BOOK VII - Page 4

Bohm on Perception and Metaphor in Scientific Discovery

For forty years following his initial 1952 statement of his hidden-variable interpretation Bohm continued to expound his views in philosophy of science, metaphysics, and epistemology.  His statements that are most relevant to the subject of scientific discovery are found in Science, Order and Creativity, particularly in the introductory chapter and in the two succeeding chapters, which altogether take up about half of the book.  In these pages he also sets forth his philosophy of perception, which he explicitly opposes to that of the positivists.  It also reveals Einstein’s influence because he says perception takes place in the mind and in terms of theories.  For example the observational data obtained by Archimedes in his bath had little value in themselves.  What is significant is their meaning as perceived through the mind in the act of creative imagination.  The principal historical change that has occurred in modern science is that this mental perception is more mediated through elaborate instruments that have been constructed on the basis of theories.  Bohm’s philosophy of perception is central to his views on discovery and he assigns a special rôle for metaphor.

Bohm believes that the development of science is now obstructed by fragmentation due to what he calls “subliminal rigidities” in thought that he calls the “tacit infrastructure” of scientific ideas.  One example of the tacit infrastructure of scientific ideas is the Newtonian notions of space and time that led Lorentz to preserve both the idea of the constancy of the velocity of light and the ideas of absolute space and time by explaining the anomalous results of the measurements of light by postulating changes in the measuring apparatus as the apparatus moves through the ether.  He proposes the sociological thesis that the tendency of the scientist’s mind to hold to what is familiar is reinforced by the fact that the overall tacit infrastructure is interwoven in the institutions on which depends the professional security of the scientist.  And he proposes the linguistic thesis that the means for breaking out of the tacit infrastructure of scientific ideas and for creating new theories is metaphor. Bohm defines metaphor as the simultaneous equating and negating of two concepts.

Metaphor is especially important for Bohm, since he maintained that microphysics and macrophysics should have the same basic ontology, such that features from the latter domain projected into the former enables a discovery strategy.  This rôle for metaphor in discovery is possible, because the realm of physics is now that of perception through the mind, and theory dominates experiment in the development of the scientific perception of nature. Bohm says that metaphor occasions creative perception and he also refers to metaphoric perception. Metaphoric perception brings together previously incompatible ideas in radically new ways.  He says that the unfolding of a metaphor that equates different and even semantically incommensurable concepts can be very fruitful.  In using the term “incommensurable” Bohm references Kuhn, and he equates his own thesis of the tacit infrastructure of scientific ideas with Kuhn’s thesis of scientific paradigm.  A paradigm is not just the articulate theory, but also the scientist’s whole way of working, thinking, communicating, and perceiving with the mind. 

However, Bohm rejects Kuhn’s thesis that normal science is without any creativity, and that revolution is completely discontinuous.  Bohm maintains that semantic incommensurability can be overcome with metaphor.  He furthermore says that revolution occurs when a new metaphor is developed, and normal science is the creative unfolding of that new metaphor.  In Bohm’s view there is much more creativity in normal science, than Kuhn admits.  Bohm also criticizes Popper’s thesis of falsifiability.  He maintains that today an excessive emphasis is being placed on falsifiability in the sense that unless a theory can be immediately or very shortly falsified, then that theory cannot be regarded as properly scientific.  A new theory with broad implications may require a long period of gestation before falsifiable consequences can be drawn from it.

Bohm also maintains that communication is essential to perception in science.  He understands communication in a very broad sense to include the individual’s own articulate mental dialogue with himself.  The scientist engages in an inner dialogue with himself as well as with his colleagues, and in this dialogue he is disposed in his thinking by the social background.  Insights enfolded in this inner dialogue must be unfolded by discourse with colleagues and eventually by publishing.  Fragmentation may proceed to the point that communication becomes blocked, because the tacit infrastructure of ideas not only limits the individual but also the whole scientific community in their creative acts of perception.  Both paradigms and specialization may cause fragmentation in this way.  One very central thesis of Bohm’s is that a fragmentation has occurred in modern microphysics between mathematical formalism and informal discourse in microphysics.  Differences in the informal discourse gave rise to an issue between Bohr and Einstein, as well as among later physicists.  Bohm considers communication to be so central to perception that he speaks of perception-communication. 

