Critical Thinking in the Chemistry Classroom and ... - ACS Publications

Research: Science and Education edited by

Chemical Education Research

Diane M. Bunce The Catholic University of America Washington, D.C. 20064

Critical Thinking in the Chemistry Classroom and Beyond

Amy J. Phelps Middle Tennessee State University Murfreesboro, TN 37132

Claus Jacob School of Biological and Chemical Sciences, University of Exeter, Stocker Road, Exeter EX4 4QD, United Kingdom; [email protected]

The philosophy–chemistry interface is not an obvious area of teaching or research, and teaching philosophy in chemistry might only be interesting to chemists if it can convey valuable knowledge that exceeds what chemists already know by experience or common sense. There is, however, plenty of room for philosophy in chemistry. One might even argue that philosophy is an essential, although “hidden” part of chemistry. Epistemology lays the foundations of chemistry as a science and philosophy teaches the kind of “critical thinking” that chemists greatly value (1). Ethics allows chemists to decide between acceptable and unacceptable experiments. More importantly, every single argument made in chemistry (the interpretation, discussion of results, conclusions drawn) has a correct or, indeed, incorrect logical structure that can be formalized and assessed in a systematic way (2). Although chemistry has many potential interfaces with philosophy, some of them might not be apparent at first. The recent introduction of two new philosophy of chemistry journals, Foundations of Chemistry and HYLE, provides this interface with its own literature (3–7). Based on these, and similar publications, it is now possible to teach philosophical topics to undergraduate chemistry students. As of July 2003, a total of eight undergraduate modules in Philosophy of Chemistry are registered on the HYLE Web site (8) covering a range of chemistry-specific philosophical topics. In 1999 the School of Chemistry at the University of Exeter introduced a new module, “History and Philosophy of Chemistry”, for second- and third-year chemistry undergraduate students. Participation in this module is voluntary as students choose six modules from a list of eight modules to participate in. During the last two years this module was attended by a considerable number of students: 38 in 2001– 2002 and 18 in 2002–2003. This provided the opportunity to study students’ ability to critically assess chemical texts before and after being exposed to basic concepts of logical statement analysis. The module in question consisted of 11 one-hour lectures and addressed basic epistemological, ethical, and logical issues in chemistry. After an introduction to the less common interfaces of chemistry, such as history of chemistry, chemistry and law, chemistry and ethics, the module briefly focused on historical aspects of chemistry and then on philosophical concepts directly relevant to chemistry. Students learned the difference between induction and deduction, discussed verification versus falsification, looked at the hallmarks of scientific theory (e.g., falsifiability, coherence, consistence), considered reduction of chemistry to physics, and were exposed to Lakatos’s ideas of negative and positive 1216

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heuristic shifts. Relevant issues from the emerging field of chemoethics, such as responsibility for new compounds, were discussed. Two lectures focused on the logical aspects of reasoning in chemical statements. In contrast to conventional chemistry teaching, the focus was shifted from “experience” in discussing the validity of chemical statements containing reasoning to a systematic, scientific analysis based on the rules of formal logic. At the beginning of the module most students were unable to recognize logical structures of underlying chemical reasoning or to determine the validity of simple rules of inference. In contrast, the majority of students exposed to the most basic concepts of logic were then able to correctly describe the underlying logical structure and validity of chemical reasoning in simple statements. Furthermore, these students greatly valued learning basic philosophical concepts. This article investigates the feasibility and practical use of teaching philosophy-based critical thinking to undergraduate chemistry students. First, we provide compelling empirical evidence that the frequently cited “common sense” of chemists to decide between well-supported and speculative conclusions is not sufficient in practice. We then describe our approach to teach basic aspects of logic to create a knowledge base that students could use to connect further reflective knowledge. We also report the successful outcome of teaching basic logical concepts in chemistry, as measured by students’ ability to assess the validity of chemical reasoning on one hand and student satisfaction on the other. The final section of this article gives an outlook at teaching selected philosophical concepts as part of the chemistry undergraduate curriculum. Logical Analysis and Common Sense

