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The Structure of Scientific Revolutions (1962;
second edition 1970; third edition 1996; fourth edition 2012) is a book about
the history of science by the philosopher Thomas S. Kuhn. Its publication was a
landmark event in the history, philosophy, and sociology of science. Kuhn
challenged the then prevailing view of progress in science in which scientific
progress was viewed as "development-by-accumulation" of accepted
facts and theories. Kuhn argued for an episodic model in which periods of
conceptual continuity where there is cumulative progress, which Kuhn referred
to as periods of "normal science", were interrupted by periods of
revolutionary science. The discovery of "anomalies" during
revolutions in science leads to new paradigms. New paradigms then ask new
questions of old data, move beyond the mere "puzzle-solving" of the
previous paradigm, change the rules of the game and the "map"
directing new research. For example, Kuhn's analysis of the Copernican
Revolution emphasized that, in its beginning, it did not offer more accurate
predictions of celestial events, such as planetary positions, than the
Ptolemaic system, but instead appealed to some practitioners based on a promise
of better, simpler solutions that might be developed at some point in the
future. Kuhn called the core concepts of an ascendant revolution its
"paradigms" and thereby launched this word into widespread analogical
use in the second half of the 20th century. Kuhn's insistence that a paradigm
shift was a mélange of sociology, enthusiasm and scientific promise, but
not a logically determinate procedure, caused an uproar in reaction to his
work. Kuhn addressed concerns in the 1969 postscript to the second edition. For
some commentators The Structure of Scientific Revolutions introduced a
realistic humanism into the core of science, while for others the nobility of
science was tarnished by Kuhn's introduction of an irrational element into the
heart of its greatest achievements.
History:
The Structure of Scientific Revolutions was first published as a
monograph in the International Encyclopedia of Unified Science, then as
a book by University of Chicago Press in 1962. In 1969, Kuhn added a postscript
to the book in which he replied to critical responses to the first edition. A
50th Anniversary Edition (with an introductory essay by Ian Hacking) was
published by the University of Chicago Press in April 2012. Kuhn dated the
genesis of his book to 1947, when he was a graduate student at Harvard
University and had been asked to teach a science class for humanities
undergraduates with a focus on historical case studies. Kuhn later commented
that until then, "I'd never read an old document in science."
Aristotle's Physics was astonishingly unlike Isaac Newton's work in its
concepts of matter and motion. Kuhn wrote "... as I was reading him,
Aristotle appeared not only ignorant of mechanics, but a dreadfully bad
physical scientist as well. About motion, in particular, his writings seemed to
me full of egregious errors, both of logic and of observation." This was
in an apparent contradiction with the fact that Aristotle was a brilliant mind.
While perusing Aristotle's Physics, Kuhn formed the view that in order
to properly appreciate Aristotle's reasoning, one must be aware of the
scientific conventions of the time. Kuhn concluded that Aristotle's concepts
were not "bad Newton," just different.This insight was the foundation
of The Structure of Scientific Revolutions. Prior to the publication of Kuhn's
book, a number of ideas regarding the process of scientific investigation and
discovery had already been proposed.
Ludwik Fleck developed the first system of the sociology of scientific
knowledge in his book The Genesis and Development of a Scientific Fact
(1935). He claimed that the exchange of ideas led to the establishment of a
thought collective, which, when developed sufficiently, served to separate the
field into esoteric (professional) and exoteric (laymen) circles. Kuhn wrote
the foreword to the 1979 edition of Fleck's book, noting that he read it in
1950 and was reassured that someone "saw in the history of science what I
myself was finding there." Kuhn was not confident about how his book would
be received. Harvard University had denied his tenure, a few years before.
However, by the mid-1980s, his book had achieved blockbuster status. When
Kuhn's book came out, in the early 1960s, "structure" was and
intellectually hot word in many fields in the humanities and social sciences,
including linguistics and anthropology, made appealing by the idea that complex
phenomena could reveal or be studied through basic simpler structures. Kuhn's
book had the effect of contributing to that idea. One theory to which Kuhn
replies directly is Karl Popper's “falsificationism,” which stresses
falsifiability as the most important criterion for distinguishing between that
which is scientific and that which is unscientific. Kuhn also addresses
verificationism, a philosophical movement that emerged in the 1920s among
logical positivists. The verifiability principle claims that meaningful
statements must be supported by empirical evidence or logical requirements.
