Jimena Canales is the Thomas M. Siebel Chair in the History of Science University of Illinois at Urbana-Champaign. Her first book, A tenth of a second (Canales, 2011), exploring the importance that precise time measurement had on modern science and society, has been widely reviewed and acclaimed. The present book grew up from the last chapter of her previous work. The Physicist and the Philosopher is the ambitious attempt to describe how the debate between Einstein and Bergson—an interplay of philosophical differences, political disagreement, and personal animosity—had a profound and far-reaching impact on our culture’s perception of “the nature of time, the role of philosophy, and the reach and power of science” (p. 8)

The book makes a very pleasant reading. It is at the same time a scholarly and technical book, but it is written in a vivid, sometimes journalistic style. The amount of material that Canales collected is extraordinary. Even if, sometimes, I would have appreciated a clearer organization, I think most readers will greatly profit from Canale’s research. Canales has the ability to present this material so that readers feel that they are witnessing the unfolding of epoch-making events, which left an indelible mark on our culture. However, Canales’ captivating style goes sometimes at the expense of a more critically detached use of the sources. This is what I found less convincing. Canales often follows the temptation to read the documentary evidence in a way that enhances its symbolic, evocative meaning, neglecting more humble, but equally plausible interpretations.

One example has been pointed out by Wayne Myrvold. Canales suggests that Bergson played a role in the decision to award Einstein the 1921/1922 Nobel prize for the discovery of the photoelectric effect but not for relativity. According to Canales, Svante Arrhenius, Chair of the Nobel Prize Committee, alluded to Bergson in his presentation of speech: “Bergson had shown that relativity ‘pertains to epistemology’ rather than to physics” (p. 4). However, as Myrvold points out, Arrhenius only says that relativity “pertains to epistemology” and that therefore philosophers, including Bergson, have discussed it (Arrhenius, 1921). The reason why Einstein was awarded the Nobel prize, but not for relativity, was probably the negative official reports drafted by Allvar Gullstrand, an ophthalmologist, member of the Nobel Committee for Physics (Pais, 1982, 509ff.). What Canales describes as the “spectacular triumph for the philosopher”, was probably the less evocative technical mistake of an ophthalmologist (Darrigol, 2015). This is not a minor point since Canales seems to suggest that Einstein’s animosity towards Bergson was also motivated by Nobel-affair.

Unfortunately, this approach to the sources is not an isolated case. Let me give you another example, Canales’ account of the Einstein-Bergson meeting and its aftermath, the central event of the book. On April 6, 1922, Einstein participated in a discussion on relativity that took place at a meeting of the Société francaise de philosophie (Einstein, 1922). Among, the participants there were French mathematicians, physicists, and philosophers, including, of course, Bergson. “There is no such thing as a philosopher’s time” Einstein concluded his reply to Bergson, “there is only a psychological time differing from a physicist’s time” (Einstein, 1922). According to Canales, this remark of Einstein was nothing but “incendiary” (p. 5).

According to Einstein, “philosopher’s time […] is a psychological and a physical time at the same time [à la fois]; yet [or], physical time may be derived from the time in the conscience” (Einstein, 1922, 107). Einstein’s derivation resembles the one that appears in his Princeton lectures whose drafts were finished in January (Einstein, 1922b, 1). We start from the “primitive notion of the simultaneity of perception”, we move to one in which more individuals agree on which perceptions are simultaneous, finally, we project this notion of simultaneity onto the “objective events independent of individuals” (Einstein, 1922, 107). Thus, we conclude “from the simultaneity of perceptions to that of the events themselves”. Physics initially accepted this conclusion as obvious. However, Einstein realized that it was not: “Yet, nothing in our conscience permits us to conclude the simultaneity of events, because these are no more than mental constructions, logical entities” (Einstein, 1922, 107; my emphasis).