Questionnaire The first step in teaching logical statement analysis to second- and third-year undergraduate chemistry students at the University of Exeter was a brief empirical evaluation of “common sense” among the 38 chemistry students attending the module “History and Philosophy of Chemistry”. Since philosophy is rarely taught as part of the chemistry undergraduate curriculum in the United Kingdom, these students had learned how to make correct statements (e.g., about a process, a reaction, biological relevance) implicitly, through gaining experience in laboratories, reading literature, and studying chemistry textbooks. At this stage, they had no prior

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Research: Science and Education

exposure to systematic logical analysis. This provided us with a “reference sample” of 38 undergraduate chemistry students. If some experience with chemistry and common sense were all it took to implicitly understand chemical reasoning, these students should be able to distinguish between logically correct and logically incorrect arguments. In addition, more advanced students should have more experience and hence score higher in such an assessment exercise. During the first lecture the 38 undergraduate chemistry students were presented with a questionnaire (Figure 1) that contained six statements with chemical content each of which was carefully based on either simple logical inference rules or classical logical fallacies (9). Students were asked to mark chemical laws, experimental observations, and conclusions and then to assess whether the conclusions drawn were logically valid, possible, or invalid.1 They were given 25 minutes to complete the assignment. Student answers were then collected by the instructor for evaluation. Interestingly, similar chemical statements, for example about deducing the presence of transition metals by observing their color in specific solutions of unknown composition,

are used by Hodges in his introduction to logic to illustrate “testing for consistency and validity” of arguments (10). This task also resembles the kind of reasoning students employ in laboratory classes to interpret experimental results. Such assessments are therefore important in chemical teaching and research: whenever project reports are written or marked, research proposals ranked, and manuscripts for publication reviewed, the question of valid, speculative, and invalid arguments arises in addition to issues regarding the reliability of empirical data. The content of the questionnaire statements was chosen to be appropriate for second- and third-year undergraduate students to rule out lack of factual knowledge as an underlying cause for incorrect answers. All examples were taken from the undergraduate teaching program and the statements were thoroughly scrutinized by several members of staff before their final version was chosen. In addition, the categories “valid”, “possible”, and “invalid” were also chosen after detailed discussions with other members of staff and postgraduate students to obtain the least biased answers at this stage.

The following six scientific statements contain conclusions based on general laws (or theories or rules) and specific experimental observations. In each of the statements, mark or underline (i) the chemical law, (ii) the experimental observation, and (iii) the conclusion drawn. Decide which of the conclusions strictly follow from the law and observation (“valid”), which might follow from the law and observation (“possible”), or which conflict with the law and observation (“invalid”). Briefly explain your choice (one to two sentences for each) on the back of the page. (1) Reduction of blue copper proteins leads to changes in the UV–vis absorption spectra of these proteins. The reaction of the blue copper protein ceruloplasmin with sulfite in the presence of EDTA leads to a dramatic change in its UV–vis spectrum indicating that sulfite is an excellent reducing agent for ceruloplasmin. Conclusion is (circle one): valid possible invalid (2) Atomic explosions on the earth’s surface generate radioactive fallout. There can be no doubt that a surface nuclear test explosion would increase the concentration of radioactive particles in the atmosphere. Conclusion is (circle one): valid possible invalid

(3) Silver nitrate has been added to a solution of a sodium halide solution and a yellow precipitate has been observed. We know that addition of silver nitrate to a sodium chloride solution leads to a white precipitate. The sodium halide solution in question cannot have been sodium chloride. Conclusion is (circle one): valid possible invalid

(4) Electrolysis of aqueous sodium chloride solutions leads to the generation of hydrogen at the cathode and chlorine at the anode. During power failure, electrolysis does not occur and therefore it is expected that chlorine gas is not observed at the anode. Conclusion is (circle one): valid possible invalid

(5) When glutathione disulfide is oxidized with hydrogen peroxide no sulfonic acids are produced. In general, oxidation of disulfides always leads to the formation of disulfide-S-oxides or sulfonic acids. Therefore disulfide-S-oxides are not produced either. Conclusion is (circle one): valid possible invalid

(6) Combustion of phenols leads to the formation of highly carcinogenic substances while combustion of alkanes results in the formation of poisonous carbon monoxide. Modern car fuels contain either high concentrations of phenols or large quantities of alkanes. Their combustion will therefore necessarily lead to carcinogens or carbon monoxide. Conclusion is (circle one): valid possible invalid Figure 1. Student questionnaire used to assess logical analysis. Students were allowed 25 min to complete the questionnaire.