Synopsis Basic approach:
Kuhn's approach to the history and philosophy of science focuses on conceptual
issues like the practice of normal science, influence of historical events,
emergence of scientific discoveries, nature of scientific revolutions and
progress through scientific revolutions. What sorts of intellectual options and
strategies were available to people during a given period? What types of
lexicons and terminology were known and employed during certain epochs?
Stressing the importance of not attributing traditional thought to earlier
investigators, Kuhn's book argues that the evolution of scientific theory does
not emerge from the straightforward accumulation of facts, but rather from a
set of changing intellectual circumstances and possibilities. Such an approach
is largely commensurate with the general historical school of non-linear
history. Kuhn did not see scientific theory as proceeding linearly from an
objective, unbiased accumulation of all available data, but rather as
paradigm-driven. “The operations and measurements that a scientist
undertakes in the laboratory are not ‘the given’ of experience but
rather ‘the collected with difficulty.’ They are not what the
scientist sees—at least not before his research is well advanced and his
attention focused. Rather, they are concrete indices to the content of more
elementary perceptions, and as such they are selected for the close scrutiny of
normal research only because they promise opportunity for the fruitful
elaboration of an accepted paradigm. Far more clearly than the immediate
experience from which they in part derive, operations and measurements are
paradigm-determined. Science does not deal in all possible laboratory
manipulations. Instead, it selects those relevant to the juxtaposition of a
paradigm with the immediate experience that that paradigm has partially
determined. As a result, scientists with different paradigms engage in
different concrete laboratory manipulations.”
Historical examples of chemistry:
Kuhn explains his ideas using examples taken from the history of science. For
instance, eighteenth-century scientists believed that homogenous solutions were
chemical compounds. Therefore, a combination of water and alcohol was generally
classified as a compound. Nowadays it is considered to be a solution, but there
was no reason then to suspect that it was not a compound. Water and alcohol
would not separate spontaneously, nor will they separate completely upon
distillation (they form an azeotrope). Water and alcohol can be combined in any
proportion. Under this paradigm, scientists believed that chemical reactions
(such as the combination of water and alcohol) did not necessarily occur in
fixed proportion. This belief was ultimately overturned by Dalton's atomic
theory, which asserted that atoms can only combine in simple, whole-number
ratios. Under this new paradigm, any reaction which did not occur in fixed
proportion could not be a chemical process. This type world-view transition
among the scientific community exemplifies Kuhn's paradigm shift.
Copernican Revolution
Main article: Copernican
Revolution
A famous example of a revolution in scientific thought is the Copernican
Revolution. In Ptolemy's school of thought, cycles and epicycles (with some
additional concepts) were used for modeling the movements of the planets in a
cosmos that had a stationary Earth at its center. As accuracy of celestial
observations increased, complexity of the Ptolemaic cyclical and epicyclical
mechanisms had to increase to maintain the calculated planetary positions close
to the observed positions. Copernicus proposed a cosmology in which the Sun was
at the center and the Earth was one of the planets revolving around it. For
modeling the planetary motions, Copernicus used the tools he was familiar with,
namely the cycles and epicycles of the Ptolemaic toolbox. Yet Copernicus' model
needed more cycles and epicycles than existed in the then-current Ptolemaic
model, and due to a lack of accuracy in calculations, his model did not appear
to provide more accurate predictions than the Ptolemy model.
Copernicus' contemporaries rejected his cosmology, and Kuhn asserts that they
were quite right to do so: Copernicus' cosmology lacked credibility. Kuhn
illustrates how a paradigm shift later became possible when Galileo Galilei
introduced his new ideas concerning motion. Intuitively, when an object is set
in motion, it soon comes to a halt. A well-made cart may travel a long distance
before it stops, but unless something keeps pushing it, it will eventually stop
moving. Aristotle had argued that this was presumably a fundamental property of
nature: for the motion of an object to be sustained, it must continue to be
pushed. Given the knowledge available at the time, this represented sensible,
reasonable thinking. Galileo put forward a bold alternative conjecture:
suppose, he said, that we always observe objects coming to a halt simply
because some friction is always occurring. Galileo had no equipment with which
to objectively confirm his conjecture, but he suggested that without any
friction to slow down an object in motion, its inherent tendency is to maintain
its speed without the application of any additional force.
