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Feyerabend
got this concept of realism from Popper.
In "Complementarity" (1958) he
references Popper's "The Aim of Science"
published in Ratio
(1957), and says it as an excellent
characterization of the classical ideal of
scientific explanation and its connection with
realism.
In this article Popper affirms that
explanations in science are given in terms of
universal laws of nature, which are conceived as
conjectural descriptions of the structural
properties of nature, that is of the world itself.
He explains that by "universal" he
means that scientific laws and theories must make
assertions about all spatiotemporal regions of the
world.
Popper also speaks of different levels of
universality, which he exemplifies by the greater
universality of Newton's laws relative to Kepler's
and Galileo's laws.
But Popper rejects a reductionist relation
between Newton's and Galileo's physics.
He states that whenever a new empirical
theory of higher level of universality successfully
explains an older theory, it does so by correcting
the older theory.
He adds that the idea of independent evidence
can hardly be understood without the idea of
discovery, of progressing to deeper layers of explanation
without the idea that there is something to be
discovered and to be discussed critically, where
deeper layers means explanation by means of more
universal laws and theories, as exemplified by
Newton's laws, which are deeper relative to
Galileo's or Kepler's laws.
This is the universalist realism that
Feyerabend maintained, until he embraced relativism.
Feyerabend characterizes Bohr's philosophical
thesis of complementarity as the exact opposite of
the classical ideal of scientific explanation, and
he says that the difference between the classical
ideal and complementarity is an instance of the
age-old issue between realism and Positivism.
Bohr's complementarity thesis is an instance
of Positivism, because Bohr maintains that the
account of all evidence must be expressed in
classical terms, and that it is not possible to
dispense with what Bohr called "forms of
perception".
Some philosophers such as Heisenberg consider
Bohr's forms of perception to be neo-Kantian.
Feyerabend notes that Positivists do not
customarily consider phenomena to have any forms,
and he therefore describes Bohr as a Positivist of a
higher order.
He also states that Bohr's instrumentalist
view of current quantum theory, which Bohr calls a
"natural generalization of classical
physics", is merely the result of retaining
classical concepts.
Both the retention of classical concepts and
the instrumentalist view of quantum theory are
contrary to Feyerabend’s Thesis I.
He therefore says that complementarity is a
statement of the fact of duality and is the way in
which the classical concepts appear within the
predictive schemes that replace classical laws on
the atomic level.
He references passages contrary to Thesis I,
in which Bohr states that the difficulties of atomic
theory cannot be evaded by replacing the concepts of
classical physics by new nonclassical conceptual
forms.
At the same time while Feyerabend views
complementarity to be the result of retaining
classical concepts, he does not simply deny the fact
of duality, or that duality will be eliminated
merely by philosophical reflection with the aid of
Thesis I.
With his distinction between the fact of
duality on the one hand and the statement of
complementarity expressing the fact of duality with
classical concepts on the other hand, Feyerabend
considers two approaches to a realistic
microphysics.
The first approach is to reinterpret the
formalism of the modern quantum theory, which is a
mathematical statement of the fact of duality.
He admits that if the quantum theory is
viewed as a predictive theory like celestial
mechanics, then a realistic interpretation does not
seem to be possible.
But he adds that if the quantum theory is
viewed as a theory containing new concepts for the
description of nature, then a realistic
interpretation of a rather unusual kind is
definitely possible.
This amounts to a proposal to construe the
contemporary quantum theory with its duality thesis
in accordance with Thesis I.
Such a reinterpretation will not retain
classical concepts, and will express the fact of
duality without expressing complementarity.
He also says that the quantum theory thus
used to form new concepts about the nature of
physical systems, may permit some features of the
macrophysical level to be derived from quantum
mechanics, and thus make duality compatible with the
universality condition for realism, even though no
such derivation has actually been accomplished to
date.
But this first approach does not seem to be
Feyerabend's preferred way to interpret microphysics
realistically, and he says explicitly that the
possibility of a realistic microphysics does not
depend on supplying a realistic interpretation for
the current quantum theory with its duality thesis.
His second and preferred approach is to
develop an entirely new microphysical theory.
