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Slide 1
Graham Bradley
Slide 2
Lecture 1 What is science? Geography and science Scientific
explanation Scientific reasoning Francis Bacon and induction David
Humes problem Karl Popper and falsification The
hypothetico-deductive method Example: climate change
Slide 3
What do you think science is? Sceptical (up to a point) Based
on observation, data, experimentation Conclusions are tentative
Theories (models) can be tested / falsified Assumes a chain of
cause and effect Explains by generalising Often quantitative and
mathematical
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But what do scientists think science is? Ask a scientist what
he conceives the scientific method to be, and he will adopt an
expression that is at once solemn and shifty-eyed: solemn because
he feels he ought to declare an opinion; shifty-eyed because he is
wondering how to conceal the fact that he has no opinion to declare
Sir Peter Medawar UCL Professor of Zoology 1951-1962 Nobel Prize in
Medicine 1960
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What are the goals of science? 1. Description Identification
and classification of entities, events & patterns 2. Prediction
Use observed regularities to infer unobserved phenomenon 3.
Explanation Explicate the causal relations between described and
predicted phenomenon 4. Stewardship/Control ( applied
science/engineering ) Apply knowledge to bring about desired
outcome
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What is scientific explanation? 1. Cause and effect to explain
a phenomenon is to say what caused it E.g. What is the cause of
lake acidification? 2. Covering laws show that phenomenon to be
explained is covered by some general law of nature E.g. Darcys Law
(groundwater flow) Q = KiA General law & particular facts
explanation Every reliable prediction is a potential
explanation
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Deduction Inference, by reasoning, from general to particular:
from theory to data Premises: i) every mammal has a heart; ii)
every horse is a mammal. Conclusion: Every horse has a heart.
Premises: i) all U shaped valleys were formed by glaciers; ii)
Wasdale is U shaped valley. Conclusion: Wasdale was formed by a
glacier Valid if the truth of premises guarantees truth of
conclusions & false otherwise. Conclusion is either true or
false Induction and deduction
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Induction Process of inferring general principles from
observation of particular cases: from data to theory Premise: every
horse that has ever been observed has a heart Conclusion: Every
horse has a heart. Premises: i) Death by cholera spatially
clustered; ii) spatial clusters around water pumps. Conclusion:
water pumps are the source of cholera. Conclusion goes beyond
information present, even implicitly, in premises Conclusions have
a degree of strength (weak -> near certain). Induction and
deduction
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The origins of science: Aristotle (384-322 B.C.E.) Plato
emphasis on a priori knowledge Aristotle greater emphasis on a
posteriori knowledge Empirical inquiry of the form within things
Elements: earth; air; fire; water; aether Teleology nature reflects
inherent purpose and direction Aristotelian view remained dominant
until 16 th C
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Attorney General, Lord Chancellor of England and philosopher
who inspired the formation of the Royal Society Rejected many a
priori assumptions of Aristotelian view and advocated the Baconian
method of inductive inquiry: Identify phenomenon and rank list of
things in which it occurs Use inductive reasoning to verify the
cause of phenomenon Francis Bacon (1561-1626) Can induction
identify causes?
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Rev. Thos. Bayes (1702-1761) Formalise scientific process via
probability Bayes Theorem: solves the inverse (inductive) problem
i.e. gives probability of a hypothesis being true given some data
and any prior knowledge THIS is how science is really done! BUT is
(sort of) subjective as requires stating priors explicitly P(H|I)
Ignored for 200 years: replaced by statistics estimate reliability
of a given set of data (compared to infinite other possible sets)
in the light of a given (null) hypothesis (model). But we dont HAVE
infinite other data sets in practive Posterior LikelihoodPrior
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Eg Laplace & the mass of Saturn Laplace (1749-1827)
estimated M Saturn from orbital data i.e. H is the posterior
prob(M|{data},I) where I was background knowledge of orbital
mechanics etc. Shaded area shows degree of belief that m 1 M Saturn
< m 2 (right to within < 0.7%) How do we interpret this pdf
in terms of frequencies? Some ensemble of universes all constant
other than M Saturn ? Distribution of M Saturn in repeated
experiments? But data consist of orbital periods, and these
multiple expts. didnt happen Posterior LikelihoodPrior Best
estimate of M Degree of certainty of M The posterior pdf expresses
ALL our best understanding of the problem
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Karl Popper (1902 - 1994) Can deduction identify causes?
