el enfoque fenomenológico en fisica

Stud. Hist. Phil. Mod. Phys., Vol. 30, No. 2, pp. 267}281, 1999( 1999 Elsevier Science Ltd. All rights reserved

Printed in Great Britain1355-2198/99 $ - see front matter

ESSAY REVIEW

The Phenomenological Approach to Physics

Steven French*

Kostas Gavroglu, Fritz ondon: A Scienti,c Biography (Cambridge: CambridgeUniversity Press, 1995), xxiv#299 pp. ISBN 0521432731.

1. Introduction

Kuhn famously described &normal science as &mop-up work (Kuhn, 1970, p. 24).The problem for the historian is how to make this interesting and engaging. Onesolution is to choose a &key "gure who lies close to the establishment ofa particular paradigm. Thus Klein gave us Ehrenfest, remembered not as one ofthe founders of quantum mechanics but as a brilliant teacher and expositor, whohelped to lay bare the foundations of the new framework (Klein, 1970). Gav-roglu in turn gives us Fritz London, a &key "gure in the further development ofthe new quantum mechanics and the means by which Gavroglu can explore therich structure of post-revolutionary modern physics. The comparison withKleins masterpiece is sustainable, I believe. Like Klein, Gavroglu not onlypresents, in a clear and accessible manner, the scienti"c &product of the life, butalso gives us a feel for the life itself. And this life was, if not &normal, then notatypical for a gifted Jewish scientist of the time.

Born in Breslau at the turn of the century, Fritz London became interested infundamental problems of epistemology while still at school but decided to studyphysics with Sommerfeld at Munich. While there he came into contact with thephilosopher PfaK nder, a well-known phenomenologist, who was so impressedwith one of Londons philosophical pieces that he o!ered to accept a rewritten

(Received 20 July 1998)* Division of History and Philosophy of Science, School of Philosophy, University of Leeds,Leeds, LS8 2LP, U.K. (e-mail: [email protected]).

PII: S 1 3 5 5 - 2 1 9 8 ( 9 9 ) 0 0 0 0 6 - 4

267

version as a thesis for the philosophy degree. After graduation, Londons interestin epistemological problems in physics led him to GoK ttingen, where Borninsisted that he do some &straight physics. Subsequently his scienti"c careertook o! and the list of achievements includes: the quantum mechanical explana-tion of the homopolar bond with Heitler, which laid the foundations of quantumchemistry; the careful work on molecular forces, understood through the uncer-tainty principle; the famous theory of superconductivity with his brother, whichtook account of the Meissner e!ect; the explanation of super#uidity in terms ofBose}Einstein condensation; and the monograph with Bauer on the measure-ment problem, well known to students in the philosophy of physics. He #edGermany for Britain in 1933 but, after failing to secure a permanent position,moved to Paris before emigrating to the U.S.A., where he was o!ered a job in theChemistry Department at Duke University. While he was there his wonderfulmonograph Super-uids was published and in 1953 London was awarded theLorentz Medal. In 1954 he died of a heart condition.

These are the bare bones of a life that, at least for that period, might bedescribed as normal. Gavroglu gives us the #esh too, from Fritzs relationshipwith his brother Heinz to the acrimonious dispute with von Laue over thelatters contribution to the theory of superconductivity. The science is handleddeftly and the life regarded sympathetically. With an afterword from Bardeen,written the year before his death, the book sits comfortably next to Kleins.

But of course, London was also abnormal, as Gavroglu emphasises: Londonnever abandoned his philosophical roots in phenomenology. There is an inter-esting book to be written on the inter-relationship between science and philoso-phy in this period, but it is here that Gavroglus touch is less sure and hisanalysis less insightful. The problem lies in getting to grips with phenomenologyitself. A little over four pages is just not su$cient to cover the work of PfaK nder,Becker and Husserl, and although over seven pages are devoted to Londonsphilosophy thesis, much of it is opaque, if not incomprehensible. However,a number of crucial points are discernible, the most important being a non-reductionist, holistic view of scienti"c theories. This &macrological view oftheories as structured wholes &would become one of Londons reference points indeveloping his own ideas about deductive systems (p. 131). Here Gavroglu leansheavily on Mormann who argues that Husserls work can be seen as a forerun-ner of the semantic approach to theories (Mormann, 1991). Whether or not thisis the case it is surely * dare I say it to a historian * unbearably whiggish towrite,

[2] even before starting his thesis, London was quite sensitive and receptive toideas related to the semantic approach in the philosophy of science (p. 15).

London also had a two-stage view of the relationship between theory andreality: the "rst stage takes us from reality to experience, as the phenomenon in

1 Page references are to Gavroglus Fritz ondon: A Scienti,c Biography (1995), unless otherwiseindicated.

268 Studies in History and Philosophy of Modern Physics

question is appropriately formulated and in the second we move from experi-ence to language and an explanatory schema. Gavroglu insists that such distinc-tions are crucial to understanding Londons work and it is interesting toconsider in a little more detail how this &normal scientists philosophy of sciencea!ected his scienti"c work.

