PY226: Philosophy of Science The structure of scientific revolutions “The transfer of allegiance from paradigm to paradigm is a conversion experience”
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PY226: Philosophy of ScienceThe structure of scientific
revolutions
“The transfer of allegiance from paradigm to paradigm is a conversion experience”
Thomas Kuhn, The Structure of Scientific Revolutions
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Kuhn’s Challenge: review
The received view of science Science is cumulative Strict distinction between context of discovery
and context of justification Strict distinction between theoretical and
observational terms Science is objective: evaluation of observation is
value-free based on method
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Paradigms and ‘normal science’
Kuhn’s analyses looked at the actual history of science. Would Popper be interested in history? Why not?
Central concept for Kuhn: paradigm Paradigms involve two related ideas: (a)
disciplinary matrix and (b) exemplars
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Paradigms, disciplinary matrix and exemplars
Scientists working in the same paradigm share background beliefs, assumptions and values.
They agree on what areas are worthwhile investigating, what methods to use, what counts as evidence, and so on.
‘Exemplars’ are used to train scientists; they are the textbook cases in which particular theories are worked out or particular laboratory techniques are used.
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Paradigms and Normal science
What happens in a paradigm? Puzzle solving: All paradigms have cases that
cannot be easily accommodated—the orbit of Uranus before the 1850s in Newtonian mechanics for example
Scientists strive to solve those puzzles as well as to extend the paradigm as far as possible to other domains
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Normal Science vs. Falsification
Normal science is ‘conservative’ because the idea is NOT to test the paradigm. The paradigm is not (usually) up for grabs.
On Popper’s view, scientists should work to reject theories
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Normal science and crisis
In ‘normal science’, anomalies—phenomena that the theory cannot accommodate—are typically ignored while scientists go about fine-tuning the paradigm.
In time, however, they accumulate. A ‘crisis’ ensues in which confidence in the
old paradigm is shaken. Some scientists start to look for alternatives.
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Crisis and revolution
In proposing alternatives, the shared assumptions and beliefs may be given up
Kuhn calls this period ‘revolutionary science’ Eventually, a successor paradigm emerges
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A pictorial schema of Kuhn’s idea of paradigm shift from psychlops.psy.uconn.edu/eric/291/291_philosci..
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Examples of paradigm change
Kuhn calls changes in paradigms ‘paradigm shifts.’
From Ptolemaic to Heliocentric astronomy: the problem of ‘epicycles’ to explain retrograde motion of planets
Possible example: pre-Keynesian economics and Keynesian economics
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Are paradigm shifts ‘rational’?
Kuhn allows that there may well be good reasons to change paradigms but they alone do not cause the change.
Other factors that may play a role: peer pressure, pressure to get funding, etc.
“The transfer of allegiance from paradigm to paradigm is a conversion experience which cannot be forced.”
What does ‘conversion experience’ suggest?
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Living in different paradigms
Since fundamental beliefs and assumptions are up for grabs in articulating a new paradigm, successive paradigms, for Kuhn, are incommensurable. (Incommensurable: meaning no common measure.)
One example: ‘planet’ in Ptolemaic and Copernican astronomy
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Consequences of Kuhn’s account
Consequences of Kuhn’s view are:
a) Science does not proceed in a linear way
b) Science is not cumulative
c) Science need not be rational
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Observation and Theory distinction
Pre-Kuhn view of observation: neutral (in order that they can play the role of either refutation or corroboration)
Kuhn argues that observation data are informed by theoretical assumptions. What scientists ‘see’ is influenced by their beliefs.
This is called theory-ladenness of observations.
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Theory-ladenness of observation
Kuhn is following the ideas of N.R. Hanson. Hanson: “Seeing is not only the having of a visual
experience; it is also the way in which the visual experience is had … observation of X is shaped by our prior knowledge of X” (Hanson cited in p.111)
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Theory-ladenness of observation
‘Theory-ladenness’ can be interpreted as follows:
1. the language we use to describe our observations are theory-laden.
2. the concepts we hold (theories we accept) inform the content of our observations
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Theory-ladenness of observation
An example of the first interpretation is the sentence “an electronic current is flowing through the parallel circuit”
This observational sentence is based on inferences using standard beliefs about electronic currents and would not be made by individuals who do not have those concepts
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Theory-ladenness of observation
The second interpretation suggests that perception is ‘plastic’ and is a more radical interpretation
If true, it would suggest that two individuals with different beliefs will not be seeing the same thing
Example: tracks in cloud chamber as evidence for positrons not cited before the theoretical postulation in 1928
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Cloud Chamber
Credit: www.scifair.org/projects/
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Theory-ladenness of observation
Counter-argument to the second interpretation The ‘seeing’ and ‘seeing as’ distinction Some one without the relevant concepts of ‘cloud
chamber’ and ‘positron’ will not see the tracks as trails left a positron. Nonetheless, they still see the marks left on the photograph
The counter-argument is basically an argument for the first interpretation
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Theory-ladenness of observation
There are examples which suggests that what we see is immune from our beliefs. Consider: the Müller-Lyer illusion below
The radical claim that perception is plastic cannot be easily held
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Theory-Ladenness of observation
Question to think about: Even if observations are not totally free of theory, would that be enough to show that observations cannot be used as ‘objective’ evidence to decide between theories?
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