This new theory would satisfy two conditions:
Firstly it would be universal, and secondly it would
be empirically adequate.
As a universal theory it will have a unified
conceptual apparatus, which when applied to the
domain of validity of classical physics, will be
just as comprehensive as the classical apparatus.
In other words the microphysical theory will
be of a higher level of universality, such that it
will also be a macrophysical theory, yet different
from classical physics.
Feyerabend explicitly compares the relation
between the new universal microphysical physics and
the classical physics, to the relation between the
relativity theory of gravitation and the Newtonian
theory of gravitation.
The empirical adequacy criterion will be
satisfied, when this realistic, universal
macrophysical theory contains the current elementary
quantum theory as an approximation.
It may therefore contradict quantum mechanics
without violating the universality criterion for
realism.
Feyerabend affirms that for a realist, the
solution of the problem of duality need not be found
in alternative interpretations of the current
quantum theory, which he says is in all probability
nothing but a predictive scheme anyway.
Instead it can be found in the attempt to
derive a completely new universal theory, which need
not contain the duality thesis or complementarity.
This new microphysical theory will supply new
concepts for interpreting the observed fact of
duality.
For ten years following these 1958 papers
Feyerabend wrote a series of articles defending and
advocating attempts to develop a new microphysics
without duality.
In these papers he contrasts his view that
there can be a realistic microphysics without
duality, with Bohr's view that all future
microphysics must contain the duality thesis.
In "Niels Bohr's Interpretation of the
Quantum Theory" in Current Issues in the Philosophy of Science (1959) he discusses what
he calls the dogmatic elements in Bohr's approach.
He objects that Bohr treats duality as an
unalterable experimental fact that must be included
in any future microphysical theory; on his Thesis I
description of experiments is not unalterable.
Feyerabend argues that the only condition
that need be satisfied by a future microphysics
theory, is that it be compatible with experimental
findings to a certain degree of approximation and
within a certain degree of accuracy that is required
for the dogmatic elements of Bohr's approach.
In this and other papers written during this
period Feyerabend sets forth his interpretation of
Bohr's philosophy, according to which all state
descriptions of quantum mechanical systems are
relations between the system and measuring devices
in action, that is to say, between microscopic
system and macroscopic apparatus.
This relational character of quantum state
descriptions results from the need to restrict the
application of any set of concepts to a certain
experimental domain due to the wave-particle
duality.
Bohr's relational view is contrasted with
both the classical view and with Heisenberg's view
of measurement in quantum theory.
Feyerabend says that both classical physics
and Heisenberg's view are variations on an
interactionist view.
In classical physics the interaction between
the apparatus and the system can be explained in
terms of the theory used to describe the system.
And on Heisenberg's view the measurement of a
quantum mechanical system involves an interaction
that disturbs the system in unpredictable ways.
Feyerabend says that Bohr's relational view
enabled Bohr to reply to the argument by Einstein,
Podolsky and Rosen (EPR), who defended the thesis
that quantum mechanical systems have definite
classical states instead of indefinite states
described by the indeterminacy relations.
This argument postulates two systems which
are separated to such an extent that no interaction
can occur between them, and therefore measurement
disturbance in one cannot affect the other.
Bohr made his thesis of indefiniteness of
state descriptions compatible with the EPR argument
by assuming that states are relations between
systems and devices rather than properties of the
systems.
The point is that while a property of the
system cannot be changed except by interaction with
the measurement device, a relation can be changed
without such interaction.
Bohr therefore views position and momentum as
relations rather than as properties of the
quantum-mechanical system.
Bohr attempts to express this by his
distinctive use of the term "phenomenon",
which he uses to refer to the observations obtained
under specific circumstances including an account of
the experimental arrangement. Therefore phenomena
cannot be subdivided, and dynamical variables cannot
be separated from the conditions of their
application.
Physical attributes no longer apply to the
object per se,
but apply to the whole experimental arrangement with
different assertions (wave or particle descriptions)
appropriate in different circumstances.
Bohr relativized the dynamical variables in
the quantum theory to the circumstances of the
experimental situation, and years later following
Bohr, Feyerabend would relativize all reality to the
circumstances of the knower's situation.