2. Eating Chemistry with a Spoon: the Group-theoretical &Reduction ofChemistry to Quantum Mechanics

As Heitler subsequently expressed it, the &fundamental problem of chemistrywas &the reason why atoms prefer to combine and form molecules consisting ofa de,nite number of atoms (Heitler, 1967, p. 13). His reductionist tendency isevident in his insistence that this was a physical problem, with the attractionexplained in terms of &physical laws prevailing within the atom (ibid.) withoutthe necessity of introducing further chemical forces. However, it became evidentthat the attraction between two hydrogen atoms could not be accounted for interms of Coulomb forces; the key, as Heitler realised one hot and disagreeableday in ZuK rich (p. 45), lay with the exchange integral, previously introduced byHeisenberg. This was something purely quantum mechanical, with no classicalanalogue and as Gavroglu notes, it is this focus on purely quantum mechanicalexplanations that also marks Londons work.

Carson has nicely charted the development of the exchange concept and, inparticular, the shift from the idea of a literal exchange of electrons to theunderstanding of its basis in the non-classical indistinguishability of the elec-trons (Carson, 1996). The Heitler}London paper is situated right at the heart ofcontemporary struggles to grasp the essentially metaphysical implications of thenew quantum mechanics. On the one hand, the mathematics itself harkenedback to the literal picture of exchange and the idea of beats; on the other, Heitlerand London noted that the electrons could not be regarded as labelled.2 On thisfundamental basis the electronic wave function of the two-atom system could bewritten in either symmetric or anti-symmetric form. With the electron spinsincorporated, the Pauli Exclusion Principle dictates that the anti-symmetricform be chosen, with spins anti-parallel. This corresponds to the state of lowerenergy and hence attraction. With the introduction of spin and the ExclusionPrinciple chemical valence and saturation could be understood and the &prob-lem of chemistry solved.

London subsequently incorporated spin into his general formulation of theExclusion Principle suitable for cases with more than two electrons and thisproved more convenient for his later work with group theory (p. 49). Thegroup-theoretical approach to these problems in chemistry was initiated byHeitler, after moving to GoK ttingen* where although Born was negative (p. 56)

2 In a letter to Born in 1936, London wrote: &[2] we were very proud when we realized that we getthe exchange degeneracy because of the similarity of the electrons (pp. 87}88; Londons emphasis).

The Phenomenological Approach to Physics 269

Heitler learned from Wigner and Weyl the recent mathematico-physical theory.His central idea was that the Heitler}London treatment of the hydrogen bondcould be extended to other molecules if it were underpinned by the theory ofirreducible representations of the permutation group, as applied to atomicphysics by Wigner and Weyl. In this manner, he claimed, &[w]e can [2] eatChemistry with a spoon (p. 54).

London, although less reductionistic than Heitler (pp. 91}92), agreed thatgroup theory provided a way of dealing with the many-body problem. In a seriesof papers in 1928 he showed that the group-theoretic formulation of quantummechanics could recover the same valence numbers and satisfy the same formalcombination rules as were expressed in the chemists semi-empirical framework(p. 57). With this work, taken together with Heitler and Rumers 1931 analysis ofthe valence structures of polyatomic molecules, it did indeed seem that chem-istry had been eaten with a spoon.

Not surprisingly, perhaps, the chemists disagreed and Gavroglu ably tracksthe ins and outs of Heitler and Londons disputes with Mulliken, Pauling andSlater (pp. 82}92).3 However, it is not so clear where Londons philosophy "ts.As Gavroglu himself notes: &It is ironic, that this "rst important paper of his wassuch a pronounced deviation from his grand schema to view theories as wholes!(p. 92). Gavroglu does claim that Londons subsequent group theoretical workcontains suggestions of an alternative non-reductive approach (p. 74 and pp.91}92) but these suggestions are never made explicit. It is noted, however, thatLondon took the fundamental problem to be

[2] the mysterious order of clear lawfulness, which is the basis for the immensefactual knowledge of chemistry and which has been expressed symbolically in thelanguage of chemical formulas (quoted on p. 56).

Here a form of the two-stage process can be reconstructed, with the "rsthaving already been completed by the chemists in a semi-empirical fashion andthe second providing a sound theoretical basis for the chemists rules andformulas. However the "rst stage notion of saturated valences could not beexplained by the &standard principles of atomic physics, but required spin, theExclusion Principle and, ultimately, group theory (pp. 56}57). Perhaps ina weak sense there is a kind of anti-reductionism here.

