“I do not feel comfortable and at home in any of the ‘isms’. It always seems to me as though such an ism is strong only so long as it nourishes itself on the weakness of its counter-ism. But if the latter is struck dead and it is alone on an open field, then it proves to be wobbly on its legs. Therefore, away with the grousing (los mit der Stänkerei)!”
Albert Einstein, letter to mathematician Edward Study, September 25, 19181
Albert Einstein was a theoretical physicist, not a philosopher in any customary sense. His contributions to, and influence upon, physical theory are rivaled, if at all, only by those of Isaac Newton at the beginning of the modern age. A rapid succession of publications, appearing within a few months of each other in the annus mirabilus 1905 brought Einstein the attention of Europe’s most prominent physicists. At the time obscurely employed as a full-time patent clerk in Bern, Switzerland, any one of three of these would suffice to ensure a glowing reputation in the annals of 20th-century physics. Best known is the paper outlining the special theory of relativity, showing that the recognized incompatibility between Maxwell’s theory of electromagnetism and classical mechanics required modifying Newtonian mechanics. Einstein himself favored the one stating the light-quantum hypothesis; of the three, only this he considered “very revolutionary”. It contains the first argument that Planck’s quantum of energy is a physical entity. And then the paper outlining the theory of Brownian motion within a few years led to experiments resulting in universal acceptance of the reality of atoms. His greatest achievement came not in 1905 but in 1915, with the relativistic theory of gravity, or “general relativity”, completed after eight years of struggle in the middle of World War I. Conceived as a theory to remove the last vestiges of fixed background structure from the physical doctrines of space and time, by 1917 Einstein had applied it to the entire universe, in so doing creating modern relativistic cosmology.
The theories of relativity, special and general, are two of three props of contemporary fundamental physical theory, extending from elementary particle theory, where special relativity is essential and gravitation is ignored, to inflationary cosmology and the origin and fate of the universe. Even Einstein’s failures are spectacular. The theory of light quanta and his call for a dual wave-particle theory of light in 1909 effectively set the table for the other revolution of 20th-century physics, the indeterministic quantum theory he would never accept. After the arrival of quantum mechanics in 1925–1926, Einstein remained a skeptic, yet called attention to phenomena (most notably, “entanglement”) nearly all the founders of quantum mechanics either dismissed as an imperfectly posed “paradox” or chose to ignore. More than any other scientist, Einstein created the basis for the current understanding of nature and indeed the universe. Time Magazine’s recognition as “Person of the Century” (December 26, 1999) was both deserved and not at all surprising.
In what sense is Einstein to be considered a philosopher? To Abraham Pais, particle physicist and author of what remains the sole scientific biography, “calling Einstein a philosopher sheds as much light on him as calling him a musician”.2 Though perhaps too harshly put, the observation is largely correct. Einstein was at most a “philosopher-scientist” (per the subtitle of Schlipp 1949). Whereas philosophers typically develop a characteristic viewpoint in dialogue with, or response to, other philosophers or philosophical traditions, as did Kant with respect to Hume (empiricism) and Leibniz (rationalism), there is very little evidence of this kind of exchange or transmission to be found in Einstein’s writings. Letters occasionally mention philosophical readings, briefly reporting praise or disagreement. There is a late reminiscence crediting texts of Hume and Ernst Mach as assisting the realization, in 1905, of the unphysical nature of the prevailing, and largely implicit, presupposition of absolute time (absolute simultaneity). Yet as the 1918 epigraph indicates, Einstein did “not feel comfortable and at home in any of the -isms”, and he shared the modern physicist’s disdain for the “squabbling” among them. Disregard for philosophical pigeon holes is evidenced in his one summary self-characterization as “a type of unscrupulous opportunist”, appearing alternately “as realist … as idealist … as positivist … as Platonist or Pythagorean”.3
To deem Einstein a philosopher even in the attenuated sense of “philosopher-scientist” would suggest that there is in fact an Einsteinian philosophy. Is there an overall narrative to be fashioned to encompass all or most of the observations of a philosophical character scattered in his writings? A looming difficulty is the largely occasional nature of many of Einstein’s philosophical remarks. Trying to find consistency presents a challenge to any synthetic portrayal of Einstein’s philosophy. This is not to say that selective attention to certain comments or to different periods of Einstein’s career hasn’t produced various attempts to assimilate him to one or another philosophical heading. Logical empiricist philosophers took inspiration from various remarks pre-1925 that appear little more than broadcasts of textbook positivism. But positivism of any variety cannot abide later notable expressions of faith in mathematical speculation, or “logical simplicity”, as a method capable of revealing nature’s innermost secrets.
