Nick Jarosz
Physics 419
Scientific Progress under Kuhn's Paradigm Shift Model
For as long as humans have built civilizations, they have found use in organizing the information
that describes the world around them. Observation and recording of natural phenomena leads to an
understanding of cycles and causal links. This knowledge allows predictions to be made. However,
throughout history, humans have encountered phenomena that do not fit their current understanding
of the way things work. It is at this point that people must evaluate their current understanding of a set
of natural phenomenon. The current understanding must then either go through a change to assimilate
the new phenomenon, or it must be discarded in favor of a new understanding. Thomas Kuhn evaluated
this process in his 1962 book, The Structure of Scientific Revolutions. In it, Kuhn assigns the name
paradigm to the understanding scientists adopt about a class of phenomena. The work scientists do to
expand the body of knowledge under each paradigm is called normal science. Kuhn contests that
scientific progress is no more than a change in paradigm, which parallels a change in perception.
Examples of this type of paradigm shift are the famous revolutions in scientific history: Newtonian
gravity, the atomic theory of matter, or Einstein's theories of relativity. I will argue the progress that
occurs through this type of paradigm shift is neither a convergence on the true nature of the universe,
nor an accumulation of understanding specific phenomenon. Instead, I argue that science progresses
using the ideas that preceded the current paradigm as tools to reshape the existing paradigm. This
reshaping may be looked at not as progress, but as a directionless change in our understanding of
natural phenomena.
To support the above claim, it is first necessary to examine the control a paradigm exercises
over the practice of normal science. Kuhn observes that normal science, which makes up the bulk of
scientific research, operates under the assumption that the existing paradigm is correct, "Normal
science does and must continually strive to bring theory and fact into closer agreement...its object is to
solve a puzzle for whose very existence the validity of the paradigm must be assumed"1. Here we see
that Kuhn goes further than simply claiming that normal science assumes the truth of the operational
paradigm; the nature of the research requires it. This can be demonstrated when examining any set of
assumptions imposed by a paradigm. An easily adapted example is Newtonian mechanics, which
assumes space and time are absolute objective features of the universe that all observers agree upon. If
the validity of this axiom was not assumed, it would be impossible to make predictions with Newtonian
mechanics. Quantities such as force, work, and velocity lose a significant amount of meaning if we do
not either assume the rigidity of space and time or define them with an alternate system. When
examining the experiments that led to major paradigm shifts, it becomes apparent that the validity of
the experiment rests on the integrity of the paradigm. If the paradigm is not assumed to be correct, then
the question that the experiment wishes to test cannot be said to be relevant question. A good historical
example of this problem is the attempt to unify Newtonian mechanics, which has no preferred reference
frame, with Maxwell's equations, which seem to require a reference frame. These clearly conflicting
assumptions must be tested if the theories are to be unified. If a scientist were to attribute validity to
one set of assumptions and not the other while designing an experiment that intended to shed light on
the conflict, the results would favor the assumed principles.
The dependence normal science has on paradigms is clearly visible in both historical and current
research. Kuhn chooses to examine John Dalton's discovery of oxygen and the emergence of the atomic
theory of matter that followed it. Dalton was primarily a meteorologist, though his research stretched
1
Kuhn pg. 80
into the fields of chemistry and physics because he studied the atmosphere extensively. Kuhn explains
that among Dalton's contemporary chemists, it was strongly believed that mixtures such as salt in water,
or air were as much chemical combinations as oxidized metals. This lack of differentiation between
mixtures and chemical combinations made the search for the atomic and chemical constituents of air
almost impossible because it was assumed that air was a chemical compound on its own, "Even if
chemists had looked for such tests, they would have sought criteria that made the solution a compound.
The mixture-compound distinction was part of their paradigm-part of the way they viewed their whole
field"2. The understanding of the atomic theory was developed partially because of the discovery that
mixtures and compounds were different, and yet, the paradigm that guided normal science research in
Dalton's time operated under the assumption that mixtures and compounds were the same thing. It
would make no sense to even question if mixtures and compounds were different because the current
scientific theory needed to assume their identity. This raises the question, how did Dalton succeed in
isolating oxygen or come to the conclusion that air was a mixture made up of chemical constituents?