This is, of course, very much a hot topic among philosophers of chemistry.4Some of the issues involved are manifested in Londons work through thetension between his emphasis on purely quantum mechanical explanations andhis non-reductive philosophy. One way of easing this tension, perhaps, is to giveup the reductionist talk of di!erent &levels and instead accept that there is one

3 On the physics side, Slater was hailed as having &slain the Gruppenpest by Condon and Shortleyin their 1935 heory of Atomic Spectra. However, their linear operators of angular momenta aresimply the generators of the rotation group SO(3).4 See, for example, Scerri (1997).


world which is very abstractly, and perhaps only provisionally, described inquantum mechanical terms. Because of the complexity of the phenomena, exactderivations are simply not feasible. Shifting from the dynamics to the symmet-ries, as described by group theory, gives us an explanation of the phenomena, orat least as much of one as we can have within these constraints. As Paulinghimself came to acknowledge, spin is central to our understanding of thechemical bond and spin is purely quantum mechanical. But this is not to saythat chemists must become physicists, or the latter mathematicians.5 The ideal-ised and partial nature of these explanations suggests that a degree of autonomywill always remain. If reduction is tied to deduction from SchroK dingers equa-tion, then Londons use of group theory is non-reductive. But this does notimply complete theoretical autonomy. It is surely time to abandon the positivis-tic view of reduction as involving a distinctive entailment relation and insteadfocus on alternative frameworks.6 Perhaps Heitlers and Londons group theor-etical work will repay careful study in this regard.

The in#uence of Londons philosophy on his science is much more apparentin his second major piece of work, his account of superconductivity.

3. The Superconductor as a Single Big Diamagnetic Atom

In 1928 Bloch published a quantum mechanical theory of electron conductiv-ity which accounted for metals, semiconductors and insulators. It failed toaccount for superconductivity, however, which was conceived of in terms of ananalogy with ferromagnetism, in the sense that persistent currents existing belowthe critical temperature were taken to be analogous to permanent magnetisationbelow the Curie point (pp. 112}113). This failure led to &Blochs theorem:superconductivity is impossible! It was the discovery of the Meissner e!ect in1933 which indicated that it was the analogy which was at fault. Instead,superconductors should be regarded as diamagnetic, a suggestion which hadbeen made previously by Frenkel in 1933 but which was set at the very heart ofLondons account with his brother Heinz (London and London, 1935).

Gavroglu follows convention in describing the London}London model as&phenomenological.7 However, London himself rejected the term and insistedthat the model should be described as &macroscopical since it goes beyond thestrictly phenomenological data. Furthermore, to take the model to be purely&phenomenological would be to ignore the importance of Londons own

5 Hartree, for example, was famously less than enthusiastic about the introduction of group theory,although he concluded: &Is it really going to be necessary for the physicist and chemist of the future toknow group theory? I am beginning to think it may be (quoted on p. 56).6 Ramsey has recently suggested the abandonment of the &levels view of reduction in favour ofa &perspectives approach which insists that &[2] there is only one reality; we make variousapproximations to capture the properties of that reality (1997, p. 246).7 See also Cartwright, Suarez and Shomar (1996).


philosophical view of theoretical construction. As Gavroglu reminds us (pp.127}128), the phenomena must "rst be formulated in a particular fashion andthen embedded in an explanatory framework. It was precisely because thephenomena of superconductivity had been represented inappropriately to beginwith that it was concluded that it was theoretically impossible.

Thus London wrote in 1935:

The progress I claim is mainly a logical one: by a new and more cautiousinterpretation of the facts I tried to avoid a fundamental di$culty (the so-calledtheorem of Bloch) which stood in the way of explaining superconductivity by thecustomary theory of electrons in metals and which could not be overcome as longas one has considered this phenomenon as a limiting case of ordinary conductivity(quoted on p. 129).

The di$culty was avoided by switching analogies, under the pressure of experi-mental results, and reformulating the phenomena. But this is only the "rst stage;complete understanding can only be reached by proceeding further and arrivingat a new explanatory schema. Stopping at the "rst stage would be to leave theprocess incomplete.

In the move to the second stage the &macroscopical theory is crucial. The term&macroscopic had a dual meaning: "rst of all, the theory was &macroscopic inthe straightforward sense that it was concerned with electric and magnetic "eldstrengths and the like. Secondly, and more fundamentally, it was macroscopic inthe sense that superconductivity was seen by London as a uniquely quantummechanical phenomenon of long-range, or macroscopic, order (the developmentof this notion of macroscopic is clearly set out by Gavroglu on p. 144). It is thislatter understanding which constrains the &microphysical or &molecular-kineticexplanation of the phenomenon. Thus London and London write that this &newdescription [2] seems to provide an entirely new point of view for a theoreticalexplanation (p. 71). And in his 1935 Royal Society presentation (London, 1935),Fritz London provides a &sketch of such an explanation, elaborating on theconcluding remarks of the joint paper where a structural similarity is drawnwith Gordons equation for electric current and charge in his relativistic formu-lation of SchroK dingers theory and the suggestion is made for the "rst time thatthe electrons are coupled in some way. This &microphysical programme is &setby the diamagnetic analogy, thus linking these two senses of &macroscopic (forfurther details see French and Ladyman, 1997). As Gavroglu notes, this pro-gramme subsequently became a &valuable heuristic for the work of Bardeen andthe idea of coupled electrons came to be expressed in the concept of &Cooperpairs (p. 209).