The apparently extreme swings of direction are frustrating to anyone looking for a convincing portrait of Einstein’s philosophical views with broad textual support. A natural accommodating strategy is then to identify a pivotal change in philosophical affinity or allegiance. A well-known attempt of this kind is that of physicist and historian of science Gerald Holton who viewed the completion of the general theory of relativity as the key episode.4 Holton, the leading Einstein scholar of his generation, portrayed Einstein’s career as a philosophical odyssey, a “pilgrimage … starting on the historic ground of positivism”, heavily under the influence of Mach. Over time, “apostasy” from Mach became more and more apparent, particularly following the triumph of general relativity, a success Einstein subsequently attributed to his belated adoption of a mathematical “speculative-constructive” method. Einstein’s philosophical terminus is then a “rationalistic realism” that essentially turned Mach’s phenomenalistic positivism “on its head” (see Chapter 8). Holton’s narrative is instructive and has been highly influential. Yet even while accurate in its broad contours, the Holton template doesn’t quite fit the facts; the young Einstein was at least as much a follower of Boltzmann (and proponent of the reality of atoms) as of Mach (who deemed atomism to be a “metaphysical” hypothesis). On the other hand, the older Einstein, Holton’s “rationalistic realist”, can still appear almost a pragmatist in the mold of Dewey, declaring “the whole of science” to be “nothing more than a refinement of everyday thinking”.5 The challenge of interpolating between ostensibly conflicting philosophical pronouncements still remains.
A clue lies in the Herbert Spencer lecture, given at Oxford on June 10, 1933. Lecturing for the first time in English, Einstein spoke “On the Method of Theoretical Physics”, a topic with definite, if somewhat constrained, philosophical import. Holton and subsequently others emphasize that the lecture can be considered something of a philosophical watershed, a public “coming out”, proclaiming a faith in mathematical simplicity as trustworthy guide to theoretical comprehension of the most fundamental underlying processes of nature. For present purposes, that of identifying a philosophy that can be warranted as Einstein’s, another message in the lecture stands out, issued in a provocative challenge near the beginning:
If you wish to learn from the theoretical physicist anything about the methods which he uses, I would give you the following piece of advice: Don’t listen to his words, examine his achievements.6
This book heeds Einstein’s advice, identifying a philosophy that is indeed his, though “philosophy” is here to be understood in the first instance in the indicated sense, namely, as illustrated by his main achievements in physical theory. It is a philosophy manifested over his entire career, consisting in the advance or critique of theory through the use, and presumed general validity, of certain principles; physical, formal, methodological, and metaphysical. While Einstein’s various remarks do reveal a philosophical viewpoint informed by decades of reading, it is a “philosophy of principles” guiding theoretical practice and shaping philosophical pronouncements rather than the other way round; as he once put it, “the (physicist) himself knows best … where the shoe pinches him”.7
Historians of physics have remarked that Einstein’s strivings and accomplishments in physical theory have a distinctive character: they reveal the quest of the natural philosopher, of one who believes that genuine understanding of physical reality is attainable only from the standpoint of a unified theoretical foundation for physics. The pursuit of such a foundation can be seen across the more than fifty-year span of his life as a physicist.
In the 17th century the idea there might be a unified foundation for all of physics originated with Descartes, for whom extension was the primary attribute of matter, motion was caused exclusively by contact, and physical explanation was necessarily causal. Classical mechanics, largely created by Newton, departed from the Cartesian model by introducing the notion of force, a program adequate for all of physical theory for more than two centuries. All physical phenomena were to be represented in terms of the concepts of space, time, material point, and force. Shortly after 1900, Einstein recognized that classical mechanics could no longer serve as the foundation it had been essentially since 1687. In his self-described “obituary” in 1946, Einstein recalled that in the wake of “Planck’s trailblazing work” in 1900, it had become clear “that neither mechanics nor thermodynamics could claim exact validity, except in limiting cases”.8 Following Maxwell and Boltzmann, most theorists regarded thermodynamics as resting upon the “molecular-kinetic theory of heat”, i.e., the assumption that physical systems are composed of molecules obeying Newtonian laws of motion and collision, and that macroscopic thermodynamic properties of systems (temperature, pressure, density, entropy, etc.) are brought about by motions and collisions of vast numbers of molecules.
