teaching scientific method: the logic of confirmation and falsification

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Teaching Scientific Method: The Logicof Confirmation and FalsificationJames W. GarrisonDivision of Curriculum & InstructionVirginia Polytechnic Institute & State UniversityBlacksburg, Virginia 24061

Michael L. BentleyDepartment of Mathematics & ScienceNational College of EducationEvanston, Illinois 60201

Introduction

Science educators generally consider the decade after Sputnik their goldenera, a time when dollars flowed freely to support the development of newscience programs and for workshops and institutes for science teachers.During that heady time, many activity- and materials-centered programs werecreated, even though the alphabet courses ultimately failed to supplant thetextbook dominance of the curriculum or teachers’ preferences for didacticinstructional methods. Of course, today’s generation of textbooks owes muchto the 1960s’ programs, and many teachers were positively influenced byNational Science Foundation (NSF) funded training. The golden era was agreat leap forward for science education.Now, after a lull of almost two decades, interest in science education has

renewed, spurred on by international competition in science and technologyand the widespread perception that U.S. students trail their counterpartsabroad in scientific literacy. Perhaps another golden era is at hand. Improvingscience education this time, however, will require more than increased fundingand new activity-based programs. Success is likely to be limited if educatorsignore the need for a deeper analysis of the nature of science as a basis forchoosing among alternatives in instructional strategies and in the content oftheir courses.The nature of science has been defined in many ways. According to

Lederman (1986), it "most commonly refers to the values and assumptionsinherent in scientific knowledge" (p. 91). That students understand the natureof science has long been a key goal of science education, prerequisite forscientific literacy (National Science Teachers Association [NSTA], 1982). Theproblem, however, is that current teaching practices and instructionalmaterials frequently misrepresent science and implicitly promote faultyreasoning. To rectify this situation, science educators need to become morethoroughly versed in the nature of science as an important area of discernmentin making programatic and instructional choices.

School Science and MathematicsVolume 90 (3) March 1990

Teaching Scientific Method 189

Unfortunately, it seems few science educators study the philosophy ofscience or follow developments in the field. Duschi (1985), quite correctly,could title a paper "Science Education and Philosophy of Science: Twenty-Five Years of Mutually Exclusive Development." In the past quarter century,a new philosophy of science has emerged, postpositivism, knowledge of whichis fundamental to understanding the nature of science. This work might serveas a needed theoretical foundation for science education. Abimbola (1983) hasindicated "that secondary school science education lacks a sense of directionas well as a theory and philosophy which should provide guidance tocurriculum development and instruction" (p. 181).The philosophy which implicitly frames much of current practice in science

education is positivism. Positivism is the idea that universal natural laws orprinciples may be induced with certainty from an empirical/experimentalfoundation. In logical positivism the problem of induction, i.e., inferring lawsfrom experience, becomes the problem of confirmation or verification.Positivism assumes a clear separation between the knower and the known.This separation is reflected in a sharp distinction between theories (beliefs) andfacts as well as facts and values. Positivism denies any role to subjectivity inthe gathering of objective knowledge. On the other hand, postpositivismasserts that universal laws can never be induced with certainty. The problemsand paradoxes of confirmation are seen as intractable. Theories and valuescannot be entirely separated from facts; there is an element of subjectivity inall objective statements. Experience is theory- and value-laden.

Educators have begun to show interest in philosophy of science and itsmeaning for teaching and learning. Educational researchers and theorists haveshown concern about the implications of postpositivistic philosophy of sciencefor educational research (e.g., Donmoyer, 1985; Howe, 1985; Macmillan &Garrison, 1984; Phillips, 1983; Tuthill & Ashton, 1983). Postpositivism canprovide direction for science education, but science educators need tounderstand the principles involved and come to grips with the complexity ofseveral unresolved issues in contemporary philosophy of science. The fact isthat many philosophers of science still see the correctness of these principles asproblematic. In this paper, important principles and issues in postpositivismwill be explored and related to possible applications in science education.

The Logic of Confirmation

Fundamental to an understanding of postpositivism are the ideas ofconfirmation and of falsification and how they provide a dynamic againstwhich scientific thought can be judged (Garrison, 1986). Confirmation ofanything from grand unified theories to the humblest hypothesis consists indrawing logical implication from some hypothesis (H) or theory (T) to someempirical-experimental conclusion (E) that says something like, "If T (or H) istrue, then E will be observed." If E is, as a matter of empirical fact,observed, the researchers would like to claim T is confirmed or verified.