The change in the language of physics occasioned by the development of quantum theory has led to a communication breakdown. Both Bohr and Einstein agreed on the mathematical formalism, but there is still no common informal language.  In fact Bohr and Einstein agreed on the test designs for quantum theory experiments.  But Bohm believes that if Bohr and Einstein had been willing to entertain a free dialogue to eliminate the rigidities that block communication, then perhaps a new creative metaphor might have emerged for microphysics.  In such a dialogue each person must be able to hold several points of view in a sort of active suspension, while treating others’ views with the consideration he gives to his own.  This would lead to the intellectual free play needed for a new creative metaphor. 

Bohm proposes his hidden-variable interpretation for consideration in this spirit.  He maintains that the interpretation of a formalism is something that is in the informal discourse, not in the measurements or the equations.  This view is fundamentally contrary to Hanson’s, who says the exact opposite.  In Bohm’s view all the available interpretations of the quantum theory, as with any other physical theory, depend fundamentally on implicit or explicit philosophical assumptions, as well as on assumptions that arise in countless other ways.  The image of the “hard-nosed” scientist, who does not admit to the existence of the philosophical assumptions in the informal language, is just another example of the subliminal influence that is exerted on scientists by the tacit infrastructure of ideas shared by the scientific community at large.

Bohm on Mathematics and Scientific Discovery

In Science, Order and Creativity Bohm maintains that there is no difference between science and philosophy.  While Hanson also states that physics is natural philosophy, Bohm’s statement means something very distinctive.  Bohm explicitly rejects the prevailing view of the aim of physics, which he says is to produce mathematical formalisms that can correctly predict the results of experiments.  He maintains that, since quantum theory and relativity theory were never understood adequately in terms of what he calls physical concepts, physics gradually slipped into the practice of talking about equations.  And he states that Heisenberg gave this practice an enormous boost with the idea that science can no longer visualize atomic reality in terms of physical concepts, and with the idea that mathematics is the basic expression of our knowledge of reality. 

Bohm proposes a radical revision of the aim of science.  He maintains that the current emphasis on mathematics has gone too far.  Therefore in stating that science is the same as philosophy, Bohm means that as philosophy had traditionally done, now science must unify knowledge instead of offering physicists a fragmentation as it has today.  In times past there was a general vision of the universe, of humanity, and of man’s place in the whole.  But specialization in modern science became narrower and led eventually to the present approach, which is fragmentary.  Bohm also opposes what he sees as another wayward aim of modern physics, which is to analyze everything into independent elements that can be dealt with separately.  This further contributes to fragmentation.  Bohm believes that the time has come to change what is meant by science.  This change is to be implemented by a “creative surge” that will eliminate the fragmentation.  Bohm’s philosophy of the aim of science is therefore coherence view.

In the fourteenth chapter of Undivided Universe Bohm offers a somewhat more balanced statement of the relation between physical concepts and mathematical concepts.  Again he says that the prevailing attitude today is to take the present mathematical formalism of quantum theory as an essential truth, and then to try to derive the physical interpretation as something that is implicit in the mathematics.  He denies that his own approach is simply a return to the historically earlier view that the mathematics merely enables the physicist to talk about the physical concepts more precisely.  His view is that the two types of concepts represent two extremes, and that it is necessary to be in a process of thinking that moves between these extremes in such a way that they complement one another.  He says he does not regard such physical concepts as particle, quantum wave, subquantum field, position, and momentum as mere imaginative displays of the meaning of the equations.  He maintains that what he is doing with his hidden-variable interpretation is moving to the other side of the extreme in the thought process and taking the physical concepts as a guide for the development of new equations.  He says that the clue for a creative new approach may come from either side, and may flow back and forth indefinitely between them. 

One must ask for the origin of the semantics for the “physical concepts.”  Clearly in Bohm’s views the context consisting of empirically adequate equations cannot determine the relativized semantics of the physical concepts, but must somehow be independent.  This is a reactionary turn in his philosophy of language.

