Transcript Philosophy of Science - Orange

Philosophy of Science
Class 8
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Classic Tradition
• The 1950’s and 1960’s marked the high
point of what is commonly referred to as the
‘classical tradition’ in science.
• What is this ‘classical tradition’?
• It is a certain basic view of the world and of
science which has been shared, to some
extent by all of the philosophers of science
we have considered so far.
Assumptions of the Classical
Tradition
• There is an outside world, which exists
independent from all observers.
• The ultimate goal of science is an accurate (as
possible) description of this observer independent
world.
• Scientists can observe the objective natural world,
in some way, and learn about it.
• the universe has underlying regularities that, if
discovered can explain the behaviour of the
universe.
General Agreement that…
• There is independent observation (if you
had twenty scientists observing something,
they would see it about the same).
• Observation is not dependent on the
particular observer, and deductive logic is
not dependent on the observer.
• Reality is also independent of any particular
observer.
Their important conclusion:
Science is Objective!
This is good because…
It means we can use science to find
out the truth about reality!
A Requirement of Science?
• The question is:
• if you lose any of these assumptions, is it still
possible to even do science?
• In other words, can you be a scientist if you don’t
believe in
– An objective reality
– A reality with causal universal laws
– An objective observer (or collectively, a group of
objective observers) who are able to draw objective
conclusions from objective observations of reality.
Two branches of Twentieth
Century Philosophy of Science
• Branch One: Logical Positivists, Popper
• Branch Two: Duhem-Quine Thesis, Kuhn
Branch Two- stayed focused on the issue of
whether or not theoretical entities actually
exist.
(Both interested in truth of hypotheses)
To say that a statement is true is
to say that it accurately
describes reality.
Reality of Unobservable Entities
• Suppose your theory has predictive
power…
• How could it have predictive power, if the
entities didn’t actually exist?
• The predictive power of theories provides
independent objective proof of the reality of
unobservable entities
16th-20th century: Adequate
Justification
• Scientific methods, scientific theories
seemed to be working!
• Science was progressing
• Just before the start of the 20th century- it
looked like science was on the verge of
figuring everything out!
• And then…
Some problematic theories
• General Theory of relativity
• Quantum Electrodynamics
• Heisenberg’s Uncertainty Principle
Quantum Electrodynamics
• The wave theory of light, the corpuscle theory of
light
 Science came up with very convincing evidence
that stated that light travelled in waves.
 It also became apparent, that evidence for the
corpuscle theory of light could not be explained by
the wave theory.
• Eventually Einstein declared that , somehow, light
behaved as both a wave and a particle.
Conventionalism
(Henri Poincaré (1854-1912), Pierre Duhem (1861-1916))
• The problem:
 theoretical statements must be either supported or refuted
with indirect tests.
 indirect tests involve (theoretical) auxiliary assumptions.
 In the face of contradictory evidence, the truth of a theoretical
statement can always be saved by stating that some auxiliary
assumption is false (a la Copernicus).
 The only way to test the truth or falsity of auxiliary
assumptions is through further indirect tests.
 But the indirect testing of the auxiliary hypotheses will
involve more auxiliary hypotheses, which will need to be
tested...
• This results in an infinite regress!
Conventionalism
(Soft Antirealism)
• The Solution:
 There is a great difference between statements made
based on direct observation and statements whose truth
is proved indirectly.
 The truth of observational statements can be determined
through observation.
 However, if you try hard enough it is always possible to
make any theoretical statement seem true
• Therefore, theoretical statements can never be said
to be either true or false.
What kind of a solution is that!
But wait, there’s more…
• Science should still use theories!
• Any number of theories can be found to help us
manage our observation statements.
• Theories must be consistent with our observations,
and help us to make predictions.
• We need not be concerned with their relation to
reality.
• Note: Conventionalism is not denying that there is
a truth of the matter about reality.
Conventionalism Tagline:
Theoretical statements can never be
declared as true or false. Theoretical
statements are merely useful in helping us
to organize (cope with) our observations.
Conventionalism sounds great
But it has put us on the path to
trouble!
Duhem-Quine Thesis
(Strong Anti-Realism)
• William Van Orman Quine (1908-2000)
• However, he took it one step further.
 Poincaré and Duhem had tried to protect observation
statements from the Auxiliary Hypothesis infinite regress.