Thus Londons second stage of understanding is already partially present inthe joint 1935 paper. The &macroscopical interpretation constrains * via thestructural similarity with Gordons equation and driven by the diamagneticanalogy * the microscopical. This e!ects only a &reduction of the possiblemechanism responsible (London, 1937, p. 795; cf. London, 1950, p. 4) and hencethe second stage remains incomplete. The macroscopic model can be seen as


a kind of half-way house, going beyond the &phenomenological and extendinginto the &theoretical but leaving the latter open to further elaboration anddevelopment (cf. Gavroglus comments on p. 143). This seems to be the viewLondon took in Volume II of Super-uids, subtitled &Macroscopic Theory ofLiquid Helium. In the preface he writes:

The term &Macroscopic Theory in the subtitle is not entirely adequate. It is meantto indicate that, as in Volume I [which covered superconductivity], it is not theplan to present a molecular-kinetic theory of this subject, a theory which in fact hasnot yet been established. On the other hand, it did not appear reasonable to keepstrictly within the limits of phenomenological physics (1954, p. xi).

However, Gavroglu argues that there is one signi"cant di!erence between thesuperconductivity and liquid helium cases which concerns the role and place ofa &molecular-kinetic theory.

4. Super6uidity and Structures

In his last year at Oxford London became interested in what he later calledthe &mystery of the &liquid degeneracy of liquid helium (pp. 147}148). Thedemonstration that liquid helium could only be solidi"ed under pressure led tothe suggestion that the liquid passed into some kind of ordered state below thetransition temperature. London originally suggested that it had a diamondlattice structure but this idea was subsequently abandoned in favour of a newmodel in terms of Bose}Einstein condensation (pp. 152}157).

Thus in his 1938 note to Nature, London writes that &[2] in the course oftime the degeneracy of the Bose}Einstein gas has rather got the reputation ofhaving only a purely imaginary existence (1938a, p. 644). After indicating thata static spatial model of liquid helium was not possible, he went on to &imaginean analogy with Blochs model of electron conductivity in metals, with thecrucial di!erence that, with helium atoms instead of electrons, &[2] we areobliged to apply Bose}Einstein statistics instead of Fermi statistics (ibid.,p. 644). London then indicates that the Bose}Einstein condensation representsa discontinuity of the derivative of the speci"c heat and although this is a phasetransition of third order, rather than one of second order as in the case of helium,the experimental values for the transition temperature and entropy agree quitefavourably with those calculated for an ideal Bose}Einstein gas.

London expanded on this suggestion in a paper for the Physical Reviewwhere he presented a proof of the Bose}Einstein condensation and shows howthis &highly idealized model can give an account of the peculiar transportphenomena of liquid helium * such as the &fountain e!ect * to qualitativeagreement with experiment (1938b, pp. 953}954). Indeed, in Super-uids hesuggested that the above numerical agreement &would perhaps not have de-served much attention (1954, p. 59) had not his model o!ered the promise ofa qualitative interpretation of the &super properties and &striking peculiarities.


In this second 1938 paper he also considers the meaning of the condensationand argues that it cannot represent a physical condensation in ordinary space,since the particles do not disappear mysteriously from space. Rather: &If one likesanalogies, one may say that there is actually a condensation, but only in mo-mentum space [2] (1938b, p. 951, Londons emphasis; cf. p. 39 of Super-uids,Vol. II, where this is seen as a &manifestation of quantum-mechanical comp-lementarity). This condensation does lead to a &characteristic peculiarity(1938b, p. 951) in ordinary space, represented by a &peculiar omnipresence in thetotal volume available to the molecules. This is once again a &macroscopicquantum e!ect and London draws the comparison with superconductivity.8

However, Gavroglu insists that in the case of super#uids, this &macroscopice!ect was implied by the formalism of the theory itself, since it incorporatedBose}Einstein statistics, whereas in that of superconductivity it was an inter-pretation imposed on the formalism. Hence, he claims, the London and Londontheory could be accepted and applied without any corresponding ontologicalcommitment (p. 236). However, this &dramatically di!erent situation (ibid.)raises a problem as it seems that, in the case of liquid helium, London deviatedfrom his own philosophy of science, thus undermining one of the central claimsof the whole book. Can we reconstruct a two-stage process in this case?