But in 1962 in "Problems of
Microphysics" in Frontiers
of Science and Philosophy (ed. Colodny)
Feyerabend was still defending the possibility of a
universal and therefore realistic microphysical
theory without duality.
He says that between 1935 and 1950 the
Copenhagen interpretation had become a creed, and
that the objections of a few opponents such as
Einstein and Schrödinger were taken less and less
seriously.
He notes that more recently there has
occurred the development of a counter movement,
which demands that the assumptions of the Copenhagen
interpretation be given up and be replaced by a
different philosophy.
These revolutionaries, as Feyerabend calls
them, have shown not only that the empirical
adequacy of the complementarity thesis is in doubt,
but also that even empirical success is not
sufficient reason to say that there can be no valid
alternative to complementarity.
He insists that future researchers need not
and indeed should not be intimidated by the
restrictions that some high priests of
complementarity would impose.
The revolutionary that Feyerabend has in mind
is the physicist, David Bohm.
Initially Bohm had accepted the Copenhagen
interpretation, but later he advanced an alternative
thesis in his "Quantum Theory in Terms of
Hidden Variables" in Physical
Review (1951), and in more detail in his books, Causality
and Chance in Modern Physics (1957) and The
Undivided Universe (1993).
His hidden-variable thesis postulates the
existence of a subquantum domain at a much smaller
and presently experimentally inaccessible (therefore
hidden) order of magnitude than the quantum domain
that is described by modern quantum theory.
In "Professor Bohm's Philosophy of
Nature", a review of Bohm's book in
British Journal for Philosophy of Science
(1961), Feyerabend says that complementarity can be
interpreted in either of two ways.
The way he finds acceptable is that in which
it functions to provide an intuitive picture for
wave mechanics, and as a heuristic principle guiding
future research.
He says that this first way is undogmatic,
since it admits the possibility of alternatives
including preferable alternatives, even though no
satisfactory alternative exists presently.
The second and unacceptable view is that of
Bohr, who maintained complementarity as a basic
philosophical principle incapable of refutation, and
to which future microphysical theory must conform.
In his review of Bohm, Feyerabend says that
Bohm argues against Bohr's dogmatic view by
affirming a role for speculation in modern empirical
physics.
In a discussion of the role of speculation in
"Problems of Microphysics" Feyerabend
rejects demands by Hanson that Bohm's theory must be
set forth as an algebraically detailed and
experimentally acceptable theory.
He admits that such criticism is appealing to
the great majority of physicists.
But he maintains that such criticism puts the
cart before the horse.
The discussion among physicists of
alternatives to the current theory plays a most
important role in the development of physics, and a
complicated physical theory cannot be invented in
its full formal splendor without some preparation.
Feyerabend later elaborated upon this thesis
in his discussion of theoretical pluralism and
counterinduction.
At this stage of his thinking he advocates
these ideas in order to encourage the development of
a new microphysical theory not containing duality.
Norwood
Russell Hanson, a professional philosopher of
science, was an influential critic of Feyerabend's
philosophy of quantum physics.
In an article memorializing Hanson's death in
1967, and appearing in Boston Studies in the Philosophy of Science, Vol. III (ed. Cohen and
Wartofsky, 1967) Feyerabend says that he changed his
views about the Copenhagen interpretation as a
result of a series of debates with Hanson, and that
by 1966 he had become persuaded of Hanson's view.
Hanson brought a different agenda to the
philosophy of microphysics than did Feyerabend.
Hanson was not driven to defend the
possibility of a universalist-realist microphysics,
but rather was attempting to explain how the quantum
theory as well as other theories are discovered.
More specifically he focused on the role of
semantics of observation and of theory language in
the discovery process.
The evolution of their two agendas brought
Feyerabend and Hanson into conflict.
Integral to Hanson's agenda was the belief
that the duality thesis will be contained in any
future microphysical theory.
This belief, which Hanson held with strong
conviction, was due to the personal influence of
P.A.M. Dirac, the physicist who developed the field
quantum theory in 1928.