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Board Exercise An exercise was then presented to the students that did not require the recognition of a particular logical structure in a statement. Incomplete horseshoe notations of the underlying rules of inference (i.e., the premises2) were written on the board and students were asked to make suggestions for conclusions that would complete the schemes, that is, determine the correct conclusions (consequents) of each rule. Students were free to suggest any answer. The latter was written on the board and a show of hands was then taken to see how many students supported each answer.

Discussion Without explicitly using logic, how well did these students do on the questionnaire? The results for the analysis, and evaluation of the six chemical statements, are given in Table 1. In total, only about half of all answers were correct (57%) with virtually no difference between second- and third-year students. There were, however, dramatic differences between the scores for each statement. Students did best in assessing statement 3 (84% correct answers). This statement follows the structure of the Modus Tollens (M.T.) and was based on first-year laboratory experiments. Both second- and third-year cohorts also did relatively well for statement 5 (61%) hence grasping the underlying structure of a Disjunctive Syllogism (D.S.). Students, however, did poorly in evaluating statement 2 that is based on a Modus Ponens (M.P.). Only 42% considered this as a valid conclusion. On the other hand, most of the students thought the conclusion in statement 4 was valid, hence committing the “fallacy of denying the antecedent” (only 47% correct). A low score was also obtained for statements 1 and 6 (53% correct) where almost half of the students did not recognize the “fallacy of affirming the consequent” (statement 1) and the validity of a “Constructive Dilemma” (C.D.).3 While it might be possible that some students did not fully understand the content of some of the statements, such an explanation for the low scores can be rejected by the fact

that many students were unable to even distinguish between law, observation, and conclusion in these statements (last column in Table 1). In addition, we can rule out difficulties with formal logic as cause of low scores, since students were not required to use tools such as the horseshoe notation for this initial task. A high percentage of “nil returns” (32% of students assessed validity but did not mark laws, experimental observations, or conclusions, although they were explicitly asked to do both) and similar scores in the assessment of the statement on the one hand and correct identification of law, experimental observations, and conclusion on the other could indicate that a large number of students were not able to analyze and assess the logical form of the statements at hand and mainly relied on common sense when deciding whether a conclusion is valid, possible, or invalid. This interpretation is supported by the numerous comments made by students that give insight into the reasoning behind their answers. Again, comments such as “All of the statements can be interpreted in many different ways. Therefore this is my personal interpretation.” (third-year student) or “seems reasonable” (third-year student) indicate that students were unable to relate general theories, observations, and conclusions in a systematic manner; that is, they were not able to use the underlying logical structure of the statements to decide whether the arguments were valid, possible, or invalid. When asked, most students actually admitted that they based their decisions on “what looked right” or “seemed to be good chemistry”, comments that might indicate an even wider problem reaching well beyond the understanding of the structure of chemical reasoning. There was also little improvement when the more advanced third-year students, who were already actively involved in research projects, were compared with the less experienced second-year students. Amazingly, the more advanced students did even worse for statements 2, 4, and 6, with only 31% of them understanding the Constructive Dilemma in statement 6. The clear absence of any improvement from year two to three also counts against the idea that chemical knowledge alone could be at the root of the low scores obtained.

Table 1. Analysis of Student Responses to Chemical Statements Correct Conclusion Statement

Correct Answer

1

p (Fallacy 1)

a

Total Students (% out of 38)

Second-Year Students (% out of 22)

Third-Year Students (% out of 16)

Students with Correct Assignmentb (% out of 38)

52.6

45.5

62.5

55.3 (50.0/62.5)c

2

v (M.P.)

42.1

45.5

37.5

28.9 (27.3/31.3)

3

v (M.T.)

84.2

81.8

87.5

57.9 (59.1/56.3)

4

p (Fallacy 2)

47.4

50.0

43.8

42.1 (45.5/37.5)

5

iv (D.S.)

60.5

54.5

68.8

42.1 (31.8/56.3)

6

v (C.D.)