The Ptolemaic approach of using cycles and epicycles was becoming strained:
there seemed to be no end to the mushrooming growth in complexity required to
account for the observable phenomena. Johannes Kepler was the first person to
abandon the tools of the Ptolemaic paradigm. He started to explore the
possibility that the planet Mars might have an elliptical orbit rather than a
circular one. Clearly, the angular velocity could not be constant, but it
proved very difficult to find the formula describing the rate of change of the
planet's angular velocity. After many years of calculations, Kepler arrived at
what we now know as the law of equal areas. Galileo's conjecture was merely
that — a conjecture. So was Kepler's cosmology. But each conjecture
increased the credibility of the other, and together, they changed the
prevailing perceptions of the scientific community. Later, Newton showed that
Kepler's three laws could all be derived from a single theory of motion and
planetary motion. Newton solidified and unified the paradigm shift that Galileo
and Kepler had initiated.
Coherence:
One of the aims of science is to find models that will account for as many
observations as possible within a coherent framework. Together, Galileo's
rethinking of the nature of motion and Keplerian cosmology represented a
coherent framework that was capable of rivaling the Aristotelian/Ptolemaic
framework. Once a paradigm shift has taken place, the textbooks are rewritten.
Often the history of science too is rewritten, being presented as an inevitable
process leading up to the current, established framework of thought. There is a
prevalent belief that all hitherto-unexplained phenomena will in due course be
accounted for in terms of this established framework. Kuhn states that
scientists spend most (if not all) of their careers in a process of
puzzle-solving. Their puzzle-solving is pursued with great tenacity, because
the previous successes of the established paradigm tend to generate great
confidence that the approach being taken guarantees that a solution to the
puzzle exists, even though it may be very hard to find.
Kuhn calls this process normal science. As a paradigm is stretched to its
limits, anomalies — failures of the current paradigm to take into account
observed phenomena — accumulate. Their significance is judged by the
practitioners of the discipline. Some anomalies may be dismissed as errors in
observation, others as merely requiring small adjustments to the current
paradigm that will be clarified in due course. Some anomalies resolve
themselves spontaneously, having increased the available depth of insight along
the way. But no matter how great or numerous the anomalies that persist, Kuhn
observes, the practicing scientists will not lose faith in the established
paradigm until a credible alternative is available; to lose faith in the
solvability of the problems would in effect mean ceasing to be a scientist. In
any community of scientists, Kuhn states, there are some individuals who are
bolder than most.
These scientists, judging that a crisis exists, embark on what Kuhn calls
revolutionary science, exploring alternatives to long-held, obvious-seeming
assumptions. Occasionally this generates a rival to the established framework
of thought. The new candidate paradigm will appear to be accompanied by
numerous anomalies, partly because it is still so new and incomplete. The
majority of the scientific community will oppose any conceptual change, and,
Kuhn emphasizes, so they should. To fulfill its potential, a scientific
community needs to contain both individuals who are bold and individuals who
are conservative. There are many examples in the history of science in which
confidence in the established frame of thought was eventually vindicated. It is
almost impossible to predict whether the anomalies in a candidate for a new
paradigm will eventually be resolved. Those scientists who possess an
exceptional ability to recognize a theory's potential will be the first whose
preference is likely to shift in favour of the challenging paradigm. There
typically follows a period in which there are adherents of both paradigms. In
time, if the challenging paradigm is solidified and unified, it will replace
the old paradigm, and a paradigm shift will have occurred.
Phases:
Kuhn explains the process of scientific change as the result of various phases
of paradigm change.
Phase 1 – It exists only once and is the pre-paradigm phase, in which
there is no consensus on any particular theory. This phase is characterized by
several incompatible and incomplete theories. Consequently, most scientific
inquiry takes the form of lengthy books, as there is no common body of facts
that may be taken for granted. If the actors in the pre-paradigm community
eventually gravitate to one of these conceptual frameworks and ultimately to a
widespread consensus on the appropriate choice of methods, terminology and on
the kinds of experiment that are likely to contribute to increased insights.
Phase 2 – Normal science begins, in which puzzles are solved within the
context of the dominant paradigm. As long as there is consensus within the
discipline, normal science continues. Over time, progress in normal science may
reveal anomalies, facts that are difficult to explain within the context of the
existing paradigm. While usually these anomalies are resolved, in some cases
they may accumulate to the point where normal science becomes difficult and
where weaknesses in the old paradigm are revealed.