Kuhn claims that Dalton's success was due, in part, to his position as meteorologist who experimented in
chemistry, "Partly because his training was in a different specialty and partly because of his own work in
that specialty, he approached these problems with a paradigm different from that of contemporary
chemists"3. Dalton's background in meteorology ensured that he viewed certain phenomenon
differently than his contemporaries in chemistry. When Dalton looked at a mixture of gasses, or salt
dissolving in water, he saw a physical process, not a chemical one. It was this mindset that allowed
Dalton to find fault with the apparent homogeneity of air. By examining this historical anecdote, it
becomes clear that normal science is very heavily dependent on the existing paradigm. We have seen
that in Dalton's case, a mental construct from outside the established field was required to create a
major advancement in chemistry. While it is true that much incremental progress is achieved with
2
3
Kuhn pg. 131
Kuhn pg. 133
normal science, a paradigm shift is needed to create revolutions in scientific theory. This raises the
question, how can revolutions occur if normal science operates assuming the current paradigm's
validity?
To address the previous issue we will examine Kuhn's theory about how new paradigms emerge.
Before the emergence of a new paradigm, scientists are typically performing research under the current
paradigm. It is impossible to be looking for a new paradigm under normal science research, as a new
paradigm is only needed when the current paradigm fails to explain the results of current normal
science research. Further, it seems improbable that the inconsistencies in the results of normal science
research should become apparent frequently. Kuhn addresses this point, and speaks about how a
scientist approaches normal science experimentation, "He knows what he wants to achieve, and he
designs his instruments and directs his thoughts accordingly"4. When framed in this light, it seems that
normal science must be tautologically correct, and in a sense this is true. As Kuhn explains earlier,
normal science, by his definition, operates under the assumption that the operational paradigm is
correct. Thus, any scientist wishing to expand knowledge under the umbrella of the current paradigm
must adhere to these assumptions. Consequently, experiments are designed to abide by these
assumptions, and not to test them. If and when scientists wish to test the validity of their paradigm, they
do so in a manner that is congruent with the paradigm. This type of testing was illustrated with the
example of Dalton's discovery of oxygen. Chemists wishing to confirm their understanding of air's
constituents in Dalton's time would have designed experiments with the assumption that air was a
compound. Further, if the chemists had accidentally isolated oxygen, nitrogen, or any other gas, they
would first attempt to attribute its new properties to that of chemical air in a way that agreed with their
understanding of it. This attribution would be done in the interest of preserving the paradigm that
framed the experiment. However, it is important to note that valid scientific paradigms must provide
4
Kuhn pg. 96
testable predictions outside the current body of knowledge. When these predictions are being tested,
anomalous data or phenomena can appear. These persistent anomalies are the seeds of a crisis that
demands revolution.
In looking at Dalton's discovery of oxygen, we have seen that paradigm shifts occur only when
normal science uncovers behaviors that demand it. Kuhn claimed that the normal science researcher
designs experiments with an anticipated result. The failure of the paradigm occurs only when scientists
encounter anomalies, seemingly at random, "Unanticipated novelty, a new discovery, can emerge only
to the extent that his anticipations about nature and his instruments prove wrong"4. When such an
anomaly occurs, the normal scientific community must evaluate its validity, and determine if it demands
a change in paradigm, "Often the importance of the resulting discovery will itself be proportional to the
extent and stubbornness of the anomaly that foreshadowed it"5. It is the cumulative nature of normal
science that unearths a crisis or conflict between paradigm based expectation and observation, and
creates the need for a new paradigm.
Despite the fact that new paradigms replace previous ones, Kuhn explains that it cannot be said
that displaced paradigms were unscientific in nature. Kuhn examines Newton's theory of gravity, which
functioned very well as a mathematical description of observed phenomena at the time, fails to provide
a qualitative explanation for how gravity functions, "The attempt to explain gravity, though fruitfully
abandoned by most eighteenth century scientists, was not directed to an intrinsically illegitimate
problem; the objections to innate forces were neither inherently unscientific nor metaphysical"6. The
Newtonian gravity paradigm was in no way unscientific, and it was and remains an accurate theory in its
domain. Newton's theory of gravity is scientific despite its failure to explain the mechanism by which
gravity works. This explanation was not fully addressed until Einstein's theory of general relativity
5
6
Kuhn pg. 97
Kuhn pg. 108
replaced the Newtonian gravity paradigm. If we adopt the opinion that the paradigms that fail to explain
every aspect of a phenomenon are unscientific in nature, we make the claim that all previous theories
have been unscientific. This claim would lead to the apparent paradox of current theories being
considered scientific, while all previous theories that helped lead to the current ones were unscientific.
If, on the other hand, we accept the scientific nature of all previous theories, we must describe how to
confirm the validity of proposed paradigms.
While examining the nature of scientific knowledge, we have arrived at an apparent paradox.
How can new paradigms be verified if all previous theories are considered equally scientific? One could
perhaps claim that a theory can be considered legitimate if it describes data with more precision than a
previous model. However, this stance carries with it the experimental error in obtaining the data.
