Theory Selection and
Discord in Quantum
Mechanics
Neal Ravindra
Professor Don Howard
Philosophical Issues in Physics
Monday, 29 April 2013
Class Presentation
Covers chapter 24, “An essential role for historical
contingency?” in Philosophical Concepts in Physics
A quick look ahead…
Background
Brief review of some early quantum mechanical ideas
Bell’s theorem, sort of relevant
Underdetermination
Inference to the best explanation
Pierre Duhem
Willard Quine
Relevance to quantum mechanics
Historical contingency?
A hypothetical scenario?
Two different schools of
thought…
The completeness of quantum mechanics?
Niels Bohr frames contextuality, and complementarity
Bohr and “the irreducible, ineliminable and
uncontrollable minimum disturbance” – Copenhagen
interpretation of quantum phenomena1
Dissatisfaction with uncertainty led to the search for an
hidden variables theory
Einstein’s belief in an objective physical reality
Remarked that the Copenhagen theory is little more
than “a highly successful provisional theory.”2
A quick note about Bell’s
theorem…
Recall that Bell’s theorem demonstrates and proves that
“no determinate, local hidden-variables theory can agree
with all of the predictions of quantum mechanics.”3
Fig. 1: Photons released from source, and entanglement measured at various angles
Quantum mechanics as a
theory…
The theory of quantum mechanics has two components4
A formalism
Copenhagen theory and Bohm theory have equivalent
formalism
An interpretation
Copenhangen interpretation differs from Bohm
interpretation
Incompatibility of the two causes a dilemma
Scientific theory functions on three levels:
Empirical adequacy
Formal explanation
understanding
Bohm’s 1952 papers, a history
David Bohm’s 1952, a rediscovery of Louis de Broglie’s quantum
theory established in 19275
Einstein and the origin of the pilot-wave (as an EM wave)5
Max Born treated the wave equation as a guiding wave
De Broglie’s poor response to an objection raised by Wolfgang
Pauli in 1927 shuts many doors
Hilary Putnam, and Heisenberg’s negative reception of Bohmian
mechanics5
Leavens, Cushing, and Daumer elaborate on the ease of
description of some quantum phenomena by Bohmian
mechanics6
“… one purpose of Bohm’s 1952 papers was to show that
trajectories are possible and that, therefore, part of the
Copenhagen dogma (completeness and, hence, the alleged
impossibility of such trajectories) is false. That it certainly did.”7
Not only Copenhagen and
Bohmian mechanics…
There are actually several highly developed attempts at
alternative interpretations to quantum phenomena
Many worlds8
Consistent histories8
Decoherence9
Modal interpretations10
Fig. 2: a quick graphic
explaining the many worlds
interpretation of quantum
phenomena
An introduction to a problem
of choice…
Quantum mechanical formalism (standard orthodox
formalism and Bohmian formalism) supports two
mutually incompatible ontologies
Cushing’s thesis on the resolution of the competition
“… the historical competition between these theories ad
the selection of Copenhagen over Bohm illustrate that
such an historically contingent process is not
meaningfully distinct from the rational reconstruction
and logical judgment of the victorious theory”11
Underdetermination of quantum mechanical theory
Underdetermination
Correlation does not imply
causation12
A simple example
Just because there is a high
incidence of violent kids
watching cartoons,
cartoons don’t necessarily
cause violence; therefore, a
high correlation
underdetermines what we
should believe about the
causal relationship
between the two12
Descartes’ evil demon12
Fig 3: a simple definition of underdetermination is a situation in
which there is insufficient evidence to decisively select between beliefs
regarding the evidence in consideration
Pierre Duhem on the acceptability
of a scientific theory
“The sole purpose of physical theory is to provide a
representation and classification of experimental laws;
the only test permitting us to judge a physical theory
and pronounce it good or bad is the comparison
between the consequences of this theory and the
experimental laws it has to represent and classify.”13
“The methods [physicists] follow are justifiable only by
experiment, and if they both succeed in satisfying the
requirements of experiments each is logically
permitted to declare himself content with the work
that he [or she] has accomplished.”13
‘Experimentum crucis’ – Bacon, Hooke, and
Newton and their interpretation of the
accpetability of a scientific theory14
Fig 4: the French physicist,
philosopher, and mathematician,
Pierre Duhem (1861-1916)
Eddington expedition to Africa in 1919
confirming Einstein’s gravitational lensing
hypothesis
Duhem – logical justification if
experimental phenomena is saved
Duhem argues that it is futile to attempt to discriminate between two
plausible theories based on a crucial experiment
“the physicist is never sure he has exhausted all the imaginable
assumptions”15
Holist underdetermination
Inability to test hypotheses in isolation leaves us underdetermined in our
response to a failed prediction12
Contrastive underdetermination
Occurs when a theory in which the evidence confirming the given theory
also confirms another, different theory12
This is the philosophical classification of the underdetermination resulting
from the Copenhagen school and Bohmian mechanics
Use good sense to discern between approaches to the modification of a set
of hypothesis (or to a theory) that produced an underdetermination
