Do Thought Experiments Manifest as Paradigm Change
within the Context of Kuhn’s Revolutionary Science?
Joaquin De La Torre-Mac Neill
I. Introduction
Science is divided into two different types (according to
Kuhn), normal science and revolutionary science. Normal
science works within: established paradigm, defined terms,
and real experiments. Normal science is confined to
sensationism in the practice of performing experiments and
recording the results, the method. Normal science denies
thought experiment a role within the method. Normal science
builds off prior scientific theory and accumulates progress
through time. Normal science often struggles to explain
anomalous evidence.
Anomaly is an essential component within revolutionary
science. Anomalies that are a result of real experimentation
are often discarded because of the (theory-laden) nature of
normal science practiced within an existing paradigm.
Thought experiments often create anomalies that can not be
solved within a paradigm. Anomalies can indicate the point
where a paradigm begins to enter into a crisis. A crisis often
gives rise to revolutionary science that can explain the
anomalous evidence and predict future results.
Revolutionary science works to create a new paradigm that
rejects theories, re-conceptualizes experiments, and
redefines terms.
A thought experiment has many definitions, according
Sorenson, a thought experiment is:
an experiment that purports to achieve its aim without the benefit of
execution. The aim of any experiment is to answer or raise its question
rationally. [italics
in original]
This definition does not imply that the experiment posed by a
thought experiment could not be performed, it is just not
necessary to achieve its aim. There are a few different types
of thought experiments as well, each with a different aim.
According to Brown (Horowitz, p124-5) there are three,
destructive, constructive, and platonic (which are
simultaneously destructive and constructive). All three types
of thought experiment are addressed within this paper. Two
different thought experiments will be examined in detail, one
by Galileo, one by Einstein. Two other uses of thought
experiment are looked at, though not in detail, by Darwin and
Schrodinger. All of these thought experiments are within
revolutionary science.
In this paper I will address thought experiments used in revolutionary science:
Galileo's falling bodies and Einstein's Elevator. Two other thought experimenters
that are addressed are Darwin and Schrodinger, although the focus will be on
their technique and the implications. Galileo’s thought experiment worked to
simultaneously destroy an accepted theory and create a new theory, the platonic
type. Einstein's is a constructive thought experiment. Schrodinger's is a
destructive thought experiment. All of them create a new paradigm in science,
this is Khunian revolutionary science.
Discovery within revolutionary science is often done through thought
experiments. Thought experiments are only performed in the mind, their role in
the method goes against the foundations of sensationism. Thought experiments
create a scenario and the conclusions of that particular situation are
representative of the world in general. This way of working from the particular to
the general also goes against sensationism.
A destructive thought experiment is most often open ended,
that is it asks a question, but does not propose an answer.
The lack of an answer to the question, raised by a
destructive thought experiment, creates a need for a new
theory that can . Theory creation involves creativity and
imagination.
II. Thought Experiments Advantages
Thought experiments enable the experimenter to isolate a
hypothesis and premise from its auxiliaries. Thought
experiments can be modified, nearly instantaneously, as
new hypotheses, premises, and theories arise. Thought
experiments allow the audience, or the student, to become
an active participant within the creation of theories
(especially in respect to a destructive thought experiment).
The involvement of the audience within the thought
experiment is a powerful epistemological (and persuasive)
tool that can construct experiments that would not be
possible in real experimentation. The author can introduce
new theories and concepts to the audience, while forging
new connections within existing evidence.
The thought experiment often includes a reconceptualization
of evidence. “Concepts never come free from physical
implications, and as such their use always provides
information about what the world is like. This of course
implies that they can err in a non-logical sense, i.e., that the
world is not exactly as presupposed by the concept, and
exposing these kind of errors is the function Kuhn ascribes
to thought experiments.”(Van Dyck, 9) This indicates a path
to discovery, which is often non-logical because when a new
paradigm is introduced, the choice between paradigms is not
always logically clear and distinct. For example, Ladyman
refers to the beginning of the Copernican revolution (p. 106).
Ladyman credits the revolution coming about as a result of
the work of many others (Galileo, Descartes, and Kepler) in
completing the theory. Although Ladyman writes, “none of
them could be sure that it would ultimately provide a more
adequate account of what we observe in the night sky”
(p107). Galileo's thought experiment analyzed in this paper
was a step toward rejecting the Aristotelian paradigm.
Galileo's platonic thought experiment could be used as an
argument against the Aristotelian paradigm.
III. Thought Experiments as Arguments
Thought experiment has been compared to forms of
argument, known by different names, in various fields of
study. For example within the discipline of rhetoric it (thought
experiment) bears a striking similarity to enthymeme.
