Karl Popper Thomas Khun Imre Lakatos Karl Popper

Karl Popper, Thomas Khun, Imre Lakatos Karl Popper (Austria���� ) – University of Vienna and London School of Economics The Logic of Scientific Discovery, 1934. Thomas Khun (USA���� ) – Harvard University The Structure of Scientific Revolutions, 1962. Imre Lakatos (Hungary���� ) – Moscow State University and University of Cambridge Falsification and the Methodology of Scientific Research Programs, 1970.

Karl Popper I Problem of demarcation A popular answer to the problem of demarcation: the epistemic enterprises on the left seek out verification or confirmation by evidence, in accordance with the inductive method; whereas the epistemic enterprises on the right do not. Pseudo- Science • seeks verification by evidence • does not seek verification by evidence • uses inductive method • does not use inductive method Popper thinks that this is wrong. He thinks that what distinguishes science from pseudo-science is not that it is verified by evidence, but rather that it makes risky predictions, that it is capable of being refuted.

Karl Popper II David Hume’s problem of induction (Enquiry Concerning Human Understanding, 1748). For Popper science does not use induction. It does not proceed by reaching conclusions about unobserved things on the basis of observed ones. Einstein’s theory is not correct on the basis of its prediction of Eddington’s observation of star’s light shifting during the solar eclipse of 1919. Rather, Einstein’s has internal logical consistency. Popper treats its theories as mere provisional conjectures. They are accepted only tentatively. Popper’s main reason for rejecting inductive logic is precisely that it does not provide a suitable distinguishing mark of the empirical, nonmetaphysical, character of a theoretical system; or in other words, that it does not provide a suitable ‘criterion of demarcation’ (Popper, pp. 11).

Karl Popper III Deductive approach for theories The method of critically testing theories, and selecting them according to the results of tests, always proceeds on the following lines. 1. From a new idea, put up tentatively, and not yet justified in any way - an anticipation, a hypothesis, or a theoretical system - conclusions are drawn by means of logical deduction. 2. These conclusions are then compared with one another and with other relevant statements, so as to find what logical relations (such as equivalence, derivability, compatibility, or incompatibility) exist between them (Popper pp. 09).

Karl Popper IV Falsifiability Popper thinks that what distinguishes science from pseudo-science is falsifiability. That is, science is capable of being refuted by evidence. Pseudo-science, on the other hand, is not falsifiable. It only gathers evidence in its favor; it never makes risky predictions which could potentially be refuted. Popper certainly admits that a system is empirical or scientific only if it is capable of being tested by experience. These considerations suggest that not the verifiability (David Hume), but the falsifiability of a system is to be taken as a criterion of demarcation (Popper, pp. 18).

Karl Popper V Falsifiability So long as theory withstands detailed and severe tests and is not superseded by another theory in the course of scientific progress, we may say that it has been “corroborated” by past experience (Popper, pp. 10). If the hypothesis entailed that we would observe a certain piece of evidence, and we didn’t observe that evidence, then it follows necessarily that the hypothesis is false. If a theory has sustained repeated attempts at refutation, then Popper says that theory is “corroborated”.

Karl Popper VI Popper holds that scientific theories are never fully justifiable or verifiable, but that they are nevertheless testable. Popper says that the objectivity of scientific statements lies in the fact that they can be tested (Popper, pp. 22). The pattern of scientific work on this account is very simple and repetitive: 1. A scientific conjecture is made. 2. Scientists try to refute it. The second step is repeated until it succeeds.

Karl Popper VII Recurring events Popper argues that the objectivity of scientific statements is closely connected with the construction of theories— with the use of hypotheses and universal statements. Only when certain events recur in accordance with rules or regularities, as is the case with repeatable experiments, can observations be tested—in principle—by anyone.

Karl Popper VIII Recurring events “We do not take even our own observations quite seriously, or accept them as scientific observations, until we have repeated and tested them. Only by such repetitions can we convince ourselves that we are not dealing with a mere isolated ‘coincidence’, but with events which, on account of their regularity and reproducibility, are in principle inter-subjectively testable” (Popper, pp. 23).

Karl Popper IX Theories Scientific theories are universal statements. Like all linguistic representations they are systems of signs or symbols. “Theories are nets cast to catch what we call ‘the world’: to rationalize, to explain, and to master it” (Popper, pp. 37 -38). Systems of theories are tested by deducing from them statements of a lesser level of universality (Popper, pp. 24). These statements in their turn, since they are to be intersubjectively testable, must be testable in like manner— and so ad infinitum (Popper, pp. 24).

Karl Popper X Theories Three requirements that the empirical theoretical system should satisfy. First, it must be synthetic, so that it may represent a noncontradictory, a possible world. Secondly, it must satisfy the criterion of demarcation. It must not be metaphysical, but must represent a world of possible experience. Thirdly, it must be a system distinguished in some way from other such systems as the one which represents our world of experience (Popper, pp. 16 -17).

Karl Popper XI Axioms and Theories A theoretical system may be said to be axiomatized if a set of statements, the axioms, has been formulated satisfying the following four fundamental requirements: 1. the system of axioms must be free from contradiction (whether self-contradiction or mutual contradiction). 2. the system must be independent, i. e. it must not contain any axiom deducible from the remaining axioms. 3. the axioms should be sufficient for the deduction of all statements belonging to theory which is to be axiomatized. 4. necessary, for the same purpose; which means that they should contain no superfluous assumptions (Popper, pp. 51).

