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Kuhn's Criticism of Popper's
Falsificationist Philosophy
Nearly ten years after Structure
Kuhn defended his thesis and replied to his critics
in Criticism
and the Growth of Knowledge.
This is not his most mature work, since at
this time he had yet to attempt language analysis.
One critic that he took very seriously is
Popper. Kuhn's
philosophy of science is not only a post-Positivist
philosophy critical of Positivism, it is also a
post-Popperian philosophy that is critical of
Popper's falsificationist theory of scientific
criticism and concept of scientific progress.
The difference between Kuhn and Popper is
explicable in large part by the differences in the
episodes in the history of science that have had a
formative influence on their respective thinking.
Popper's philosophy of science was
principally influenced by the episode in which the
physics profession made the transition from Newton's
theory of gravitation to Einstein's relativity
theory. On
the other hand Kuhn's philosophy was principally
influenced by earlier episodes in his Aristotle
experience and in the transition from Ptolemy's
geocentric theory to Copernicus' heliocentric
theory. The
noteworthy difference between these episodes is that
the transition to Einstein's theory is often viewed
as involving a crucial test, the celebrated eclipse
test of 1919, while the transitions to Newton’s
and Copernicus' theories, like the transition to
Lavoisier's oxygen theory of combustion discussed by
Conant, are not associated with any crucial tests
but involved various nonempirical considerations.
Popper views these nonempirical considerations as
external impediments to progress in science, while
Kuhn views them as internal and integral to the
development of science.
Kuhn's explicit criticism of Popper is given
in "Logic of Discovery or Psychology of
Research?" in Criticism
and the Growth of Knowledge.
In this paper Kuhn begins by describing the
similarities between his views and Popper's that
also separate both their views from those of the
Positivists. He
notes that both he and Popper are concerned with the
dynamic processes by which scientific knowledge is
developed, instead of the logical structure of the
products of scientific research, and that therefore
both of them look to the history of science.
He furthermore notes that both of them draw
many of the same conclusions from the history of
science particularly about which fields are sciences
and which are not, that both are realists, and that
both reject the Positivist idea of a neutral or
theory-independent observation language.
Then Kuhn turns to the contrasts between his
views and Popper's.
He maintains that even though he and Popper
draw the same conclusions about which fields are
sciences and which are not, they arrive at their
shared conclusions by very different ways that may
be contrasted as different gestalts of the same situations.
Popper maintains that scientists test
theories and attempt to falsify them with a critical
attitude. Kuhn
maintains his thesis of normal science according to
which a theory is not tested critically, but instead
functions as a premise for puzzle-solving research
with currently accepted theory supplying the rules
of the game. Kuhn
says that the type of tests that Popper discusses,
such as the eclipse test of Einstein's theory of
relativity in 1919, is rare in science, and he
identifies this rare type of research as
extraordinary or revolutionary science.
He says that Popper has mistakenly
characterized the entire scientific enterprise in
terms that apply only to its occasional
revolutionary parts, and that he is turning Popper
on his head, when Popper demarcates scientific from
nonscientific fields.
In Kuhn’s view it is the abandonment of
critical discourse rather than its adoption that
makes the transformation of a field into a science.
Once a field has made that transition,
critical discourse recurs only at moments of crisis,
when the basis of the field is again in jeopardy.
Therefore Popper's and Kuhn's lines of
demarcation coincide only in their outcomes and not
in their criteria; for their respective criteria
they reference different aspects of scientific
activity.
Then Kuhn goes on to say that even during
revolutionary phases of science, the choice between
paradigms is not a choice in which critical testing
can play a decisive role.
Kuhn references Popper's "Truth,
Rationality, and the Growth of Knowledge" in Conjectures
and Refutations, where Popper states that the
Ptolemaic theory was replaced before it had been
tested. In
this article Popper maintains that such instances
reveal that crucial tests are decisively important,
so that scientists have reason to believe that the
new theory replacing the old one is better and
nearer to the truth.