Phase 3 – If the paradigm proves chronically unable to account for
anomalies, the community enters a crisis period. Crises are often resolved
within the context of normal science. However, after significant efforts of
normal science within a paradigm fail, science may enter the next phase.
Phase 4 – Paradigm shift, or scientific revolution, is the phase in which
the underlying assumptions of the field are reexamined and a new paradigm is
established.
Phase 5 – Post-Revolution, the new paradigm's dominance is established and
so scientists return to normal science, solving puzzles within the new
paradigm. A science may go through these cycles repeatedly, though Kuhn notes
that it is a good thing for science that such shifts do not occur often or
easily.
Incommensurability:
According to Kuhn, the scientific paradigms preceding and succeeding a paradigm
shift are so different that their theories are incommensurable — the new
paradigm cannot be proven or disproven by the rules of the old paradigm, and
vice versa. (A later interpretation by Kuhn of 'commensurable' versus
'incommensurable' was as a distinction between languages, namely, that
statements in commensurable languages were translatable fully from one to the
other, while in incommensurable languages, strict translation is not possible.)
The paradigm shift does not merely involve the revision or transformation of an
individual theory, it changes the way terminology is defined, how the
scientists in that field view their subject, and, perhaps most significantly,
what questions are regarded as valid, and what rules are used to determine the
truth of a particular theory. The new theories were not, as the scientists had
previously thought, just extensions of old theories, but were instead
completely new world views. Such incommensurability exists not just before and
after a paradigm shift, but in the periods in between conflicting paradigms. It
is simply not possible, according to Kuhn, to construct an impartial language
that can be used to perform a neutral comparison between conflicting paradigms,
because the very terms used are integral to the respective paradigms, and
therefore have different connotations in each paradigm. The advocates of
mutually exclusive paradigms are in a difficult position: "Though each may
hope to convert the other to his way of seeing science and its problems,
neither may hope to prove his case.
The competition between paradigms is not the sort of battle that can be
resolved by proofs. (p. 148)" Scientists subscribing to different
paradigms end up talking past one another. Kuhn states that the probabilistic
tools used by verificationists are inherently inadequate for the task of
deciding between conflicting theories, since they belong to the very paradigms
they seek to compare. Similarly, observations that are intended to falsify a
statement will fall under one of the paradigms they are supposed to help
compare, and will therefore also be inadequate for the task. According to Kuhn,
the concept of falsifiability is unhelpful for understanding why and how
science has developed as it has. In the practice of science, scientists will
only consider the possibility that a theory has been falsified if an
alternative theory is available that they judge credible. If there is not,
scientists will continue to adhere to the established conceptual framework. If
a paradigm shift has occurred, the textbooks will be rewritten to state that
the previous theory has been falsified. Kuhn further developed his ideas
regarding incommensurability in the 1980s and 1990s.
In his unpublished manuscript The Plurality of Worlds, Kuhn introduces the
theory of kind concepts: sets of interrelated concepts that are characteristic
of a time period in a science and differ in structure from the modern analogous
kind concepts. These different structures imply different
“taxonomies” of things and processes, and this difference in
taxonomies constitutes incommensurability. This theory is strongly naturalistic
and draws on developmental psychology to “found a quasi-transcendental
theory of experience and of reality.”
Exemplar:
Kuhn introduced the concept of an exemplar in a postscript to the second
edition of The Structure of Scientific Revolutions (1970). He noted that
he was substituting the term 'exemplars' for 'paradigm', meaning the problems
and solutions that students of a subject learn from the beginning of their
education. For example, physicists might have as exemplars the inclined plane,
Kepler's laws of planetary motion, or instruments like the calorimeter.
According to Kuhn, scientific practice alternates between periods of normal
science and revolutionary science. During periods of normalcy, scientists tend
to subscribe to a large body of interconnecting knowledge, methods, and
assumptions which make up the reigning paradigm (see paradigm shift). Normal
science presents a series of problems that are solved as scientists explore
their field. The solutions to some of these problems become well known and are
the exemplars of the field.
Those who study a scientific discipline are expected to know its exemplars.
