1 Science and Pseudoscience I NTROD UCTION Parapsychology is defin ed by its practitioners as the study of extrasensory perception (ESP) and paranormal powers such as telekines is. ESP includes such all eged psyc hi c ph enomena as telepathy, clairvoya nce, and precog- nition. Shunned for decades by th e sc ientific establishment, parapsychol- ogists received offi cial recognition in 1969 when the Ameri can Assoc iation for the Advancem ent of Science (the AAAS) admitted the Parapsycholog- ical Association as an affili ate member. Many scientists are unhappy with this decision, since they regard parapsychology as a pseudoscience. In 1979, th e renowned phys icist John A. Wheeler wrote a blistering letter to the president of the AAAS urging that th e pa ra psychologists be expelled from the associati on. Wheeler wrote, "We have enough charlatanism in t!.is country today without needing a sci entific organization to prostitute itself to it. The AAAS has to make up its mind whether it is seeking popularity or wheth er it is stri ctl y a sc ientific orga niza ti on.'" The debate about th e nature of sc ience-about its scope, methods, and aims-is as old as sc ience itsel f. But this debate becomes especiall y heated when one group of practitioners accuses another group of practi c- ing pseudoscience. In the twentieth century many individuals, groups, and th eories have been accused of being pseudoscientifi c, including Freud and psyc hoanalysis, as trol ogy, beli evers in the paranormal, Immanuel Velikov- sky and Erich von Daniken (whose best-selling books W orlds in Collision and Chariots of the Gods excited the wrath of Carl Sagan and the scientific establishment), and, mos t recentl y, th e self-styled advoca tes of creation- science. The proponents of as trology, the paranormal, psychoanalys is, and creation-science engage in research, write books, and publish articl es, but th eir work is typically found in popular magazines and bookstores rather than refereed journals and science librari es. They are seldom funded by 1 2 CH. I SCIENCE AND PSEUDOSC IEN CE the National Science Foundation or elected to the National Academy of Sciences. They are outside of the sc ientific establishment and are kept out by those who regard th emselves as real sc ientists. If our only concern were to label certa in people "pseudoscientists," we might simply check where th eir work is published and how their the- ories have been received by th e sc ientific community. But we are con- cerned with the reasons certain doctrines are considered pseudoscientific; it is th ose reasons that interest philosophers of science. Some philosophers have proposed necessary conditions for genuine science. That is, they have offered characteristi cs that any discipline or field of study must possess in order t6 qualify as genuine sc ience. These characteri stics are often called demarcation criteria because they can be used to differentiate science from its counterfeit: if a discipline fail s to meet one of these conditions, then it is judged to be nonsc ientific. In the twentieth century, philosophers of sc ience have often disagreed about demarcation criteria. In this chapter Karl Popper, Thomas Kuhn, Imre Lakatos, and Paul Thagard each defend a different set of necessary conditions for genuine science. Popper's view, that a scientific theory must be open to refutation by making testable predictions, has been very influ- ential, especially among working scientists. Kuhn, Lakatos, and Thagard all reject Popper's claim that falsifiability is the hallmark of genuine sci- ence but disagree about what should replace it. All three address whether a theory or discipline's claim to scientific legitimacy depends on historical considerations, such as how theories have developed over time. The chapter ends with an exchange of views between Michael Ruse and Larry Laudan about the credentials of creation-science. Ruse, a prominent philosopher of biology, served as an ex pert witness in a trial concerning the constitutionality of an Arkansas law requiring public school biology teachers to present creati onism as a viable scientific alternati ve to evolutionary theory. Under Ruse's guidance, the judge in the case drew up a list of five criteri a for ge nuine science and concluded that creation- science fail ed on all fiv e counts. Laudan not only criticizes the items on this list (w hich includes Popper's falsifiabi lity) but also doubts whether there are any demarcation criteri a th at all sc ientific theories must sa tisfy. • Notes I. Quoted in Jack W. G rove, In Defence of