Thomas Khun I Kuhn general assumptions A scientific community cannot practice its trade without some set of received beliefs. Normal science often suppresses fundamental novelties because novelties are necessarily subversive of its basic commitments. Research is "a strenuous and devoted attempt to force nature into the conceptual boxes supplied by professional education". A shift in professional commitments to shared assumptions takes place when an anomaly subverts the existing tradition of scientific practice. These shifts are what Kuhn describes as scientific revolutions—"the tradition-shattering complements to the tradition-bound activity of normal science". New assumptions (paradigms/theories) require the reconstruction of prior assumptions and the reevaluation of prior facts. This is difficult and time consuming. It is also strongly resisted by the established community.

Thomas Khun II Normal science is predicated on the assumption that the scientific community knows what the world is like - scientists take great pains to defend that assumption. Normal science "means research firmly based upon one or more past scientific achievements, achievements that some particular scientific community acknowledges for a time as supplying the foundation for its further practice". Normal science must be sufficiently unprecedented to attract an enduring group of adherents away from competing modes of scientific activity and Normal science must be sufficiently open-ended to leave all sorts of problems for the redefined group of practitioners (and their students) to resolve, i. e. , research. "The road to a firm research consensus is extraordinarily arduous”.

Thomas Khun III Paradigms Normal science achievements are called paradigms. Paradigms help scientific communities to bound their discipline in that they help the scientist to 1. create avenues of inquiry. 2. formulate questions. 3. select methods with which to examine questions. 4. define areas of relevance. 5. [establish/create meaning? ] A paradigm is essential to scientific inquiry—"no natural history can be interpreted in the absence of at least some implicit body of intertwined theoretical and methodological belief that permits selection, evaluation, and criticism".

Thomas Khun IV Paradigms How are paradigms created, and how do scientific revolutions take place? 1. Inquiry begins with a random collection of "mere facts”. 2. During these early stages of inquiry, different researchers confronting the same phenomena describe and interpret them in different ways. 3. In time, these descriptions and interpretations entirely disappear. 4. A preparadigmatic school (movement) appears. 5. Such a school often emphasizes a special part of the collection of facts. 6. From the competition of preparadigmatic schools, one paradigm emerges 7. A paradigm grows in strength and in the number of advocates, 8. The preparadigmatic schools (or the previous paradigm) fade.

Thomas Khun V Paradigms Paradigm transforms a group into a profession or a discipline. 1. formation of specialized journals. 2. foundation of professional societies. 3. claim to a special place in academia. Paradigm gain their status because “they are more successful than their competitors in solving a few problems that the group of practitioners has come to recognize as acute". But more successful does not mean completely successful with a single problem or notably successful with any large number of problems (or facts). Initially, a paradigm offers the promise of success. Normal science consists in the actualization of that promise

Thomas Khun VI Anomalies Discovery can be made by anomalies. Normal science does not aim at novelties of fact or theory and, when successful, finds none. Discovery novelty of fact. Discovery begins with the awareness of anomaly. Novelty emerges only with difficulty, manifested by resistance, against a background provided by expectation. Fundamental novelties of fact and theory bring about paradigm change.

Thomas Khun VII Anomalies The paradigm change is complete when the paradigm/theory has been adjusted so that the anomalous become the expected. Unanticipated outcomes derived from theoretical studies can lead to the perception of an anomaly and the awareness of novelty. The emergence of a new theory is generated by the persistent failure of the puzzles of normal science.

Thomas Khun VIII Failure of existing puzzles is the prelude to a search for new ones. A scientific revolution is a noncumulative developmental episode in which an older paradigm is replaced in whole or in part by an incompatible new one.

Imre Lakatos I Lakatos’s solution borrowed elements from both Popper and Kuhn, but both in this juxtaposition, and in its layering of additional features, it provided a different approach to describing and appraising scientific theories. Lakatos’s model of scientific change goes beyond Popper’s by shifting the unit of appraisal from individual theories to sequences of theories. Lakatos labeled these scientific research programs (SRPs) They comprise a series of theories linked by a set of constitutive and guiding assumptions.

Imre Lakatos II SRPs The hard core (or hard core assumptions) comprises the fundamental premises of a scientific research program. The hard core is protected by a negative heuristic, which is the rule that forbids scholars within this scientific research program from contradicting its fundamental premises or hard core (e. g. , in response to newly discovered evidence that seems to disconfirm theory). Alteration of the hard core would result in the creation of a new SRP, because the hard core essentially defines the SRP; if it changes, the SRP changes. A scientific research program also has a protective belt of auxiliary hypotheses. These are propositions that are tested, adjusted and readjusted, and replaced as new evidence comes to bear.

Imre Lakatos III Intra-program problemshift The replacement of one set of auxiliary hypotheses with another constitutes an intra-program problemshift—it is “intra” or within the program because only the protective belt, not the hard core, is changed. Intra-program problemshifts should be undertaken in accordance with the program’s positive heuristic, a set of suggestions or hints that guide the development of specific theories within the program. Despite the negative heuristic, scholars sometimes develop new theories which interfere with the hard core, thus creating a new research program through an inter-program problemshift. Lakatos argues that SRPs should be judged on the basis of rational criteria: their ability to successfully generate predictions of novel facts that are subsequently corroborated with empirical evidence.