 They said that observation statements could be declared true or
false simply by observing them (direct testing) and so they
were safe from the infinite regress that befell statements that
relied on indirect testing.
• Quine disagreed. He did not see a difference
between theoretical and observational statements.
Trusting Observations
• Consider the simple observation: “my car is
blue”.
• How would you verify the truth or falsity of
this statement?
Theory of the World
• In order to verify that the car is really blue,
you must already have certain beliefs like:
– “The true colour of this car is apparent to me
when the sun is shining, because then the light
rays correctly reflect and provide me with
information about the colour of the car”.
• These beliefs are part of a theory about
the world. (Your own personal theory)
• Theory? Oh no! Infinite regress!
Important Detail!
• Quine is not saying that the problem is that our
senses are fallible.
• Quine is saying:
– All of our direct observations are necessarily connected
to theory (through our network of beliefs)
– All theory is vulnerable to the auxiliary hypothesis
problem (as shown by Duhem and Poincaré)
– Therefore- Even our direct observations are vulnerable
to the auxiliary hypothesis problem.
Strong Antirealism Tagline:
There is no distinction between
observation and theory. All
statements are vulnerable to
revision. (All statements are neither
true nor false.)
Realism Tagline:
Scientific theories describe, to some
approximation, the way nature
really is. Unobservable entities
really do exist.
Starting to Challenge Objectivity
• The antirealism philosophers: Picking at
objectivity…
• Classic tradition: scientists can become
passive receptacles for what the world
wishes to reveal. (methods of
Bacon,Galileo)
• The antirealists: It isn't that simple. We can't
be passive observers of reality.
Subjectivity
• Reality would be said to be subjective if the nature of
its existence depended on whether or not it was being
observed and how it was being observed.
• A person is said to be subjective when their
observations or perceptions of reality are influenced by
their own beliefs, desires or experiences.
• For example, whether or not chocolate ice cream tastes
good is a subjective matter.
• Not necessarily bad…
Bad for the Classical Scientists
• According to the classical tradition:
• Personal Subjectivity is bad for science!
(Why?)
• Scientists must be trained to be objective!
• This is possible. (Bacon, Galileo)
• Antirealists are starting to challenge the
idea that this is possible…
• But what is the alternative? No science?
Thomas Kuhn (1922-1996)
• The Structure of Scientific
Revolutions (1962):
 the assumptions of the classical
tradition (including the presence
of objectivity in science) are bad
assumptions
 science works perfectly well in
the absence of total objectivity.
Physicist, Historian, Philosopher
Paradigms
• According to Kuhn, every scientists
approaches the world from within a
particular framework of understanding.
• Kuhn calls this framework a paradigm.
• This framework shapes the way the scientist
perceives the world, and determines, in part,
how the world is perceived.
The origin of personal paradigms
• Fledgling scientists (i.e. those of you in this class
who are doing science degrees) gain their
framework by being exposed to examples of
applications of the theories.
• You learn about the meaning of existing scientific
theories through exposure to these examples.
• Newton’s theories (gravity? momentum?). The
pendulum examples.
• By seeing how Newton’s theories are applied to
this situation, I learn about the meaning of
Newton’s theories.
Exemplars
• In scientific community, at a given time, has
certain standard examples of how a theory might
be applied- i.e. the pendulum examples.
• Kuhn called these standard examples exemplars.
• By being exposed to these exemplars, students of
science come to understand the meaning of a
theory, and can then go on to use it in novel
contexts.
An Exemplar example
• The idea of exemplars can be applied to more
than just scientific theories.
• Imagine that you want to learn the meaning of the
word ‘bird’.
• Someone might teach you the meaning of this
word by taking you to the zoo and showing you
sparrows, robins, ducks, ostriches and penguins,
each time stating “That’s an example of a bird”.
• Hopefully you will then be able to apply the word
‘bird’ correctly to new types of birds.
The origin of paradigms
• When science begins to investigate a certain aspect of
nature, there are no paradigms or theories.
• Very quickly however, individuals develop their own
theories about the natural phenomenon.
• Over time, these theories become more general and
comprehensive- they become generic theories
• Initially, there are a number of competing generic
theories, but eventually one generic theory comes to be
favoured by scientists.
• This generic theory then becomes a paradigm, which
will be passed on to new scientists in the area.