52.6

68.2

31.3

50.0 (40.1/62.5)

---

56.6

57.6

55.2

46.1 (42.4/51.0)

total

a v = valid, p = possible, iv = invalid; M.P. = Modus Ponens, M.T. = Modus Tollens, D.S. = Disjunctive Syllogism, C.D. = Constructive Dilemma, Fallacy 1 = Fallacy of confirming the consequent, Fallacy 2 = Fallacy of denying the antecedent. b c

The percentage of correct assignments of laws, orbservations, and conclusions. A total of 32% of the students did not make these assignments.

The percentage of correct assignments is given for second- and third-year results, respectively, in the brackets.

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The apparent difficulty with recognizing the logical structure of simple chemical statements seems not to be the only cause of students’ mistakes. The second exercise, whose results are shown in Table 2, indicates that students could not derive the rules of inference.4 Apart from the Constructive Dilemma (statement 6), poor performance in the assessment of the chemical statements (Table 1) was associated with difficulties in completing the inference rules (Table 2). This was particularly obvious in the case of the two fallacies, where ∼40% of students thought they could use these fallacies to deduce the conclusions from the premises. Similarly, just 26% of students used the Modus Ponens correctly. The second, more abstract exercise also eliminated possible doubts that the content of statements might have led students to give wrong answers in the questionnaire. The failure of students’ common sense that is apparent in Table 2 has nothing to do with the content of such statements. It is due to an apparent weakness in logical thinking that is also likely to be at the root of the corresponding results presented in Table 1. While considerably more complex studies would obviously be required to evaluate the knowledge and actual use of logic among chemistry students, these simple studies should be sufficient to demonstrate several important points. Firstly, common sense or implicit familiarity is not sufficient to grasp logical inference rules. Such philosophical thoughts are not trivial or somehow inherent in conventional chemical education or practice. Since they form the basis of our

deductive thinking in all realms, including chemistry, mastery and good use of these rules, even implicitly, is essential for chemistry students. Unlike physicists, chemists cannot exclusively rely on mathematical models to determine validity. The validity of many chemical statements is based on empirical data and logically drawn conclusions. The Modus Tollens, for example, is frequently used to rationalize “negative controls”, the Modus Ponens is employed to predict experimental outcomes, and the Disjunctive Syllogism is important to indirectly assign an effect to one of two (or more) entities by ruling out the other(s). Secondly, some of the chemists in question seem to have grave difficulties recognizing a logical structure of a statement. This task might be even more difficult than actually using the inference rules. With the exception of one statement (statement 3), less than half, and in one case less than a third of students were able to recognize the structure of the statements (Table 2). This has serious implications since there is a highly important epistemological as well as logical difference between an (experimental) premise and a “deduced” or even speculative conclusion: experimental premises are based on “data” while conclusions are inferences from these premises. Thirdly, although students steadily improve their factual chemical knowledge from year two to three this progress in itself does not seem to lead to improved linguistic or logical skills. A significant number of final-year students were ini-

Table 2. Results of Handling of Inference Rules by Students Statement 1

2

3

4

5

6

Premises

Explanation

Correct Answer

Inference Rulea

Concl. 1b

Concl. 2

Concl. 3

Ac

Abstain

S⊃P

S implies P

none

Fallacy 1

S

~S

---

---

---

P

P observed

(fallacy)

42%

37%

---

5%

16%

S⊃P

S implies P

P observed

Pd

---

---

---

---

S

S present

(P)

26%

---

---

26%

47%

M.P.

S⊃P

S implies P

S not present

~P

P not observed

(~S)

S⊃P

S implies P

none

~S

S not present

(fallacy) Q present

M.T.

Fallacy 2

D.S.

~S

---

---

---

---

75%

---

---

25%

0%

~P

P

---

---

---

40%

20%

---

40%

0%

Q

~Q

---

---

---

64%

4%

---

16%

16%

P⵪Q

P or Q present

~P

P not present

P⊃Q

P implies Q

Q or S observed C.D.

Q⵪S

Q⵩S

Q

---

---

R⊃S

R implies S

(Q ⵪ S)

72%

24%

4%

0%

0%

P⵪R

P or R present

a

M.P. = Modus Ponens, M.T. = Modus Tollens, D.S. = Disjunctive Syllogism, C.D. = Constructive Dilemma, Fallacy 1 = Fallacy of confirming the consequent, and Fallacy 2 = Fallacy of denying the antecedent. b

The sample size was 38 students. Students’ suggestions for conclusions are given with percentage of students believing this to be the correct answer.

c d

“A” was a conclusion, based on the premises, that did not fit into conclusions 1, 2, or 3.

