Einstein: His Life and Universe

impurities emitting alpha particles. Each emitted alpha particle leaves a track in the mica. The track is real, and it makes little difference whether a physicist or other human being or a chinchilla or a cockroach comes along to look at it. What is important is that the track is correlated with the direction of emission of the alpha particle and

could be used

to measure the emission. Before the emission takes place, all directions are equally probable and contribute to a branching of histories. I am grateful to Murray Gell-Mann for his help with this section. See also Gell-Mann, 135– 177; Murray Gell-Mann and James Hartle, “Quantum Mechanics in the Light of Quantum Cosmology,” in W. H. Zurek, ed.,

Complexity, Entropy and the Physics of Information

(Reading, Mass.: Addison-Wesley, 1990), 425–459, and “Equivalent Sets of Histories and Multiple Quasiclassical Realms,” May 1996, www.arxiv.org/abs/gr-qc/9404013. This view is derived from the many-worlds interpretation pioneered in 1957 by Hugh Everett.

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. The literature on Einstein and realism is fascinating. This section relies on the works of Don Howard, Gerald Holton, Arthur I. Miller, and Jeroen van Dongen cited in the bibliography.

Don Howard has argued that Einstein was never a true Machian nor a true realist, and that his philosophy of science did not change much over the years. “On my view, Einstein was never an ardent ‘Machian’ positivist, and he was never a scientific realist, at least not in the sense acquired by the term ‘scientific realist’ in later twentieth- century philosophical discourse. Einstein expected scientific theories to have the proper empirical credentials, but he was no positivist; and he expected scientific theories to give an account of physical reality, but he was no scientific realist. Moreover, in both respects his views remained more or less the same from the beginning to the end of his career.” Howard 2004.

Gerald Holton, on the other side, argues that Einstein underwent “a pilgrimage from a philosophy of science in which sensationalism and empiricism were at the center, to one in which the basis was a rational realism ... For a scientist to change his philosophical beliefs so fundamentally is rare” (Holton 1973, 219, 245). See also Anton Zeilinger, “Einstein and Absolute Reality,” in Brockman, 123: “Instead of accepting only concepts that can be verified by observation, Einstein insisted on the existence of a reality prior to and independent of observation.”

Arthur Fine’s

The Shaky Game

explores all sides of the issue. He develops for himself what he calls a “natural ontological attitude” that is neither realist nor antirealist, but instead “mediates between the two.” Of Einstein he says, “I think there is no backing away from the fact that Einstein’s so-called realism has a deeply empiricist core that makes it a ‘realism’ more nominal than real.” Fine, 130, 108.

37

. Einstein to Jerome Rothstein, May 22, 1950, AEA 22-54.

38

. Einstein to Donald Mackay, Apr. 26, 1948, AEA 17-9.

39

. Einstein 1949b, 11.

40

. Gerald Holton, “Mach, Einstein and the Search for Reality,” in Holton 1973, 245. Arthur I. Miller disagrees with some of Holton’s interpretation. He stresses that Einstein’s point was that for something to be real it should be measurable

in principle

, even if not actually measurable in real life, and he was content using thought experiments to “measure” something. Miller 1981, 186.

41

. Einstein 1949b, 81.

42

. Einstein to Max Born, comments on a paper, Mar. 18, 1948, in Born 2005, 161.

43

. Einstein, “The Fundamentals of Theoretical Physics,”

Science

, May 24, 1940; Einstein 1954, 334.

44

. For example, Arthur Fine argues, “Causality and observer-independence were

primary

features of Einstein’s realism, whereas a space/time representation was an important but

secondary

feature.” Fine, 103.

45

. Einstein, “Physics, Philosophy and Scientific Progress,”