sorts of phenomena or to invent new theories.
This conformism proceeds both from a
professional education, which is an indoctrination
in the prevailing paradigm set forth in the
student's current textbooks and laboratory
exercises, and from a consensus belief shared by the
members of the scientific specialty that the
paradigm seems sufficiently promising as a guide for
future research and that acceptance of it is both an
obligatory and a justified act of faith.
Conformity to the paradigm assumes a
recognizable function, which is to focus the group's
attention upon a small range of relatively esoteric
problems, to investigate these problems in a depth
and detail that would not be possible if quarrels
over fundamentals were tolerated, and to restrict
the research resources of the profession to solvable
problems, where the solutions are solvable precisely
because they agree with the paradigm and are
interpretable in its terms.
(2) Anomaly Phase.
Normal science is a cumulative enterprise
having as its aim the steady extension of the scope
and accuracy of scientific knowledge represented by
the prevailing paradigm. Successful normal science does not find any novelties.
But anomalies occur as the extension of the
paradigm proceeds.
In fact the paradigm is the source of the
concepts needed for recognizing the new fact and for
giving it anomaly status.
The normal reaction to an anomaly is a
modification of the articulate rules and theories
associated with the consensus paradigm, so that the
anomalous fact can be assimilated.
Success in such modification is a noteworthy
achievement for a normal science researcher.
Isolated anomalies that are not assimilated
are normally set aside under the assumption that
eventually they will be reconciled, and normal
science research continues with the consensus
paradigm. Scientists
are not easily distracted by anomalies from
continued exploration of the promise of a generally
still satisfactory paradigm.
Kuhn rejects Popper's falsificationist
philosophy, stating that if every failure to fit
were ground for theory rejection, all theories ought
to be rejected at all times.
(3) Crisis Phase.
So long as the consensus paradigm is
relatively successful, no alternatives to it are
advanced. But
eventually the anomalies become more numerous and
more serious, and also the modifications necessary
to assimilate those anomalies that can be
assimilated, produce a certain amount of paradigm
destruction. In
due course some members of the profession lose faith
and begin to propose alternatives.
The construction of alternative theories is
always possible, because there is an arbitrary
aspect to language that permits many theories to be
imposed on the same collection of data.
When the consensus underlying the prevailing
paradigm begins to erode enough that some members
begin to exploit this arbitrary element and to
create new theories, the profession has entered the
phase of crisis.
Crises are the crossing of the threshold into
extraordinary or revolutionary science.
(4) Revolutionary Phase.
Kuhn postulates what he calls a "genetic
parallel" between political and scientific
revolutions. Just
as political revolutions are inaugurated by a
growing sense that existing institutions have ceased
adequately to meet the problems posed by an
environment that they have in part created, so too
scientific revolutions are inaugurated by a growing
sense that an existing paradigm has ceased to
function adequately in the exploration of the aspect
of nature to which the paradigm itself had
previously led the way.
Political revolutions aim to change political
institutions in ways that 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.
As alternatives are formulated, society is
divided into competing camps, those who support the
old institutions and those who support the new.
Once this polarization has occurred,
political recourse fails, because there is no
supra-institutional framework for adjudication of
differences. Kuhn
says that like the choice between competing
political institutions, that between competing
paradigms is a choice between incompatible modes of
community life.
In a scientific revolution the semantical and
ontological incommensurability between rival
paradigms excludes the possibility of any common
framework for communication or reconciliation.
Kuhn does not describe incommensurability in
terms of Whorf's linguistic relativity thesis, as
did Feyerabend thirteen years later.
Instead Kuhn invokes Hanson's thesis of gestalt switch, and references Hanson's Patterns of Discovery published four years earlier.
He compares the change of paradigm to the
visual gestalt
switch. A
certain gestalt is needed for the physics student to see the world as seen
by the scientist, when for example the latter sees
the electron’s track in the cloud chamber and the gestalt
which is learned by the student is provided by the
prevailing normal science paradigm.
When at times of revolution the normal
science tradition changes, then the scientist's
perception of his environment must be re-educated;
he must see with a new gestalt. This change of
paradigm is not achieved by deliberation and
interpretation, but rather by a sudden and
unstructured gestalt
switch. While
the members are individually experiencing the gestalt
switch, the profession is divided and confused, and
there is a communication breakdown between members
having different paradigm gestalten.
(5) Resolution Phase.
Kuhn does not believe that issues in
scientific revolutions are resolved by crucial
experiments or by any other kind of empirical
testing. In
normal science testing is never a test of the
paradigm, but rather it is a test of a
puzzle-solving attempt to extend the paradigm, and
involves a comparison of a single paradigm with
nature. Failure
of the test is not a failure of the paradigm, but
rather is a failure of the scientist.
In revolutionary science tests occur as part
of the competition between two rival paradigms for
the allegiance of the scientific community.
However, these tests do not have a
compellingly deciding function.
There can be no scientifically or empirically
neutral system of language or concepts for these
tests, since the paradigms are incommensurable, and
those who maintain the old paradigm must experience
a conversion to the new gestalt.
Tests serve only to persuade that the new
paradigm is the more promising guide for future
normal science research.
The actual decision about the future
performance of the new paradigm is based on faith.
As early supporters of the new paradigm show
success, others follow until there is a new normal
science consensus paradigm.
The procession has come full circle to a new
consensus paradigm.
In the final chapter of Structure
of Scientific Revolutions Kuhn discusses the
concept of scientific progress that is consistent
with his theory of the historical development of
science. He
maintains that the semantics of the term
"progress" is determined by reference to
the research work of normal science, and
specifically by the puzzle-solving type of work in
normal science in the absence of competing schools.
Progress occurs in extraordinary science by
the transition to a new consensus paradigm, because
in the judgment of the specialized scientific
community the new paradigm promises to resolve
outstanding problems that had occasioned the crisis
and transition, and to preserve the community's
problem-solving ability to treat the assembled data
with growing precision and detail, even though the
ability to solve problems cannot be a basis for
paradigm choice.
The Evolution of Kuhn’s
Philosophy
The evolution of Kuhn's central thesis of
incommensurability may be divided into three phases.
Firstly as in his Structure of Scientific Revolutions he described the idea in terms
of completely wholistic gestalt
switches. Some
philosophers such as Feyerabend had no problem with
the wholistic character of Kuhn’s
incommensurability thesis, but many others saw its
problematic implications for scientific criticism.
In his autobiographical discussion published
in The Road
Since Structure (2000) Kuhn reports that shortly
after writing Structure
of Scientific revolutions Hesse told him in
conversation that he needed to explain how science
is empirical and what difference observations make. He reports that he had agreed and that he replied he had not
previously seen it that way.
Therefore Kuhn entered a second phase
beginning with Criticism
and the Growth of Knowledge (1970), in which he
continued to invoke gestalt
switches, but he also introduced his idea of partial
communication permitted by
incommensurability-with-comparability in the attempt
to deflect the irrationalism that critics such as
Popper and others found in his views.
But as Shapere complained, Kuhn offered no
analysis of meaning to explain meaning change.
Then in his third phase Kuhn attempted
language analysis to explain his thesis of
incommensurability with comparability. His papers dealing with these attempts at linguistic analysis
are reprinted in Road
Since Structure (2000).
The sections below will consider firstly
Kuhn’s criticisms of Popper’s views, secondly
some of the criticisms by various philosophers of
his views expressed in Structure
of Scientific Revolutions and his replies to
these criticisms, thirdly the favorable reception of
his views by sociologists, and finally his belated
turn to language analysis.
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