The correct answer is given in bold.

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tially unable to explicitly analyze or evaluate the reasoning behind chemical statements—and this just a couple of months before they are expected to engage in cutting-edge research. Therefore there can be little doubt that value can be added to the training of chemistry students by teaching the use of basic concepts of logic as part of a “critical thinking” module. We will now show how basic concepts of critical thinking can be taught as part of the chemistry curriculum and what impact this might have on students’ reasoning— and perhaps also the quality of chemical education provided in the United Kingdom and elsewhere. Constructing a Philosophy–Chemistry Interface in Student-Centered Learning

Need for Critical Thinking Exercise Although there is an evident need to teach critical thinking as part of the undergraduate chemistry curriculum, this task is far from trivial. Philosophical disciplines such as epistemology, ethics, and logic use extra-chemical concepts. The constructivist model of student learning (11, 12) assumes that knowledge is constructed in a social context that includes a number of different learning situations (e.g., student–instructor interactions, exposure to conflict situations and discrepant events). Constructive explanations are frequently based on an “information-processing model” (13). Importantly, these models do not allow all new information to be incorporated into students’ knowledge but rather filter new events, observations, and instructions through a pre-set, although flexible, “perception filter” that allows students to relate new impressions to pre-existing knowledge, to use analogies, and to build concept maps. Therefore it remains unclear how “philosophical” knowledge that is not directly related to pre-existing chemical or everyday concepts could be connected with students’ previously acquired understandings. While philosophy students slowly learn the basics of their subject, a lengthy introduction to philosophy obviously cannot be added to the chemistry curriculum because of time constraints. Moreover, since the selected philosophical concepts to be taught have little in common with other parts of the curriculum, chemistry students naturally find it difficult to integrate this kind of thinking into their wider conceptual context. Nevertheless, it is possible to use applied examples from chemistry rather than other sciences [see the Byerly (9) and Hodges (10) examples] and also to fall back on students’ common knowledge acquired independently of chemistry lectures. During the course of the module “History and Philosophy of Chemistry” it was therefore necessary to define reasonable learning outcomes first and only then to develop the educational strategy.5 At the logic–chemistry interface educational goals were defined along the lines of a method for statement analysis that should, in theory, enable a systematic and comprehensible assessment of statements (2, 14–17): students should learn to methodically assess aspects of chemical reasoning, primarily in written texts (formal statement analysis). They should recognize the logical structure of simple chemical statements, give their formal structures in horseshoe notation, and decide whether the formal arguments at hand were logically valid or invalid. In doing so, the students 1220


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should understand the differences between the formal, logical aspects of an argument and its content-related, scientific aspects—and to become aware of possible mistakes. While the mastery of “advanced” logical concepts or elaborate formalisms (“philosophical jargon”) was clearly not a learning outcome, it was nevertheless hoped that students would be able to build on this kind of critical thinking in the future.

Presenting Logical Rules of Inference To achieve these learning outcomes, students were provided with a short list of logical rules of inference, which were explained in detail during the lecture using a range of chemistry-specific examples. Learning these rules, including their horseshoe formalism, was an interactive process set in an active-learning situation. First, students were confronted with problems of “chemical reasoning” similar to the ones given in Figure 1: see Table 3 and the ones used by Hodges (10). They were asked to abstract from the context of these statements (e.g., from their previous experience with particular copper, iron, or manganese salts) and focus on “what is said in the statement”. They were then instructed to identify the premises and conclusions, “translate” the statement into the horseshoe formalism and, using the latter, determine the validity of these arguments. In doing so, students also had to decide which rule of inference or fallacy was at the heart of a particular statement. This exercise was repeated several times, until all of the most commonly used rules of inference had been addressed at least once. Students were then confronted with a range of statements similar to the ones shown in Figure 1, again taken from familiar chemical laboratory classes to allow a connection with previous experience and the knowledge just obtained. At this stage students were asked to compare their assessment of the argument structure (“how things are said”) with the actual chemical content of the passage (“what is said”). Students were also encouraged to develop their own example statements for common rules of inference and analyze each other’s statements. Discussion The outcome of such evaluation exercises is rather interesting since it provides insight into students’ reasoning. At the beginning, most students realized that some of the conclusions drawn from the experimental results were merely possible, but not certain. Although some students engaged in discussions about the reliability of the conclusions, most students approached such texts by simple “trial and error”. For example, they discussed “other metals” that could possibly have led to a particular color in solution. Since their analysis focused on content it was severely limited by the chemistry they actually knew. For example, some students were not aware of other “blue ions” in solution and were sure that this must be copper, simply because they had not yet learned about various other metals. In short, students argued to the best of their chemical background knowledge and their approach towards the truth of conclusions was, at least at the beginning, without system or method. During the two lectures, students became more critical of conclusions and began to apply the rules of inference, including some of the horseshoe formalism. Although some students continued to have difficulties in “translating” a given


