Presentation on theme: "Karl Popper Popper replaces induction with falsification"— Presentation transcript:
1 Karl Popper Popper replaces induction with falsification Science is not distinguished from non-science on basis of methodology. No unique methodology specific to scienceScience consists mostly of problem solving.
2 Karl Popper All observations are selective and theory laden A demarcation between science and pseudo-science is established by falsification. A theory is scientific only if it is refutable by a conceivable eventEvery genuine test of a scientific theory is based on an asymmetry between verification and falsification
3 Sir Karl Popper ( )Falsification is the idea that science advances by unjustified, exaggerated guesses followed by unstinting criticism.Any "positive support" for theories is both unobtainable and superfluous; all we can and need do is create theories and eliminate errorScientists never actually use induction. It is impossible to verify propositions by reference to experience
4 Falsificationism (1) Scientific Method Is there a scientific method? What justifies scientific claims to knowledge?Can we distinguish scientific method from non-scientific ways of thinking? (demarcation)Does science progress?
5 Falsificationism (1) Falsificationism ‘No criterion of truth’: Two Arguments:No Theory/observation distinction:‘Here is a glass of water’ is theory ladenIn accepting the statement we must accept a significant amount of theoryWe have only as much justification for accepting the observation statement as we do for the theory
6 Falsificationism (1) We can’t! Falsificationism ‘No criterion of truth’:Two Arguments:No Theory/observation distinction:Upshot: we cannot use observation to establish the truth of a theoryHow can we establish the truth of scientific theories?We can’t!
7 Falsificationism (1) Confirmation and Pseudoscience Good scientific practice:E.g. Einstein’s general relativityConjecture: mass of the sun bends the path of lightApparent locationActual locationmoon
8 Falsificationism (1) Confirmation and Pseudoscience Good scientific practice:E.g. Einstein’s general relativityConjecture: mass of the sun bends the path of lightIf the apparent location of the observed star doesn’t shift, the theory is wrong.It will have been refuted.The mark of a scientific theory is whether it can be falsified by observation
9 Falsificationism (1) Conjecture and Refutation: “Falsificationists… prefer an attempt to solve an interesting problem by a bold conjecture, even (and especially) if it soon turns out to be false, to any recital of a sequence of irrelevant truisms” (CR: 231)This gives us:(i) a glimpse of scientific method(ii) a demarcation criterion for science
10 Falsificationism (1) Scientific method: Scientific theories have deductive consequencesThey can be falsified but not confirmed.The objective of scientific theorizing is to put forward (bold) hypotheses and then test them in order to falsify themTheories are falsified by basic statements(what is a basic statement?)
11 Falsificationism (1) Demarcation: Scientific theories are those that can be falsified by basic statements.Good scientific theories do not make themselves immune from falsification by use of ad hoc hypotheses
12 Falsificationism (1) Progress of Science: Science progresses by eliminating theories that have been falsified?But does it progress?A scientific theory cannot be shown to be true. But some scientific theories do have varying degrees of success. They resist falsification.