The value of paradigms
• They provide direction and motivation for
scientists. (e.g. “I wonder what effect increased
gravity has on pendulum behaviour?)
• Furthermore, they allow scientists who share the
same paradigm to effectively work together and
communicate their findings in a consistent and
comprehensible manner.
Using Paradigms
• Scientists will look for ‘facts’ relative to and try to
solve puzzles relative to their paradigm.
• Scientists will seek out observations that support
their paradigms.
• Scientists will try to clarify and expand the
paradigm by developing precise laws, accurately
measuring physical constants and applying their
paradigm to new phenomena not yet specifically
covered by the paradigm.
Paradigm Example
• Atomic Paradigm:
– Everything is composed of small indivisible particles
called atoms.
– Different substances are composed of different types of
atoms, or, sometimes, different combinations of types
of atoms.
• Phlogiston Paradigm:
– Everything is composed of water, air, earth or fire, in
some combination. (Phlogiston was the name given to
the essence of fire).
– Different combinations of these four substances lead
matter to provoke different sensations in people.
Applying the two different
paradigms
• look for ‘facts’ relative to and try to solve puzzles
relative to their paradigm. Atoms vs.....
Phlogiston…
• Seek out observations that support their
paradigms. Atoms vs........ Phlogiston
• Try to clarify and expand the paradigm by
developing precise laws, accurately measuring
physical constants and applying their paradigm to
new phenomena not yet specifically covered by
the paradigm. Atoms vs..... Phlogiston
Normal Science
• A particular paradigm will provide scientists with
both problems to solve and expectations of what
solutions they will find.
• Most of the time, this is how science progresses.
(normal science).
• However, occasionally, events arise that result in
an overthrowing of the existing paradigm and its
replacement with a new paradigm.
• The new paradigm is often radically different and
not compatible with the old paradigm.
Scientific Anomalies
• What causes the overthrowing of an existing
paradigm?
• Generally speaking paradigms are quite stable. If
observations or results are not compatible with the
paradigm they tend to be ignored or their
relevance diminished in scientific circles.
• Sometimes, however, an anomaly is so
problematic that it can’t be ignored.
Scientific Crisis!
• Suppose a problem is too large for science to just
ignore.
• In this case, scientists might try modifying some
parts of their existing paradigm (e.g. changing or
adding auxiliary hypotheses).
• Every effort will be made to hold onto the
paradigm.
• Eventually, however, too many of these anomalies
may build up, precipitating a crisis in that area of
science.
Scientific Revolution
• When a crisis occurs, a new paradigm is
sought out to replace the existing paradigm.
• Kuhn called the event where one paradigm
was rejected and another found to replace it
a scientific revolution.
Incremental Progress
• Generally speaking, the old paradigm and the new
paradigm are not compatible. Facts in one do not
translate into facts in the other.
This runs contrary to the commonly held idea that,
over time, science gradually increases its
knowledge about the natural world.
• Kuhn describes different paradigms as being
incommensurable
Differences between Paradigms
• According to Kuhn, no aspect of the paradigms
are spared this incommensurability.
• Paradigms do not share:
 Facts
 Problems and solutions
 Terms (even if they happen to have the same form, they
do not share meaning)
 Statements or subject matter
Kuhn’s Strong Position
• Can Kuhn really mean what he is saying
here?
• Wouldn’t measurements and basic
observations (like “Smoke rose into the
air”) still be consistent across paradigms?
Paradigm- A world filter
• According to Kuhn, a paradigm is like a filter that
affects every aspect of the way we perceive the
world.
• To gain a better understanding of what this means,
consider the following analogy- the helmet analogy:
• All scientists wear special helmets, which
transmit to them the sights, sounds, smells, of
the real world. However, the helmet also acts
as a filter and changes this sensory
information when it is passed to the scientist.
Different Paradigms, Different
Worlds
• For scientists whose helmets have the same filter,
the world will appear the same.
• For scientists who do not share the same filter,
even simple observations will be experienced
differently.
• A paradigm is like one of these filtering helmets. It
completely determines our perspective of the
world.
• Kuhn believes we need the filter provided by
the paradigm in to have any understanding of
the world.
Kuhn the Relativist?
• Kuhn does not think that different paradigms
provide more or less accurate version of reality.
