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In his "The Rationality of Scientific
Revolutions" in Problems
of Scientific Revolution Popper distinguishes
between the sociological and the logical or rational
dimensions in the history of science, when he
distinguishes ideological from scientific
revolutions. By
an ideology he means any nonscientific theory,
creed, or view of the world that is attractive or
interesting to people including scientists.
He cites the Copernican and Darwinian revolutions
as examples of scientific revolutions that gave rise
to ideological revolutions, because each changed
man's view of his place in the universe.
But these were also scientific revolutions
in so far as each overthrew a dominant scientific
theory, the one a dominant astronomical theory, the
other a dominant biological theory.
He also cites Einstein's relativity theory as
a revolution, a truly scientific revolution, that
gave rise to operationalism and supported
Positivism, even though Einstein later rejected
these ideologies.
And Popper also refers to the subjectivist
interpretation of quantum theory as an ideology,
although in 1982 he proposed a crucial experiment
that he thought could decide against it.
The wholistic thesis of the semantics of
language is used by many Pragmatists to explain
events that have been observed in the history of
science: the impediment that language creates both
to the development of new theories and to the
communication of new theories within a profession.
However, Popper relegates all semantical
analysis to the status of a variation on the
essentialist metaphysical thesis; in his
autobiography in Philosophy of Karl Popper he admonishes the reader never to let
himself be "goaded" into taking seriously
problems about words and their meanings.
He maintains that words "merely"
play a technical or "pragmatic" role in
the formulation of theories, just as the letters in
written words play such a role in the formation of
the words. Contemporary
Pragmatists do not believe that language has so
passive a role in concept formation and human
cognitive processes, as Popper believes.
And it may be noted that contemporary
Pragmatists are as anti-essentialist as Popper; one
need only recall Quine's rhetorical ridicule that
an essence is merely a meaning wedded to a word.
Popper's philosophy does not offer a theory
of semantical description to reconcile the
phenomenon of semantical change with his views on
the decidability of criticism.
The Philosophy of Science
Popper`s philosophy comprehensively addresses
the four basic topics of philosophy of science.
His explicit rejection of the Positivist and
essentialist naturalistic philosophies of the semantics
of language represents a basic problem shift, a
reconceptualization of science as viewed by
philosophy of science.
Criticism
The central feature of Popper’s philosophy
of science is his falsificationist criterion, and
its consequent rejection of the naturalistic thesis
of the semantics of language and redefinition of the
concept of theory.
Theories are conjectures that are created by
the human imagination, and similarly the meanings
associated with the theories' constituent terms must
also be created artifacts distinguished as world 3
objects. The
theories do not originate by any natural process
such as induction, and similarly the constituent
meanings are not determined by any natural process
such as perception. The theories are not permanently established by verification
or confirmation, and similarly the meanings are not
permanently established by virtue of any
foundational ontology.
Theories are routinely falsified as a part of
the progress of science.
The paradigmatic case for Popper is the
transition from Newton's mechanics to Einstein's
relativity theory.
Einstein's theory does not include Newton's
as a special case, but rather contradicts and
corrects Newton's theory, and therefore describes an
alternative ontology.
And in such cases the new theory offers a
higher degree of information content as indicated by
the relative sizes of the classes of potential
falsifiers, such that even before empirical tests
are attempted, it is possible to recognize that the
new theory is preferable if it survives the test.
Crucial experiments are methodologically and
historically important decision procedures in the
progress of science.
In the case of the transition from Newton's
theory to Einstein's theory a crucial experiment was
performed in 1919, in which Einstein's theory made
the more accurate prediction within the range in
which the deviation between the two theories was
experimentally distinguishable.
Crucial experiments are not only effective
for deciding between theories, but are
characteristic of the growth of science toward
greater information content and verisimilitude.
Popper rejects the wholistic variation on the
artifactual theory of meaning, because it implies
that crucial experiments are invalid because the
alternative theories cannot share common background
assumptions with univocal semantics, and because it
implies in general that scientific criticism is
undecidable. Both
in his 1982 introduction to
Realism and the Aim of Science and as early as
his Logic of
Scientific Discovery in 1934, Popper has
maintained that the falsifying basic statements like
all empirical statements cannot be verified, and
that therefore it is impossible to prove
conclusively that an empirical scientific theory is
false. He
also states that every falsification can be tested
again for motivating an agreement among interested
scientists about the test outcome.
He maintains that there have historically
been successful scientific revolutions, which were
occasioned by successful falsifications, and he
rejects the view that falsification plays no role in
the history of science.
But he offers no theory of meaning
description that would enable him to reconcile the
phenomenon of semantical change with his thesis of
crucial experiments and the rational growth of
science. Contrary
to Kuhn, Popper maintains that communication
problems are merely difficulties and not
impossibilities.
But without a metatheory of semantical
description for analyzing semantical change, Popper
cannot explain why communication is not impossible,
because he cannot explain why it is merely
difficult.
Explanation
Popper’s theory of scientific explanation
has been called the hypothetico-deductive thesis.
In his chapter on theories in Logic
of Scientific Discovery he states that to give a
causal explanation of an event means to deduce a
statement that describes the event, using as
premises of the deduction one or more universal laws
together with certain singular statements called
initial conditions.