From a completely different direction, Maxwell’s field theory of electromagnetism successfully unified physical optics and the theories of electricity and magnetism, showing that light itself was an electromagnetic phenomenon. This was a revelation to the young Einstein. But in 1900 Planck had also shown what he himself was reluctant to admit, that thermal radiation – the energy emitted and absorbed by matter – had a particulate and non-Maxwellian character. At least by 1905, Einstein understood that Maxwell’s theory was not fully compatible with Planck’s law successfully describing the spectrum of blackbody radiation. If – Einstein argued from two directions in 1905 – the point particle mechanics of Newton failed for very rapid periodic processes (as in matter-radiation interactions) as well as for systems moving at or near the speed of light, what might replace Newtonian mechanics, assumed the foundation of all of physics, including thermodynamics? It was “as if the ground had been pulled out from under one’s feet, with no firm foundation on which to build anywhere” (1946, p. 45). Progress toward a new unified foundation, if possible at all, might be made only by building from a secure basis. Where, amidst the turmoil and uncertainty of turn-of-the century physical theory, might this be found?
By 1905 Einstein had placed epistemic bets on three prescriptive injunctions: the relativity principle, the light principle, and what he termed “Boltzmann’s principle”, the definitional connection between thermodynamic entropy and probability on which Boltzmann anchored the probabilistic interpretation of the second law of thermodynamics. The first two, both postulates of special relativity, affirmed just those features of mechanics and electromagnetism deemed essential and indispensable to each. Any future advance in mechanics or electromagnetic theory would have to admit their empirical validity. But this was a lesson Einstein learned from the principle named after Boltzmann. By at least 1904, Einstein realized theoretical progress or unification can be attained by according certain physical principles wider empirical validity than a particular theory based upon on that principle (see Chapter 3).
The cited “obituary” obliquely refers to this realization. In explaining how he came to introduce the postulate that the laws of physics must satisfy the principle of relativity, Einstein relates that he was inspired by the example of thermodynamics. Thermodynamics impressed him as a particular type of physical theory, a theory of principle: in essence, one whose empirical validity in most general forms, extending beyond particular applications or formulations, could be summarized by confirmed facts of projected universal scope, the prohibition of two kinds of perpetual motion, corresponding to the first two laws of thermodynamics. In Boltzmann’s principle and in the energy principle (conservation of energy) Einstein recognized two core postulates underlying all thermodynamic phenomena but of broader validity than recognized in the existing statistical treatment of thermodynamics. He would then use this understanding to highlight the significance of energy fluctuation phenomena, natural processes lying outside the purview of classical thermodynamic treatment, pointing to the non-classical and quantum character of the physical micro-world.
Principles also guided Einstein to the general theory of relativity. The path was opened in 1907 by an insight that led to the “principle of equivalence”. Loosely construed (see Chapter 6 for a careful statement), it affirms that in certain ideal situations, an observer inside a closed cabinet would not be able to observationally distinguish between the effects of gravity and those of uniform acceleration in a gravity-free region. The insight proved the crucial heuristic for extending the principle of relativity from the inertial frames of special relativity to the non-inertial frames of accelerating systems, and so to gravitational phenomena. The motivation for such an extension was deeply philosophical, prompted by Mach’s earlier critique of Newton’s explanation of inertial effects, a treatment that implicitly relied on the metaphysical notion of absolute space. On the eight-year path to general relativity, Einstein repeatedly referred to Mach’s attempt to “relativize inertia”, and on completion of the theory, Einstein would state (wrongly, as is now known) that global (cosmological) solutions of the theory’s field equations rest upon “Mach’s principle”. That principle, as will be seen, was intimately intertwined in Einstein’s thought with another, a “principle of general relativity” that turns out to be a merely formal principle, the “principle of general covariance”, pertaining to the invariant form equations take in any permissible coordinate system. General relativity, resting on the three above principles, also prompted Einstein’s statement of still another principle in 1931, the so-called “cosmological principle”, affirming “all locations in the universe are equivalent; in particular the locally averaged density of stellar matter should therefore be the same everywhere”.9 The cosmological principle remains today a widely held methodological assumption of many cosmological models (see Chapter 11).
