Karl Popper's Falsification Principle
============================================================================ I hope that this page will get you interested in studying this great man and his theories of science and politics. I have collected a number of quotes (*) from various sites with the links to those sites. Please visit them and read the quotes in their context. There you will also be made aware of many other aspects of Popper's work. All emphasis in the quotes below is my own. (*) All copyrights belong to their respective owners. ============================================================================ Sir Karl Popper (1902-94) Austrian (later British) scientific, social and political philosopher - particularly important for his understanding of science as progressing by the falsification of hypotheses. ============================================================================ Sir Karl Popper (1902-1994) The most important philosopher of science since Francis Bacon (1561-1626), Sir Karl Popper finally solved the puzzle of scientific method, which in practice had never seemed to conform to the principles or logic described by Bacon. Instead of scientific knowledge being discovered and verified by way of inductive generalizations, leaping from data into blank minds, in terms that go back to Aristotle, Popper realized that science advances instead by deductive falsification through a process of "conjectures and refutations." http://www.friesian.com/popper.htm ============================================================================ Google: "Karl Popper" http://www.google.com/search?sourceid=navclient&q=%22Karl+Popper%22 Google: "Karl Popper"+falsification http://www.google.com/search?sourceid=navclient&q=%22Karl+Popper%22%2Bfalsification Karl Popper books at Amazon.com http://www.amazon.co.uk/exec/obidos/search-handle-url/index%3Dbooks-uk%26field-author%3DPopper%2C%20Karl%20R./026-4340882-8822034 ============================================================================ Science as Falsification by Karl R. Popper (The end of this section refers directly to astrology - PL) With Einstein's theory the situation was strikingly different. Take one typical instance - Einstein's prediction, just then confirmed by the finding of Eddington's expedition. Einstein's gravitational theory had led to the result that light must be attracted by heavy bodies (such as the sun), precisely as material bodies were attracted. As a consequence it could be calculated that light from a distant fixed star whose apparent position was close to the sun would reach the earth from such a direction that the star would seem to be slightly shifted away from the sun; or, in other words, that stars close to the sun would look as if they had moved a little away from the sun, and from one another. This is a thing which cannot normally be observed since such stars are rendered invisible in daytime by the sun's overwhelming brightness; but during an eclipse it is possible to take photographs of them. If the same constellation is photographed at night one can measure the distance on the two photographs, and check the predicted effect. Now the impressive thing about this case is the risk involved in a prediction of this kind. If observation shows that the predicted effect is definitely absent, then the theory is simply refuted. The theory is incompatible with certain possible results of observation, in fact with results which everybody before Einstein would have expected.[1] This is quite different from the situation I have previously described, when it turned out that the theories in question were compatible with the most divergent human behavior, so that it was practically impossible to describe any human behavior that might not be claimed to be a verification of these theories. These considerations led me in the winter of 1919-20 to conclusions which I may now reformulate as follows. 1. It is easy to obtain confirmations, or verifications, for nearly every theory - if we look for confirmations. 2. Confirmations should count only if they are the result of risky predictions; that is to say, if, unenlightened by the theory in question, we should have expected an event which was incompatible with the theory - an event which would have refuted the theory. 3. Every "good" scientific theory is a prohibition: it forbids certain things to happen. The more a theory forbids, the better it is. 4. A theory which is not refutable by any conceivable event is non-scientific. Irrefutability is not a virtue of a theory (as people often think) but a vice. 5. Every genuine test of a theory is an attempt to falsify it, or to refute it. Testability is falsifiability; but there are degrees of testability: some theories are more testable, more exposed to refutation, than others; they take, as it were, greater risks. 6. Confirming evidence should not count except when it is the result of a genuine test of the theory; and this means that it can be presented as a serious but unsuccessful attempt to falsify the theory. (I now speak in such cases of "corroborating evidence.") 