On the other hand Feyerabend's agenda at that
time was that a universalist-realistic microphysical
theory is possible, precisely because the duality
thesis need not be contained in any future
microphysics, since according to Thesis I the
observed experimental fact of duality can be revised
by a new microphysical theory. Hanson's principal
statement of his philosophy of science is set forth
in his
Patterns of Discovery (1958).
In this work he recognizes the
interdependence of observation and theory in a
manner similar to Feyerabend's Thesis I, and Hanson
describes observation as theory-laden.
In the "Introduction" to his Realism,
Rationalism and Scientific Method (1981)
Feyerabend comments that his Thesis I is not exactly
the same as Hanson's doctrine that observation is
theory-laden, because unlike Hanson, Hesse and
others, he maintains that observation terms are
fully theoretical and have no purely observational
core.
Feyerabend’s view is thus slightly
different from Hanson's thesis of phenomenal seeing.
Nonetheless Hanson was no more sympathetic
than Feyerabend to Bohr's view that the concepts of
classical physics must be used for observation in
all of physics.
Hanson
criticizes Feyerabend by maintaining that duality is
stated by the quantum theory formalism itself, and
that duality is not merely a philosophical thesis
appended to the formalism, which might be replaced
by an alternative interpretation not expressing
duality.
Hanson finds the duality thesis stated by the
mathematics of the de Broglie-Einstein relations and
also by the Dirac operator calculus, which enables
any wave-mechanical description to be transformed
into an equivalent matrix-mechanical one.
Feyerabend seems not actually to have
maintained the position that Hanson criticizes, even
in the first of his two approaches to a realistic
microphysics given in "Complementarity"
(1958).
However, Hanson repeats this line of attack
nearly ten years later in "Physical
Implications of Quantum Physics" in The Encyclopedia of Philosophy
(ed. Edwards, 1967), where he characterizes
Feyerabend as maintaining that the metaphysical
views in the Copenhagen interpretation should be
abandoned as indefensible, and that the minimal
scientific content consisting of algebraic
transformations and factual data is quite compatible
with some interpretation markedly different from the
Copenhagen one.
Perhaps this is just the way in which Hanson
viewed Feyerabend's call for a new microphysics
without duality, even though Feyerabend was very
clear in stating that his second approach is not
just an alternative interpretation of the elementary
quantum theory, but rather is an entirely new
microphysical theory related to elementary quantum
theory as Einstein's relativity theory is to
classical physics.
Nonetheless, the thrust of Feyerabend's
attack is against Bohr's thesis that classical
concepts in the complementarity description of the
fact of duality must occur in microphysics including
any future microphysics.
In "Comments on Feyerabend's' Niels
Bohr's Interpretation of the Quantum
Theory'..." (1959) Hanson states what he
considers to be the minimal essentials of the
Copenhagen interpretation: Firstly he maintains that
past and present microphysical experience make it
probable but in no sense necessary that any future
microphysical theory will incorporate the quantum
postulate and the duality principle.
Secondly he notes that there presently exists
no coherent, currently workable and fully
articulated conception of a microphysical theory,
which can do without the quantum postulate and the
duality principle.
He maintains that Feyerabend is correct to
score the strident statements of Bohr and Rosenfeld,
when they violate the history of physics by
suggesting that any future microphysics will of
necessity guarantee things like complementarity.
But he adds that Bohr's metaphysics is not an
indispensable part of the Copenhagen interpretation,
and he therefore distinguishes the "Copenhagen
interpretation" from the "Bohr
interpretation".
He states that if the Bohr interpretation is
cut away, then what remains is a liberalized
Copenhagen interpretation, which is entirely
defensible.
And he maintains that there are good
contingent arguments in support of the expectation
that any future microphysics will incorporate the
quantum postulate and the duality principle, and
emphasizes that presently there exists no working
alternative to the current quantum theory
notwithstanding all its awkward features.
But Feyerabend's response to Hanson's
criticisms did not result in a liberalized
Copenhagen interpretation.
What Feyerabend produced is an elevation of
the Bohr interpretation to a generalized and quite
radical relativistic philosophy of knowledge.
It seems unlikely that Feyerabend understood
what Hanson wanted to cut away from Bohr’s
Copenhagen interpretation.
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