“Enthymemes are similar to thought experiments because
they both lack the necessary premises to create formal
syllogisms.”(Crick, 23) A thought experiment used as an
argument by Darwin: “the audience is led from thought
experiment to thought experiment, and after the audience is
fully committed, it can read the passage on natural selection
and consider it true, even though, taken on its own, Darwin's
guiding metaphor rests on only the most intangible of
foundations.” (Crick, 39) This technique of 'leading' the
audience to the conclusion is an important component of
thought experiments in general. Darwin uses thought
experiments to question an accepted truth about the world.
This is a powerful tactic that did not begin, or end, with
Darwin. That tactic is the use of thought experiment as a
persuasive (rhetorical) tool to communicate an idea that will
most certainly have a negative reception.
The rhetorical use of thought experiment to communicate an
idea (or theory) to an audience (that is certain to have a
negative reaction to the said idea) can not be separated
without losing an essential component of thought
experiment. Norton (in his chapter about thought
experiments within Einstein's work) goes about reconstructing a thought experiment into statements of logic
within an argument, in an attempt to understand the thought
experiment. Crick criticized Norton for trying to take the
“rhetorical power” (or the persuasiveness) away from
thought experiments when he tried to reduce them to
arguments. Crick maintains, “If thought experiments can be
fully reconstructed with only the tools of logic, then they can
also be controlled.” This attempt at controlling thought
experiments eliminates a key function which they, alone,
hold within discovery (theory creation). This attempt to
control thought experiments their epistemological value is
taken away.
Epistemologically, thought experiments are invaluable.
Thought experiment allows the audience to perform an
experiment and reach the conclusions by themselves that,
often, could not be performed in reality. A good
(constructive) thought experiment will have the audience
thinking of the conclusion before it is even stated. This
technique of teaching an audience change within, and
among, concepts is an important process found in thought
experiment. Another role of thought experiment is that they
undermine the accepted 'truth' in persuasive manner (often
that is nearly impossible to rationally reject). Presenting the
accepted evidence and concepts in a context that leads the
audience (or the student) to realize the irrationality (or within
Galileo's case, reductio ad absurdum) of the current view.
Often a result of a thought experiment is that a new theory is
accepted. Existing concepts are re-defined and new
connections between concepts are identified. This is referred
to as the ability to destroy an accepted theory and create a
new theory at once [see Galileo below] Brown considers the
Platonic type of thought experiment, “quite remarkable. They
are simultaneously destructive and constructive. At one and
the same times they can destroy the old theory and create a
new one.” (Brown 9)
IV. Galileo's & Einstein's Thought Experiments
First we look at one of Galileo's thought experiments. Galileo
was questioning an accepted truth, the Aristotelian view, that
objects fall at a rate proportional to their mass. Leading up to
the publishing of his book, that contained the following
thought experiment, he published a dialogue discussing
falling bodies to question the accepted truth. His goal was to
demonstrate the self-contradictory nature of the Aristotelian
view, exposed by the thought experiment. The Aristotelian
theory of falling objects stated that the rate an object falls is
directly related to its mass, that is an object with greater
mass falls faster than an object with less mass. Galileo
proposed: if an object of less mass were tied to an object of
greater mass how would the object of less mass affect the
rate the object of greater mass fell? Would the object of less
mass cause the object of greater mass to fall at a slower
rate? The Aristotelian conclusion is that the two objects
together fall slower and faster than the heavy object by itself.
This anomaly undermined the established teachings of the
time. When one performs the thought experiment, it
becomes obvious the established 'truth' of the time was
false. Not only does Galileo's thought experiment destroy the
accepted truth, it also provides space for his theory to be
created. Galileo's theory was that the rate objects fall has no
relation to their mass. Once one performs the thought
experiment Galileo's theory becomes obviously correct and
the Aristotelian theory of falling bodies is incomprehensible.
Galileo's thought experiment reduces the Aristotelian theory
of falling bodies to the absurd. As a result Galileo's theory of
falling bodies explained the anomaly created by his thought
experiment and predicted the future evidence of further
experimentation.
This is a magnificent example of the power of the thought
experiment, as it both destroyed the paradigm and created a
new one. The tool was used throughout history before
Galileo, though not so masterfully. He used it to dismantle
the established belief structure of the time, Aristotelianism.
Epistemologically, this argument could not be refuted
because it explained the anomaly and predicts future
experimental evidence. It changed the way people of that
time accepted the official teaching.
Next we look at a constructive thought experiment, one of
Einstein's, the elevator experiment. Imagine a physicist is
drugged and wakes up in an elevator. The elevator is far
removed from any gravitational fields, in space. The
physicist experiences zero gravity and must attach herself to
the floor to keep from floating up to the ceiling. A rope is
attached to 'a being' in space that begins to pull the elevator
at a uniform rate of acceleration. She is no longer floating.