Impossible to verify a universal statement which would require
infinite observations Possible to falsify a universal statement
with a single counter-observation Falsifiction is deductive: if the
single case is false then it logically follows that the universal
case is also false Popper stated some theories thought to be
scientific at the time are unfalsifiable and therefore not science
e.g. Freuds psychoanalysis; Marxist theory Reference: Popper, K.,
1959. The Logic of Scientific Discovery
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Example: Climate Change What has caused global warming?
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How much of the observed change is due to natural variability
and how much to anthropogenic influences?
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Natural Variability and Climate Change Internal mechanisms
Ocean/atmosphere interaction e.g. ENSO Thermohaline circulation
External mechanisms Ash from volcanic eruptions Variability in
solar irradiance
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Effect of Volcanic Ash
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Variations in Solar Irradiance
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Anthropogenic carbon dioxide
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Competing Hypotheses H 1 The observed record is consistent with
natural climate variability only H 2 The observed record is
consistent with natural and anthropogenic forcing Use proxy record
of global temperature and General Circulation Models to test the
hypotheses
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First Hypothesis: The observed temperature record is consistent
with natural climate forcing only Falsified
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Second Hypothesis: The observed temperature record is
consistent with natural and anthropogenic climate forcing
Corroborated
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Problems of Falsification Most scientists are not trying to
falsify theories: e.g. When asked What if relativity had been
falsified? Einstein replied: I would have been sorry for the dear
Lord as my theory is correct. Tenacity It may be good to hold on to
a falsified theory Popper: He who gives up a theory too easily in
the face of apparent refutations will never discover the
possibilities inherent in his theory e.g. Uranus didnt conform to
Newtons laws - the discovery of Neptune Corroboration Degree of
testing a theory has undergone Popper argued a highly corroborated
theory has a greater level of truthlikeness, but the logical
conditions for comparison cannot be met Popper was unable to
provide a logical method of consistently choosing between
unfalsified theories
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1. Realism: physical world is real; 2. Presuppositions: world
is orderly and comprehensible; 3. Evidence: science demands
evidence; 4. Logic: science uses standard, settled logic to connect
evidence and assumptions with conclusions; 5. Limits: many matters
cannot usefully be examined by science; 6. Universality: science is
public and inclusive; 7. Worldview: science must contribute to a
meaningful worldview. Gauch (2006): Seven pillars of Science
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Summary Scientific methods address empirical claims Demarcation
criteria: empirical, laws, testable etc Scientific explanations:
cause & effect, covering laws Scientific reasoning: inductive
or deductive The problem of induction Karl Popper and falsification
The hypothetico-deductive method Final thought: How do scientists
choose between unfalsified theories?
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Reading: Okasha, S., 2002. Philosophy of science, a very short
introduction Recommended introduction for the general reader. Also
available as audio book. Chalmers, A. F., 1999. What is this thing
called science? 3 rd edition Recommended text for anyone with an
interest in the philosophy of science. Inkpen, R., 2005. Science,
philosophy and physical geography Introduction to philosophy of
science for physical geography undergraduates. Gauch, H. (2003) The
Scientific Method in Practice Gauch, H. (2006) Science, Worldviews
and Education, Sci. and Edu., DOI 10.1007/s11191-006-9059-1. see
bothon Moodle Montello, D. R. and Sutton, P. C., 2006. An
introduction to scientific research methods in geography Beginners
guide to empirical aspects of human and physical geography
research, with well balanced introduction on the philosophy of
science and its place in geography. Orme, A. R., 2002. Shifting
paradigms in geomorphology Geomorphology, Vol. 47, Issues 2-4,
pages 325-342 A paper of particular interest to physical
geographers.
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Whats in a theory? Natural Science Social Science Humanities
Sets of assumptions, ideas, arguments and conclusions An analytic
structure designed to provide a general explanation of observations
A set of interpretive principles that facilitate a specific
rational or moral analyses