The problem with the employment of
nonevidential and nonlogical criteria
(aka good sense) to eliminate
underdetermination
“But these reasons of good sense do not impose themselves
with the same implacable rigor that the prescriptions of
logic do. There is something vague and uncertain about
them; they do not reveal themselves at the same time with
the same degree of clarity to all minds.”13
Willard Quine and universal
underdetermination
The role of good sense:
“nothing more than a loose association reflecting
the relative likelihood, in practice, of our choosing
one statement rather than another for revision in
the event of recalcitrant experience”16
“Much
latitude of choice as to what statements to
reevaluate in light of any single contrary
experience”16
Fig 5: Willard van
Quine suggested that underdetermination
challenges applied to all knowledge claims13
The only test of a belief is whether it fits into a
web of connected beliefs that accords well with our
experience on the whole13
Orman Quine (19082000), an American
philosopher , professor at
Harvard
Inference to the best explanation:
another criterion for theory selection
A.k.a. abduction or hypothesis selection criterion
Charles Sander Peirce on IBE17:
An inference that a certain hypothesis that adequately explains
phenomena represents the truth
There may be equally plausible phenomena, but experimentation
and repetition should reinforce the validity of the induction
Abductive validation – one explanation is validated, or a theory is
chosen over others, because it is considered the best explanation
of the set of empirical data
Best explanation often chosen based on aesthetic qualities
(simplicity, elegance, etc)
Difference between underdetermination and IBE?
Underdetermination as a tool for leveling the playing field
IBE as a method of raising one theory to the top of the hill
Back to quantum mechanics…
Copenhagen school and Bohmian mechanics: two theories
that are empirically adequate
Not a problem if differences between ontologies is
insignificant
The ontologies entailed by these two interpretations are
radically different and incompatible with one another
Inherent indeterminacy is incompatible with absolute
determinism
Observational indistuingishability between the two
interpretations coupled with conflicting ontology makes a
complete, clear picture of the underlying physical structure
of the universe impossible
A more complete picture of the
process of the selection of accepted
theories
Since there is no evidential criteria employed to discern
the credibility of the Copenhagen interpretation,
nonevidential criteria must have employed to accept the
theory
Sociological factors often breaches the realm of the
scientific enterprise to influence the scientific body of
knowledge
Theory acceptance is not entirely subjective
Fashion selective criteria (coherence, beauty, simplicity)
Political expedience factors, and professional development
influences
Cushing’s worry
Popular acceptance of empirically adequate theories
may exclude an equally empirically successful theory
that entails a more accurate world view
“For instance, Einstein allowed the theoretical (or
logical) possibility of more than one empirically
adequate theory, but then went on to declare that at
any given time the ‘world of phenomena’ (that sounds
pretty objective) uniquely determines one theory as
superior to all others.”18
Dilemma for the realist
Realism
The object of perception has real existence – it has n
objective or absolute existence and isn’t reducible or
dependent on a perceiving agent
The two-fold dilemma:
Accept the Copenhagen interpretation and suffer from
the measurement problem, contextuality, and fuzzily
defined complementarity
Realize the underdetermination of interpretation in
quantum mechanics and fail to choose one theory over
the other using logical principles, resulting in despair
between the simultaneous existence of viable theories
that propose indeterminacy and absolute determinism
An argument between the
antirealist and the realist
Antirealist begins with the
Copenhagen interpretation of
quantum mechanics, finds no
coherence in microrealm and finds it
impossible to explain the macrorealm
with a coherent ontology
Realist develops a coherent ontology
in the macrorealm but struggles to
explain the microrealm
Bohmian mechanics looks pretty
good to her (or him) because
Bohm is able to determine a time
evolution path for a particle in a
space-time background, preserving
classical sensibilities and relativistic
invariance
Fig 6: a
graphic that
scales across
small scale
phenomena
and the
macroscopic
realm of the
entire earth
The convenience of
interpretation Schrodinger on the absence of a dilemma for quantum
mechanical theory:
The description of the universe as deterministic or
indeterministic is a matter of convenience, “The most that
can be decided is whether the one or the other concept
leads to the simpler and clearer survey of all the observed
facts.”3
The 1927 Solvay Conference
The 1927 Solvay Conference
in Brussels considered the
Copenhagen interpretation as
the only serious and plausible
quantum mechanical theory
Proponents stifle opposition
to Copehnagen interpretation
Copenhagen interpretation
becomes the norm in physics
Professions depend on
furthering the Copenhagen
interpretation
Fig 7: the 1927 Solvay Conference in Brussels
in which 17 of the 29 attendees had won or
would eventually win the Nobel prize.