Later in "Aim of Science" in Ratio
(1957), reprinted both in Objective
Knowledge and in Realism
and the Aim of Science, he defines a causal
explanation as a set of statements by which one
describes a state of affairs to be explained,
statements which he calls the "explicandum",
by deduction from a set of explanatory statements,
which he calls the "explicans.” The explicans
must logically entail the explicandum,
and it must not be known to be false.
Furthermore, the explicans
must be independently testable, so that it is not ad
hoc. This
means that the explicandum must not be the only evidence relevant to the explicans;
the explicandum must have a variety of testable consequences, and
especially consequences that are different from the explicandum.
The Logical Positivist concept of explanation
is also described as hypothetico-deductive in the
above sense. But
there are also fundamental differences between
Popper's and the Logical Positivists' views. Of central importance to Popper's concept of scientific
explanation is the thesis that causal explanation
need not describe certain things, or in other words
that it need not have a certain semantics describing
a certain ontology needed to supply science with
foundations, such as the phenomenolist ontology.
Popper's view therefore differs from the
Positivist view that causal explanation must have a
semantics with such ontological categories as
sensations, elementary phenomena, or sense data.
And it also differs from the Romantic view of
causal explanation in social science, which requires
a mentalistic ontology.
In Poverty
of Historicism Popper rejects the Romantic
requirement of intuitive understanding of purpose
and meaning produced by sympathetic imagination.
In its verstehen
version this mentalistic ontological requirement for
causal explanation in social science becomes a
theory of scientific criticism.
He maintains that this requirement goes
beyond causal explanation, and he proposes his
doctrine of the unity of method in both natural and
social science, the method that he describes in Logic
of Scientific Discovery.
In Popper's philosophy of science
"causal explanation" is defined in terms
of the function that theories perform in realizing
the aim of science, and not in terms of some
foundational ontology.
His view of causal explanation is the result
of his rejection of the naturalistic philosophy of
meaning. Without
the naturalistic theory of semantics there is no
basis for requiring any particular ontology
including the particular ontology's concept of
causality, in order to be able to give a causal
explanation. Rejection
of the naturalistic thesis implies the rejection
of all ontological criteria for causal explanation
as well as the rejection of the distinction between
observation language and theory language and of the
idea of the existence of an ontological foundation
for science. Thus
Popper says that explanation is of the known by the
unknown in the sense of conjectural, instead of by
the known in the sense of the permanently
established foundation.
In this respect Popper is in the company of
the contemporary Pragmatists; Quine for example
calls the view that there are ontological criteria
for causal explanation the "genetic fallacy.”
Popper’s rejection of ontological criteria
for causal explanation became complicated in later
years by his idea of metaphysical research
programmes. The
metaphysical research programme is not atemporal and
eternal like the ontological foundations of the
essentialists and of the Positivists.
It is part of the historical problem
situation at a particular juncture in the history of
a science, and it is also untestable at the point in
time, and therefore “metaphysical” in Popper’s
sense. Most
notably in Popper's view, at the given point in the
history of the science the metaphysical research
program functions as an ontological criterion for
what constitutes a satisfactory explanation.
This complication arises from Popper's way of
demarcating between science and metaphysics, which
appeared many years before he introduced the idea of
metaphysical research programmes into his philosophy
of science, as he did in his later discussions of
quantum theory.
As early as 1955 in "Demarcation Between
Science and Metaphysics" in Conjectures
and Refutations he states that all physical
theories say much more than the physicist can test,
and that whether this "more" belongs to
physics or should be eliminated as a metaphysical
element is not easy to say.
And in 1958 in "On the Status of Science
and of Metaphysics" reprinted in the same book
he says that one can discuss irrefutable
metaphysical theories rationally in the sense that
one can discuss their ability to solve the problems
that they purport to solve, that is, in relation to
their problem situation.
This complication has its origin in the
residual status of metaphysics in Popper's
philosophy. Metaphysics
for him contains a great heterogeneity of types of
knowledge, which need have nothing in common, but
their irrefutable character and therefore their
nonscientific status.
Historically philosophers have not treated
metaphysics in so residual a manner, but instead
have offered positive characterizations of
metaphysics, which have sometimes been called
"transcendental metaphysics", and which
are not typically viewed merely as protoscience.
For example issues such as realism versus
idealism are viewed as transcendental and as incapable
of empirical resolution at any time. In the concluding paragraph of the concluding section of the
concluding volume of the Postscript,
Popper states that there may be a criterion of
demarcation within metaphysics between what he calls
"rationally worthless" metaphysical
systems on the one hand, and metaphysical systems
that are worthy of discussion and thought on the
other hand. He
does not characterize the basis for such a
demarcation within metaphysics, but his motivation
for recognizing the existence of protoscientific
metaphysics within residual metaphysics seems
clearly to have been the result of the influence of
Kuhn. In
the 1982 "Introductory Comments" in Quantum
Theory and the Schism in Physics Popper compares
metaphysical research programmes to Kuhn's concept
of paradigm, while stressing that metaphysical
research programmes must be seen in terms of a
situation that can be rationally reconsidered, and
that scientific revolutions viewed as changes of
paradigms are due to rational criticism.
In this context he references his 1975
"Rationality of Scientific Revolutions",
where he distinguishes between scientific and
ideological revolutions, and then sets forth
criteria for rational criticism of scientific
revolutions like Einstein's even before any
experimental testing is attempted.
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