7. Some genuinely testable theories, when found to be false, are still upheld by their admirers - for example by introducing ad hoc some auxiliary assumption, or by reinterpreting the theory ad hoc in such a way that it escapes refutation. Such a procedure is always possible, but it rescues the theory from refutation only at the price of destroying, or at least lowering, its scientific status. (I later described such a rescuing operation as a "conventionalist twist" or a "conventionalist stratagem.") One can sum up all this by saying that the criterion of the scientific status of a theory is its falsifiability, or refutability, or testability. II I may perhaps exemplify this with the help of the various theories so far mentioned. Einstein's theory of gravitation clearly satisfied the criterion of falsifiability. Even if our measuring instruments at the time did not allow us to pronounce on the results of the tests with complete assurance, there was clearly a possibility of refuting the theory. Astrology did not pass the test. Astrologers were greatly impressed, and misled, by what they believed to be confirming evidence - so much so that they were quite unimpressed by any unfavorable evidence. Moreover, by making their interpretations and prophesies sufficiently vague they were able to explain away anything that might have been a refutation of the theory had the theory and the prophesies been more precise. In order to escape falsification they destroyed the testability of their theory. It is a typical soothsayer's trick to predict things so vaguely that the predictions can hardly fail: that they become irrefutable...... Thus the problem which I tried to solve by proposing the criterion of falsifiability was neither a problem of meaningfulness or significance, nor a problem of truth or acceptability. It was the problem of drawing a line (as well as this can be done) between the statements, or systems of statements, of the empirical sciences, and all other statements — whether they are of a religious or of a metaphysical character, or simply pseudo-scientific. Years later — it must have been in 1928 or 1929 — I called this first problem of mine the "problem of demarcation." The criterion of falsifiability is a solution to this problem of demarcation, for it says that statements or systems of statements, in order to be ranked as scientific, must be capable of conflicting with possible, or conceivable, observations. http://www.freethought-web.org/ctrl/popper_falsification.html ============================================================================ What Makes A Theory Scientific? "Science is what we have learned about how to keep from fooling ourselves." - physicist Richard Feynman The big question about a theory is whether it's right or wrong. Unfortunately, it's impossible to know that a scientific theory is right. The theory may agree beautifully with all the evidence - today. But science isn't like mathematics. There can be no guarantee about what evidence we will discover tomorrow. So, we go for the next best thing, which is proving theories wrong. That's easy. You just find some evidence that contradicts what the theory says. The theory is then falsified and stays that way. So, a scientific theory is one which can in principle be falsified. The theory has to make strong statements about evidence. If the statements aren't strong, then the theory fits any evidence, and is unfalsifiable. That's bad. It's bad for three very practical reasons. First, a theory which can't make predictions is a dead end. Second, it would be useless. Oil companies are very pleased that geologists can predict where to drill for oil. And third, if we have two rival theories, we want to use evidence to choose between them. If they are unfalsifiable, then evidence doesn't do that for us. -------------------------------------------------------------------------------- A Scientific Example The classical scientific example is Einstein's Theory of General Relativity. Einstein didn't just expect everyone to believe him. In his 1916 paper, he said that the Sun's gravity would bend light. He predicted that a photograph taken during a solar eclipse would clearly show the effect. Starlight passing near the Sun would bend, and the stars would show up in just slightly the wrong place. If they didn't, then his theory would be falsified. Sure enough, pictures of the 1919 eclipse showed that exact amount of bending. The pictures falsified Newton's "Law" of Gravitation, and left Relativity standing. Did that prove General Relativity right? No, of course not, because Relativity may still turn out to mispredict something else. And, in fact, several alternatives - such as the Brans-Dicke theory - have been proposed down through the years. At the moment, Relativity is once again the only theory still standing. But there's no way to guarantee that it will stay on top. It isn't proven. Like all other scientific theories, it is