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Research: Science and Education Table 3. Horseshoe Notation of Selected Rules of Inference Including Two Frequently Committed Fallacies Applied to Examples from Chemistry Horseshoe Representation

Rule of Inference

Example from Chemistry

Modus Ponens (M.P.)

P⊃Q P -------------∴Q

Copper(II) ions are blue in aqueous solution. A given solution of copper(II) sulfate in water is therefore blue.

Modus Tollens (M.T.)

P⊃Q ~Q -------------∴~P

Copper(II) ions are blue in aqueous solution. A given sulfate salt solution is not blue. Hence it is not a copper(II) sulfate solution.

Disjunctive Syllogism (D.S.)

P⵪Q ~P -------------∴Q

A given salt is either copper(II) or iron(II) sulfate. It is not iron(II) sulfate. Therefore it is copper(II) sulfate.

Constructive Dilemma (C.D.)

P⊃Q R⊃S P⵪R -------------∴Q ⵪ S

Copper(II) salts make blue and manganese(VII) salts make purple solutions. A given solution contains either a copper(II) or a manganese(VII) salt. It is therefore either blue or purple.

Hypothetical Syllogism (H.S.)

P⊃Q Q⊃R ______ ∴P ⊃ R

In aqueous solution silver and chloride ions form silver chloride. Silver chloride forms a precipitate. Therefore silver and chloride ions form a precipitate in aqueous solution.

Fallacy of Denying the Antecedent

P⊃Q ~P _____ ∴~Q

Copper(II) ions are blue in aqueous solution. A given aqueous solution of a sulfate salt is not a copper(II) sulfate solution. Hence it is not a blue solution.

Fallacy of Affirming the Consequent

P⊃Q Q _____ ∴P

Copper(II) ions are blue in aqueous solution. A given solution of a sulfate salt is blue. Hence it is a copper(II) sulfate solution.

statement into the correct logical formalism throughout the module, most of them became more systematic and scored higher in the tasks set. It was therefore interesting to issue the questionnaire (Figure 1) to students that had undergone this kind of training, but had not seen the questionnaire before. The following section provides empirical evidence of the student learning achieved as part of this module. Learning Outcomes and Student Evaluation

Questionnaire To quantify the learning experience, the questionnaire shown in Figure 1 was issued to a group of 18 second- and third-year undergraduate chemistry students that had already completed training in basic logical concepts as described in the previous section. These students took the module in 2002– 2003, that is, one year after the original “reference group” of 38 students. The 18 students were not identical with the original students and had not seen the questionnaire before. There www.JCE.DivCHED.org

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was no difference in academic performance between the two cohorts as judged by their first- and second-year marks. The major difference between the two groups was therefore the point at which they were issued the questionnaire, that is, before or after having received the basic training in logical analysis of reasoning in chemical statements.

Discussion The results obtained for the 18 students exposed to critical thinking show a higher number of correct responses than the results from the 38 students who were not exposed to critical thinking prior to completing the questionnaire (Table 4). These results hint at a steep initial learning curve. While students in both groups started with virtually no prior knowledge of logic or the systematic evaluation of arguments, the 18 students exposed to only two lectures of logical thinking had not only become considerably more critical but also began to use logic, rather than common sense, to discuss the validity of statements.


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Table 4. Analysis of Student Responses to the Chemical Statements Using Formal Logica Statement

Correct Answerb

Total of Students with the Correct Conclusion (% out of 18)

Percent of Students with Correct Assignmentd (% out of 18)

Percent of Students Using Horseshoe Formalism As Part of Their Answer (% out of 18)

1

p (Fallacy 1)

83.3 (52.6)c

72.2 (55.3)

77.8

2

v (M.P.)