But Kuhn argues not only had these theories
not been put to the test before they were replaced,
but furthermore none of them were replaced before it
had ceased adequately to support a puzzle-solving
tradition. Kuhn
notes that both he and Popper agree that no theory
can be conclusively falsified, that all experiments
can be challenged either as to their relevance or to
their accuracy, and that every theory can be
modified by a variety of ad hoc adjustments without ceasing to be the same theory.
But he argues that in Popper's philosophy
recognition of such things operates merely as a
qualification of his philosophy, even though these
things occur in the history of science.
Kuhn cites as an example that the state of
astronomy was a scandal in the early sixteenth
century, but most astronomers nevertheless thought
that normal adjustments to a basically Ptolemaic
model would be sufficient to set the situation
aright. In
this sense the Ptolemaic theory had not failed any
test. However
a few astronomers including Copernicus thought that
the difficulties must lie in the basic Ptolemaic
approach itself rather than in the particular
versions of Ptolemaic theory.
Kuhn says that Popper's error is the belief
that logical criteria can dictate the falsification
of a theory and determine theory choice during
revolutions. Logical
falsification presumes that a theory can be cast or
recast such that all events are either
corroborating, falsifying or irrelevant instances.
But this cannot be done unless the theory is
fully articulated and its terms sufficiently
defined, so that it is possible to determine their
applicability in every possible case.
Kuhn says that no theory can in practice
satisfy such a requirement, and that he had
introduced the term "paradigm" to
underscore the dependence of scientific research on
concrete examples that supply what would otherwise
be gaps in the specification of the content and
application of scientific theories.
Kuhn illustrates the semantical and
pragmatical considerations captured by the term
"paradigm" with a discussion of swans and
the stereotype theory "all swans are
white". Kuhn
says that after a scientist has made his
investigation and has found no instances of nonwhite
swans, making the generalization explicit adds
little or nothing to what is already known from the
investigation.
And if later one finds a black bird that
otherwise appears to be a swan, then one's behavior
will be the same whether or not one has made the
explicit generalization that all swans are white.
With or without the explicit generalization a
decision must be made with respect to the
possibility of black swans.
Observation cannot force a falsifying
decision. Only
if one had previously committed oneself to a full
definition of "swan", one that will
specify its applicability to every conceivable
object, could one be logically forced to rescind
one's generalization.
And Kuhn says that there is no good reason
for such a commitment to any such explicit
generalization; it is an unnecessary risk.
Similarly in science the scientist who is
confronted with the unexpected, must always do more
research in order to articulate his theory further
in the area that has just become problematic.
He may reject his theory in favor of another,
and may do so for good reason, but no exclusively
logical criterion can dictate the conclusion that
the theory has been falsified, or that it has not
been falsified.
Just as the investigator of swans need not
make the decision as to whether whiteness is a
defining characteristic of swans, until he can
investigate further the apparently anomalous case of
the black but otherwise swan-looking bird, so too
the scientist has the same freedom to choose, and is
not logically compelled to conclude that current
theory has been falsified by apparently anomalous
instances and test outcomes.
Kuhn says that further empirical
investigation is needed to answer such questions as
how do scientists actually make the choice between
competing theories, and how scientific progress is
to be understood.
He says that the type of answer to these
questions must in the final analysis by
psychological or sociological.
He agrees with Popper's rejection of answers
given in terms of the scientists' psychological
idiosyncrasies, but he advocates investigation of
the common elements induced by education of the
licensed membership of the scientific group.
Popper's
Criticism of Kuhn’s Normal Science Thesis
Popper’s criticism in reply to Kuhn is set
forth in "Normal Science and its Dangers"
in Criticism and the Growth of Knowledge. He criticizes the aim of normal science as set forth by Kuhn,
and he rejects the historical relativism that he
finds in Kuhn's thesis. Popper notes that he and
Kuhn agree that the normal work of the scientist
presupposes a theory that supplies the scientist
with a generally accepted problem situation for his
work. Interestingly
he also states that he has always said that some
dogmatism is necessary, because giving in to
criticism too soon may preclude finding out where
the real power of a theory lies.