190 Teaching Scientific Method

Schematically, this pattern of argument may be represented in prepositionallogic this way:

PI T -> E If T is true, we will see E

P^ E ______ We see E____________C T Therefore, T is true.

In scientific inquiry the logical sign "-^ is usually meant to convey somenecessary connection, such as, for example, causality. The problem is that thisschema is logically invalid, representing what is commonly called "the fallacyof affirming the consequent." Premises one and two (Pi and P^) may be trueand the conclusion (C) nonetheless false. For example, the Phlogiston Theoryimplied that burning and calcination released phlogiston which had negativeweight; the combustible bodies do weigh more after burning. Therefore, thetheory of phlogiston is confirmed. What the inductionist fallacy means is thateven a welt-confirmed theory still may be wrong.

School science promotes faulty reasoning if the logic of confirmation, whichinvolves a logical fallacy, is taught as if it were valid. Such instruction, beingunintentional and unrecognized, is part of the hidden curriculum. Sciencetextbooks provide evidence that the fallacy of affirming the consequent isentrenched in the hidden curriculum. The positivistic orientation of textbooksis usually most explicit in the introduction or first chapter, where the natureof science is often described. Frequently included is a statement about thescientific method, often presented as a series of steps beginning withobservations or questions, proceeding to the formation of hypotheses andtests, and ending in conclusions (Appenbrink, Hounshell, Halper-Slote, &Smith, 1981; Moyer & Bishop, 1986).For example, in their chemistry text, Smoot, Price, and Smith (1983) say to

the student, "Someday you may decide to pursue a career as a scientist andseek facts about our world. As a scientist you will make observations. Youwill also hypothesize (make predictions based upon your observations) andthen experiment to test your hypotheses. In this way you will add to thecollection of facts that scientists have already recorded" (p. 7). In a sample ofa half dozen current science textbooks examined for this paper, the type ofreasoning process underlying what is described as the scientific method is notdiscussed. A few texts do state that scientific knowledge is tentative, but donot say why. For example, in their general science text Moyer and Bishop(1986) state, "Scientific laws and theories cannot be proven. They aremaintained as long as observations support them" (p. 39). In a physics text,Williams, Trinklein, & Metcaife (1984) state, *’In a sense, there is no suchthing as absolute truth in science. The validity of a scientific conclusion isalways limited by the method of observation and, to a certain extent, by theperson who made it" (p. 5). Here and in other texts examined, however, thelimits of the method are not delineated.



A further example of how the inductionist fallacy is promotedunintentionally in textbooks is in the way verificationist language is woveninto descriptions of events in the history of science. For example, the widelyused Biological Sciences Curriculum Study (BSCS) Green Version (1973), abiology text, in discussing the search for the vector of malaria states, "Wehave learned now that it was the mosquitos, not the marshes, that wereprimarily involved. But centuries passed before this hypothesis was proved"(P. 14).A confirmation bias is the psychological (as opposed to logical) tendency to

see only positive instances of a theory or hypothesis and ignore negativeinstances, experiences or experiments. Confirmation bias is obvious in thestudent activities provided in textbooks. All the texts examined present theiractivities in a particular, common pattern. First a problem is stated or aquestion asked. Then the aim(s) of the investigation, the student objectives, orthe purpose(s) are stated. Then follows a list of materials and the procedures.At the end are questions about the results which guide students to theintended conclusions. This cookbook method is repeated in text after text andthe hidden lesson is that right answers are reached by this procedure, that is,straightforward induction. For example, in Pasachoff, Pasachoff, and Cooney(1983), a physical science text, an activity entitled "Doing Physical Science" isintended as "practice using the scientific method" (p. 11). Students test theeffect of various concentrations of salt on the boiling point of water. Underthe section titled "Analysis," the student is asked, "What conclusion can youdraw from this experiment? Explain why you think it is correct" (p. 11). As iscommon to activities in science texts, premises aren’t listed or discussed andthe results are assumed to confirm the hypothesis or predictions, withoutquestion.German (1986) cites confirmation bias in students* testing of hypotheses as

a finding in a number of excellent empirical studies including some of hisown. Elliott and Nagel (1987) examined nine major newly publishedelementary school science series and found, in all cases, the texts emphasized"carrying out cookbook-style hands-on activities with predetermined results"(p. 9). The tacit teaching of the fallacy of affirming the consequent, althoughperhaps not the cause of confirmation bias, nevertheless may contribute tosustaining it. A conjecture: The bias should be stronger among students in thelater grades and among those specializing in the pre-college sciencecurriculum. This conjecture is worth considering and, of course, falsifying.