The philosophy of prescriptive principles, comprised of those above, and others to be discussed, informed not only Einstein’s achievements as a theoretical physicist but also his failures. These are essentially two: an unwillingness to accept the irreducibly probabilistic character of quantum theory, and correspondingly the ill-fated effort to replace it, a three-decades-long attempt to produce a “unified field theory”. This was to be an extension of general relativity in which particles were mathematically characterized through particular solutions of the field equations, and the quantum behavior of matter and radiation indeed could be deemed probabilistic, but only in the sense of classical statistical mechanics where probabilities and averages are proxies for knowledge of exact positions and velocities of enormous numbers of particles. In effect, both failures are a consequence of Einstein’s conception of what a fundamental physical theory is, and what it should aim to do. These aspects of his philosophy are alluded to in a letter to Schrödinger of June 17, 1935:
From the point of view of principles, I absolutely do not believe in a statistical basis for physics in the sense of quantum mechanics, despite the singular success of the formalism of which I am well aware. I do not believe that such a theory can be made general relativistic. Aside from that, I consider the renunciation of a spatio-temporal setting for real events to be idealistic-spiritualistic. This epistemology-soaked orgy ought to burn itself out.10
And again in 1949:
What does not satisfy me in [quantum mechanics], from the standpoint of principle [Was mich an der Theorie vom prinzipiellen Standpunkt aus nicht befriedigt], is its attitude towards that which appears to me to be the programmatic aim of all physics: the complete description of any (individual) real situation (as it supposedly exists irrespective of any act of observation or substantiation).11
On the other hand, since Einstein’s death the tide of positivism in theoretical quantum physics has waned. Programs today within the foundations of quantum mechanics seek to implement something of a realist vision of quantum theory, though that vision is not Einstein’s. Just what that vision amounts to is taken up in this book’s latter chapters; there it will be shown to fall rather short of the contemporary doctrine termed “scientific realism”. Still another reason from his divergence from realism appears in a distinction he drew between “theories of principle” and “constructive theories”.
Responding to a query posed by an editor of the Times of London in late November 1919, the suddenly famous Albert Einstein wrote a brief account of relativity theory in German, sending it to the Times’ Berlin correspondent. Appearing in the Times on November 28 as “Einstein On His Theory”12 Einstein affirmed that relativity theory is a two-story building, the theory of special relativity on the ground floor, supporting the general theory one flight up. Both, Einstein noted, were examples of a particular type of physical theory termed “principle theories”. Employing a distinction similar to those previously used by Henri Poincaré and H.A. Lorentz, Einstein observed that “principle theories” differ in kind from most other fundamental physical theories that are “constructive” in character.
Constructive theories “attempt to build up a picture of the more complex phenomena out of the materials of a relatively simple formal scheme from which they start out”. “Building up” is naturally a synthetic process; the “more complex phenomena” are constructed from “materials of a relatively simple formal scheme” – that is, from elementary processes deemed capable of bringing about or producing the phenomena of interest. The phrase “relativity simple formal scheme” suggests that the materials of construction have some latitude to entertain a wide variety of underlying elementary processes, as long as they, and their hypothesized actions, are readily conceived and mathematically tractable. As had Lorentz, Einstein pointed to the kinetic theory as an exemplary constructive theory. The “molecular-kinetic theory” of heat (see Chapter 2) explains the thermodynamic properties of gases when the system is in thermal equilibrium under the assumption that the gas is a vast number of molecules in rapid motion. Macroscopic thermodynamic properties – pressure, volume, temperature, entropy – are explained by positing that molecular motions obey the laws of classical mechanics and by introducing probability considerations, such as the relative numbers of molecules in each distinct state (e.g., possessing a certain velocity) at a given time. The kinetic theory, and its extension by statistical mechanics to non-equilibrium systems approaching equilibrium, are canonical examples of the explanatory paradigm of reduction of one theory to another, wherein the laws of the theory pertaining to observable phenomena and relations are regarded as deriving from laws of a theory pertaining to unobservable microphysical objects and processes.13 Einstein’s 1905 paper on Brownian motion employed the “molecular-kinetic theory” to explain the observable (through a microscope) random motions of grains of pollen suspended in a liquid as due to chaotic thermal motions of the liquid’s unobservable constituent molecules. In the annals of science, Einstein thus played a key role in demonstrating the reality of atoms, a triumph of realism (see Chapter 3).
