Philosophy%20226f:%20Philosophy%20of%20Science - PowerPoint PPT Presentation

Title: Philosophy%20226f:%20Philosophy%20of%20Science


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Philosophy 226f Philosophy of Science Prof.
Robert DiSalle (rdisalle_at_uwo.ca) Talbot College
408, 519-661-2111 x85763 Course Website
http//instruct.uwo.ca/philosophy/226f/
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Philosophy of Science in the 20th Century What
was the Received View? Science is empirical
the ultimate criterion for judging a scientific
theory is its agreement with the empirical
facts. Science is rational scientists judgments
in general are influenced by empirical facts and
logical inferences from them-- not by
extraneous social, psychological, or political
motives Science is cumulative The achievements
of scientists are permanent possessions of
science in general-- facts that can be built upon
by future scientists
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Scientific Philosophy, a.k.a. Logical
Empiricism In general, statements can either be
true or false. If true, this means If it is a
logical or mathematical truth, it can be
logically derived from first principles. If it is
a statement about what there is in the real
world, or any matter of empirical fact, it can be
verified by some observations. If false, this
means either that it is logically contradictory,
or that it is contradicted by the facts.
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Verification and Meaning A statement that cannot
be verified by any empirical observation or
logical reasoning, even in principle, is neither
true nor false. It is completely
meaningless. Example Nothing nothings is
neither true nor false. It simply has no
cognitive content. Whatever content it might have
is emotional rather than cognitive. (It is not a
direct statement about any state of affairs. It
is an indirect statement about the emotional
state of the speaker.)
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Deductive logic (drastically oversimplified) All
A are B. X is an A. Therefore X is
B. Inductive logic All copper we have tested
conducts electricity. X is a piece of copper yet
to be tested. Therefore X will conduct
electricity.
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The logic of induction (cf. David Hume) All A
observed so far are B.   i.e. All A are B X is
an A not yet observed.     i.e. X is not an A
Therefore X is B.       X is B. What does
it take to confirm a universal generalization?
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Falsificationism (Karl Popper) Scientific
theories are never truly verified. Moreover, to
be always verified is not a virtue in a
scientific theory. Verification and
falsification are asymmetrical No accumulation
of confirming instances is sufficient to verify a
universal generalization. But only one
disconfirming instance suffices to refute a
universal generalization. Scientific theories are
distinguished by the fact that they are capable
of being refuted. They are falsifiable.
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Example Confirming Freudian psychoanalysis How
do we know that repressed memories of infantile
sexual desires are the causes of neurosis?
These desires are revealed in our dreams,
Freudian slips, free associations, and other
symptoms. They are the latent content
expressed symbolically. How do we determine the
true meaning of these symbols? We interpret
them-- which requires us to apply Freuds theory.
What if the patient denies the interpretation?
The patient is resisting, which indicates that
the interpretation is correct and therefore
disturbing to the patients conscious mind..
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Pseudo-science A theory with the empirical
trappings of real science, including a system
of theoretical concepts and a wealth of
corroborating evidence. But a pseudo-science has
built-in defense mechanisms against possible
refutation. The Freudian theory provides an
interpretation for every conceiveable symptom of
the patient. Its predictions therefore can
never be refuted.
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Einsteins General Relativity If it had failed
its famous test of 1919, no one would have taken
it seriously. But it passed the test, and
Newtons theory of gravitation was refuted.
Albert Einstein (1879-1955) On the
electrodynamics of moving bodies (1905) The
foundation of the general theory of relativity
(1916)
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Empirical test of general relativity vs.
Newtonian gravitation
Light from a star passing near the Sun should be
deflected. The evidence is the displacement of
the stars apparent position.
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How the observation worked
Path of the eclipse
Actual observation
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Gravitational lensing as we now know it
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Einstein and Eddington, looking pretty pleased
with themselves
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The Methodology of Scientific Research
Programmes (Imre Lakatos. 1922-1974)
How do scientists decide whether, or when, their
theory is refuted? How do we explain why
scientists persist in working on theories in the
face of counter-examples?
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Lakatos Scientific theories are not really
falsifiable. They are research programmes that
consist of a hard core of fundamental
principles that contain what the theory really
says about the world, and a protective belt of
auxiliary hypotheses that explain how the
fundamental principles apply to particular cases,
and how to deal with apparent discrepancies.
These include ceteris paribus (other things
being equal) clauses that accommodate problematic
cases. Contrary to Popper, even good theories
have defense-mechanisms.
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Newtonian Gravitation Theory Predicts that every
acceleration of every body can be traced to an
interaction with some other body, according to
their masses and the distance between them.
What to do when we observe an acceleration that
has no visible source? Is the theory refuted? No
The theory demands that the missing mass be found.
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1687-1727 Newton breaks his head against the
problem of the motion of the moon, which he
cannot predict precisely from his law of
gravitation 1748 Clairaut solves the problem of
the motion of the moon using Newtons theory and
better mathematical techniques. 1821 A slight
discrepancy is noted between the actual motion of
Uranus and the motion predicted by Newtons law
of gravitation. Astronomers puzzle over it for a
while. 1843 John Crouch Adams deduces, from
Newtons law and Uranus orbit, the approximate
location of a new planet. 1846 The new planet is
discovered by Adams and Leverrier.