83.3 (42.1)

61.1 (28.9)

77.8

3

v (M.T.)

94.4 (84.2)

61.1 (57.9)

83.3

4

p (Fallacy 2)

61.1 (47.4)

61.1 (42.1)

83.3

5

iv (D.S.)

83.3 (60.5)

50.0 (42.1)

33.3

6

v (C.D.)

77.8 (52.6)

50.0 (50.0)

55.6

---

80.6 (56.6)

59.3 (46.1)

68.5

total a

Students received 2 lectures in logical analysis as part of the module “History and Philosophy of Chemistry” prior to answering the questionnaire.

b

v = valid, p = possible, iv = invalid; M.P. = Modus Ponens, M.T. = Modus Tollens, D.S. = Disjunctive Syllogism, C.D. = Constructive Dilemma, Fallacy 1 = Fallacy of confirming the consequent, and Fallacy 2 = Fallacy of denying the antecedent. c

Results in brackets for the 38 students questioned before training are given for comparison.

d

The percentage of correct assignments of laws, orbservations, and conclusions. Results in brackets for the 38 students questioned before training are given for comparison.

Comparison of the performance of the two student cohorts indicates the following major differences. Overall, the 18 chemistry students with basic training in logical evaluation of reasoning scored considerably higher in the questionnaire (80.6% correct answers versus 56.6% for students not exposed to concepts of explicit logical thinking), in some cases almost twice as high (statement 2). In addition, there was evidence that students also began to recognize the more common logical rules of inference in simple statements (the percentage of students with correct assignment increased overall and more than doubled for statement 2). Using the horseshoe formalism, students were now able to systematically assess the statements, firmly decide on the logical validity of conclusions, and, equally importantly, communicate the reasons for such decisions. Amazingly, more than two-thirds of the students familiar with the horseshoe formalism (68.5%) made good use of it—although they were not specifically instructed to do so. As a consequence, most students recognized the benefits of this formalism and used it for the task at hand. The group of 38 students not previously exposed to the horseshoe formalism were, of course, unable to use it— with clear implications for the correctness of their answers (Tables 1 and 4). Moreover, students had clearly become more critical of the statements at hand. They were very careful to decide on the validity of arguments and spent considerable time and effort in analyzing the statement before making their decision. This is hardly surprising, of course, since students had been exposed to the problem of invalid arguments and the rules of inference during the lectures. Nevertheless, this kind of “problem awareness” among students can be considered as a major learning outcome successfully achieved during this module.

Evaluation by Students While teaching basic logic clearly led to an improvement in students’ ability to critically evaluate the reasoning behind statements, the question of the wider benefits of teaching this 1222


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kind of critical thinking as part of the chemistry undergraduate curriculum remained. We therefore decided to put this issue, occasionally also raised by other professional chemists, to the 18 chemistry students attending the module. While a detailed discussion of the module’s student evaluation would be too time consuming, a few major points can be made. During the last lecture of the module, the 18 students were presented with a two-page evaluation form that contained a range of statements and asked, on a scale from 1 to 10, whether they agreed (strongly agree is 10) or disagreed (strongly disagree is 1) with these statements. Student answers were collected anonymously at the end of the lecture and scores were averaged for each question. Students agreed that “Critical thinking is an important part of my undergraduate education that complements other topics of chemistry education” (average 7.0兾10) and also agreed that “The topics addressed here are not directly covered in any other parts of our chemistry curriculum” (8.5兾10). This clearly contradicts assumptions that students taking a conventional U.K. chemistry curriculum “somehow” learn this kind of systematic critical thinking during mathematics or laboratory classes. Interestingly, students strongly disagreed with the idea that “The philosophy of chemistry would be better taught in the laboratory than the lecture theater” (2.6兾10). Students also appreciated that “The use of logical formalism has made it easier to understand the structure of arguments” (7.5兾10). This does not, of course, imply that students must learn logical formalism to be able to think critically. Nevertheless, concepts such as the horseshoe notation to analyze the validity of arguments seem to have provided a valuable tool to these students rather than just “philosophical jargon”. This is in agreement with the extensive use of this formalism by the 18 students as described above. Interestingly, students also appreciated lectures on critical thinking for other reasons. They agreed, for example, that “The opportunity to look at science, in particular chemistry, from a different perspective is beneficial” (7.7兾10). Occasionally taking a different perspective and developing a more