Principle theories, on the other hand, have a top-down axiomatic character. Accounts of the phenomena of interest are derived on the basis of “empirically discovered” postulates or principles, i.e., “general characteristics of natural processes” which all physical events are required to satisfy. Principle theories “employ the analytic not the synthetic method”; that is, from a postulational starting point, they license logical rather than causal-dynamical inferences. Einstein identified thermodynamics as a paradigm of a principle theory. Here, the “universally experienced fact” of the impossibility of a perpetuum mobile stands at the pinnacle of the theory, from which a large number of empirical regularities in the theory of heat may be inferred. The theories of relativity, both special and general, he explained, are principle theories in this sense.
Einstein’s intent, however, is not to rehearse an already recognized difference between types of physical theory so much as it is to point to the explanatory weaknesses of both theories of relativity. For the two types of theory differ not only methodologically and structurally, but also have distinct epistemic virtues:
The advantages of the constructive theory are completeness, adaptability, and clearness, those of the principle theory are logical perfection and security of the foundations.14
The virtue of “completeness” is associated with constructive theories, a point to which return is made when considering Einstein’s objection that quantum mechanics is “incomplete”. Remarkably, Einstein then insists that constructive theories alone yield understanding:
When we say that we have succeeded in understanding a group of natural phenomena, we always (immer) mean that we have found a constructive theory that embraces them.15
This is an astonishing admission, since the two theories of relativity are not constructive theories but principle theories, as Einstein readily admits. Yet reserving the accolade of understanding to constructive theories is not altogether surprising. It is fully in accord with the reductionist scientific maxim that explanations of phenomena remain incomplete until a causal mechanism or elementary process can be identified and can be shown to be capable of producing the observed effects. A principle theory, without an underlying component describing elementary processes, does not do this.
One can well ask what might have been Einstein’s intent in choosing to introduce his theories of relativity through the prism of the principle theory/constructive theory distinction. By the end of November 1919, Einstein’s relativistic theory of gravity was already four years old, though it had only just come to the wider world’s attention in the London announcement on November 6 of the British solar eclipse observations of the previous May. He was well aware that the general theory of relativity was essentially incomplete; its treatment of matter-energy was nothing more than a skeleton that needed to be filled out in a field theory of matter. He had not rested on his laurels during these years but – prompted by the efforts of others to provide such a theory – was already engaged in attempting such a completion. This would become known as the program of unified field theory. It would require bringing all fundamental interactions into a geometrical broadening of the space-time setting in which he had placed gravitation. These efforts would continue for more than three decades, and they were ultimately all unsuccessful. Once before, in 1910–1911, Einstein embarked on such a constructive path when he sought to construct the quanta of radiation from a nonlinear generalization of Maxwell’s theory of the electromagnetic field; during this time, he even expressed skepticism about the existence of quanta; perhaps they were not, after all, fundamental if they could be constructed, i.e., derived from more fundamental field processes. These efforts had come to naught, and were rather quickly given up. But the broader idea of constructing particles, with their discrete size and charge, within a field theory returned with the completion of general relativity. Now one had to begin from an unknown theory of the total field that must satisfy certain principles, above all, the “principle of general relativity”.