Attendees include Marie Curie, Bohr,
Einstein, Henriot, Ehrenfest, Herzen,
Schrodinger, Pauli, Hesienberg, Dirac, de
Broglie, Planck, Lorentz, and Compton
An alternative historical
scenario?
Einstein’s three core commitments
Event-by-event causality
The preservation of locality and subluminal information travel
Rationality and objectivity of the physical world
A lack of encouragement and support for alternative
interpretations to the well backed and less flawed Copenhagen
interpretation19
The problems of Einstein’s electromagnetic pilot wave
De Broglie’s weak defense of guiding wave equations, and poor
response to Pauli’s objection
Erwin Madelung’s inconsistencies in hidden variables theory
With the flip of a coin…….?
In summary
Scientists today accept the Copenhagen interpretation of
quantum phenomena
Rejection of Bohmian interpretation
No point in dislodging the Copenhagen interpretation
Thus, a hugely influential scientific theory that dominates
our body of physical scientific knowledge…
…is affirmed in part because of societal, political, and
historical situations characteristic of the developmental
period of quantum mechanics
… lacks resolute and complete objective, empirical, and logical
support
Food for thought
In light of this chapter, it seems impossible to divorce the
scientific enterprise from societal pressure and humanity’s
nonlogical inclinations. In the words of Cushing, “Science,
even in its products or laws remains historical or contingent
in an essential manner.”20 Do you agree?
Does the reality that things went a certain way at certain
crucial junctures instead of a different, equally viable way
imply that non-objective, nonlogical reasons are just as
important factors as empirical success and other objective
criterion in determining the correct theory to be
incorporated into the body of scientific knowledge?
More food…
Do you agree with the historian Comer vann Woodward’s
statement that, “Inevitability is an attribute that historical
events take on after the passage of sufficient time,”
especially considering that if Bohm’s interpretation of
quantum mechanics was given some legitimacy, research and
study into the consequences of the theory could have
yielded more powerful branches of science and more
successful predictions than those that the Copenhagen
interpretation provided? Isn’t there an opportunity cost in
choosing to support the Copenhagen interpretation over
Bohm’s interpretation regardless of whether or not you
think the Copenhagen interpretation was correctly chosen
(was it?)?
And more food…
“The human understanding, when any proposition has been once laid down
(either from general admission and belief, or from the pleasure it affords), forces
everything else to add fresh support and confirmation; and although most
cogent and abundant instances may exist to the contrary, yet either does not
observe or despises them, or gets rid of and rejects them by some distinction,
with violent and injurious prejudice, rather than sacrifice the authority of the
first conclusions”20
How guilty are we of this?
What does this imply for the inherent weakness in the construction of a
scientific body of knowledge as one subjected to folklore and subjective
intuitions and societal inclinations rather than pure, hard, cold, objective
calculation?
What do you think serves as sufficient criteria in the selection of one theory over
another?
Any criteria for selecting one theory over another when both theories adequately
explain the same phenomena?
References Cited
1Cushing,
Philosophical Concepts in Physics, pp. 306
2Cushing,
pp. 307
3Cushing,
pp. 324
4Cushing,
pp. 332
5Goldstein,
Sheldon, “Bohmian Mechanics” 2001
6Cushing
1994, Quantum Mechanics: Historical Contingency and the
Copenhagen Dominancy
7Cushing,
pp. 338
References Cited, continued
8Vaidman
2002
9Bacciagaluppi
10Lombardi
2003
and Dieks 2002
11Cushing,
Philosophical Concepts in Physics, pp. 345
12Stanford
and Zalta 2009
13Cushing,
pp. 346, excerpt of Duhem 1974, 217.
14Lakatos
1974
References cited, continued
15Cushing,
pp. 345, excerpt of Duhem 1974
16Cushing,
pp. 346, excerpt of Quine
17Igor
Douven 2011
18Cushing,
pp. 348
19Cushing
Quantum Mechanics 1994
20Cushing
excerpts, section 24.4