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critical attitude towards one’s subject area is also desirable from an academic point of view. Being critical of chemistry does not mean rejecting it. Quite the opposite, it might actually provide the basis for more fruitful discussions among chemists and nonchemists about chemistry, ultimately enabling chemists to better define and defend their science in public. Conclusions Critical thinking is not only an important aspect of chemistry itself, it is also becoming an increasingly important transferable skill students are expected to have mastered during their time at university. While chemistry actually provides an almost ideal opportunity for critical reflection owing to its many interfaces with epistemology, logic, ethics, and even aesthetics, most chemistry departments, at least in the United Kingdom, do not fully exploit these opportunities to advance critical thinking inside chemistry (e.g., statement analysis) and in the wider social context. While the studies undertaken at University of Exeter show the need for such thinking inside chemistry, they also provide an early outline of the possible learning goals and methods that could be incorporated into teaching aspects of philosophy as part of the chemistry curriculum. At this stage, teaching philosophy in chemistry clearly is in its infancy and these studies should be seen in this context: lecturers and students have to manage without a textbook; most examples from the theory of science relate to physics and astronomy rather than chemistry; and a universal curriculum for these programs does not yet exist.6 De facto, the Philosophy of Chemistry modules at universities are taught by very able and enthusiastic chemists and philosophers, but without the appropriate teaching support normally available to university teachers. It can only be hoped that this situation will improve in the near future. Another aspect of teaching this subject—restructuring of conventional chemistry curricula—will also have to be addressed. Although introducing the “History and Philosophy of Chemistry” module at the University of Exeter as an option meant to remove other topics from the chemistry curriculum of some students, this was not to the students’ disadvantage. Most of the students attending this module did not aim for a career as research chemists but went on to study subjects that explicitly rely on critical thinking, such as criminology,7 bioinformatics, or pedagogy. Interestingly, several of these subjects are well served by postgraduate students with skills from both chemistry and philosophy. Perhaps the notion that chemistry students do not only have to learn chemistry but also a few topics of “meta-chemical” subjects might as well be an incentive to rethink some of the chemistry curricula in the near future and thus to bridge the unfortunate gap between natural sciences and humanities even further. It seems from our module evaluation that most of our students would agree.

Notes 1. Students were told that the empirical content of the premises is empirically correct (“true”). Their task was to confirm or deny logical validity of the arguments (i.e., conclusions drawn). Although any scientific statement based on empirical data is open to change and can have only relative scientific validity this does not mean that the logical validity of an argument is also relative. 2. In logic, premises are defined as stated reasons used to support the conclusion. In this specific context, one of the premises is based on a chemical law, the other on experimental observations. 3. For philosophical correctness, it should be mentioned that some philosophers are critical of interpreting all conditionals as material conditionals. This has implications on the formal fallacies of the conditionals. The fallacies presented in the questionnaire have, however, apparent counter-examples: protein degeneration would be another explanation of spectral changes; chemical reactions on the electrodes could account for continuation of chlorine gas formation. 4. To avoid any misunderstandings: Students were not asked to reproduce the rules of inference from their memory. Rather, their task was to suggest a correct syllogism based on their everyday reasoning and experience with reasoning in chemical arguments. This was done before the students were shown the correct rules of inference. 5. This section applies to both student cohorts, the 38 student “control group” and the 18 students that were first exposed to the lectures and then asked to evaluate the statements given in the questionnaire (Figure 1). 6. This situation is slowly improving. Journals such as Foundations of Chemistry, HYLE, and Ambix provide valuable teaching support. HYLE, for example, has just released an issue on chemoethics. See http://www.hyle.org/journal/issues.htm (accessed May 2004). 7. One of the students attending this module decided to do an undergraduate project in this field before moving into criminology. Her work has now been published in Ambix (17).

Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Acknowledgments

11. 12. 13. 14.

The author would like to thank Michael Akeroyd (Bradford College) and John Dupré, James Tucker, Gregory Giles, and Fiona Fry (University of Exeter) for their valuable comments while preparing this manuscript.

15. 16. 17.

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