forever tentative. -------------------------------------------------------------------------------- Bad Examples First, a conspiracy theory: "Whenever my computer glitches, it is because an Invisible Pink Unicorn has messed with it." Note that this is unfalsifiable, because you can't detect an Invisible Pink Unicorn. There's no way to prove it isn't there. Next, some humor from David Canzi: "According to the Just So Theory of Instantaneous Cosmogenesis, the universe came into existence suddenly, just as it is. This theory predicts that, if we examine reality, we will observe that things are the way they are. The theory is falsifiable: If things were not the way they are, it would be proven false. Observation has shown that things are, indeed, the way they are. Thus the theory is proven." http://www.cs.colorado.edu/~lindsay/creation/falsify.html ============================================================================ Karl Popper Karl Popper is generally regarded as one of the greatest philosophers of science of this century. He was also a social and political philosopher of considerable stature, a self-professed ‘critical-rationalist’, a dedicated opponent of all forms of scepticism, conventionalism, and relativism in science and in human affairs generally, a committed advocate and staunch defender of the ‘Open Society’, and an implacable critic of totalitarianism in all of its forms. One of the many remarkable features of Popper’s thought is the scope of his intellectual influence. In the modern technological and highly-specialised world scientists are rarely aware of the work of philosophers; it is virtually unprecedented to find them queuing up, as they have done in Popper’s case, to testify to the enormously practical beneficial impact which that philosophical work has had upon their own. But notwithstanding the fact that he wrote on even the most technical matters with consummate clarity, the scope of Popper’s work is such that it is commonplace by now to find that commentators tend to deal with the epistemological, scientific and social elements of his thought as if they were quite disparate and unconnected, and thus the fundamental unity of his philosophical vision and method has to a large degree been dissipated. Here we will try to trace the threads which interconnect the various elements of his philosophy, and which give it its fundamental unity. Section Headings: Life Backdrop to his Thought The Problem of Demarcation The Growth of Human Knowledge Probability, Knowledge and Verisimilitude Social and Political Thought -- The Critique of Historicism and Holism Scientific Knowledge, History, and Prediction Immutable Laws and Contingent Trends Critical Evaluation Bibliography Other Internet Resources Related Entries http://plato.stanford.edu/entries/popper/ **** The Problem of Demarcation On this criterion of demarcation physics, chemistry, and (non-introspective) psychology, amongst others, are sciences, psychoanalysis is a pre-science (i.e. it undoubtedly contains useful and informative truths, but until such time as psychoanalytical theories can be formulated in such a manner as to be falsifiable, they will not attain the status of scientific theories), and astrology and phrenology are pseudo-sciences. Formally, then, Popper’s theory of demarcation may be articulated as follows: where a ‘basic statement’ is to be understood as a particular observation-report, then we may say that a theory is scientific if and only if it divides the class of basic statements into the following two non-empty sub-classes: (a) the class of all those basic statements with which it is inconsistent, or which it prohibits - this is the class of its potential falsifiers (i.e. those statements which, if true, falsify the whole theory), and (b) the class of those basic statements with which it is consistent, or which it permits (i.e. those statements which, if true, corroborate it, or bear it out). http://plato.stanford.edu/entries/popper/#Dema ============================================================================ While no number of observations in conformity with the hypothesis that, say, all planets have elliptical orbits can show that the hypothesis is true or even that tomorrow's planet will have an elliptical orbit, only one observation of a non-elliptical planetary orbit will refute the hypothesis. Falsification can get a grip where positive proof is ever beyond us; the demarcation between science and non-science lies in the manner in which scientific theories make testable predictions and are given up when they fail their tests. http://www.xrefer.com/entry/553218 ============================================================================ The Karl Popper Web Karl Popper's 1934 Bombshell In 1934 Popper published what many regard as his Magnum Opus The Logic of Scientific Discovery. The famous chemist Wachtershauser said that this is a "gem" and that it liberated him from a sterile accounting view of science. Wachtershauser subsequently went on to develop one of