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Graham Bradley

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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

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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