In his note for Nature London explicitly states that his intention is to showthat a static spatial model &of whatever regular con"guration is not possible andthen &[2] to direct attention to an entirely di!erent interpretation of thisstrange phenomenon (1938a, p. 643). This di!erent interpretation is that ofa highly non-standard liquid, one that is very similar to a gas. As in thesuperconductivity case, the elaboration of this new model is motivated bya combination of experimental and theoretical considerations in which the roleof analogy is fundamental. This is clearly set out in the "rst two chapters ofVol. II of Super-uids (cf. Gavroglu, p. 150), where he writes,

[2] this system does not represent a liquid in the ordinary sense. There are nopotential barriers as in ordinary liquids to be overcome when an external stress isapplied. The zero point energy is so large that it can carry the atoms over thebarriers without requiring the intervention of the thermal motion. In this respectthere seems to be a greater similarity to a gas than we are used to assume inordinary liquids. This view is supported by the extremely signi"cant fact that liquidhelium I, which on "rst sight appears to be quite an ordinary viscous liquid,actually has a viscosity of a type ordinarily found only in gases and not in liquids(1954, p. 37; Londons emphasis).

Having reconceptualised the phenomenon, one can then move to the secondstage. One of the characteristic features of this strange gas-like liquid is the

8 It is noticeable that he again points out that in the latter case the macroscopic phenomena can beunderstood in terms of a &peculiar coupling in momentum space, &as if there were something likea condensed phase& in this space (London, 1983b, p. 952; Gavroglu, 1995, p. 158). This suggestionwas subsequently and independently taken up by Feynman, Ginzburg and Schafroth (p. 246).Feynman went on to develop the quantum statistical explanation of super#uidity (Mehra, 1994,pp. 348}391).


discontinuous transition noted above and here we have a structural similaritywith a Bose}Einstein (but not Fermi}Dirac) gas which exhibits a similardiscontinuity. On this basis the theoretical understanding can be built up. This isexplicitly the way in which London develops his approach in Super-uids andone is tempted to suggest that here he might be reconstructing these develop-ments in accordance with his philosophy. Of course the mechanism behind thequantum condensation is better developed than in the superconductivity case,but it should be noticed that this model is also both partial and, ontologically,relatively autonomous.

It is partial because, as London emphasises, there was no adequate theory ofliquids:

[2] it is obvious that the theoretical basis given thus far is not to be consideredmore than a quite rough and preliminary approach to the problem of liquidhelium, limited chie#y by the lack of a satisfactory molecular theory of liquids(1938b, p. 954).

As for autonomy, just as the London}London model of superconductivitycould be applied and developed in the absence of a detailed mechanism for theelectron coupling, so could the &macroscopic theory of liquid helium. Afterpresenting his model of a Bose}Einstein liquid, London writes that

[2] an understanding of a great number of the most striking peculiarities of liquidhelium can be achieved, without entering into any discussion of details of molecu-lar mechanics, merely on the hypothesis that some of the general features of thedegenerating ideal Bose}Einstein gas remain intact, at least qualitatively, for thisliquid, which has such an extremely open structure. This is an assumption whichmay be judged by the success of its consequences in describing the facts, pending anultimate justi"cation by the principles of quantum mechanics (1954, pp. 59}60; hisemphasis).

He then acknowledges Tisza as being the "rst to recognise &[2] the possibilityof evading the pitfalls of a rigorous molecular-kinetic theory by employing thequalitative properties of a degenerating Bose}Einstein gas to develop a consis-tent macroscopic theory (ibid; the changing nature of Londons view of Tiszaswork is nicely documented by Gavroglu, pp. 159}163; see also pp. 198}206 andpp. 214}217). Again, this &macroscopic theory not only described the &factsconcerning liquid helium II in terms of a common theoretical basis but alsomade speci"c predictions of the properties of the liquid.

Viewed this way, a degree of commonality can be discerned in both cases:there was a critical reconceptualisation of the phenomenon* from an analogywith ferromagnetism to that with diamagnetism in the case of superconductivity,and from a quasi-crystalline state to a Bose}Einstein liquid in the case ofHelium II * which is embedded within, or represented by means of, a &macro-scopic theory, accompanied by a move to a &molecular-kinetic understandingwhich is only partial. And in both cases, London remained convinced that thephenomena could only be explained through the crucial role of purely quantummechanical notions, as Gavroglu emphasises (pp. 235}236).


