Transcript Science and Scientific Discovery

Science and
Scientific Discovery
Time Series Test
William at 6 months, before first Christmas
Conclusion: Getting Christmas presents
makes children hate Santa. Possible
maturation threats, and hatred of dad for
letting mom dress him that day. Note that
no instrumentation threat indicates Santa is
real.
William at 18 months, after first
Christmas
What Counts as Scientific
Knowledge?
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We “know” many things:
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The sun rises in the morning
Its best to treat others as you want to be treated
Water boils at 100c
The working class is exploited
Wars are caused by bargaining failures
Which of these statements count as scientific?
Philosophy of Science is a theory of knowledge
(ontology) and a theory about the progress of
knowledge (epistemology).
Science and Its Rivals
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Primary divide between non-science and
science:
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Science explains outcomes in terms of natural
laws, non-science permits supernatural
causes.
Secondary divide between science and
pseudo-science.
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Science is falsifiable, pseudo-science is not.
Popper
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Science and Pseudo-science
Many systems of thought share a similar
structure: premises are taken as given and
implications are derived logically.
 This is true for theories, as well as ideologies.
 All can be useful guides for human behavior.
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The key difference between science and
pseudo-science (and non-science) is the
criterion of falsifiability.
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Theories are open to potential refutation.
Ideologies (and religions) are not.
Hypothetico-Deductive Reasoning
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Falsifiability implies that deduction is the only
valid form of scientific reasoning.
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Induction cannot be falsified. Correlation between X
and Y stands as “fact.”
Thus, much of what scientists do – that is, observe –
was classified as non-science.
Also implies that the task of science is to
disconfirm theories.
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Theories can only be supported. Valid theories are
those not yet proven false.
Scientists immediately reject theories once
disconfirming evidence is found (naïve falsification).
Critique
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Principle of falsification still important.
Tests still aim, in part, to disconfirm theories.
But Popper’s criterion and its implications did not
embody what people who identify themselves as
scientists actually do.
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Scientists typically pursue confirming experiments.
Scientists do not reject theories because they
encounter some disconfirming evidence.
Steven Weinberg (Nobel in Physics): there “is no
theory that is not contradicted by some experiment.”
Kuhn
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Structure of Scientific Revolutions (1962).
Paradigm is a set of generally (if not
universally) shared assumptions that
underlay one or more theories.
Represented in “textbook” version of the field.
 Paradigm initiates new entrants to the field
into the dominant set of ideas.
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Normal Science
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Normal Science: occurs within a paradigm.
Does not search for disconfirming evidence or
anomalies.
Ambition is to extend the paradigm to already
known and new phenomena, to explain more
phenomena in terms of the theory.
Normal science is puzzle solving according to
the rules (assumptions) laid down by the
paradigm.
Phenomena that do not fit the paradigm are
often not even “seen.”
Revolutionary Science
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In extending the paradigm, scientists encounter
unresolved puzzles or anomalies.
Accumulation of anomalies eventually brings the
paradigm into question, but does not lead to the
falsification or rejection of the paradigm.
Revolution occurs only when a new and better
theory able to resolve the anomalies arises.
Science does not proceed by naïve falsification
but by the development of better theory.
Role of Assumptions
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Assumptions are never “true.” They embody the
analogy that informs the theory. Theories are
intended to capture the “essence” of a particular
setting/event/process.
In normal science, assumptions are treated as
unproblematic. They “make sense” given the
utility of the prevailing paradigm.
In revolutions, assumptions are called into
question and some or all are overthrown.
Previous assumptions are now regarded as
naïve.
Paradigm Change
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Science is an inherently social phenomena.
“Knowledge” depends on the assent of the
community of scholars.
Choice of a new paradigm is dependent on the
subjective judgment of the relevant community
of scientists.
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Tests, anomalies, and explanations only make sense
in terms of a particular paradigm. Because they
possess incommensurable assumptions, difficult to
have “head-to-head” competitions between theories
from different paradigms.
There are few decisive tests, since the very meaning
of the test typically differs across paradigms.
Adoption of a paradigm is an “all-or-nothing” affair.
Paradigm Change continued
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Most important, the full problem-solving abilities
of new paradigm are not yet demonstrated at the
time the paradigm is adopted.
Choice of paradigm, then, is a collective
exercise based on beliefs and, in part, on
subjective judgments of relevant scholars. Led to
charge of science as “mob psychology.”
Kuhn later clarified his position, aruging that new
paradigms are accepted because they are more:
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Accurate
Consistent
Broad in scope
Simple and elegant
Fruitful of new research findings.
Kuhn’s Conception of Science
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For Kuhn, science is distinguished from pseudoscience by the existence of a paradigm.
Progress only occurs within the set of
assumptions and rules that define what is worth
studying, what is known, and what particular
observations mean; that is, progress occurs only
within paradigms.
Pre-science is found when multiple competing
approaches exist.
Ironically, during periods of revolutionary
science, scientists are not really “doing” science.
Critique
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Sociological and subjective nature of
paradigm choice has left many
philosophers unsettled.
Debate has focused on what objective
processes and criteria may guide
paradigm choice.
Popper, one of the great defenders of an
open society of debate and deliberation,
was deeply disturbed by Kuhn’s subjective
view of science and the apparent reliance
on consensus as the basis of knowledge.
Lakatos
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The Methodology of Scientific Research
Programmes (1970)
Synthesizes Popper and Kuhn by focusing on
research programs defined as a series of
theories sharing a common “hard core” of
assumptions.
Following Popper, Lakatos also emphasizes
falsification, but believes this only happens,
following Kuhn, when a better theory emerges.