Bohm’s Philosophy of Science

Aim of Science

Bohm’s view of the aim of science contains a fundamental ambiguity.  One aim is to supply a basically uniform and consistent ontology for science admitting variations at different orders of magnitude.  But it does not admit to the inconsistency or pluralism that exists between quantum theory and relativity theory, which Heisenberg called the schism in physics, and which Bohm called fragmentation.  This is the integrating aim that Bohm has in mind when he says that physics is philosophy.  His philosophy of the aim of science is a coherence agenda. 

The other aim is the more conventional one in contemporary physics, the aim of producing more empirically adequate equations.  Bohm maintains that these two aims of science need not and should not be divergent, even though lamentably they presently diverge. And he believes that the fragmentation in contemporary physics is due to an exclusive concern with the formal language, the equations of mathematical physics. 

Scientific Discovery

Bohm’s philosophy of scientific discovery follows from these views on the aim of science.  The fragmentation-produced divergence between these aims will be eliminated and both aims will be more adequately realized, if physicists attend to both the formal and the informal language, to both the mathematical and physical concepts.  Employing figures of speech such as analogy and metaphor containing physical concepts will facilitate developing better equations.

Scientific Criticism

Bohm’s views on scientific criticism do not lead him to invalidate the empirical adequacy of the Schrödinger wave function or the Heisenberg indeterminacy relations.  Like other critics of the Copenhagen interpretation he advocates developing an alternative interpretation for the equations of the quantum theory.  He never denies that the second aim of science, the production of empirically superior equations, has been realized by the equations of the quantum theory.  But just as there is an ambiguity in his aim of science, so too there is a corresponding ambiguity in his criteria for scientific criticism.  He spent most of his career attempting to persuade the physics profession that there exists another criterion that is unabashedly philosophical.  That criterion is the integrated, consistent ontology for both microphysics and macrophysics.  And some physicists like John Bell and some philosophers like Karl Popper were persuaded to pursue this coherence agenda. 

Scientific Explanation

Bohm does not set forth an explicit statement of his philosophy of scientific explanation.  But if satisfaction of the criteria for scientific criticism is taken as yielding a scientific explanation, then Bohm’s philosophy of scientific explanation follows from his views on criticism.  The salient consideration in this context is the rôle for a uniform and consistent ontology in his integration aim of science and its associated criterion for scientific criticism.

Hanson on the Copenhagen Interpretation and Scientific Discovery

Hanson criticizes all three of the objectives in Bohm’s agenda for future physics.  Hanson’s argument against Bohm’s first objective that an alternative to the Copenhagen interpretation is possible, is to deny that an alternative to the Copenhagen interpretation is possible until a new mathematical quantum theory formalism is developed, because on his thesis the Copenhagen interpretation is not a semantics supplied by related philosophical or metaphysical ideas about the subject, but rather is the semantical interpretation resulting from the logicogrammatical form of the theory’s mathematical formalism.  Therefore contrary to physicists such as Bohm and Landé, and contrary to philosophers such as Feyerabend and Popper, the Copenhagen interpretation even after disengagement from what Hanson calls Bohr’s “naïve epistemology”, is not just one of several alternative semantical interpretations.  It is the unique interpretation that is defined by the relationships in the mathematical formalism.  This amounts to accepting the thesis of relativized semantics.

In Concept of the Positron and elsewhere Hanson distinguishes the Copenhagen interpretation from what he calls the Bohr interpretation.  He rejects efforts by philosophers such as Feyerabend to include what Feyerabend admits are the dogmatic elements of the Bohr interpretation in the Copenhagen interpretation.  The dogmatic elements consist particularly in what Hanson calls Bohr’s naïve epistemology with its “forms of perception”.  Perhaps it could be said with caution that with the rejection of Bohr’s naïve epistemology Hanson’s philosophy of quantum theory is one that Heisenberg might have formulated, had Heisenberg rejected Bohr’s epistemological ideas, which are formative in his doctrine of closed-off theories, and instead followed through on Einstein’s aphorism that theory decides what the physicist can observe. 