5. A Phenomenological Solution to the Measurement Problem?9

Londons only contribution to the foundations of quantum mechanics wasthe monograph he wrote with Bauer on the theory of observation (London andBauer, 1939). The intention was to re-present, in more accessible form, vonNeumanns classic analysis and to make explicit the role of consciousness ine!ecting the reduction of the wave function. Jammer has previously pointed tothe phenomenological basis of the London}Bauer account (Jammer, 1974, pp.482}486) but as Gavroglu notes (p. 179), he gets the origins wrong and hisdescription is thin to say the least. Gavroglu himself gives a detailed analysis(pp. 169}175) but then concedes too much to Shimonys famous rejection ofwhat is taken to be an extension of quantum mechanics into psychology(Shimony, 1963). Shimonys conclusion is that the London}Bauer approach&rests upon psychological presuppositions which are almost certainly false.(ibid., p. 772). However, these presuppositions are not philosophically neutraland need to be understood from the perspective of Londons own philosophy.

Some indication of the latter is given in the Introduction to the monographwhere they write:

Without intending to set up a theory of knowledge, although they were guided bya rather questionable philosophy [namely the positivistic emphasis on &observablequantities], physicists were so to speak trapped in spite of themselves into discover-ing that the formalism of quantum mechanics already implies a well-de"ned theoryof the relation between the object and the observer, a relation quite di!erent fromthat implicit in naive realism, which had seemed, until then, one of the indispens-able foundation stones of every natural science (London and Bauer, 1983, p. 220).

Thus in a measurement situation the observer herself must be considered to bea &system, subject to the theory. What we have then is an ensemble of threesystems, &(object x)#(apparatus y)#(observer z) (ibid., p. 251) described by theglobal wave function

((x, y, z)"&ktkuk(x)v

k(y)w

k(z) , (1)

where the di!erent states of the observer are represented by the wk. For us,

considering this combined system as an object, there is little di!erence betweenthe description of this situation and that in which only the object#apparatusare considered. The observer, however, has a completely di!erent impression:

For him it is only the object x and the apparatus y that belong to the externalworld, to what he calls &objectivity. By contrast he has with himself relations ofa very special character. He possesses a characteristic and quite familiar facultywhich we can call the &faculty of introspection. He can keep track from moment tomoment of his own state. By virtue of this &immanent knowledge he attributes to

9 With regard to this section, I am particularly grateful to Matt Taylor for letting me have advancecopies of chapters of his Ph.D. thesis on Husserl (Taylor, 1998).


himself the right to create his own objectivity * that is, to cut the chain ofstatistical correlations summarized in ( (x, y, z)"&

,tkuk(x)v

k(y)w

k(z) by declar-

ing, &I am in the state wk [2] (ibid., p. 252; London and Bauers emphasis).

The new wave function for the system is therefore not produced by somemysterious interaction between apparatus and object. Rather, &[i]t is only theconsciousness of an &I who can separate himself from the former function((x, y, z) and, by virtue of his observation, set up a new objectivity in attributingto the object henceforward a new function t (x)"u

k(x) (ibid.).

According to Shimony two psychological questions must be investigated:

[2] whether mental states satisfy a superposition principle, and whether there isa mental process of reducing a superposition (1963; p. 760).

He then considers whether a range of psychological phenomena, such asperceptual vagueness, indecision or con#ict of loyalty, could be interpreted asinstances of superposition, or whether superposition holds in the unconscious;and he concludes that in both cases the answer is &no. As for the secondquestion, the reduction of the wave function could be seen as a result of thenon-causal, creative mental activity of the observer. However, he argues, a) nomore creativity is felt in the case of a quantum measurement than in the case ofa &fully determined classical one; and b) evolutionary theory makes it di$cult tounderstand how irreducibly stochastic behaviour could occur in complex organ-isms and not in the &primitive entities at the base of the whole process.

Unfortunately this response mis-characterises the London}Bauer approachand misses its phenomenological underpinnings. There has, of course, been anenormous amount of discussion concerning the phenomenological understand-ing of consciousness in general, and the evolution of Husserls view of the ego inparticular. However, in the ogical Investigations (Husserl, 1900}1901) (explicit-ly cited by London and Bauer, together with the Ideas (Husserl, 1913),10 Husserlconceives of the ego as just another empirical unity which is constituted by, andthus only appears in, a re#ective act of consciousness. In the Ideas, and later, inthe Paris lectures, he maintains that this ego can survive the &phenomenologicalreduction but not, according to Taylor (1998) as a Cartesian substance. To saythat the ego appears every time we re#ect on our consciousness is just to say thatthere is an ego from the phenomenological perspective (ibid.). The ego cantherefore be understood as &[2] an in"nite cohesion of synthetically connectedacts (Husserl, 1929, p. 29) and to these acts belong all levels of reality, such as&ideas as when we describe nature and the world or treat them theoretically:

In this way we persistently create for ourselves new con"gurations of objects, inthis case ideal objects, which have for us lasting reality. If we engage in radicalself-examination* that is, return to our ego [2]* then all these forms are seento be creations of spontaneous &I-activity [2]. There we also "nd all the sciences,which, through my own thinking and perceiving, I bring to reality within myself(ibid., p. 30).