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The theory of gravity, which, by so many
applications, has become a means of discovery, as
certain as by observation itself, has made known
to the mathematician several new
inequalities...enabled him to predict the return
of the comet of 1759....He has been enabled by
this means to deduce from observation, as from a
rich mine, a great number of important and
delicate elements, which, without the aid of
analysis, would have been forever hidden from
view.... Laplace, Mécanique céleste
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Mercurys perihelion is found to precess at a
rate that does not agree with Newtons theory.
The difference is 43 per century. 1855-1916
various hypotheses are advanced to explain this
discrepancy between theory and observation. For
example --is there another planet (Vulcan)
near to Mercurys orbit? --does the force of
gravity vary, not as r2, but as r2.000000097
? --is there a cloud of matter near the sun that
affects Mercurys orbit? 1916 Einstein shows
that general relativity predicts precisely the
missing 43.
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Lakatos The fundamental difference is between
progressive and degenerating research
programmes. Progressive research programmes lead
to novel predictions, new problems, and new
solutions. Degenerating programmes spend their
time trying to adjust after the fact to new
information, and to protect themselves from
refutation by constant adjustment. The
pseudo-sciences are really degenerating
programmes whose practitioners are mainly devoted
to defending the programme against contrary
evidence. The progressive programmes view
contrary evidence as a challenge that will
broaden and deepen the theory.
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Thomas Kuhn on Scientific Revolutions (cf. The
Structure of Scientific Revolutions,
1962.) Paradigm Kuhns idea that a scientific
theory is not just a set of theoretical
principles. It is an entire world-view,
consisting of --Metaphysical views about the
nature of the world and the things in
it --methodological rules about correct
scientific practice --a conception of what
constitutes a legitimate scientific question and
what doesnt --a conception of what constitutes a
scientific fact --paradigm exemplars of the
right kind of problem to solve and the right way
to solve it.
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A paradigm, therefore, determines not only a set
of beliefs about the world. It also defines
what counts as good science, and even determines
what counts as a scientific fact. It is a
conceptual framework that determines how the
world looks to those who have accepted it. It
defines not only the scientific outlook for
practitioners of a particular science, but also
the scientific form of life.
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There are two aspects to the history of any
science Normal science science pursued within
the constraints of a particular paradigm, without
questioning its principles. The characteristic
activity is puzzle solving, i.e. answering
questions set by the paradigm using the methods
sanctioned by it. Revolutionary science a time
of decreasing confidence in the existing paradigm
(because of the accumulation of unsolved
puzzles), and conflict with alternative
paradigms. This is like a political crisis, with
uncertainty, and conflict among many views, until
a new order becomes established and a single
paradigm takes a position of authority.
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Some philosophical claims arising from Kuhns
view The conflict among paradigms cant be
settled on any rational methodological grounds,
because each paradigm contains its own view of
rational scientific methodology. The conflict
cant be resolved by an appeal to the facts,
since each paradigm contains a view of what
counts as a fact, and will determine how its
adherents view the facts. Different paradigms
are in fact incommensurable, not comparable by
any neutral standard. Adherents of different
paradigms live in different worlds, and speak
different languages that are not
inter-translatable. A change of paradigm involves
changes in the meanings of basic theoretical
terms.
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The replacement of one paradigm by another cant
be viewed as progressive on any objective
grounds. Since adherents of different paradigms
define the questions differently, and accept
different standards for a good answer, the
conflict between them has no neutral
resolution. A scientific revolution has to be
regarded as a social and psychological phenomenon
rather than as a purely intellectual one. For an
individual scientist, the change in point of view
is more like a religious conversion than a
rational process of comparing theories against
the facts.
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Some historical claims arising from Kuhns
view Scientists with different theoretical
viewpoints generally fail to understand one
another. Competing paradigms appeal to different
and conflicting sets of facts, and proceed by
conflicting methods. The arguments made in favor
of one theory cannot be fully understood by, or
persuasive for , adherents of the other. New
paradigms introduce new theoretical terms, or
change the meanings of old ones, in ways that are
incomprehensible to anyone who doesnt already
accept the new theory.
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A new paradigm doesnt explain more than its
predecessor. Even if it can explain things that
the old theory couldnt, it will typically fail
to explain many things that the old theory could
explain. (This has been called Kuhn loss. The
history of science is not cumulative new
theories cant incorporate the successes of older
ones, because they have a completely different
view of what counts as success. The new theory
redefines the old theory in its own terms.
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Kuhns list of values for judging scientific
theories Accuracy degree of agreement with the
available empirical data Consistency freedom
from logical contradictions Simplicity lack of
unnecessary complication unity Scope Range of
phenomena that fall within the theorys
grasp Fruitfulness Power to generate new
principles, problems, solutions, predictions,
etc. Question Does agreement on these values
imply agreement on their application, their
relative importance, etc?
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