13 Falsificationism (1)“We must not look upon science as a body of ‘knowledge’, but rather as a system of hypotheses which in principle cannot be justified, but with which we work as long as they stand up to tests, and of which we are never justified in saying that we know that they are ‘true’, or ‘more or less certain’ or even ‘probable’
14 Kuhn (1) Thomas Kuhn (1922-1996) The Copernican Revolution (1957) The Structure of Scientific Revolutions (1962)History of science not compatible with rationalist viewProgress of science not cumulative, driven by the application of a method
15 Kuhn (1) Thomas Kuhn (1922-1996) The Copernican Revolution (1957) The Structure of Scientific Revolutions (1962)No obvious science/non-science demarcationNo context of discovery/context of justification distinction
16 Kuhn (1) Kuhn’s History of Science Two projects: Descriptive — what is the structure of scientific history?Normal science Scientific revolutionExplanatory — why does the history of science have this structure?Paradigms
17 Kuhn (1) 1. Kuhn’s History of Science Descriptive Project: Immature ScienceRevolutionNormal ScienceCrisisAnomalies
18 Paradigm Diagram old paradigm unexplained observations competing new paradigmsincommensuratepuzzle solvingone dominant paradigmMopping up operationunsolved puzzles ignoredunexplained observationsunexplained observations and alternative interpretation ignored until enough accumulates to overturn current paradigm
19 Kuhn (1) 1. Kuhn’s History of Science Immature Science: No prevailing school of thoughtVarious disparate theoriesCompetition
20 Kuhn (1) 1. Kuhn’s History of Science Normal Science: Stability Determination of significant factsMatching facts with theoriesArticulation of theories (refinement and extension)“puzzle -solving” neither tests nor confirms its theories
21 Kuhn (1) 1. Kuhn’s History of Science Normal Science: Driven by a paradigm (more later):Commonly held set of beliefs, procedures, techniquesAgreement upon questions of importAgreement on what counts as a solutionAgreement upon standards of evaluation
22 Kuhn (1) 1. Kuhn’s History of Science Anomalies: Not all expectations are borne outSome anomalies lead to further discoveries (e.g. orbit of Uranus)Some simply ignoredTroublesome anomaliesChallenge key theoretical conceptsResist solutionsInhibit application of theory
23 Kuhn (1) 1. Kuhn’s History of Science Crisis: Weight of accumulated anomaliesNo agreement on how anomalies are to be dealt withDoubts arise
24 Kuhn (1) 1. Kuhn’s History of Science Revolution: A new paradigm emergesOld Theory: well established, many followers, politically powerful, well understood, many anomaliesNew Theory: few followers, untested, new concepts/techniques, accounts for anomalies, asks new questions
25 Kuhn (1) 1. Kuhn’s History of Science Revolution: A new paradigm emergesAre old and new theories compared by some rational procedure?“A new scientific theory does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it” (Planck)
26 Kuhn (1) Scientific Revolutions The Ptolemaic model The earth is at the centre of the planetary systemProblem:How to explain the retrograde motion of planets
27 Kuhn (1) Scientific Revolutions The Ptolemaic modelThe earth is at the centre of the planetary systemProblem:How to explain the retrograde motion of planetsDeferentEarthPlanetEpicycle
28 Kuhn (1) Scientific Revolutions The Ptolemaic modelThe earth is at the centre of the planetary system
29 Kuhn (1) Scientific Revolutions The Ptolemaic Model: Problems: Complexity: epicycle upon epicycleThe accumulation of anomaliesNo clear way forward
30 Kuhn (1) Scientific Revolutions The Copernican model The sun is at the centre of the planetary systemProblem:How to explain the retrograde motion of planets
31 Kuhn (1) Scientific Revolutions The Copernican model The sun is at the centre of the solar system
32 Kuhn (1) Scientific Revolutions The Copernican Revolution was not the consequence of an old theory with less ‘empirical content’ being replaced by a new theory with moreNo appeal to reason alone‘propaganda’To discover how scientific revolutions are effected, we shall therefore have to examine … the techniques of persuasive argumentation within the quite special groups that constitute the community of scientists (SSR: 94)
33 Kuhn (1) 2. Explanatory Project Two Questions: If this is the course of the history of science, why?Why aren’t competing theories/traditions measured against each other by some rational procedure?
35 Kuhn (1) Explanatory Project Why is normal science stable? It is conducted wholly within the terms of a disciplinary matrix:questionsproceduresproblemsprioritiesstandards of evaluationAll are generated by the disciplinary matrix
36 Kuhn (1) Explanatory Project Why is theory change revolutionary? Theory change is brought about by a ‘gestalt switch’ a complete change of world viewThere is no neutral point from which one can assess theories from two paradigms simultaneously