And he says that while he has been only dimly
aware of the distinction that Kuhn makes between
normal and revolutionary science, he admits that
normal science in Kuhn's sense does exist.
But Popper maintains that the normal
scientist in Kuhn's sense is a scientist who has
been badly taught, since he does not think
critically, a problem that Popper says he finds in
quantum theory today.
Popper expresses the opinion that uncritical
normal science is dangerous both to science and to
our civilization.
He also takes exception to Kuhn's view that
normal science as Kuhn conceives it is actually
normal in the history of science.
Kuhn's thesis of a single dominant theory may
fit astronomy, but it does not fit the theory of
matter or the biological sciences.
Popper questions Kuhn's historical accuracy.
But Popper is principally concerned with
Kuhn's historical relativism and with the thesis
that philosophers of science should look to
sociology and psychology of science instead of
attempting a logical analysis, as Popper did in his
own work. He
argues that Kuhn's historical relativist thesis of
the dynamics of science is not a sociological or a
psychological one but rather a logical one, and he
furthermore maintains that it is a mistaken one.
He says that Kuhn's view that scientists must
agree on fundamentals and on the framework of those
fundamentals, in order to discourse rationally and
critically, is what he calls "The Myth of the
Framework".
Popper admits that at any moment we are
prisoners caught in the framework of our theories,
expectations, past experiences, and language.
But he adds that we are prisoners only in a
Pickwickian sense, because if we try, we can break
out of our framework into a better and roomier one.
He emphasizes that his central point is that
a critical discussion and a comparison of the
various frameworks are always possible.
He denies that different frameworks are like
mutually untranslatable languages.
In Popper's view the Myth of the Framework is
the principal bulwark of irrationalism, and it
merely exaggerates a difficulty into an
impossibility. There are difficulties in discussion between people brought
up in different frameworks, but Popper says that
nothing is more fruitful than such discussions.
An intellectual revolution may look like a
religious conversion; a new insight may strike one
like a flash of lightning.
But this does not mean that one cannot
evaluate former views critically and rationally in
the light of new ones.
It is simply false to say that the transition
from Newton to Einstein is an irrational leap, and
that the two theories of gravitation are not
rationally comparable.
In science we can say that we have made
genuine progress, and that we know more than we did
before such transitions occurred.
Therefore, Popper says that all of Kuhn's own
arguments go back to the thesis that the scientist
is logically forced to accept a framework, since no
rational discussion is possible between
frameworks. This
is not a historical, sociological, or psychological
argument, but is a logical one, and it is a mistaken
one. Popper
says that science is subjectless in the sense that
it is not bound to any framework.
Popper reaffirms his own thesis that the aim
of science is to find theories, which in the light
of critical discussion get nearer to the truth and
have increased the truth content.
Popper rejects Kuhn's proposal of turning to
psychology and sociology for enlightenment about the
aims of science and about the nature of scientific
progress. He
rejects all psychologistic and sociologistic
tendencies, and furthermore says that in comparison
to physics, psychology and sociology are riddled
with fashions and uncontrolled dogmas. He concludes by answering Kuhn's question, "Logic
of Discovery or Psychology of Research?” with the
reply that while Logic of Discovery has little to
learn from the Psychology of Research, the latter
has much to learn from the former.
Feyerabend
on Theory Proliferation vs. Consensus Paradigm
Feyerabend's criticism of Kuhn is given in
his "Consolations for the Specialist" in Criticism
and the Growth of Knowledge.
He says that the doctrine of normal
science is an ideology that Kuhn propagandizes
among social scientists.