The Logic of Falsification

As it turns out, the logical pattern followed in carrying out the confirmationof a theory or hypothesis involves committing a logical fallacy. This is a veryimportant point because insofar as most science teachers teach the logic ofconfirmation without question they are tacitly fostering bad forms ofreasoning in their students (it is ironic that science educators often seem to



emphasize the relation between science and mathematics and yet ignore therelation between science and the even more fundamental discipline of logic).The first to fully appreciate the intractability of the problem of induction

and reject verificationism altogether was Sir Karl Popper. Summarizing hisown position, Popper (1968) states that "the criterion of the scientific statusof a theory is its falsifiability, or refutability, or testability" (p. 39). Hecontends that, "There is neither a psychological nor a logical induction. Onlythe falsity of the theory can be inferred from empirical evidence, and thisinference is a purely deductive one" (pp. 54-55). Formal logic certainlysupports his claim. Consider the following logical schema for refutation:

PITP^not E

Cnot T

E If T is true, we will see E

We do not see E_____Therefore, T is not true.

Unlike the schema for confirmation, this form of deductive reasoning,known as modus tollens, is logically valid. Summing up, Popper declares ineffect that all reasoning is either deductive or defective and that the growth ofscience consists of a continuing series of conjectures and refutations. Popper(1968) writes: ". . . there is no more rational procedure than the method oftrial and error�of conjecture and refutation: of boldly proposing theories; oftrying our best to show that these are erroneous; and of accepting themtentatively if our critical efforts are unsuccessful" (p. 51). In his GeneralTheory of Relativity in 1915, Einstein predicted light would be deflected whenit came near massive objects, like stars. This phenomenon could not bepredicted from Newton’s theory of gravity. The scientific community rapidlyaccepted Einstein’s theory over Newton’s when, in 1919, Arthur Eddingtonreported that light from a distant star was seen to bend, as predicted, aroundthe sun. General Relativity has met every experimental test to which it hasbeen subjected to this date. Thus it seems that the method of conjectures andrefutations secures the growth of science upon the firmest of logicalfoundations.The place of Popper’s concept of falsification in science and science

education is an issue discussed by German (1986) who in turn relies onAbimbola (1983). Their discussion is accurate, though abbreviated. Neitherfully acknowledges the fact that Popper entirely rejects the scientific methodof confirmation, that is, the method of induction. For example. Popper wouldnever agree with German’s (1986) statement that it is possible for "students todiscover the value of falsification inductively" (p. 320). Note, this does notmean that German is necessarily wrong to make such a statement, rather thatthere may be difficulties with Popper’s position, which will be consideredlater. Regardless, Popper has a powerful logical principle to call on in supportof his position. The implications of this for science education are, first, that inteaching scientific processes, teachers should provide opportunities forstudents to design, implement, and critique their own investigations.



Important objectives would be that students (a) experience creatingknowledge, (b) logically critique their work, and (c) judge the credibility ofconclusions. For secondary students, perhaps the most important purpose ofscience investigations and experiments would be that students understand thereasoning process underlying what is described as the scientific method so thatthey know why scientific knowledge is tentative, that deduction only is to betrusted in science, and that science progresses by conjectures and refutations.The thinking required of students to learn the above is not natural, that is,

the type of logic involved here is not likely to be learned or appreciatedspontaneously from experience without assistance. It is important, therefore,that teachers guide students in discussing and analyzing their labs andactivities. Students can learn also from guided study of cases in the history ofscience.