Further, it is possible to create a very precise mathematical model that describes a phenomenon that
could have nothing to do with the nature of reality. We saw Newton's theory of gravity provides an
excellent mathematical framework for gravity, though it does not describe the mechanism by which it
works. Kuhn contests that paradigms are no more than man-made ideas, "Are theories simply man-mad
interpretations of given data? The epistemological viewpoint that has most often guided Western
philosophy for three centuries dictates an immediate and unequivocal, Yes!"7. This implies that all
paradigms can be considered scientifically valid because they are of our own construction. A paradigm
shift is nothing more than the a change in mental interpretations. The paradigm has no connection to
the physical world, it is an artifact of our own creation, created by a psychological need to sort
information in a logical order. Kuhn likens the mental paradigm shift to the gestalt switch studied in
psychology, in which a person can see both a vase or two faces in the same photo, "two men with the
same retinal impressions can see different things; the inverting lenses show that two men with different
7
Kuhn pg. 126
retinal impressions can see the same thing"8. The scientific paradigm shift identifies itself separately
from a visual or psychological gestalt switch in one way; the scientific gestalt switch is irreversible. The
irreversibility of the scientific paradigm is ensured by both the presence of objective sources of the
crisis, and the conflicting set of assumptions that exist between two subsequent paradigms. The crises
that create scientific revolutions are objective phenomena or data. While the paradigm represents a
mental representation, the anomalous data that finds problem with the current paradigm is very real
and objective. In the revolution started by Dalton's work, the objective source was the isolation of a gas
from normal air that had very different qualities than air itself. The existence of oxygen is an objective
phenomenon; it cannot be ignored or explained by a paradigm that says air is a chemical compound.
Secondly, a new paradigm must have assumptions that differ in some way from the previous paradigm.
Newton's assumptions about the rigid nature of space and time are in conflict with relativity's claim that
space and time are subject to change based on relative velocity. Both sets of assumptions cannot be
kept while they are in conflict, and the presence of the objective phenomenon ensures that only the
newly emerged paradigm can remain.
Kuhn adds an additional comment on the nature of paradigm shifts. The ability for paradigms to
exist while they ignore certain questions, as Newton's gravity did, means that normal science lacks a
language of true objectivity. The assumptions that normal science requires result in "a language that like those employed in the sciences - embodies a host of expectations about nature and fails to function
the moment these expectations are violated"8. This lack of objectivity in the language of normal science
is congruent with the paradigm creation process we have examined. Just as in the case of Dalton's
discovery of oxygen, paradigms fail when anomalous phenomenon repeatedly appear in the process of
testing the current paradigm's predictions. Thus, we have resolved the apparent paradox between the
legitimacy of current scientific paradigms and the scientific nature of displaced paradigms. This solution
8
Kuhn pg. 127
demands that paradigm shifts are nothing more than mental constructs though this idea successfully
matches the nature of scientific revolutions as we have observed them.
Now that we have successfully identified the method by which scientific revolutions occur, we
can move on to an analysis of that progress. The identification of paradigm shifts as a strictly mental
phenomenon led to a logically consistent explanation of scientific progress. Kuhn argued that this
paradigm shift model shows the progress of science lacks linearity, in contrast to the way science is
traditionally taught. I will argue that this lack of linearity, coupled with the mental nature of paradigms,
indicates that science is not a converging accumulation of facts but a directionless change in perception.
Traditionally, science history is presented in a manner that conveys a simplicity and a linearity that
simple doesn't reflect the true nature of progress. Linearity implies that every paradigm replaces the
one that preceded it because it provides a more accurate description of existing phenomenon, and
accommodates new phenomenon as well. This description ignores the fact that the search for a new
paradigm is not the goal of normal science, and paradigm shifts cannot be predicted by normal science.
Kuhn describes this progress by looking at Dalton's discovery of oxygen once more. In describing the
practice of reflecting on paradigm changes, Kuhn says, "The result is a persistent tendency to make the
history of science look linear or cumulative, a tendency that even affects scientists looking back at their
own research"9. He goes on to attach this idea to John Dalton, who described the atmosphere in which
his discoveries took place in a way that seems to contradict himself. In Dalton's later accounts, he
records his progress as if he were interested in studying the chemical constituents of air at the beginning
of his experimentation. However, when his early records are examined, from before his determination
he isolated a gas that has properties unique from normal air, Dalton does not appear to have any
insights about what he has refined, nor does he feel he has accomplished his goal. It was only after
Dalton successfully isolated oxygen that he realized that his work required a change in paradigm. Kuhn
9
Kuhn pg. 139
describes this process as, "What all of Dalton's accounts omit are the revolutionary effects of applying to
chemistry a set of questions and concepts previously restricted to physics and meteorology. That is what
Dalton did, and the result was a reorientation toward the field"9. Dalton was unaware that he was
searching for oxygen, and when he succeeded in isolating it, he didn't identify the implications until after
the field had changed to accept previously incompatible questions. The normal science research that
was occurring in Dalton's time was not searching for evidence of an atomic theory of matter, it simply
happened by accident. It was only after the discovery had occurred that Dalton and the scientific
community accepted it as being the next step forward in understanding chemistry. The linearity of
science is an artifact we create when looking back at previous discoveries. Meanwhile, we ignore the
fact that current normal science research does not know where the next revolution will come from, just
as normal science researchers did not know in the past. This post revolutionary imposition of linearity
gives insight into one last characteristic of revolutions; their invisibility.