While at various points in his career he would proffer theoretical proposals that may be regarded as “constructive” in the indicated sense, Einstein was predominately and preeminently a theorist who built upon principles regarded as universally applicable. Both theories of relativity were erected upon a respective “principle of relativity”. It seems ironic and paradoxical that Einstein would extol the explanatory virtues furnished only by constructive theories even as he became the icon of scientific genius on the basis of principle theories. There is another way to understand this. The de facto choice in the matter stemmed not from any modesty of ambition. Rather it tells a great deal about the epistemology and methodology of Einstein, both young and old, for whom half a loaf was better than none. Just as constructive theories remained the explanatory gold standard of physics on account of their capacity to provide comprehensive understanding, the virtues of principle theories, namely, “logical perfection and security of the foundations”, were assets that could be acquired within the existing state of physical knowledge. To Einstein, the way forward lay in attempting to build empirically confirmed theories upon prescriptive injunctions, principles stipulated to be universally valid that accordingly placed restrictions upon the possible laws of nature. Einstein’s principles are not explanations, but postulates. This path admittedly gives something of a rationalist a priori character to the two theories of relativity. Late in life, Einstein portrayed the fateful decision to pursue the route of a principle theory, the path that led him to special relativity, as his one real option, a kind of Hobson’s choice, writing of his “despair” at the time of any prospect of finding any true constructive laws underlying the pertinent electrodynamical phenomena.16
Still, the example set with both special and general relativity – the use of principles of invariance (for that is what both principles of relativity are, however named) to constrain the class of possible laws of nature – proved a salutary lesson to theoretical physics in the 20th century and beyond. Appropriately, Princeton physicist Eugene Wigner, winner of the 1963 Nobel Prize for the pioneering use of symmetry principles in nuclear and molecular physics, described this as “Einstein’s greatest discovery”.
One can say, in fact, that Einstein’s greatest discovery was the establishment of the importance of invariance principles.17
Together with a lifelong passion for theoretical unification, one lasting bequest to theoretical physics is the innovative use of principles of symmetry to constrain the dynamics of theories, viewing these principles not as corollaries to the dynamical laws but as axioms restricting the allowable dynamics.
Because of the close interconnection between what is here understood as Einstein’s philosophy and his achievements and endeavors in physical theory, this book has a considerably different format than might be expected in a book about a particular philosopher. Physics and the history of physics occupy much of the center stage. An effort has been made to present this material in a way that is both accessible to non-specialists and is reasonably self-contained regarding Einstein’s innovations and interventions. Very little higher mathematics has been used, and where it has, for example, with the metric tensor gµv of general relativity, the symbols occur only for expository purposes. This is not to say that this book will not make demands on the reader. But it is the author’s belief that this mode of presentation is needed to avoid the sin of anachronism, of assimilating Einstein to other, and later, philosophical currents.
1Einstein, letter to mathematician Edward Study, September 25, 1918. CPAE 8 (1998) Part B, Doc. 624.
2Pais, Abraham, “Subtle Is the Lord …” The Science and the Life of Albert Einstein. New York: Oxford University Press, 1982, p. 318.
3Einstein, “Reply to Criticisms” (1949), p. 684. “(The scientist) must appear to the systematic epistemologist as a type of unscrupulous opportunist: he appears as realist insofar as he seeks to portray a world independent of acts of perception; as idealist insofar as he looks upon concepts and theories as free inventions of the human mind (not logically derivable from what is empirically given); as positivist insofar as he regards concepts and theories as justified only to the extent to which they afford a logical representation of relations between sensory experiences. He may even appear as Platonist or Pythagorean insofar as he considers the viewpoint of logical simplicity as an indispensable and effective tool of his research” (translation slightly modified).
4Holton, Gerald, “Mach, Einstein, and the Search for Reality”, Daedalus v. 97 (1968), pp. 636–73. Page references to the reprint in Holton, Thematic Origins of Scientific Thought: Kepler to Einstein. Cambridge, MA: Harvard University Press, 1988, pp. 237–77.
5Einstein, “Physik und Realität”; “Physics and Reality”, Journal of the Franklin Institute v. 221, no. 3 (March, 1936), pp. 313–47; pp. 349–82. The translation by J. Picard is reprinted in Albert Einstein, Ideas and Opinions. New York: Crown Publishers, 1954, pp. 290–323; p. 290.
6Einstein, “On the Method of Theoretical Physics”, Philosophy of Science v. 1, no. 2 (April 1934), pp. 163–9; p. 163.
7“On the Method of Theoretical Physics” (1936), p. 313; p. 290.
8“Autobiographical Notes” (1946), p. 52; p. 53.