10 Gavroglu makes no mention of any further in#uence of Husserls later work.


The emphasis on our creativity is signi"cant. London and Bauer talk of theobserver attributing to himself &the right to create his own objectivity. In a typedaddition inserted by London in his own copy of the monograph, he writes:

Accordingly, we will label this creative action as &making objective. By it theobserver establishes his own framework of objectivity and acquires a new piece ofinformation about the object in question (London and Bauer, 1983, p. 252).

There is no absolute framework of objectivity residing in some &I which issomehow apart from the whole process of observation and which then, byre#ecting on &its mental states, collapses the superposition of these states.Rather the very act of observation itself is a creative construction of objectivitywhich &cuts the chain of statistical correlations. The quantum mechanicalformalism correctly describes the state of the composite object in terms ofa superposition but from &inside that object, as it were, the observer in the act ofobservation creates her own objectivity in the double sense of constructingthe &I and in doing so, separating this &I from the composite and thus gainingthe right to choose among the di!erent components of the mixture predictedby the theory (ibid., p. 251). From this phenomenological perspective thecollapse of the wave function is seen to be part of the two-sided constitution,through the act of re#ection, of the &I itself at one pole (Husserl, 1900}1901,p. 251) and the object at the other. Prior to this act there simply is no &I toobserve the superposed states of consciousness; it is only in the creative act itselfthat both the &I and object emerge and the collapse occurs.

Now, however, there is an apparent contradiction between this idea of thepure product state being brought about by an &act of objectifying, and theapparent ability of measuring arrangements to act as "lters producing purecases of the object system (London and Bauer, 1983, p. 257). Reconciliation isachieved, according to London and Bauer, by noting that although we canattribute pure states to those particles which have passed through the "lter, wecannot know which atoms have the property in question since the "lter neverputs any individual object into a new pure state. Thus, they claim, our attribu-tion of the pure state is bought at the cost of the individuality of the object,which remains absolutely &anonymous (ibid.). Such a claim is contentious, ofcourse, but it does mesh with Londons earlier insistence, in the work withHeitler, that electrons, for example, cannot be labelled.11 London and Bauercontinue by insisting that most measurements are not to do with the propertiesof individual systems but rather with general properties of species of systems.They conclude:

Quantum mechanics, truly a &theory of species, is perfectly adapted to thisexperimental task. But given that every measurement contains a macroscopicprocess, unique and separate, we can hardly escape asking ourselves to what extent

11 As noted above, in fn. 2, London emphasised the &similarity of electrons in a letter to Born, justthree years before the publication of the monograph with Bauer.


and within what limits the everyday concept of an individual object is stillrecognizable in quantum mechanics (ibid.).

It is interesting that the term &macroscopic again crops up here and it playsa key role in London and Bauers response to concerns regarding objectivity. Atthe beginning of their "nal section, &Scienti"c Community and Objectivity, theyacknowledge that it appears as if quantum mechanics has driven us towardssolipsism. However, they insist, there is still objectivity in the sense of agreementas to what constitutes the object of investigation. How is this so?

First of all, the act of observation is a &macroscopic, non-quantal act (Londonand Bauer, 1983, p. 258). Hence its e!ects on the apparatus can be neglected andthe individuality of the observer can be abstracted away, creating a &collectivescienti"c perception in which a second observer, looking at the same apparatus,will make the same observations.12 However, there is the further worry that theobjects themselves have been reduced to nothing but phantasms produced bythe observer. As they point out, the objectivity of &naive realism is grounded onthe possibility of continuous connection between the properties of an object andthe object itself, even when it is not being observed. In quantum mechanics thatpossibility is no more. Nevertheless we are still able to interpret or predictexperimental results (ibid., p. 259) and this is enough. It is at this point that theycite Husserl for his systematic study of the necessary and su$cient conditions foran object of thought to possess objectivity and be an object of science.

This is not to say that the introduction of phenomenology into this context isunproblematic. Margenau famously criticised it on the grounds that whereasscientists adopted a fallibilist attitude towards empirical data (and had de-veloped theoretical criteria for the rejection of illusory data), the phenomenolo-gist was guilty of the uncritical admission of introspective evidence which wasregarded as stable and indubitable (and thus had no similar criteria for exclud-ing &abortive introspections (Margenau, 1950, p. 463).13 Still, an appreciation ofthe phenomenological basis of London and Bauers approach to the measure-ment problem is surely necessary for a clear understanding of it.

London and Bauer end their monograph with the remarks that:

One can doubt the possibility of establishing philosophical truths by the methodsof physics, but it is surely not outside the competence of physicists to demonstratethat certain statements which pretend to have a philosophical validity do not. Andsometimes these &negative philosophical discoveries by physicists are no lessimportant, no less revolutionary for philosophy than the discoveries of recognizedphilosophers (op. cit., p. 259; London and Bauers emphasis).