There is no fixed set of exemplars, but for a physicist today it would probably
include the harmonic oscillator from mechanics and the hydrogen atom from
quantum mechanics. Kuhn on scientific progress The first edition of The
Structure of Scientific Revolutions ended with a chapter titled
"Progress through Revolutions", in which Kuhn spelled out his views
on the nature of scientific progress. Since he considered problem solving to be
a central element of science, Kuhn saw that for a new candidate paradigm to be
accepted by a scientific community, "First, the new candidate must seem to
resolve some outstanding and generally recognized problem that can be met in no
other way. Second, the new paradigm must promise to preserve a relatively large
part of the concrete problem solving ability that has accrued to science
through its predecessors. While the new paradigm is rarely as expansive as the
old paradigm in its initial stages, it must nevertheless have significant
promise for future problem-solving. As a result, though new paradigms seldom or
never possess all the capabilities of their predecessors, they usually preserve
a great deal of the most concrete parts of past achievement and they always
permit additional concrete problem-solutions besides.
In the second edition, Kuhn added a postscript in which he elaborated his ideas
on the nature of scientific progress. He described a thought experiment
involving an observer who has the opportunity to inspect an assortment of
theories, each corresponding to a single stage in a succession of theories.
What if the observer is presented with these theories without any explicit
indication of their chronological order? Kuhn anticipates that it will be
possible to reconstruct their chronology on the basis of the theories' scope
and content, because the more recent a theory is, the better it will be as an
instrument for solving the kinds of puzzle that scientists aim to solve. Kuhn
remarked: "That is not a relativist's position, and it displays the sense
in which I am a convinced believer in scientific progress."
Philosophy:
The first extensive review of The Structure of Scientific Revolutions
was authored by Dudley Shapere, a philosopher who interpreted Kuhn's work
as a continuation of the anti-positivist sentiment of other philosophers of
science, including Paul Feyerabend and Norwood Russell Hanson. Shapere noted
the book's influence on the philosophical landscape of the time, calling it
“a sustained attack on the prevailing image of scientific change as a
linear process of ever-increasing knowledge.” According to the philosopher
Michael Ruse, Kuhn discredited the ahistorical and prescriptive approach to the
philosophy of science of Ernest Nagel's The Structure of Science (1961).
Kuhn's book sparked a historicist "revolt against positivism" (the
so-called "historical turn in philosophy of science" which looked to
the history of science as a source of data for developing a philosophy of
science), although this may not have been Kuhn's intention; in fact, he had
already approached the prominent positivist Rudolf Carnap about having his work
published in the International Encyclopedia of Unified Science.
The philosopher Robert C. Solomon noted that Kuhn's views have often been
suggested to have an affinity to those of Georg Wilhelm Friedrich Hegel. Kuhn's
view of scientific knowledge, as expounded in The Structure of Scientific
Revolutions, has been compared to the views of the philosopher Michel
Foucault.
Sociology:
The first field to claim descent from Kuhn's ideas was the sociology of
scientific knowledge. Sociologists working within this new field, including
Harry Collins and Steven Shapin, used Kuhn's emphasis on the role of
non-evidential community factors in scientific development to argue against
logical empiricism, which discouraged inquiry into the social aspects of
scientific communities. These sociologists expanded upon Kuhn's ideas, arguing
that scientific judgment is determined by social factors, such as professional
interests and political ideologies. Barry Barnes detailed the connection
between the sociology of scientific knowledge and Kuhn in his book T. S.
Kuhn and Social Science. In particular, Kuhn's ideas regarding science
occurring within an established framework informed Barnes's own ideas regarding
finitism, a theory wherein meaning is continuously changed (even during periods
of normal science) by its usage within the social framework.
The Structure of Scientific Revolutions elicited a number of reactions
from the broader sociological community. Following the book's publication, some
sociologists expressed the belief that the field of sociology had not yet
developed a unifying paradigm, and should therefore strive towards
homogenization. Others argued that the field was in the midst of normal
science, and speculated that a new revolution would soon emerge. Some
sociologists, including John Urry, doubted that Kuhn's theory, which addressed
the development of natural science, was necessarily relevant to sociological
development.
Economics:
Developments in the field of economics are often expressed and legitimized in
Kuhnian terms. For instance, neoclassical economists have claimed “to be
at the second stage [normal science], and to have been there for a very long
time – since Adam Smith, according to some accounts (Hollander, 1987), or
Jevons according to others (Hutchison, 1978).” In the 1970s, Post
Keynesian economists denied the coherence of the neoclassical paradigm,
claiming that their own paradigm would ultimately become dominant. While
perhaps less explicit, Kuhn's influence remains apparent in recent economics.