the main theories of the origin of life. Frank Tipler, the famous cosmologist, regards this as the most important book this century. In one majestic and systematic attack, psychologism, naturalism, inductionism, and logical positivism are swept away and replaced by a set of methodological rules called Falsificationism. Falsificationism is the idea that science advances by unjustified, exaggerated guesses followed by unstinting criticism. Only hypotheses capable of clashing with observation reports are allowed to count as scientific. "Gold is soluble in hydrochloric acid" is scientific (though false); "Some homeopathic medicine does work" is, taken on its own, unscientific (though possibly true). The first is scientific because we can eliminate it if it is false; the second is unscientific because even if it were false we could not get rid of it by confronting it with an observation report that contradicted it. Unfalsifiable theories are like the computer programs with no uninstall option that just clog up the computer's precious storage space. Falsifiable theories, on the other hand, enhance our control over error while expanding the richness of what we can say about the world. Any "positive support" for theories is both unobtainable and superfluous; all we can and need do is create theories and eliminate error - and even this is hypothetical, though often successful. Many superficial commentaries are keen to point out that other people stressed the importance of seeking refutations before Popper. They overlook the fact that Popper was the first to argue that this is sufficient. http://www.eeng.dcu.ie/~tkpw/ ============================================================================ Popper proposed an alternative scientific method based on falsification. However many confirming instances there are for a theory, it only takes one counter observation to falsify it: only one black swan is needed to repudiate the theory that all swans are white. Science progresses when a theory is shown to be wrong and a new theory is introduced which better explains the phenomena. For Popper the scientist should attempt to disprove his/her theory rather than attempt to continually prove it. Popper does think that science can help us progressively approach the truth but we can never be certain that we have the final explanation. http://www.philosopher.org.uk/sci.htm     ============================================================================ As Raphael notes, Einstein stimulated Popper's enthusiasm for physics. What distinguished Einstein from Marx, Freud and Adler was that his ideas were susceptible of test, and hence of refutation. For instance, before Einstein's Theory of Relativity could be said to be valid, a particular event had to take place, in the Solar System, which was impossible according to classical Newtonian principles. When a star's rays were indeed seen to be bent, by the gravitational pull of the sun, Einstein's prediction was fulfilled. Relativity had survived a key test that might have led to its refutation. This single instance had not proved Einstein to be entirely right, only righter than the now refuted Newton. Since there were only two eligible competitors, Einstein's theory was temporarily triumphant, but not unquestionably or conclusively. . . . "Popper," says Raphael, "came early to the idea of scientific method: scientists proved their good faith by seeking the most stringent ways of falsifying their hypothesis - that is, of detecting flaws in their own work. Any idea that cannot conceivably be refuted is not scientific. It may, however, have interest-value for other reasons." In the light of this cautious generosity, Popper could argue - against the philosophical current both in Vienna and, later, in England - that metaphysics was not a useless subject. What he did challenge, implacably, was 'scientism', which involved metaphysicians and sociologists passing off their all-embracing theories as scientific. Popper argued that while metaphysics might be stimulating, it could never be scientific. He argued that scientific method implied being accessible to challenges devised by others. Hence knowledge could not be a matter of personal conviction, however sincere; nor could an untestable theory be warranted by the intuitive genius of no matter how brilliant a philosopher. To Popper, for anything to qualify as knowledge it had to be open to examination, and to the risk of disproof, by the most rigorous possible critics. In other words, fallibility was not evidence of the weakness of a theory; on the contrary, the possibility of refutation guaranteed engagement with reality. Theories that were alleged to be about the world, but which could never conceivably be falsified, were for that very reason not about the world. Thus Marx and Freud, however seductive their critical or diagnostic astuteness, were revealed to be unscientific by their systematic inability to imagine, let alone supply, circumstances under which their ideas might be proved fallacious. Popper