With his rejection of the Bohr interpretation Hanson places himself in agreement with Bohm and Feyerabend, when the latter maintain that the quantum theory is not permanently valid; they agree that the current quantum theory may be superseded.  But contrary to these authors he also considers duality to be the defining characteristic of the Copenhagen interpretation and integral to the formalism.  Because he maintains that the Copenhagen interpretation is defined by the logicogrammatical form of the mathematical formalism itself, he defends it as the only interpretation “that works”.  He therefore says that in the absence of any algebraically detailed and experimentally adaptable alternative, the Copenhagen interpretation represents the conceptual possibilities currently open to practicing physicists, and that it will not be abandoned until it is completely replaced by an alternative, completely detailed, algebraically articulated theory.

Hanson does not attack the thesis in Bohm’s second objective that the history of physics suggests future microphysical theory will describe phenomena at the lower order of magnitude than the current quantum theory.  In fact the idea of developing a heuristic for future theory development is closely related to Hanson’s interest in discovery.  But Hanson does not accept Bohm’s proposal of a subquantum hidden-variable theory, which Bohm believes may serve as a heuristic for future microphysics.    Hanson proposes his own historical thesis on scientific discovery, which was greatly influenced by the Cambrian physicist Paul A. Dirac.  Dirac (1902-1984) was a theoretical physicist at Cambridge University, who shared the Nobel Memorial Prize for physics in 1933 with Schrödinger. 

Dirac had published a methodological statement on the future of physics in his “The Evolution of the Physicist’s Picture of Nature: An account of how physical theory has developed in the past and how, in the light of this development, it can perhaps be expected to develop in the future” (Scientific American, May, 1963).  In this brief informal paper Dirac contrasted the theory-development approaches of Schrödinger and Heisenberg.  Dirac was much more sympathetic to the former’s approach, according to which the development of physical theory should be guided by the aesthetics of the mathematics in the theory unlike the latter’s approach in which a mathematical formalism is developed by data analysis.

However, this is not the issue in Dirac’s views that influenced Hanson, whose view was more similar to Heisenberg’s approach, in which theory originates with the experimental data.  Hanson was influenced by Dirac’s historic accomplishment, the transformation theory developed by Dirac in 1928, which not only combines relativity and quantum mechanical descriptions of electron properties, but also enables physicists to exhibit duality by transforming mathematically the wave description into the quantum description and vice versa.  Both in his “Copenhagen Interpretation of Quantum Theory” in the American Journal of Physics (1959) and in his chapter “Interpreting” in Concept of the Positron, Hanson states that objections to the Copenhagen interpretation arise from a failure to appreciate the historical and conceptual rôle duality had played in Dirac’s 1928 paper.

Hanson reports that in personal conversation Dirac had told him that the Copenhagen interpretation figured essentially in development of Dirac’s relativistic quantum field theory, and that it was not merely a philosophical afterthought appended to the mathematical formalism.  This personal conversation with Dirac more than anything explains Hanson’s motivation for maintaining that the Copenhagen interpretation is integral to the formalism of the quantum theory.  He argues against Feyerabend that even if it were possible to have a minimum statement of quantum theory with no more interpretation than is required barely to describe the facts, this is what Dirac felt he had, and Dirac’s paper would not have been the paper that it actually was, had its assumptions been purified of the Copenhagen interpretation, as Feyerabend advocates.  But for his thesis of scientific discovery Hanson turned not to Dirac’s aesthetic thesis, but to the logical thesis proposed by the historic founder of pragmatism, Charles S. Peirce.

Hanson’s argument against Bohm’s third objective that a future hidden-variable theory will resolve the difficulties in current quantum theory, is that Bohm and other advocates of alternatives to the Copenhagen interpretation offer nothing but promises.  In Quanta and Reality Hanson calls Bohm’s proposal a “congeries of excitingly vague, bold-but-largely-formless, promising-but-as-yet-unarticulated speculations”. The Copenhagen interpretation on the other hand is a “working theory” however imperfect it may be, and a speculation is never an alternative to a working theory.