• Returning to our analogy, it is not that some
helmets have less of a filter than others.
• Given this, does Kuhn think that any one
paradigm is any better than any other paradigm?
• This is similar to the question we discussed earlier
about theories- how do you decide which theories
are better than other theories?
Kuhn Tries to avoid Relativism
• Kuhn most emphatically does not wish to be considered
a relativist.
• He develops a number of criteria on which to compare
paradigms.
• Briefly, they are (Hung p.384):
–
–
–
–
–
–
–
Problem solving ability
Quantitative Precision
Predictive power (ability to make unexpected predictions)
Consistency
Simplicity
Aesthetics
Future Promise
Evolutionary Science
• Kuhn does thinks that the paradigms of science,
over time, get closer and closer to meeting his
criteria- automatically!
• How does he think this happens?
• Kuhn was a fan of Darwin’s theory of evolution
and believed that, in some sense, it was applicable
to the generation of paradigms in science.
Evolving Paradigms
• Kuhn believed that paradigms are chosen through
an evolutionary process.
• Multiple paradigms compete with each other for
selection by the scientific community.
• The paradigm that is the fittest (based on the
criteria proposed by Kuhn for evaluating
paradigms) is selected as the current paradigm.
• New paradigms are created by scientists and are
enter in the ‘paradigm competition’.
Kuhn and Truth
What is Kuhn’s position on truth (and falsity)?
• Kuhn doesn’t think the idea of truth really makes
much sense.
• Remember that our earlier definition of a true
statement was a statement which accurately
corresponded with the way ‘the world out there’
existed.
• According to Kuhn, the statements we make and the
‘facts’ we discover are determined by which
paradigm we have.
• Consequently the idea of truth doesn’t make sense.
Differences between Kuhn and
Classicists- I
• Classic Science:
– Science depends for its success on critically
assessing proposed hypothesis.
– Science must determine, as rigorously as
possible, the truth value of proposed hypothesis
• Kuhn:
– Science is not about critical inquiry. Rather
science is about maintaining the status quo
(whatever it may be at the time)
Differences between Kuhn and
Classicists- II
• Classical Science:
– Testing is critical in science- in particular for
determining the truth and falsity of theories
• Kuhn:
– Science operating under a paradigm does involve
testing, but the testing does not address the
validity or truthfulness of the paradigm itself.
– Testing only exists to test consequences or facts
that are derived within the context of the
paradigm.
Differences between Kuhn and
Classicists- III
• Classical Science:
– Science allows for the steady accumulation of
knowledge about the natural world.
• Kuhn:
– Science is cumulative while operating under a
particular paradigm, but when this is
overthrown and replaced by a new paradigm,
science must begin collecting ‘knowledge’ from
scratch again.
Criticisms of Kuhn
• There are two main directions taken in
criticisms of Kuhn:
• The relativist direction
• The objectivist direction
The Relativist Direction
• Kuhn wished to deny that he was a relativist, but
his theory of paradigms is perilously close to
being relativistic.
• The only aspect of Kuhn’s philosophy which saves
him from this are his criteria for evaluation of
paradigms.
• However, even Kuhn acknowledges that these
criteria are vague and difficult to explain precisely.
He intends them only as guidelines, rather than as
rules for good paradigm creation
Embracing Relativism
• Consequently, philosophers often say that Kuhn
cannot avoid being a relativist, despite his
efforts.
• Some philosophers, like Paul Feyerabend (19241994), embraced relativism in science (and in
general).
• These philosophers say Kuhn’s theory of science
is relativist, but that is just fine!.
• Other philosophers who believe that science is not
relative say that this reveals the incorrectness of
Kuhn’s ideas.
The objectivity direction
• Other philosophers argue that Kuhn is wrong
when he tries to suggest that science is subjective.
• Their objections typically involve attempts to find
problem with Kuhn’s conception of paradigms and
how science functions using these paradigms.
• For instance, Israel Scheffler (1923 - present)
argues, among other things, that basic
observations, at least, are consistent among
scientists, regardless of their personal biases or the
theories held by them.
Lakatos- An attempt to
compromise
• Kuhn’s philosophical ideas were too controversial
to be adopted wholesale by the philosophical or
scientific community.
• However, they were taken seriously enough that a
serious effort was made to incorporate aspects of
Kuhn’s ideas into the traditional view of science.