His principal methodological criticism of
Kuhn's philosophy is that Kuhn's theory cannot
explain the transition from a monistic normal
science to a pluralistic revolutionary science,
since the impossibility of a semantically neutral
observation language makes a plurality of
alternative theories a precondition for the
transition to be brought about. Firstly he notes
that he and Kuhn had discussed their views while
both were at the University of California at
Berkeley. And
he says that while he recognizes the problems that
interest Kuhn, notably the omnipresence of
anomalies, he is unable to agree with Kuhn's theory
of science, which he also calls an ideology.
Feyerabend maintains that Kuhn's ideology can
give comfort only to the most narrow-minded and the
most conceited kind of specialist, that it tends to
inhibit the advancement of knowledge, and that it is
responsible for such inhibiting tendencies in modern
psychology and sociology.
He elaborates on his view that Kuhn's theory
is an ideology.
He states that Kuhn's presentation contains
an ambiguity between the descriptive and the
prescriptive mode of presentation, and that as a
result more than one social scientist has pointed
out to him that after reading Kuhn's book, he at
last knows how to turn his field into a science.
Feyerabend reports that the recipe that these
social scientists have taken from Kuhn consists of
such practices as restricting criticism, reducing
the number of comprehensive theories to one,
creating a normal science that has this one theory
as its paradigm, preventing students from
speculating along different lines, and making more
restless colleagues conform and do serious work.
He then asks whether or not Kuhn's following
among sociologists is an intended effect, whether or
not it is Kuhn's intention to provide a
historical-scientific justification for
sociologists' need to identify with some group. In criticism of Kuhn, Feyerabend concludes that it is
actually Kuhn's intention to provide an ambiguity
between the descriptive and the prescriptive modes
of presentation, and that Kuhn wishes to exploit the
propagandistic potentialities in this ambiguity. He says that Kuhn wants on the one hand to give solid,
objective historical support to value judgments,
which he and others regard as arbitrary and
subjective, while on the other hand Kuhn also wants
to leave himself a safe line of retreat.
When those who dislike Kuhn's implied
derivation of values from facts object, Kuhn's line
of retreat consists of telling them that no such
derivation can be made, and that the presentation is
purely descriptive.
Feyerabend next turns his criticism to Kuhn's
thesis as a descriptive account of science. The central thesis of his criticism of Kuhn is that the
latter's theory of science leaves unanswered the
problem of how the transition from the monistic
normal-science period to a pluralistic revolutionary
period is brought about.
Feyerabend notes that both he and Kuhn admit
to what he calls the methodological principle of
tenacity, which he defines as the scientist's
selection from a number of theories one which
promises in the particular scientist's view to lead
to the most fruitful results, and then sticking to
the selected theory even if the anomalies it suffers
are considerable.
He then asks how this principle can be
defended, and how it is possible to change
allegiance to paradigms in a manner consistent with
it. He
answers that the principle of tenacity is
reasonable, because theories are capable of
development and may eventually be able to
accommodate the anomalies that their original
versions were incapable of explaining.
This is because relevant evidence depends not
only upon the theory, but also upon other subjects,
which are conventionally called auxiliary sciences.
Such auxiliary sciences function as
additional premises in the derivation of testable
consequences, and these premises infect the
observation language in which the testable
consequences are expressed, thereby providing the
very concepts in terms of which experimental results
are expressed.
But it happens that theories and their
auxiliary sciences often develop out of phase, with
the result that apparently refuting instances may
turn out not to indicate that a new theory is doomed
to failure, but instead may indicate only that it
does not fit in at present with the rest of science.
Therefore scientists can tenaciously develop
methods that permit them to retain their theories in
the face of plain and unambiguously refuting facts,
even if testable explanations for the clash with
facts are not immediately forthcoming. The
significance of the principle of tenacity, the
practice whereby scientists no longer use
recalcitrant facts for removing a theory, is that a
plurality of alternative theories can coexist in a
science at any given time.