Here is where Canales’ interpretative style steps in. She quotes only the italicized part of the latter passage (p. 47), and refers ‘these’ to the “psychological conceptions of time” (p. 47) (cf. also Canales, 2016, 64). In this way, the reader has the impression that Einstein deemed psychological time a mere ‘mental construction,’ which “did not correspond to anything concrete” (p. 47). This is, however, misleading. Reading the entire passage, one can see that ‘these’ actually refers to ‘events.’ Thus, for Einstein, the ‘objective events independent of individuals’ are ‘mental constructions, logical entities.’ I suspect that the French constructions mentales corresponds to the German Gedankenkonstruktionen or gedankliche Konstruktionen, expressions which are common in Einstein’s writings and that Einstein used referring to Bergson in his Diary (see below). Thus, a better translation might have been ‘conceptual construction’ or something along that line. What Einstein seems to argue is that it is not legitimate to conclude from psychological simultaneity of sensation to the physical simultaneity of objective ‘events,’ because the latter are ‘conceptual constructions’ ((This is what Einstein explicitly wrote to Moritz Schlick a few years before. Einstein distinguished “‘elements’ in Mach’s sense” (sensations) and ‘events.’ He claims that there are different “gedanklichen Konstruktionen” that can be used to connect these Machian elements. However, this constructions does not need to agree on the events because these “surely belong to the conceptual constructions [den begrifflichen Konstruktionen]” (Einstein to Schlick, Jan. 21, 1917; CPAE, Vol. 8, Doc. 343; my emphasis; cf. Howard, 1984))). Relativistic space-time is a “freely chosen” (Einstein, 1922a) conceptual construction. As it turns out, in it there is no place for the notion of ‘now,’ which plays a fundamental role in psychological time.¹ But there is no reason to expect that there should be a correspondence between psychological and abstract physical space-time. The only justification of the latter is that it successfully accounts for the known facts (Einstein, 1922b, 2,a).

Let me offer some further evidence which does not appear in Canales’ book. In May 1922, a few weeks after the Paris meeting, Langevin (who also attended the meeting) gave three lectures in Zurich on Einstein’s relativity theory, the first of which was such a great success. The journalist E. Bovet asked Langevin the reason of the public’s surprising interest for relativity theory, whether it was because relativity was seen as freedom from the materialistic view of the world (Bovet, 1922). Langevin did not answer, but Einstein did. In his reply dated June 7, 1922, Einstein insisted that relativity was only a minor modification of the traditional “physical-causal world-picture”. The latter is a “logical system for representing space-time events in which mental [geistigen] essences (will, feeling, etc.) do not apply directly”. To avoid the conflict “between the various sorts of ‘realities’ that physics and psychology deal with,” he continues, Spinoza and Fechner respectively founded the theory of psychophysical parallelism, the claim that psychological and physical are two sides of the same coin, a doctrine that “which, quite frankly, completely pleases me” (Einstein, 1922a). Thus, far from considering only the physically real, Einstein considered “[p]hysics […] one possible way among others equally justified to put  experience in a certain order” (Einstein, 1922a). The physics’ conceptual tools “are freely chosen by us”, so that they satisfy “known facts with a minimum of hypothesis” (Einstein, 1922a). Relativistic space-time is one of these conceptual tools. It turns out that in it there is no place for the notion of absolute simultaneity, which plays a fundamental role in psychological time. But there is no reason to expect a correspondence between psychological and physical space-time. The latter is a free conceptual construction, and its only justification that it successfully accounts for the known facts.

This is exactly the opposite of Canales’ interpretation, but it seems to me at least equally plausible, even if far less ‘incendiary.’ This reading seems to be consistent with Einstein’s early reaction to Bergson’s book (Bergson, 1922) during his Japan trip between 1922 and 1923. Canales quotes (p. 46) Einstein’s remark in the October 9, 1922 entry of his travel diary (CPAE, Vol. 13, Doc. 379): “The philosophers constantly dance around the dichotomy: the psychologically real and physically real, and differ only in evaluations in this regard” (CPAE, Vol. 13, Doc. 379). Sometimes they dismiss the first as “mere individual experience” and sometimes they deem the second as a “mere conceptual construction” (Gedankenkonstruktion). Bergson, in Einstein’s view, criticizes that objectification of abstract mathematical space, but at the same time “unwittingly” (unvermerkt) objectifies the psychological time: “he does not have many scruples in objectifying the psychologically-given [Psychisch-Gegebenen]” (CPAE, Vol. 13, Doc. 379). Moreover, Einstein found at least puzzling that Bergson did not express the same concerns about space as well. After all, we can equally distinguish between psychological space (tactile, visual, etc. space), and abstract mathematical space, and, in this case too, we do not expect that the latter corresponds to the former (cf. Einstein, 1922b, 20f.). By the way, the claim that ‘there is no philosophical space,’ but only a psychological and a mathematical space would have sounded far less ‘incendiary.’

Thus, the passages quoted by Canales also allow a less dramatic reading. Einstein expressed a maybe flawed or naive, but, after all, a fair critique of Bergson’s philosophical doctrine. However, Canales points out that, just after the Japan trip, Einstein’s attitude towards Bergson became more hostile. In some of the best and original parts of the book, Canales nicely reconstructs the background of Einstein’s and Bergson’s engagement into the International Committee on Intellectual Cooperation (CIC) of which Bergson was president. Canales conjectures that their political disagreement in that context might explain Einstein’s more aggressive tones. Canales quotes from a letter to Solovine as evidence (Einstein to Solovine, May 20, 1923; CPAE, Vol. 14, Doc. 34).

