1 6 0 D O C U M E N T 1 4 0 D E C E M B E R 1 9 2 5 to nominate him for Prague, where a new chair for natural philosophy is supposed to be set up. The young philosopher Carnap,[9] who has now applied for the appointment as lecturer at Vienna and whom I earlier recommended to your kind attention, must in the meantime have sent you his publications.[10] Some of these still have a couple of weak spots, and I ask you please not to judge him solely by the available printed papers. His newer work, especially the book Konstitutionstheorie that was submit- ted as his Habilitation, which hopefully will be printed in the coming year, are on a very high level this extensive book seems to me to be a quite extraordinary, downright fundamental achievement.[11] —A short time ago, Mr. Reichenbach published in Zeitschrift für Physik, 34, p. 32, a paper, “On the Physical Consequences of Relativistic Axiomatics,”[12] about which I would like to comment in closing, because it seems to indicate the limits of the axiomatic method quite clearly.[13] The expositions at the bottom of p. 43, ff., are logically all right, but in my opinion only show that in his axiomatics no distinction can be found between the spec. theory of rel. and Lorentz’s theory (with the contraction hypothesis), which seems self-evident to me because the equations are, of course, the same in both.[14] The real difference between the two theories, which is a philosophical one and is elusive along the purely logical route of axiomatics,[15] is probably quite aptly put—to employ precisely that manner of speech that Reichenbach rejects—as dealing with an ad hoc thought-up hypothesis.[16] Since, logically speaking, although the spec. theory of rel. must make just as many basic assumptions as Lorentz’s, in the former they do dovetail on their own within the framework of the relativity concept, and the contraction hy- pothesis is psychologically in fact not thought up ad hoc,[17] whereas for Lorentz- Fitzgerald it figures as an ad hoc appended piece.— The final arguments of the pa- per—about the possible interpretation of Miller’s experiments—do not seem to me to get at the philosophical heart of the matter, either.[18] If it really were proven by those experiments (which is, of course, certainly not the case) that a particular di- rection (the one of the “ether wind”) is privileged, one would have to give up rela- tivistic physics and even if it were possible to uphold relativity by means of assuming particular “body axioms,”[19] one would surely not go down that path. However, in this regard the axiomatic consideration just acts indifferently.[20] For that reason it seems to me that one actually cannot, after all, in the very strict sense, speak of physical consequences of the axiomatics. These questions do seem to me to be of philosophical importance, and I would be wholeheartedly thankful if you would write me a line saying whether I am right. To you and yours I wish the very best in life and work in the New Year and re- main, in deepest gratitude and fond admiration, your M. Schlick