• In particular, Imre Lakatos (1922-1974) tried to
develop a comprehensive philosophy of science
that integrated Popper and Kuhn.
• How could Lakatos hope to unify two such
seemingly disparate theories?
Combining Popper and Kuhn
• Recall that, for Popper, the most important aspect
of science was its effort to falsify proposed
hypotheses.
• Even though this seemed like a promising and
original idea, we discussed a number of serious
problems with Popper’s efforts to make
falsification the core of scientific practice.
• Lakatos tries to fix this by redefining the idea of
falsification, using some ideas put forward by
Kuhn (and Feyerabend).
Competing Theories
• According to Lakatos, falsification of a theory
only occurs relative to another theory.
• Lakatos says that that a theory is false if it is
compared with a competing theory and:
– The new theory has higher empirical content- which
means that it predicts some facts that aren’t predicted
by the original theory
– The new theory manages to explain all of the
observations that the old theory could explain- it
encompasses the old theory
– Some new aspect of the new theory have already been
corroborated.
A strange characterization of
‘False’
• If a new theory meets all of these criteria then the
old theory is considered to be falsified, relative to
the new theory.
• The new theory can be said to be better than the
old theory, and should be adopted by science.
• We can see that this isn’t the idea of falsified that
we tend to use. Lakatos still called this
‘falsification’ because of the parallels to role of
falsification in Popper’s theory.
An Objective Kuhn? A
Subjective Popper?
• When considering Lakatos we can see how he
tried to reach a compromise between Popper and
Kuhn by:
• Changing some of Popper’s ideas to make them
more subjective (like his idea of falsification)
• Changing some of Kuhn’s ideas to make them
more objective (like his idea of paradigm shifts)
Present Day Philosophy of
Science
• We have arrived at present day philosophy of
science!
• Philosophers of Science continue to scrutinize
science…
• With new scientific activities they ask- is this really
science? Is it following the accepted methods of
science?
• With science in general they debate issues like- how
objective/subjective is science? Is
objectivity/subjectivity good or bad in science? What
role should science play in our society?
Next Week- Final Test
• Included some review questions in last
week’s slides
• This week talked about
– Classical Science (and philosophy of science)
– The realism/anti-realism debate
– Kuhn’s theory of science
Some questions to get you
thinking about…
• The Classical Tradition
– What was the classical tradition? What
characterized the classical tradition? When did
it start and stop? What assumptions did
classical science make? What caused the
classical tradition to be cast aside by some
scientists and philosophers? How does
philosopher x’s theory compare with the
assumptions of the classical tradition (e.g.
Comte, Popper, Duhem, Quine, Kuhn, etc. etc.)
Some questions to get you
thinking about…
• The realism anti-realism debate
– What was the realism/anti-realism debate? Which
philosophers are anti-realists? Why are they called antirealists? How many types of anti-realism did we
discuss? What is the difference between soft and hard
anti-realism? What is the difference between Duhem’s
and Comte’s thoughts/arguments regarding theoretical
entities? Did Quine agree with Duhem? If yes, in what
way? If no in what way? State Duhem’s argument. State
Quine’s argument. Are you convinced by Duhem’s
argument? If yes, are you convinced by Quine’s
argument? If no, how can you save Duhem’s argument
from Quine?
Some questions to get you
thinking about…
• Subjectivity/Kuhn
– Define subjectivity. Define Objectivity. What is the
difference between saying that the world is subjective
and saying that a person is subjective? Why did
scientists in the classical tradition think that subjectivity
was so problematic for science? What did Kuhn think
about subjectivity and science? If Kuhn said
subjectivity was okay and the classicists said it wasn’twhat led them to such different conclusions about
subjectivity? How does Kuhn describe the progression
of science? According to Kuhn, how does a person
become a scientist. Describe the historical progression
of science, according to Kuhn. Cont…
Some questions to get you
thinking about…
• Kuhn, cont…
– What stages does science pass through, according to
Kuhn? What is the connection between Kuhn and
evolution? What are some criticisms of Kuhn? How did
Lakatos attempt to unite the classic tradition and
Kuhn’s theory?
• General
– Can you create a timeline of all philosophers discussed
after the midterm? Can you say what their major
theory was, what motivated them to create their theory
and two problems with their theory?