12 Husserl insisted that the world is experienced not as our own private world but as an intersubjec-tive one, containing objects accessible to all.13 This is based on his earlier 1944 essay &Phenomenology and Physics, reprinted in Margenau(1978, pp. 317}328). Margenau was a physics student of Londons and went on to work in the theoryof molecular forces (Margenau, 1950, p. xxii; Gavroglu, 1995, pp. 68}69).


These are sentiments which many of us working in the philosophy of physics willsurely agree with.

6. Conclusion

At the beginning of the preface to his book, Gavroglu records that, as heplunged deeper and deeper into the research, London became a very realperson to him (p. xiii). Rich in detail and insight, Gavroglus work gives us themeasure of the man along both scienti"c and social dimensions. It stands asa "tting tribute to a remarkable "gure.

Acknowledgements2Aspects of this review have been discussed with OtaH vio Bueno, RichardFrancks, James Ladyman, Peter Simons and Mauricio SuaH rez. I am grateful to them and to JeremyButter"eld for helpful suggestions. The "nal responsibility for any errors or infelicities rests with me,of course.

References

Carson, C. (1996) &The Peculiar Notion of Exchange Forces. I: Origins in QuantumMechanics, 1926}1928, Studies in History and Philosophy of Modern Physics 27,23}45.

Cartwright, N., Shomar, T. and SuaH rez, M. (1996) &The Tool Box of Science: Tools forBuilding of Models with a Superconductivity Example, in W.E. Herfel et al. (eds),heories and Models in Scienti,c Processes (Editions Rodopi), pp. 137}149.

French, S. and Ladyman, J. (1997) &Superconductivity and Structures: Revisiting theLondon Approach, Studies in History and Philosophy of Modern Physics 28, 263}293.

Heitler, W. (1967) &Quantum Chemistry: the Early Period, International Journal ofQuantum Chemistry 1, 13}36.

Husserl, E. (1900}1901), ogical Investigations, transl. J.N. Findlay (New York: Human-ities Press, 1970).

Husserl, E. (1913) Ideas: General Introduction to Pure Phenomenology, transl. W.R. Boyce(London: Gibson).

Husserl, E. (1929) he Paris ectures, transl. P. Koestenbaum (The Hague: MartinusNijho!, 1964).

Jammer, M. (1974) he Philosophy of Quantum Mechanics (New York: Wiley).Klein, M. J. (1970) Paul Ehrenfest: he Making of a heoretical Physicist (Dordrecht:

North-Holland).Kuhn, T. S. (1970) he Structure of Scienti,c Revolutions, 2nd edn (Chicago: University of

Chicago Press).London, F. (1935) &Macroscopical Interpretation of Supraconductivity, Proceedings of

the Royal Society of ondon A152, 24}34.London, F. (1937) &A New Conception of Supraconductivity, Nature 140, 793}796 and

834}836.London, F. (1938a) &The j-Phenomenon of Liquid Helium and the Bose}Einstein

Degeneracy, Nature 141, 643}644.London, F. (1938b) &On the Bose}Einstein Condensation, Physical Review 54, 947}954.London, F. (1950) Super-uids, Vol. I, (New York: Wiley).London, F. (1954) Super-uids, Vol. II, (New York: Wiley).


London, F. and Bauer, E. (1939) a he&orie de &Observation en Me& canique Quantique(Paris: Hermann).

London, F. and Bauer, E. (1983) &The Theory of Observation in Quantum Mechanics, inJ. A. Wheeler and W. H. Zurek (eds), Quantum heory and Measurement (Princeton:Princeton University Press), pp. 217}259.

London, F. and London, H. (1935) &The Electromagnetic Equations of the Supraconduc-tor, Proceedings of the Royal Society of ondon A149, 71}88.

Margenau, H. (1950) he Nature of Phyiscal Reality (New York: McGraw-Hill).Margenau, H. (1978) &Phenomenology and Physics, in H. Margenau (ed.), Physics and

Philosophy: Selected Essays (Dordrecht: Reidel), pp. 317}330.Mehra, J. (1994) he Beat of a Di+erent Drum: he ife and Science of Richard Feynmann

(Oxford: Oxford University Press).Mormann, T. (1991) &Husserls Philosophy of Science and the Semantic Approach,

Philosophy of Science 58, 61}83.Ramsey, J. (1997) &Molecular Shape, Reduction, Explanation and Approximate Con-

cepts, Synthese 111, 233}251.Scerri, E. (1997) &The Case for the Philosophy of Chemistry, Synthese 111, 213}232.Shimony, A. (1963) &Role of Observer in Quantum Theory, American Journal of Physics

31, 755}777.Taylor, M. (1998) &Husserl and the Cartesian Epistemological Programme, Ph.D. Thesis,

University of Leeds.


el enfoque fenomenológico en fisica

Documents