The letter, written to an old friend, lists without any line breaks (the original is reproduced in Einstein and Solovine, 1987) a series of apparently unrelated issues: Einstein’s trip to Japan and Palestine, Solovine’s trip to the United States, the royalty payments from the publisher Gauthier-Villars, the drafts of a book of Charles Nordmann (1922), Einstein’s resignation from CIC, and, finally, the “serious blunders” in Bergson’s book. “May God forgive him”, he concluded the letter (Einstein to Solovine, May 20, 1923; CPAE, Vol. 14, Doc. 34). “In four short sentences Einstein referenced God, politics, and relativity”, and Canales found revealing that Einstein’s dated the latter with “reference to a religious holiday, Pentecost 1923, instead of to the calendar date” (p. 123). This a quite exemplary case of Canales’ interpretive style, in which the attempt is made to uncover hidden relations between the parts of a text. However, Canales’ approach can get off track. The fact that the political ICC-case and Bergson’s book are mentioned one after another may suggest a causal connection, but it does not prove it. The reference to God and the use of Pentecost as a date may suggest a quasi-religious feeling permeating the letter. However, the letter can also be read as an informal list of quite mundane affairs.

It is nevertheless not to exclude that Einstein was drawn by personal animosity towards Bergson. Einstein used quite harsh words also in a letter to Ehrenfest. The point is whether his accusation area motivated by an actual disagreement about Bergson’s treatment of relativity theory. Canales that central issue asymmetry/asymmetry of clocks in this case of clock or twin paradox. Everyone knows that travelled distance measured by, say, two identical odometers (with the same turns-per-mile ratio) mounted on two identical vehicles depends on the path that the vehicles have taken in space. A straight path in space is shorter then a curved one. Special relativity claims that that clocks resemble odometers more that common sense would assume: the elapsed as measured by identical clocks (with the same rate-of-ticking) depends on the pre-history of the clock, i.e., on its path through space-time (clock effect). The only difference is that a straight path in space-time is the one with longer elapsed time. However, it is worth to emphasize, that the rate-of-ticking of a good clock is supposed to be independent of the prehistory of the clock (clock hypothesis). This is the very definition of a ‘good’ clock. Appropriately modified, these results of special relativity still hold in the general theory.

Do ‘good’ clocks exist in nature? Which are they? This is a different set of questions to which relativity theory do not provide any answer. One has to proceed tentatively, to identify some physical process as a good clock. Using the aging process of identical twins as a clock instead of some inanimate mechanism, say the decay of an atom is an odd choice. However, under the assumption, that the two twins maintain the same rate-of-aging (clock hypothesis), it is in principle possible to use the difference in age at the end of the trip as the measure of elapsed time (clock effect). One might use the difference in tiredness of two identical twins to measure distances, under the assumption that they consume the same amount energy per mile. The aging process of twins is of course not a good clock, just like their tiredness is not a good odometer. However, this does not change the conceptual point.

Let me go back to Bergson. Bergson’s ‘Achilles’ heel,’ as Canales calls it, was the following: he did not understand in which sense the two twins’ situations are symmetrical (the rate-of-aging is the same) in which sense they are not (the elapsed time is different). I follow here Canales’ presentation, which is quite apologetic. However, it did show that Bergson was simply confused. Bergson initially claimed that Einstein was wrong because the two clocks were ‘absolutely reciprocal,’ “completely interchangeable” (p. 64). “After receiving numerous criticisms from Einstein’s allies,” Canales writes, “he explained himself more fully” (p. 64f.). Canales’s wording is, however, hard to justify. It is not that Einstein’s ‘allies’ attacked Bergson for some partisan reason: Bergson was simply wrong. He himself realized later that “acceleration created a dissymmetry” (p. [)65]. However, the conclusion that Bergson drew from this is a non-sequitur: “Since a difference existed, one connected to a difference in time, then their times were not equal in every sense” (p. 65). What does ‘in every sense’ mean? The twins are supposed to be identical, but the paths they traveled in space-time are not. “Could their different trajectories, memories, and experiences be neglected?” (p. 66). The identity of the twins is, of course, an intentionally unrealistic assumption. We all know that there are no twins with perfectly identical rate-of-aging, and, in fact, we use the rate-of-decay of muons which fit the bill of a good clock better. “Would the effects of time dilation affect biological beings? Yes, answered Einstein. Not so quick, replied Bergson” (p. 317). But the relativity theory does not predict that time affects biological beings more than previous theories; the point is that, in principle, the aging of biological beings could be used to measure elapsed time. Special relativity simply predicts that for the twin at rest a longer time has passed, then for one embarked in a high-velocity interstellar trip. Bergson’s further claim that, nevertheless, “philosophical differences would remain between the two twins” (p. 166). However, this is, if I might say, the very definition of ‘handwaving.’