For instance, the abstract of Olivier Blanchard's paper “The State of
Macro” (2008) begins: For a long while after the explosion of
macroeconomics in the 1970s, the field looked like a battlefield. Over time
however, largely because facts do not go away, a largely shared vision both of
fluctuations and of methodology has emerged. Not everything is fine.
Like all revolutions, this one has come with the destruction of some knowledge,
and suffers from extremism and herding.
Political science:
In 1974, The Structure of Scientific Revolutions was ranked as the
second most frequently used book in political science courses focused on scope
and methods. In particular, Kuhn's theory has been used by political scientists
to critique behavioralism, which claims that accurate political statements must
be both testable and falsifiable. The book also proved popular with political
scientists embroiled in debates about whether a set of formulations put forth
by a political scientist constituted a theory, or something else. The changes
that occur in politics, society and business are often expressed in Kuhnian
terms, however poor their parallel with the practice of science may seem to
scientists and historians of science. The terms "paradigm" and
"paradigm shift" have become such notorious clichés and
buzzwords that they are sometimes viewed as effectively devoid of content.
Criticisms:
The Structure of Scientific Revolutions was soon criticized by Kuhn's
colleagues in the history and philosophy of science. In 1965, a special
symposium on the book was held at an International Colloquium on the Philosophy
of Science that took place at Bedford College, London, and was chaired by Karl
Popper. The symposium led to the publication of the symposium's presentations
plus other essays, most of them critical, which eventually appeared in an
influential volume of essays. Kuhn expressed the opinion that his critics'
readings of his book were so inconsistent with his own understanding of it that
he was "...tempted to posit the existence of two Thomas Kuhns," one
the author of his book, the other the individual who had been criticized in the
symposium by "Professors Popper, Feyerabend, Lakatos, Toulmin and
Watkins."
A number of the included essays question the existence of normal science. In
his essay, Feyerabend suggests that Kuhn's conception of normal science fits
organized crime as well as it does science. Popper expresses distaste with the
entire premise of Kuhn's book, writing, “the idea of turning for
enlightenment concerning the aims of science, and its possible progress, to
sociology or to psychology (or. . .to the history of science) is surprising and
disappointing.”
Concept of paradigm:
In his 1972 work, Human Understanding, Stephen Toulmin argued that a
more realistic picture of science than that presented in The Structure of
Scientific Revolutions would admit the fact that revisions in science take
place much more frequently, and are much less dramatic than can be explained by
the model of revolution/normal science. In Toulmin's view, such revisions occur
quite often during periods of what Kuhn would call "normal science."
For Kuhn to explain such revisions in terms of the non-paradigmatic puzzle
solutions of normal science, he would need to delineate what is perhaps an
implausibly sharp distinction between paradigmatic and non-paradigmatic
science.
Incommensurability of paradigms:
In a series of texts published in the early 1970s, Carl R. Kordig asserted a
position somewhere between that of Kuhn and the older philosophy of science.
His criticism of the Kuhnian position was that the incommensurability thesis
was too radical, and that this made it impossible to explain the confrontation
of scientific theories that actually occurs. According to Kordig, it is in fact
possible to admit the existence of revolutions and paradigm shifts in science
while still recognizing that theories belonging to different paradigms can be
compared and confronted on the plane of observation. Those who accept the
incommensurability thesis do not do so because they admit the discontinuity of
paradigms, but because they attribute a radical change in meanings to such
shifts.
Kordig maintains that there is a common observational plane. For example, when
Kepler and Tycho Brahe are trying to explain the relative variation of the
distance of the sun from the horizon at sunrise, both see the same thing (the
same configuration is focused on the retina of each individual). This is just
one example of the fact that "rival scientific theories share some
observations, and therefore some meanings." Kordig suggests that with this
approach, he is not reintroducing the distinction between observations and
theory in which the former is assigned a privileged and neutral status, but
that it is possible to affirm more simply the fact that, even if no sharp
distinction exists between theory and observations, this does not imply that
there are no comprehensible differences at the two extremes of this polarity.
At a secondary level, for Kordig there is a common plane of inter-paradigmatic
standards or shared norms that permit the effective confrontation of rival
theories.
