Transcript PPTX file
Graham Bradley Lecture 2 Is science rational and progressive? Realism and instrumentalism Inference to the best explanation Criteria for theory choice Logical positivists Thomas Kuhn and revolutions in science Constructivism Examples: plate tectonics and geomorphology A scientific realist says... “A 1950s education in Freud, Marx, and modernism is not a sufficient qualification for a thinking person. Indeed, the traditional intellectuals are, in a sense, increasingly reactionary, and quite often proudly (and perversely) ignorant of many of the truly significant intellectual accomplishments of our time. Their culture, which dismisses science, is often nonempirical. It uses its own jargon and washes its own laundry. It is chiefly characterized by comment on comments, the swelling spiral of commentary eventually reaching the point where the real world gets lost.” John Brockman (science publisher – www.edge.org) Scientific Realism versus Instrumentalism Scientific realism – the aim of science is to provide true theories of the world All theories are attempted descriptions of reality Instrumentalism (anti-realism) – the aim of science is to provide predictive theories only Not ‘global anti-realism’ i.e. poststructuralism (language trap) Science provides true descriptions of the observable universe but has no knowledge of unobservable universe Scientific theories are instruments to predict observations Do scientific theories represent reality? 1. How do we know current theories are true if past theories were found to be false? Quantity and quality of observational evidence 2. How do we know which theories are true if multiple theories are consistent withdata? Science requires additional criteria to make an ‘inference to the best explanation’ Inference to the Best Explanation A type of non-deductive inference On Christmas morning presents had been left by the tree and the mince pies and sherry were gone! Late on Christmas Eve footsteps were heard on the staircase Who delivered the presents and ate the goodies? We learn to infer the ‘best explanation’ based on personal criteria and experience natural selection intelligent design What are the criteria for choosing explanations? Accuracy, scope, consistency, fruitfulness, simplicity etc. E.g. Evolution by natural selection explains similarities by descent from a common ancestor replication & mutation & competition → adaptation Simplicity (parsimony) and explanatory power are evidence of its truth Ockham’s razor But how do we know that reality is simple and not complex? natural selection intelligent design ASIDE: parsimony (simplicity) Occam’s razor: principle that simpler explanations have more explanatory power (fewer params) and easier to falsify In absence of any other info strong statistical case to choose simpler BUT: this doesn’t mean simplest is best/right…. The Logical Positivists (1920s to 1960s) Impressed by objectivity of science and verification ‘Context of discovery’ – historical, emotional, subjective ‘Context of justification’ – testing, evidence, objective e.g. Kekule and the structure of benzene They thought philosophy of science should address justification of theory They were not interested in history Thomas Kuhn (1922 - 1996) Is sociology of science important? An historian of science who thought that ignoring history gives a naïve picture of the scientific enterprise Interested in ‘scientific revolutions’ – when scientific ideas are replaced by radically new ones e.g. Einsteinian revolution in physics, Darwinism in biology, plate tectonics in geology Reference: Kuhn, T. S., 1962. “The Structure of Scientific Revolutions” Paradigms Shared assumptions, beliefs and values that unite the community and allow ‘normal science’ to take place Two components: A set of fundamental theoretical assumptions accepted by the scientific community A set of ‘exemplars’ – classic problems solved by these theoretical assumptions ‘Normal’ Science A paradigm defines ‘normal science’ for a period sets the standards and specifies objectives for relevant research coordinates research and initiates students into the tradition Scientists work within a paradigm to solve minor puzzles When anomalies are few they are ignored Revolutionary Science As anomalies accumulate a crisis develops Confidence in the old paradigm breaks down Fundamental scientific ideas are up for grabs Paradigm shift – a new paradigm is established Example 1: Tectonic shifts in paradigm? 19th century: Static Continents Observations: uplifted strata, geological folds and faults E.g. James Dana – Manual of Geology (1863) Explanations (no unifying theory): undermining due to volcanic eruptions sudden formation of volcanic vapours weight of accumulated formations movement of the globes interior fluids temperature related expansion and contraction Earlier 20th century growing unease Observations: matching coastlines continuity of Permo- Carboniferous glacial sediments similar fossils records Explanation: continental drift (Alfred Wegener, 1912) Not generally supported due to lack of evidence for a suitable mechanism Later 20th century: Plate Tectonics…a paradigm shift? Observations: earthquake zones & deep earthquakes beneath ocean trenches variable magnetic field direction in rocks of different ages (1956) magnetic striping at ocean ridges suggests seafloor spreading (1961) Explanations: constructive margins, subduction zones etc Unifying theory for geology & geomorphology of the Earth Can paradigms be compared? Kuhn - alternative paradigms so different they cannot be compared - no common language for translation e.g. Newtonian and Einsteinian physicists (supposedly) have a different concept of mass and in discussion they talk past each other Criticism of ‘incommensurability’: If it is agreed that theories are incompatible then they must be comparable and cannot be incommensurable Kuhn: Newton’s and Einstein’s theories are incompatible Are data independent and objective? Cannot isolate theory-neutral data because: Perception is conditioned by background beliefs Reporting of data is couched in theoretical language Criticisms of ‘theory-ladenness of data’: Data may be adequately free of theoretical contamination to be acceptable to proponents of alternative paradigms e.g. Believers in geocentric and heliocentric paradigms could still agree on statements like ‘on 14th May the Sun rose at 5:30 am’ Some criticisms of Kuhn’s ideas... ‘Between Kuhn’s “normal science” and “extraordinary science” there are many gradations’ (Popper, 1970) ‘If an experiment does not hold out the possibility of causing one to revise one’s views, it is hard to see why it should be done at all’ (Medawar, 1979) Example 2: Changing paradigms in geomorphology? Catastrophism uniformitarianism Shift (Orme, 2002 – Geomorphology 47) landscape cycles quantitative methods Shift (Orme, 2002 – Geomorphology 47) Kuhn’s controversies: Is science rational? Adopting a new paradigm involves a degree of faith and is not purely based on objective evidence The transfer of allegiance from one paradigm to another is a ‘conversion experience’ Peer pressure plays a large role in paradigm acceptance Is science progressive? ‘Facts’ about the world are paradigm-relative Scientific knowledge is not necessarily cumulative Does the concept of objective truth even make sense? Kuhn’s clarifications… Science may be viewed as rational Incommensurabilty between paradigms is partial Paradigm choice is made by reasonable shared criteria: accuracy, scope, consistency, simplicity, fruitfulness etc. Paradigm choice based on reasonable shared criteria is rational Science may be viewed as progressive ‘Conceived as a set of instruments for solving technical puzzles in selected areas, science clearly gains in precision and scope with the passage of time. As an instrument, science undoubtedly progresses’ So….. ‘When the facts change, I change my mind. What do you do sir?’ (JM Keynes, 1930 ….maybe) Changing your mind is not a bad thing: to refuse to change position in light of new evidence is surely irrational Scientific method aims to codify this process, BUT…. So...can the scientific method be rigorously defined? Many have attempted to define the criteria for a good theory Simplicity (parsimony), breadth, goodness of fit etc. No rigorous algorithm (sequence of instructions) Kuhn claimed there is no algorithm for theory choice Science appears to conform to a looser definition and more relaxed concept of rationality than often assumed Summary Realism and instrumentalism Inference to the best explanation Logical positivists emphasis on theory Thomas Kuhn’s emphasis on history Paradigms, normal and revolutionary science Science is more loosely defined than often assumed Science is rational when viewed against shared criteria As an instrument, it progressively solves empirical questions Final thought: What are appropriate and inappropriate applications of science in geography?