Canales is very gifted in making this evocative use of the textual evidence, an approach which is often literary powerful. However, as I have tried to show, in some cases, a less sensationalistic reading of the sources is also possible. The 1922 Bergson-Einstein meeting becomes emblematic of a dramatic clash between the philosopher and the physicist if one embraces Canales’ hermeneutic style. Otherwise, it can simply be seen as the evidence that Einstein, for better or worse, did not appreciate the conception of time of a philosopher, Bergson. At the 1922 Paris meeting, Einstein discussed with another philosopher, Émile Meyerson (p. 276ff.). He read his book on relativity (Meyerson, 1925) during another long trip, the one to South America in 1925, but, in this case, he was enthusiastic (Einstein, 1928). In conclusion, the reader should take advantage of the impressive amount of historical sources that Canales was able to collect in this book, and which goes far beyond Bergson and Einstein. However, the reader should also be warned not to uncritically embrace Canales’ use of these sources. The Bergson-Einstein debate was an important debate indeed, but possibly not the incarnation of the titanic battle between ‘The two Cultures.’

Abbreviations

CPAE Albert Einstein (1987–). The collected papers of Albert Einstein. Ed. by John Stachel et al. 15 vols. Princeton: Princeton University Press, 1987–.

References

Arrhenius, Svante (1921). Nobel Prize in physics 1921. Presentation speech. Dec. 10, 1921. eprint: http://www.nobelprize.org/nobel_prizes/physics/laureates/1921/press.html.

Bergson, Henri (1922). Durée et Simultanéité. À propos de la théorie d’Einstein. Paris: Alcan, 1922.

Bovet, Ernest (1922). “Une simple question à Monsieur Langevin.” Wissen und Leben 15 125, 645–650.

Canales, Jimena (2011). A tenth of a second. A history. Chicago: University of Chicago Press, 2011.

— (2015). The physicist and the philosopher. Einstein, Bergson and the debate that changed our understanding of time. Princeton: Princeton University Press, 2015.

— (2016). Einstein’s bergson problem: communication, consensus and good science. In: Cosmological and psychological time. Ed. by Yuval Dolev and Michael Roubach. Cham et al.: Springer Nature, 2016, 53–72.

Darrigol, Olivier (2015). “Mesh and measure in early general relativity.” Studies in history and philosophy of science part B: Studies in history and philosophy of modern physics 52, 163–187.

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Einstein, Albert (1922a). “[Response to Bovet, 1922].” Wissen und leben 15, 902.

— (1922b). Vier Vorlesungen über Relativitätstheorie, gehalten im Mai 1921, an der Universität Princeton. Braunschweig: Vieweg, May 1922. Repr. in CPAE, Vol. 7, Doc. 71.

— (1928). “A propos de ‘La Déduction Relativiste’ de M. Émile Meyerson [Meyerson, 1925].” Revue philosophique de la France et de l’étranger 105, 161–66.

Einstein, Albert and Maurice Solovine (1987). Letters to Solovine. 1906–1955. New York: Philosophical Library/Open Road, 1987.

Howard, Don (1984). “Realism and conventionalism in Einstein’s philosophy of science. The Einstein-Schlick correspondence.” Philosophia naturalis 21, 618–29.

Meyerson, Émile (1925). La déduction relativiste. Paris: Payot, 1925. tr. The Relativistic Deduction. Epistemological implications of the theory of relativity. Dordrecht: Reidel, 1985. with a review by Albert Einstein.

Myrvold, Wayne (2016). Did Bergson influence Einstein’s Nobel prize? May 10, 2016. eprint: http://filosothots.blogspot.de/2016/05/did-bergson-influence-einstein-s-nobel.html.

Nordmann, Charles (1922). Einstein et l’univers. Une lueur dans le mystère des choses. Paris: Hachette, 1922.

Pais, Abraham (1982). Subtle is the Lord. The science and the life of Albert Einstein. New York: Oxford University Press, 1982.

Speziali, Pierre, ed. (1972). Albert Einstein-Michele Besso. Correspondance 1903–1955. Paris: Hermann, 1972.