did not deny that Freud and Marx were interesting and innovatory as moralists or social critics; what he denied fervently, as Raphael notes, was the claim, as dear to them as to their followers, that they were scientists. The philosophers of the influential Vienna Circle - among them, Rudolph Carnap and Otto Neurath - seemed to concur with Popper. As 'logical positivists', they had argued that any proposition that could not be verified was meaningless. As Raphael notes, positivism intended to banish metaphysics from intellectual esteem. It aimed to establish the universality of the scientific outlook. However, logical positivists faced a central problem, albeit and old one, concerning verification. The Scottish philosopher David Hume (1711-1776) had pointed out that there was no logical reason to believe that because the sun rose yesterday, and this morning, it would certainly do so tomorrow. In the physical sciences it could never be logically certain that effect would follow cause. In view of this, the verification of a scientific law could never be conclusive. Popper maintained that unless the problem of induction could be resolved (and, he insisted, it could never be), positivism's Verification Principle had no warrant to ascribe meaning to science. As Raphael notes, Popper proposed that the problem of scientific method, and hence of verification, be looked at in a different way. In fact, he argued, it was not the case that scientific thought proceeded on the basis of accumulated observations of regularities. Scientific theories were never inductively proved by virtue of a plethora of instances that, at some moment, amounted to a law. Absolute verification was a chimera, Popper argued. He argued that what lent plausibility to scientific hypotheses was their ability to survive stringent challenges that their authors or their peers designed to test them. Popper argued that science did not proceed by showing why, or that, certain things happened; it established that - if a theory were valid - certain things could not happen. As Raphael notes, we begin to recognise something to be the case when to deny it would be to fly in the face of demonstrable facts. By the same token, science cannot 'discover' a tautology, since to deny it is merely self-contradictory. Theories such as Marxism, which affect to be infallible, can only be elaborate tautologies, protected from refutation by their circularity, Popper argued.  Kaleem Omar http://www.jang.com.pk/thenews/sep2001-weekly/tapest-06-09-2001/#5 ============================================================================ "Ancillary to Popper's vision of science was that of the scientist as an honest man.  Civilization and science were intimately linked in the sociology of knowledge.  The personal honesty of a researcher might be admirable, but it could never supply a validation.  A scientist's work had, by definition, only to be open to honest scrutiny by his peers. Such openness to challenge was integral to progress.  In science there might be guesswork; there could not be privilege.  Scientific method was both central to human progress and a paradigm of responsible community.  No scientist could claim to have struck theoretical gold without making his findings available to public assayers. And when the alchemist was found not to have turned lead into gold, he could not save his theory by redefining his lead as a special form of gold.  Genius might (as Einstein did) amaze, but it could not by itself certify: without the humility to endure examination, there could be no valid pride in achievement." Frederic Raphael, in Popper, The Great Philosophers Series, Routledge, New York 1999 Thus we can see that the methods and theories of Hulda Clark and many others fail miserably. ============================================================================ The Open Society and Its Enemies is Popper's supreme political work. Synopsis First published in 1945, this text's demolition of totalitarian political systems was widely cited as an influence on the collapse of Eastern European communism at the beginning of the 1990s. Popper was awarded the 1976 Lippincott Award of the American Political Association for this book. http://www.amazon.co.uk/exec/obidos/ASIN/0415174902/o/qid=999384387/sr=2-1/ref=sr_sp_bow_1_1/026-4340882-8822034 ============================================================================ Popper was also a controversial man, and not without his faults: A Skeptical Look at Karl Popper by Martin Gardner "Sir Karl Popper, who died in 1994, was widely regarded as England's greatest philosopher of science since Bertrand Russell. Indeed a philosopher of worldwide eminence. Today his followers among philosophers of science are a diminishing minority, convinced that Popper's vast reputation is enormously inflated. I agree." http://www.freethought-web.org/ctrl/gardner_popper.html ============================================================================
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