This pluralism is strategic to Feyerabend,
because in his view the fact that theory determines
observation implies that theories are not compared
with nature, but must be compared with other
theories. Alternative
theories function to accentuate the differences
between one another, such that the principle of
tenacity itself may eventually urge the elimination
of a theory. Hence,
if a change of paradigms is the function of normal
science then one must be prepared to introduce
alternatives to a given theory.
Feyerabend notes that in fact Kuhn himself
has described in detail the magnifying effect which
alternatives have upon anomalies, and has explained
how revolutions are brought about by such
magnifications.
Feyerabend therefore proposes a second
methodological principle, the principle of
proliferation, and he asks rhetorically, why not
start proliferating theories at once, and why allow
a purely normal science, as Kuhn conceives it, ever
to come into existence?
Feyerabend then switches from a purely
methodological perspective to a historical one, and
replies to his own rhetorical question about theory
proliferation vs. normal science consensus.
Using his methodological principles of
tenacity and proliferation to examine the history of
science, he maintains that normal science is a big
myth. He
argues that even though there are scientists who
practice puzzle-solving normal science, there is no
temporally separated periods of monistic normal
science and pluralistic revolutionary science.
He supports a view initially proposed by Imre
Lakatos, a professor of logic at the University of
London, that the practices of tenacity and
proliferation do not belong to successive periods in
the history of science, but rather are always
copresent. Feyerabend
says that the interplay between tenacity and
proliferation is an essential feature of the actual,
historical development of science.
It is not the puzzle-solving activity that is
responsible for the growth of knowledge, but the
active interplay of a plurality of tenaciously held
views. It
is the continuing intervention of new ideas and the
attempts to secure for them a worthy place in the
competition that leads to the overthrow of old and
familiar paradigms.
Feyerabend furthermore maintains that
revolutions are basically matters of appearance, and
that during a revolution there is actually no
profound structural change such as a transition from
normal to extraordinary science as described by
Kuhn. Thus,
instead of advocating conformity to a monolithic
consensus paradigm, as Kuhn does, Feyerabend issues
a plea for hedonism, by which he means the
continuing practice of the theory-proliferating
principle of tenacity.
Feyerabend took occasion to comment more
favorably on Kuhn's philosophy, and to relate Kuhn's
views to his own where they manifest similarities.
One aspect of Kuhn's philosophy that
Feyerabend considers to be important is the concept
of paradigm. Feyerabend says that Kuhn expanded on
Wittgenstein's criticism of the Logical Positivist
emphasis on rules and formal aspects of language,
and that Kuhn made this criticism more concrete.
He also says that by introducing the notion
of paradigm, Kuhn stated above all a problem.
Kuhn explained that science depends on
circumstances that are not described in the usual
accounts, that do not occur in science textbooks,
and that have to be identified in a roundabout way.
However, most of Kuhn's followers, especially
in the social sciences, did not recognize the idea
as a statement of a problem, but regarded Kuhn's
account as a presentation of a new and clear fact.
Feyerabend maintains that by using the term
"paradigm", which is awaiting explication
by research, as if explication had already been
completed, they started a new and most deplorable
trend of loquacious illiteracy.
Feyerabend finds three noteworthy aspects in
Kuhn's treatment of the relations between different
paradigms. Firstly
different paradigms use sets of concepts that cannot
be brought into the usual logical relations of
inclusion, exclusion, or overlap, and that
incommensurability is the natural consequence of
identifying theories with paradigms or, as
Feyerabend calls them, traditions. Secondly different paradigms make researchers see things
differently, such that researchers in different
paradigms not only have different concepts, but also
have different perceptions.
Thirdly paradigms have different methods
including intellectual as well as physical
instruments for practicing research and evaluation
results. He
says that it was a great advance to replace the idea
of theory with the idea of paradigm, which includes
dynamic aspects of science.
He notes that his earlier work had
principally been concerned only with the first of
the three mentioned aspects, and then only with
theories.
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