She detaches herself from the floor and she can stand up
right as if she were within a gravitational field (such as ours
on earth). All the other objects in the elevator 'fall' to the floor
just as they would behave within a gravitational field, no
longer floating in mid-air. The physicist begins to wonder
what has changed, has she suddenly come into contact with
a gravitational field? Obviously she was not within the
gravitational field a few moments ago. Why, if she is now
within a gravitational field, are she and the elevator not
falling towards whatever body's gravitational field she has
come into contact with? Suddenly she notices a hook in the
middle of the roof of the elevator with a steel cable attached
to it. Now she figures out what has happened. The cable
gradually lowered the elevator down into a gravitational field
and the elevator is now at rest. Would she be wrong to
assume that she is now stationary, and that before she was
in motion? Could she possibly figure out that the opposite
was in fact the case? She would not be wrong, but this does
make 'a powerful argument for generalized postulate of
relativity.' (Einstein quoted in Nersessian, 178) That is,
postulate one:”The laws by which the states of physical
systems undergo change are not affected, whether these
changes of state be referred to the one or the other of
two systems of coordinates in uniform translatory
motion”
Einstein goes about proving the principle of equivalence in
this thought experiment. The principle of equivalence states
that the laws of physics are the same in an accelerated
frame as they are within gravitational field. This allowed
Einstein to address motion rather than force when
discussing gravity. Later Einstein generalized this special
relativity into general relativity. Norton (p137) reconstructs
the thought experiment and reconstructs it in the form of an
argument. Norton maintains that Einstein takes an “inductive
step: (a) the case is typical and will hold for all observable
phenomena and (b) the presence of the chest [in our
example an elevator] and observer are inessential to the
equivalence.” Einstein was correct in generalizing from the
particulars in his thought experiment and a new paradigm
was created, that of general relativity.
V. Destructive Thought Experiment
A destructive type of thought experiment enables a theorist
to create a problem, without knowing a definite answer to it.
This offers an opportunity for other individuals to look at the
same problem, and attempt to solve it. Each individual can
offer insights and background knowledge that will vary
greatly. Once a paradigm has been rejected, theorists must
question the foundations and assumptions that that
paradigm was built upon. This willingness to question the
current practices of normal science creates an environment
that encourages creativity and new ideas. Rather than the
stifling and constricting world that is normal science,
revolutionary science looks for new ideas and theories to
explain the anomaly and resolve the contradictions raised.
The forming of thought experiment into statements of logic
eliminates the epistemological value that teaches the
audience about the reconceptualization of ideas and
concepts.
A destructive thought experiment was used to question the
Copenhagen interpretation of quantum physics.
Schrodinger's cat-in-a-box thought experiment showed the
Copenhagen interpretation “to have a very bizarre and highly
counter-intuitive consequence.”(Brown 5) This created a
problem that has not been answered. A few theories have
been created that question the assumptions made by the
Copenhagen interpretation, although none have been
proven.
The ability of thought experiment to pose a question without
a clear answer encourages others to address the problems
(raised by the thought experiment) and to create (discovery)
new theories and concepts within a new paradigm.
Nersessian elaborates on this point, “often the insights [from]
thought experiments... are in the form of problems such as
the representations lead to contradictory or physically
impossible situations. This warrants thinking that something
is wrong with a certain way of representing the world and
investigating the problem indicated by the outcome.”
(Nersessian 179) Nersessian illustrates how an accepted
theory's assumptions can be questioned when pushed to the
limit of human representations, through thought experiment.
This is when representations within normal science begin to
reach the limit and discovery of novel theories within
revolutionary science must come into play. Creation of novel
theories is often the only way to solve anomalies that arise
as a result of destructive thought experiments.
Kuhn puts the idea of discovery within revolutionary science
in the form of paradigms. “Discovery, commences with the
awareness of anomaly, i.e., with the recognition that nature
has somehow violated the paradigm-induced expectations
that govern normal science. It then continues with a more or
less extended exploration of the area of anomaly.” (Kuhn,
p.52-53) Kuhn views the history of science through
paradigms. These paradigms influence the experimenter to
expect nature to yield evidence that will support the
accepted theory. Thought experiment is often involved
through the transition of one paradigm, and the beginning of
another. Anomalies are important components that
destructive thought experiments use to expose false
assumptions and limits within a scientific paradigm.
VI. Conclusion
There are many ways of investigating the anomalies and
contradictions that arise from thought experiments. Often the
only way to solve the puzzles created by thought experiment
is to question the very foundations upon which an entire
science was built upon. This questioning of normal science
practices and assumption can, along with glaring anomalies,
create a crisis within a science. The crisis can, and often
does, lead many scientists to abandon an entire paradigm of
science and choose a different paradigm. Paradigm choice
is often influenced by thought experiment. A destructive
thought experiment can expose the limits of a
representational system's ability to explain novel
phenomena. Another constructive thought experiment can
introduce a new: theory, conceptual framework, and redefine terms to better explain the evidence. Platonic thought
experiments both destroy an old theory and create a new
one. Thought experiments manifest themselves as paradigm
change within revolutionary science.
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