9“Zum kosmologischen Problem der allgemeinen Relativitätstheorie”, Sitzungsberichte der Preußischen Akademie der Wissenschaften, Phys-Math. Klasse (1931), pp. 235–7; p. 235. As reprinted in Dieter Simon (ed.), Albert Einstein: Akademie-Vorträge: Sitzungsberichte der Preußischen Akademie der Wissenschaften 1914–1932. Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA. Published online, 9 August 2006, pp. 361–4; p. 361.
10As translated in Arthur Fine, The Shaky Game: Einstein Realism and the Quantum Theory. Second edition. Chicago: University of Chicago Press, 1996, p. 68.
11“Reply to Criticisms”, p. 667.
12Einstein, CPAE 7 (2002), Doc. 25; pp. 206–13. Translation as “What Is the Theory of Relativity?” in Ideas and Opinions, 1954, pp. 227–32.
13The classic philosophical account of the reduction of thermodynamics to statistical mechanics is given in Nagel, Ernst, The Structure of Science. New York: Harcourt, Brace and World, Inc., 1960, chapter 11. A critical, and more sophisticated, discussion is Sklar, Lawrence, Physics and Chance. Cambridge: Cambridge University Press, 1993; chapter 9.
14Ibid., p. 228.
15Ibid.
16“Autobiographical Remarks” (1946), p. 52; p. 53.
17“Symmetry in Nature” (1972), as reprinted in J. Mehra and A.S. Wightman (eds.), Eugene Paul Wigner: Philosophical Reflections and Syntheses with annotations by G. Emch. Berlin, Heidelberg, New York: Springer, 1995, pp. 382–99; p. 390.
Six invaluable resources are:
1. The Collected Papers of Albert Einstein. Princeton: Princeton University Press. Abbreviated in this book as CPAE. Beginning with volume 1 in 1987 (The Early Years 1879–1902), additional volumes continue to appear up to volume 13 in 2012 (Writings and Letters 1922–23). Certain texts within each volume appear in English translation in a supplementary separate volume. Remarkably, the volumes and supplements are freely available online, http://einsteinpapers.press.princeton.edu/
2. Schilpp, Paul A. (ed.), Albert Einstein: Philosopher-Scientist. Evanston, IL: Northwestern University Press, 1949. Besides containing interesting essays on aspects of Einstein’s work and thought by both physicists and philosophers, the Schilpp volume has Einstein’s “Autobiographical Notes”, completed in 1946, pp. 2–95, in the original German with facing page translation; and “Reply to Criticisms”, completed in 1949, in Schilpp’s translation. For those who read German, the translation should be compared with Einstein’s German text, “Bemerkungen zu den diesem Bände Vereinigten Arbiten”, in the German edition of the Schilpp volume, Albert Einstein als Philosoph und Naturforscher. Stuttgart: W. Kohlhammer Verlag, 1955, pp. 493–511.
3. Pais, Abraham, “Subtle Is the Lord …” The Science and the Life of Albert Einstein. New York: Oxford University Press, 1982. The scientific biography, with technical details and much else.
4. Albert Einstein: Ideas and Opinions. New York: Crown Publishers, 1954. An English translation of a collection of popular and philosophical texts that first appeared in German in 1934.
5. Janssen, Michel, and Christoph Lehner (eds.), The Cambridge Companion to Einstein. New York: Cambridge University Press, 2014. Essays on various aspects of Einstein’s physics and philosophy by leading Einstein scholars.
6. Calaprice, Alice, Daniel Kennefick, and Robert Schulmann (eds.), An Einstein Encyclopedia. Princeton, NJ and Oxford, UK: Princeton University Press, 2015. Both a good place to begin and a useful reference work.
While the number of books and other materials on Einstein’s work is truly enormous, among my favorites are:
Bernstein, Jeremy, Einstein. New York: The Viking Press, 1973 (Modern Masters series, edited by Frank Kermode).
Fine, Arthur, The Shaky Game: Einstein, Realism and the Quantum Theory. Second edition. Chicago: University of Chicago Press, 1996.
Ohanian, Hans C., Einstein’s Mistakes: The Human Failings of Genius. New York and London: W.W. Norton and Co., 2008.