APPENDIX A APHORISM ON THEORETICAL PHYSICS The sentence was written down by Paul Ehrenfest in one of his scientific notebooks, ENB:1, 29, p. 1 (NL-LeRM, Ehrenfest Archive). It is dated from the entry preceding it (an extract of a paper from the 14 August 1925 issue of Science) and the time span of the notebook (25 December 1924–January 1926). [Leyden, between 14 August 1925 and January 1926] Die speziellere Theorie ist die bessere wenn sie nicht die falschere ist. AD. [95 872].