To see the invisibility of scientific revolutions, one can examine any revolution, but we will
restrict our examination to Dalton's discovery of oxygen as it has been our main example. The process
by which normal science is carried out insures that when a crisis occurs, the revolution remains invisible
until after it has been accepted by the community. When scientists are educated, they are not taught to
identify revolutions, they are taught how to carry out normal science because normal science is what
scientists do. Scientists are educated to accept the current paradigm as a necessarily assumed truth and
explore its predictions. They are also shown that the set of historical theories progressed in a linear
fashion in which more accurate theories replace less accurate ones. Kuhn describes this form of
presentation as "the textbook tendency to make the development of science linear hides a process that
lies at the heart of the most significant episodes of scientific development"10. Further, Kuhn comments
on this tendency as creating misconceptions, "those misconstructions render revolutions invisible"10.
10
Kuhn pg. 140
The imposition of the linear historical structure coupled with the nature of normal science ensures that
revolutions remain invisible. This can be approached in a different way when one considers the
questions that must be asked to bring on revolution. Questions that find problems with the current
paradigm do not assume the paradigm is correct. If a scientist carrying out normal science research
encounters a phenomenon that cannot be explained by the current paradigm, they must still approach
the problem assuming the paradigm is correct. If scientists failed to do this, theories would be
abandoned too quickly to make any substantive progress within them. It is only after a great persistence
of the problem that scientists are forced to question their initial assumptions. The validity of these
questions cannot be accounted for by the current paradigm as the questions themselves demand a
solution which is in conflict with the assumptions of the paradigm. When a new paradigm is developed
and tested to ensure it can explain both the new phenomenon as well as the old paradigm, the
legitimacy of the questions born out of crisis can finally be addressed. Put simply, revolutions cannot be
identified until after a paradigm shift is complete. This accounts both for the invisibility of revolutions as
well as the irreversibility of paradigm shifts. This post revolutionary validation process is consistent with
neither a linear progression of facts nor a predictable direction in the progress of science.
Science is often thought of as being a cumulative process, and, in a sense, this is true. Normal
science accumulates facts and data within a paradigm, and this process continues until data is
discovered that cannot be explained under the current paradigm. The data that causes this trouble,
however, is never the goal of normal science. Normal science only seeks to expand a body of knowledge
given a set of assumptions and explore the predictions that can be made with those assumptions.
However, certain persistent and unexplained phenomenon are found in this process. It cannot be
predicted when the conflicting data will be found or when a crisis will occur. It is for this reason that the
time and location of paradigm shifts cannot be predicted. Further, when conflicts are found with the
current paradigm, there is no guarantee that a paradigm shift will occur. In most cases, normal science
researchers will ignore this data as anomalous and be content with the incompleteness in the current
paradigm. This was the case when Newton failed to explain how gravity acted at a distance and yet his
theory was still accepted. This means paradigm shifts occur only when the intellectual climate is ready to
accept the change. When this climate occurs is not clear. This should come as no surprise as a paradigm
is a strictly mental structure. Lastly, it has been established that the apparent linearity we see in science
history is a product of our own creation and provides no guarantee the next revolution lies along any
predictable path. In Dalton's case, the realization that air was a mixture did not physically change air, it
only changed the scientific community's understanding of it. Similarly, all other revolutions in science
have merely been changes in mental perception. These changes rely on the intellectual climate they are
brought into to survive. The result is an unpredictable and directionless process of change. Nature
remains as it always has, it is only the way we understand it that changes. For this reason, it should be
no surprise that revolutions seem to occur at random. Revolutions are strictly mental processes, that
occur only when we are ready to accept a new understanding of existing evidence.
Bibliographic Information:
Kuhn, Thomas S. The Structure Of Scientific Revolutions. Chicago, IL : University Of Chicago Press, 1996.
Print.