Science (Toronto: Un ivers ity of To- ronto Press, 1989), 137. See also Martin Gardner, Science: Good, Bad and Bogus (Buffalo, N.Y.: Prometheus Books, 1981), 185-206. The Parapsychological Asso- ciation is still a member of the AAAS . KARL POPPER Science: Conjectures and Refutations Mr. Turnbull had predicted evil consequences, ... and was now doing the best in his power to bring about the verification of his own prophecies. - Anthony Troll ope • I When I received the list of participants in this course and realized that I had been asked to speak to philosophical colleagues' I thought, after some hesita tion and consultation, that you would probably prefer me to speak about those problems which interest me most, and about those develop- ments with which I am most intimately acquainted. I therefore decided to do what I have never done before: to give you a report on my own work in the philosophy of science, since the autumn of 1919 when I first began to grapple with the problem, 'When should a theory be ranked as scientific?' or 'Is there a criterion {or the scientific character or status o{ a theory?' The problem which troubled me at the time was neither, 'When is a theory true?' nor, 'When is a theory acceptable?' My problem was different. I wished to distinguish between science and pseudo-science; knowing very well that science often errs, and that pseudo-science may happen to stum- ble on the truth. I knew, of course, the most widely accepted answer to my problem: FROM Karl Popper, Coniectures and Refutations (London: Routledge and Kegan Paul, 1963 ), 33-39. 0. This essay was or iginall y presented as a lecture at Peterhouse College at Cam- br idge University in the summer of 1953 as part of a course on developments and trends in contemporary British philosophy, organized by the British Council. It was originally published as "Philosophy of Science: A Personal Report:: in British Philosophy in Mid·Century, ed. C. A. Mace, (London: All en and Unwin, 1957). 3 4 C H. I SC I ENC E AND P SEUDOSC I ENCE that science is distinguished fro m pseudo-science-or from 'metaphysics' - by its empirical method, whi ch is essentiall y inductive, proceeding from obse rvation or experiment. But this did not satisfy me. On the contrary, I often formulated my problem as one of distinguishing between a genuinely empirical method and a non-empirical or even a pseudo-empirical method- that is to say, a method which, although it appeals to observati on and experiment, nevertheless does not come up to sc ientific standard s. The latter method may be exempl ifi eq by as tro logy, with its stupendous l1)a ss of empirical evidence based on observation-on horoscopes and on biographies. But as it was not the example of astrology which led me to my prob- lem I should perhaps brieAy desc ri be th e atmosphere in which my prob- lem arose and the exa mples by wh ich it was stimulated. After the coll apse of th e Austrian Empire th ere had been a revolution in Austria: the air was full of revolutionary slogans and ideas, and new and often wi ld theori es. Among the theori es which interested me Einstein's theory of relati vity was no doubt by rar the most important. Three others we re Marx's theory of history, Freud's psycho-a nalysis, and Alfred Adler's so-ca ll ed 'i ndividual psychology'" There was a lot of popul ar nonsense ta lked about these theories, and especiall y about relativity (as still happens eve n today), but I was fortunate in those who introduced me to the study of this theory. We all - the small circl e of students to which 1 belonged-were thrilled with the res ult of Eddington's eclipse observations whi ch in 1919 brought the first important confirmation of Einstein 's th eory of gravitation. It was a great experi ence for us, and one which had a lasting influence on my intellectual devel- opment.t T he three other theori es 1 have mentioned we re also wi dely discussed among students at that ti me. 1 myse lf happened to come into personal contact with Alfred Adler, and even to co-operate with him in his soc ial $ For a fascinating autobiograp hica l account of Popper's yo uthful Airtat ion and painful disenchantment with Marx ism, see "A Crucial Year: Marxism; Science and Pse udoscience," in The Ph ilosophy o( Karl Popper, ed . Pa ul A. Schil pp (La Sali e, III .: Open Court , 1974), 1: 23 - 29. There is also an extended criticism of Freud in Karl R. Popper, Realism and the Aim o( Science (New Yo rk : Routl edge, 1983), 163-74. t Einste in's general th eory of relativity entails that light rays must bend in a grav- itati onal fi eld.