Peirce, Retroductive Logic, and Semantical Constraints in Discovery

Hanson was influenced by Charles S. Peirce, but he did not accept Peirce’s views on observation.  In his “How to Make Our Ideas Clear” (1878) Peirce set forth his pragmatic maxim, which says that our conception of the practical effects that we conceive an object might have, is the whole of our conception of that object.  He distinguishes observed facts from judgments of fact, and says that observations have to be accepted as they occur, while judgments of fact are controllable.

According to Peirce’s theory of scientific discovery, hypotheses are judgments of fact expressed in propositions, and all such propositions are additions to observed facts that are sense impressions of singular events associated with particular circumstances.  That which is added to observed facts by propositions Peirce calls practical knowledge, and it is something that is controllable but subject to error.  Hypotheses are the result of inference, and Peirce distinguishes inductive and abductive types of inference.  Abduction (which Hanson calls “retroduction”) involves both formulating of various hypotheses and then selecting of one hypothesis by testing its ability to account for surprising facts.   The difference between abduction and induction is that the former involves guesswork and originality, while the latter only tests a suggestion previously made.  Once the hypothesis is formulated, abduction is an inference that satisfies the following form: 1) a surprising fact, C, is observed; 2) if A were true, then C would occur as a matter of course; 3) hence, there is reason to hypothesize that A is true.  This is not a deductive conclusion, because it is actually a logical fallacy known as affirming the consequent clause of the conditional statement. 

Peirce opines that Kepler’s development of his three laws is the greatest piece of retroductive reasoning ever performed.  He rejects J.S. Mill’s view that Kepler merely generalized on Tycho’s data, and that there was no reasoning in Kepler’s procedure.  Peirce maintains that at each step of Kepler’s investigation, Kepler had a theory that approximated the data, that Kepler modified his theory to make his theory closer to the observed facts, and that the modifications were never capricious.  Hanson adds that given a choice between two hypotheses, the simpler is preferable, where simplicity is to be understood not as a logical simplicity but rather as an instinctive simplicity, because unless man has a natural bent in accordance with nature’s, he has no chance of understanding nature at all.

In his chapter on theories in Patterns of Discovery Hanson rejects both the hypothetico-deductive and the positivists’ inductive accounts of scientific discovery.  He rejects the inductivist thesis that enumerating and summarizing observable data enable development of scientific theories, as the positivists maintained for the development of empirical generalizations.  He states that empirical laws explain, they do not merely summarize.  He also rejects the hypothetico-deductive thesis that scientists start from hypotheses for the development of theories, as Popper maintained.  He says that scientists do not start from hypothesis, but rather they start from data.  The initial inference is not from higher level hypotheses to observations, but the other way around.

The article setting forth his most mature views on retroduction is “Notes Toward A Logic of Discovery” in Perspectives on Peirce (ed. Bernstein, 1965), which includes summaries of Hanson’s earlier papers.  The logic of retroduction pertains to the scientist’s actual reasoning, which proceeds from an anomalous situation to the formulation of an explanatory hypothesis that fits the anomaly into an organized pattern of concepts.  In Patterns of Discovery Hanson refers to the pattern of concepts as a “conceptual gestalt”, which functions to make the anomalous situation appear intelligible.  The conceptual gestalt supplies the semantics for the theory or hypothesis.  In Hanson’s philosophy the semantics of observation is variable, while in Peirce’s it is fixed and uncontrollable.

In “Notes...” he says that the formal criteria for the retroductive logic of discovery are the same as those for the hypothetico-deductive logic of explanation.  They both contain the same elements: a hypothesis, statements of initial conditions, and the conclusion deductively derived from the hypothesis and statements of initial conditions.  One difference between them is the direction of the inference.  In the hypothetico-deductive logic the inference is from the hypothesis and statements of initial conditions of an experiment, to the statements describing the observed outcome of the experiment as a conclusion.  This process is used for experimental testing, and if the results are not anomalous, it also serves as the logic of the explanation of the resultant phenomenon.  But in the retroductive logic the direction of inference is in the opposite direction.  The statement reporting an observed experimental outcome describes an anomaly relative to what is expected, and the problem is one of finding the hypothesis capable of functioning in a hypothetico-deductive account that will explain the anomalous situation as occurring as a matter of course. 