Some Complexities and Shortcomingsin the Logic of Falsification

But it is not quite that simple. The logical paradise constructed by Popper isnot perfect. It was Lakatos (1970), a student of Popper’s, who among othersand most prominently called attention to the shortcomings of what he calleddogmatic falsification, that is, the idea that an entire theory could be refutedby one contrary hard fact. Lakatos recognized that a theory is internallycomplex, a conjunction of statements. A theory comprised of n number ofstatements could be written as T = (Sl and S2 and . . . Sn). Now consider asimple logical equivalence known as De Morgan’s law. This law says that thelogical expression [not (A and B)] is logically equivalent (written =) to (not Aor not B). Review again the schema of refutation:

PI (Sl and S2 and. . .Sn) -> E

PS not E___________________C not (Sl and S2 and . . . Sn)

Now, rewriting this to use De Morgan’s law,

PI (Sl and S2 and. . ,Sn) -> E

P^ not E___________________C not Sl or not S2 . . . or not Sn

The point of all this logic is that no single experiment or set of experiments,crucial or otherwise, refutes an entire theory, but only one or a fewinterrelated statements, quite possibly leaving the core of the theory intact.This situation is known as the underdetermination of theory by logic. Thisbasic schema may deflect a refutation away from what Lakatos called basicstatements, or core assumptions, that is, those statements especially cherished



by the research tradition. Hence creationists are frustrated in their attempts torefute the theory of evolution though they can cite instances of contrary facts.The core of the theory remains intact despite gaps, instances of circularreasoning, and other imperfections.

Lakatos* response to the underdetermination of theory by logic is to saythat any ad hoc adjustment to a theory made to preserve certain basicstatements must not only account for the refuting phenomena, but additionalphenomena as well. In Lakatos’ (1970) own words, "A given fact is explainedscientifically only if a new fact is also explained with it" (p. 119).Theory is not only underdetermined by logic, it is also underdetermined by

experience, or experiment. One way of expressing this underdetermination isto say that given any finite body of data, there are an infinite number oftheories that could account for the body. Consider the followingoversimplified example. Suppose we are given some imaginary collection ofdata relating an independent variable X and a dependent variable Y. Let thetheory accounting for this data be comprised of a single statement: amathematical function that fits all the data points (observations) in Figure 1.The reader is probably thinking the choice must be a linear equation (y =

mx + b), yet an infinite number of equations could be constructed to fit thesame points. In the present case, the choice of equations probably would becompelled by aesthetic considerations, a preference for elegance andsimplicity, but what if the data have been plotted in polar coordinates instead?Should the theory choice be relative to the background framework in thisway? Is it? These complex and difficult issues cannot be taken up here, muchless decided.The difficulties engendered by the underdetermination of theory by logic

and experience combine to yield what has come to be called a holistic view ofscience. Quine (1981) has described this view as follows:

. . . total science is like a field of force whose boundary conditions areexperience. A conflict with experience at the periphery occasionsreadjustments in the interior of the field. Truth values have to beredistributed over some of our statements. Reevaluation of somestatements entails reevaluation of others, because of their logicalinterconnections. . . . Having reevaluated one statement we mustreevaluate some others which may be statements logically connected withthe first. . . . But the total field is so underdetermined by its boundaryconditions, experience, that there is much latitude of choice as to whatstatements to reevaluate in the light of any single contrary experience. Noparticular experiences are linked with any particular statements in theinterior of the field, except indirectly through considerations ofequilibrium affecting the field as a whole, (pp. 42-43)


Teaching Scientific Method

Figure 1. An imaginary plot of data.

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To the challenges offered by underdetermination and holism could be addedthe difficulties of theory-ladenness and incommensurability. The idea oftheory-ladenness, a term attributed to Hanson (1958), is that all experience is,at least in part, dependent on the conceptual structure of theories. It isthrough theory that meaning is created from observations. Thus theobjectivity of experience is questionable; there are no hard facts. The notionof incommensurability of theories was popularized by Kuhn (1962). It means,as the phrase itself indicates, that no common measure, either empirical orlogical, can be found between two (or more) competing theories. These aredifficult ideas and cannot be fully explicated here. Moreover, all thesechallenges to strict falsificationism remain more or less controversial.What is the science teacher to do with all this? These are certainly complex

issues and far from being settled even within the community of philosophers



of science. Nevertheless, science teachers ought to be aware of these issuessince they are fundamental to understanding the nature of science, and since amajor goal of the curriculum is that students will understand the nature ofscience. In planning every class, science teachers have to make choicesconcerning the content to be taught and the activities and teaching methods to

be used. The content and methods of instruction ought to reflect accuratelythe nature of science and certainly should not promote fallacious forms ofreasoning, such as inductionist verificationism. An understanding of the issuesand principles that are at the core of the enterprise of science should helpteachers make wiser choices in these matters. This is a frontier area in scienceeducation, requiring much more research and reflection.The problematic principles and unresolved issues in the philosophy of