In 1973, Hartry Field published an article that also sharply criticized Kuhn's
idea of incommensurability. In particular, he took issue with this passage from
Kuhn: Newtonian mass is immutably conserved; that of Einstein is convertible
into energy. Only at very low relative velocities can the two masses be
measured in the same way, and even then they must not be conceived as if they
were the same thing. (Kuhn 1970). Field takes this idea of incommensurability
between the same terms in different theories one step further. Instead of
attempting to identify a persistence of the reference of terms in different
theories, Field's analysis emphasizes the indeterminacy of reference within
individual theories. Field takes the example of the term "mass", and
asks what exactly "mass" means in modern post-relativistic physics.
He finds that there are at least two different definitions:
Relativistic mass: the mass of a particle is equal to the total energy of the
particle divided by the speed of light squared. Since the total energy of a
particle in relation to one system of reference differs from the total energy
in relation to other systems of reference, while the speed of light remains
constant in all systems, it follows that the mass of a particle has different
values in different systems of reference.
"Real" mass: the mass of a particle is equal to the non-kinetic
energy of a particle divided by the speed of light squared. Since non-kinetic
energy is the same in all systems of reference, and the same is true of light,
it follows that the mass of a particle has the same value in all systems of
reference. Projecting this distinction backwards in time onto Newtonian
dynamics, we can formulate the following two hypotheses: HR: the term
"mass" in Newtonian theory denotes relativistic mass. Hp: the term
"mass" in Newtonian theory denotes "real" mass. According
to Field, it is impossible to decide which of these two affirmations is true.
Prior to the theory of relativity, the term "mass" was referentially
indeterminate. But this does not mean that the term "mass" did not
have a different meaning than it now has. The problem is not one of meaning but
of reference. The reference of such terms as mass is only partially determined:
we don't really know how Newton intended his use of this term to be applied. As
a consequence, neither of the two terms fully denotes (refers). It follows that
it is improper to maintain that a term has changed its reference during a
scientific revolution; it is more appropriate to describe terms such as
"mass" as "having undergone a denotional refinement."
In 1974, Donald Davidson objected that the concept of incommensurable
scientific paradigms competing with each other is logically inconsistent.
"In his article Davidson goes well beyond the semantic version of the
incommensurability thesis: to make sense of the idea of a language independent
of translation requires a distinction between conceptual schemes and the
content organized by such schemes. But, Davidson argues, no coherent sense can
be made of the idea of a conceptual scheme, and therefore no sense may be
attached to the idea of an untranslatable language."
Incommensurability and perception:
The close connection between the interpretationalist hypothesis and a holistic
conception of beliefs is at the root of the notion of the dependence of
perception on theory, a central concept in The Structure of Scientific
Revolutions. Kuhn maintained that the perception of the world depends on
how the percipient conceives the world: two scientists who witness the same
phenomenon and are steeped in two radically different theories will see two
different things. According to this view, our interpretation of the world
determines what we see. Jerry Fodor attempts to establish that this theoretical
paradigm is fallacious and misleading by demonstrating the impenetrability of
perception to the background knowledge of subjects. The strongest case can be
based on evidence from experimental cognitive psychology, namely the
persistence of perceptual illusions. Knowing that the lines in the
Müller-Lyer illusion are equal does not prevent one from continuing to see
one line as being longer than the other. This impenetrability of the
information elaborated by the mental modules limits the scope of
interpretationalism.
In epistemology, for example, the criticism of what Fodor calls the
interpretationalist hypothesis accounts for the common-sense intuition (on
which naïve physics is based) of the independence of reality from the
conceptual categories of the experimenter. If the processes of elaboration of
the mental modules are in fact independent of the background theories, then it
is possible to maintain the realist view that two scientists who embrace two
radically diverse theories see the world exactly in the same manner even if
they interpret it differently. The point is that it is necessary to distinguish
between observations and the perceptual fixation of beliefs. While it is beyond
doubt that the second process involves the holistic relationship between
beliefs, the first is largely independent of the background beliefs of
individuals. Other critics, such as Israel Scheffler, Hilary Putnam and Saul
Kripke, have focused on the Fregean distinction between sense and reference in
order to defend scientific realism. Scheffler contends that Kuhn confuses the
meanings of terms such as "mass" with their referents. While their
meanings may very well differ, their referents (the objects or entities to
which they correspond in the external world) remain fixed.
Subsequent commentary by Kuhn:
In 1995 Kuhn argued that the Darwinian metaphor in the book should have been
taken more seriously than it had been.
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