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Appendix

I shałl try to answcr your questions to thc bcst of my ability. i) Do you rcmcmber this story (about St. Mcycr’s mccting with Ernst Mach)? Ycs,

I do rcmcmber Meyer relatir.g it scveral times, always in thc same way. 2) Do you acccpt Stefan Meyers account of it? Of coursc I do, knowing from long friendship Mcycr’s upright, truthful charactcr. 3) Do you think Mach changcd his attitudc towards atoms? Ycs I do. But I also think that Mcycr’s words about “cin ganzes Wcltbild" bcing changcd is not to be taken too litcrally. I do not think that Mach will havc givcn up his posi-tivistic yiews, but only conccdcd that atoms now fitted into them. 4) When did the mccting happen? I don’t know, but I do not think that Meyer would havc hesitated long to show Mach thc spinthariscope when it be-came known in 1903.³

Fritz Chmclka publishcd an artide in 1966 which supported Meyer’s contcntion and which may hnvc becn bascd 011 an independent sourcc: "MaclYs student. Anton Lampa, reported, howcver (in his lecture), that Mach had becn grently shaken when shown scimillations for thc first timc, flnshcs of light, which originatc by the impingement of alpha partides from a radioactivc preparation on a zinc sulfidc screcn, and which madc the effeets of atom nudci immcdiatcly visiblc.^,M

Meyer, Przibram, and Chmclka have surcly presented a strong casc for the affirmative, that the spinthariscope cpisode did takc place, and that Mach was strongly affccted by it; nonctheless, the cvidencc against both the cpisode and its impact is also considcrablc. In particular, Mach ncver mentioncd the cpisode either in his publishcd writings or in his known corrcspondcncc. Furthcrmorc, hc wrotc cxtensively on the reality of atoms after 1903, thc ycar the spinthariscope was intro-duced into Vienna, and hc continucd to deny their cxistence until his dcath. Also, a former student and long-timc friend specifically asked Mach whether reccnt discoverics had changcd his mind, and according to Bohuslav Brauner thc answcr was negative:

As one of thc oldest pupils of Mach who worked with him on fluores-ccncc in 1877 ³ⁿd enjoyed his warm friendship sińce 1876, I often had an opportunity of discussing atomism with him. Not long bcforc the War, I was sitting with him in his garden in Vienna, and I rcmcmber that he said to mc: "Atomism is a good working hypothcsis for thc study of chcm-istry; it must be uscd with great carc on studying and working in science; but it is extrcmely dangerous as a noctic. theory.” ... At thc beginning of thc War, I asked him in a letter whether hc considcrcd thc rcsults of all thc obscrvations in radioactivity as a proof of thc cxistcncc of atoms, and hc replied to me vcrbally: "I do not make myself a prosclytc of my idcas—

do not make yoursclf a prosclytc on atomism." Hc ncvcr changcd his ideas up to his dcath.⁵

Herę arc somc quotations publishcd by Mach after 1903 including scvcral originally written betwccn 1910 and 1915. They all support Brauner and thc contention that Mach did not change his attitude toward thc rcality of atoms. To he prccisc, the first two quotations wcrc written before 1903 but retaincd in all editions after that timc. The third quotation was originally written and publishcd in 1910. The fourth, fifth, and sixth quotations were written in thc late 1890$, 1913, and 1915, rcspcctively, and wcrc publishcd for the first time in 1905, 1921, and 1933 (sec notes 6-11, bibliography, and Joachim Thiclc, "Ernst Mach*Bibliographic,” Centaurus, 8 (1963), 189-237).

Atoms cannot be pcrceived by thc senses; likc all substances they arc things of thought. Furthermore, atoms arc invcstcd with properties that absolutcly contradicted the attributes hithcrio obscrved in bodics.³

Still less, therefore, will the monstrous idea of employing atoms to ex-plain psychical processcs cver get possession of us, seeing that atoms arc but the symbols of thosc peculiar complexcs of scnsational elements which we mect with in thc narrow domains of physics and chemistry.⁷

The rcsults of thc atomie theory can be just as manifold and useful if or.e is not in such a hurry to treat atoms as realities. Therefore all honor to thc beliefs of physicists! But I mysclf cannot make this particular belief my own.^#

Our geometry always refers to objeets of sensuous cxpcrience. But thc moment we begin to operatc with mcrc things of thought likc atoms and moleeules, which from their vcry naturę can neuer be wadę thc objeets of sensuous contemplation. we are under no obligation whatcver to think of them as standing in spatial relationships which arc peculiar to thc Eudidcan thrcc-dimcnsional space of our sensuous cxpericncc. This may be rccom-mended to thc spccial attention of thinkers who dccm atomistic spccula-tions indispcnsable.⁰

I must, howevcr, as assurcdly disdaim to be a forerunner of the rcla-tivists as I withhold from thc atomistic belief of thc present dav.¹⁰

I do not considcr thc Newtonian principlcs as complctcd and pcrfcct; yet in my old age, I can acccpt thc theory of rclativity just as little as I can acccpt the cxistcncc of atoms and other such dogma.¹¹

One explanation would be that perhaps Mach did observe the spin-thariscopc scintillations but was not as impressed as Meyer thought. As another cxplanation one might speeulate that Mach was only tern-