science also must be acknowledged by those who would advocatepostpositivistic philosophy of science as providing guidance to sciencecurriculum and instruction. If the philosophy of science is to become afoundation of science education, a course in the philosophy of science oughtto be required of all college science majors and pre-service science teachers. Asfor practicing science teachers, Abimbola’s (1983) recommendation, thatamong other things, they "should be encouraged to take summer courses inthe philosophy and history of science through provision of funds for thispurpose," seems to be on target. Teachers will need help in examining howpositivistic concepts are communicated through their courses and in adoptingwhatever new content and instructional practices are necessary to moreaccurately represent the nature of science in the curriculum. Without somedirect attempt at translation into practice, this information will not be usefulto science educators. If the history and philosophy of science are to take theirproper place in science education, a major effort must be made to introducesuch a perspective in both the inservice and preservice teacher educationcurriculum.

In any event, science education is not likely to proceed into a second goldenera without a more adequate foundation. Whatever foundation we choosewould require and deserve a major commitment and role in science teachereducation.

References

Abimbola, 1. 0. (1983). The relevance of the "new" philosophy of science forthe science curriculum. School Science and Mathematics, 83(3), 181-193.

Appenbrink, D., Hounshell, P. B., Halper-SIote, S., & Smith, 0. (1981).Physical science. Englewood Cliffs, NJ: Prentice-Hall, Inc.

Biological Sciences Curriculum Study. (1973). Biological science: An inquiryinto life (3rd ed.). Boulder, CO: Author.

Donmoyer, R. (1985). The rescue from relativism: Two failed attempts and analternative strategy. Educational Researcher, 14(10), 13-20.

Duschi, R. A. (1985). Science education and philosophy of science:



Twenty-five years of mutually exclusive development. School Science andMathematics, 85(1), 541-555.

Elliott, D. L., & Nagel, K. C. (1987). School science and the pursuit ofknowledge�deadends and all. Science and Children, 2^(8), 9-12.

Garrison, J. W. (1986). Some principles of postpositivistic philosophy ofscience. Educational Researcher, 15, 12-18.

German, M. E. (1986). Falsification in experimental and classroomsimulations. School Science and Mathematics, 86(4), 306-321.

Hanson, N. R. (1958). Patterns of discovery. Cambridge, England: CambridgeUniversity Press.

Howe, K. R. (1985). Two dogmas of educational research. EducationalResearcher, 7^(8). 10-18.

Kuhn, T. (1962). The structure of scientific revolutions. Chicago,IL: University of Chicago Press.

Lakatos, I. (1970). Falsification and the methodology of scientific researchprogrammes. In I. Lakatos & A. Musgrove (Eds.), Criticism and the growthof knowledge (pp. 91-196). Cambridge, England: Cambridge UniversityPress.

Lederman, N. G. (1986). Students’ and teachers’ understanding of the natureof science: A reassessment. School Science and Mathematics, 86(2), 96-99.

Macmillan, C. J. B., & Garrison, J. W. (1984). Using the "new philosophy ofscience" in criticizing current research traditions in education. EducationalResearcher, 75(10), 15-21.

Moyer, R., & Bishop, J. (1986). General science. Columbus, OH: Charles E.Merrill Publishing Company.

National Science Teachers Association. (1982). Science Technology andSociety: Science Education for the 1980s. Washington, DC: Author.

Pasachoff, J. M., Pasachoff, N., & Cooney, T. M. (1983). Physical science.Glenview, IL: Scott, Foresman and Company.

Phillips, D. C. (1983). After the wake: Postpositivistic educational thought.Educational Researcher, 72(5), 4-12.

Popper, K. R. (1968). Conjectures and refutations in the growth of scientificknowledge. New York: Harper Torchbooks.

Quine, W. V. 0. (1961). Two dogmas of empiricism. In From a logical point

of view (2nd ed.) (pp. 20-488). Cambridge, MA: Harvard University Press.Smoot, R. C., Price, J. S., & Smith, R. G. (1983). Chemistry: A modern

course. Columbus, OH: Charles E. Merrill Publishing Company.Tuthill, D., & Ashton, P. (1983). Improving educational research through the

development of educational paradigms. Educational Researcher, 72(10),6-14.

Williams, J. E., Trinklein, F. E., & Metcaife, H. C. (1984). Modem physics.New York: Holt, Rinehart and Winston, Publishers.


teaching scientific method: the logic of confirmation and falsification

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