Argued “science” was the progressive
falsification of theory.
Lakatos
“A scientific theory T is falsified if and only if
another theory T’ has been proposed with the
following characteristics: (1) T’ has excess
empirical content over T: that is, it predicts novel
facts, that is, facts improbable in the light of, or
even forbidden, by T; (2) T’ explains the previous
success of T, that is, all the unrefuted content of
T is included (within the limits of observational
error) in the content of T’; and (3) some of the
excess content of T’ is corroborated.”
Lakatos
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Thus, “no experiment, experimental report,
observation statement or well-corroborated lowlevel falsifying hypothesis can lead to
falsification. There is no falsification before the
emergence of a better theory.”
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Unlike Popper, Lakatos is a sophisticated
falsificationist.
Unlike Kuhn, Lakatos argues for an objective criterion
of progress: the prediction of new facts.
Lakatos’ Heuristics
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For Lakatos, a research program is defined by
its key assumptions. These form the “hard core”
of the scientific research program (SRP).
This hard core is protected by a negative
heuristic, the rule that forbids scholars working
within a SRP from contradicting the hard core.
To deal with inconsistent evidence, Lakatos
argues that SRPs develop a positive heuristic or
“protective belt” of auxiliary hypotheses.
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Such auxiliary hypotheses can include additional
assumptions or restrictions on scope that make the
theory consistent with observed facts.
Roughly equivalent to Kuhn’s problem solving.
Progressive v. Degenerative SRPs
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The key question is whether these auxiliary
hypotheses are progressive or degenerative.
If anomalies are reconciled with the hard core
and produce novel facts that are then
corroborated, the intra-paradigm problem shift is
progressive.
If the amendment is ad hoc, the SRP is
degenerative.
A degenerative SRP can, in conjunction with the
rise of a new theory, lead to falsification and the
replacement of T by T’.
Science and Progress
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For Lakatos, as for Popper, the prediction
of new facts is central to the concept of
science and scientific progress.
Contrary to Popper, however, for Lakatos it
is not falsification per se, but the ability to
uncover new facts that separates science
from pseudo-science.
So, what is “science”?
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Theory must be founded on natural laws.
Theory must be falsifiable.
Theory must produce hypotheses that are
corroborated by evidence.
Disconfirmation is “overblown.” Most
research progresses by solving puzzles
using the ideas within the hard core of a
research program.
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Rewards go to those who solve particularly
hard puzzles.
Conditions of Science continued
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Predictions of new facts that are then
corroborated by evidence is the ideal.
Scientific revolutions or paradigm shifts
are rare. Challenging or amending the
hard core is not what science is usually
about.
Changing “how we think about the
universe” occurs at several levels, from
resolving particularly difficult puzzles to
developing a new paradigm.
Political science is on the cusp
of becoming a science.
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American politics is probably already a science,
if by that we mean (following Kuhn and Lakatos)
that there is a shared paradigm or SRP (largely
rational choice). Research is conducted with
broad agreement on assumptions, what
constitutes knowledge, what are the puzzles
worth solving.
International relations and comparative politics
are still pre-scientific, but well on their way to
becoming a science by adopting the hard core of
rational choice theory as well.
Lessons for Your Research
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Since science is a social enterprise, your
work counts only by how it is received by
the scientific community. This reception is
partly subjective. You must argue your
case in the face of sometimes conflicting
and ambiguous criteria.
Even though we may agree on the
conditions that make a theory “better,” we
can still disagree and, therefore, argue
over which particular theory best fits those
conditions.
Valid Scientific Arguments
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You are solving a genuine and significant
puzzle within the field.
The evidence corroborates your theory
and hypotheses.
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This is a question of research design. The
better your research design, the stronger your
argument will be.
Your amendment to the hard core is
progressive. Resolving the puzzle
uncovers additional implications that are
also empirically corroborated.
Scientific Arguments continued
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Since multiple theories may exist in the
protective belt or positive heuristic, your
theory is more elegant, broader in the
range of phenomena its predicts/explains,
and supported better by the evidence than
its plausible rivals.
In rare cases, you have sufficiently altered
the hard core that you have created a new
research program.
Guide to Writing a Scientific Paper
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The Point (one and only one): one sentence.
The Argument: the point is your conclusion here.
The Purpose:
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Steps can be approached through the scientific method:
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An argument: demonstrate the plausibility of your assumptions
and the deductive validity of your conclusion
An empirical paper: exploration, counterexamples, correlation,
causal test
Observe
Explain/hypothesize
Construct a test
Draw inferences
Update
These steps are distinct from the process of writing your
paper
Writing the Paper
1) Introduction (1 page or 3 paragraphs):
states puzzle, summarizes two sides to
debate, makes the point.
2) Literature Review (2 pages or less):
outlines the two sides to debate, the major
issues, and why you take one side or the
other.
3) Your Argument/Explanation: state your
argument and core analogy.
Writing the Paper
4) Your constructs and construct validity.
5) Your test/correlation/exploration: state
your research design explicitly and clearly.
6) Describe your data.
7) Discuss potential econometric concerns
and resolutions.
8) Present results, interpreting them in light
of theory/hypotheses.
9) Conclusion: discuss external validity, with
attention to the limits of your findings.
Final Suggestions
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Cite the major pieces in the literature, be
generous.
Proofread. Style, punctuation, spelling matters!
Share with colleagues in ever enlarging circles.
Feedback is important because we don’t know
which analogies, presentation strategies, etc.,
will work. After getting reactions from friends and
mentors, distribute more widely to participants in
the debate.
Criticism is always helpful – be grateful that
someone took the time to read and comment on
your work.