But the difference between the hypothetico-deductive and the retroductive types of inference is not just a matter of the directionality of the inference.  They are also different because the former is determinate, while the latter is not.  In hypothetico-deductive inference consistent premises must produce consistent and unique conclusions, while in the retroductive inference there may be many alternative and mutually inconsistent hypotheses that are able to explain deductively the formerly anomalous test outcome from the same set of statements of initial conditions.  From this nondeterminate character of retroductive inference Hanson concludes that retroduction cannot yield a uniquely specific and detailed hypothesis.  But he maintains that it can yield an indication of the type of hypothesis that is most plausibly to be considered as worthy of serious attention.  And the decision about what type of hypothesis is the most plausible depends in turn on the structure of presently accepted theories and on the shape of the most reliable conceptual frameworks that highlight types of hypotheses for the problem solver.   Therefore, much as it is only against the background of the intelligible and the conceptually comprehensible offered by existing theories that the anomalies stand out at all, so it is also in these same terms that the scientist comes to know which types of hypotheses will do the job and which do not.

Reflection on this analysis reveals why Hanson defends the Copenhagen interpretation, understood as the semantics that is defined by the formalism of the quantum theory.  The Copenhagen interpretation is the type of hypothesis that (in Hanson’s view) will most plausibly resolve the current ano­malies to Dirac’s relativistic quantum theory, just as it had enabled Dirac to develop his field quantum theory in 1928.  Hanson also maintains that the conceptual gestalts constituting the semantics for currently accepted theories not only supply some guidance for the creation of new theories, but also offer what he calls “conceptual resistance”, which must be overcome for making scientific discoveries.  The development of a new theory requires a new gestalt just as in the reinterpretation of an ambiguous drawing, and similarly there is a resistance to such a change.  In Patterns of Discovery Hanson illustrates this in the historical episode in which Kepler developed the theory that the orbit of Mars is elliptical.  In formulating this theory Kepler had to reject the traditional belief held since Aristotle that the orbits of the planets must be circular, because unlike sublunar motions the celestial motions are perfect.

This is also the thesis in Hanson’s most significant historical analysis set forth in his Concept of the Positron.  This work is excellent original historical research in which Hanson interviewed several physicists including the three principals in the episode: 1936 Nobel-laureate Carl Anderson, 1933 Nobel-laureate P.A.M. Dirac, and 1948 Nobel-laureate P.M.S. Blackett.  All three physicists discovered the positron, but only Blackett recognized that the particle discovered experimentally by Anderson was the same one that was postulated theoretically by Dirac. Dirac’s 1928 paper offered a relativistic quantum theory that was Lorentz-invariant, but it also contained negative energy solutions that could not be eliminated.  Originally he had hoped that these strange solutions could be construed as protons, and then he thought of them as vacancies which are positive charge solutions with the mass of the electron.   This constituted the gradual development of his prediction of the existence of positive electrons before they were observed.  In 1932 Anderson made photographs of electron tracks in the cloud chamber, and he concluded that one of them showed a positive electron, because the charge of the particle was positive while its mass was too small to be that of a proton.  Dirac had published his theoretical paper on the positron a year before Anderson’s photograph.  In 1933 Blackett and Occhialini reported that the Anderson particle and the Dirac particle are the same thing, by using the new observation technique in which the particles take photographs of themselves in the detectors.

Hanson states that one reason Anderson did not recognize any connection between his cloud chamber experiments and Dirac’s quantum theory, is that such experiments rely on concepts that are largely classical in nature such as track-leaving particles.  But the greatest conceptual constraint, the one that led many physicists to reject the idea of a positron, the positive electron, was in the semantics of “electron”.  That semantics was such that an intimate association between the electron and the proton, and between the two basic units of electricity, negative and positive charges, made the very idea of a particle other than a proton or an electron very difficult to conceive.  Just as positive/negative exhaust the totality of electrical charge, so too the proton/electron was thought to exhaust the totality of charged particles, since the proton and the electron came to be viewed not as carrying the charge but as being the charge.  Hence there was a conceptual resistance to the idea of a third type of charged particle built into the structure of classical electrodynamics and the elementary particle theory.

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