 There are anticipations of the principle theories-constructive theories distinction in the nineteenth-century electrodynamics literature, James Clerk Maxwell, in particular, being a source from which Einstein might well have drawn (see Harman 1998). At the turn of the century, the “physics of principles” was a subject under wide discussion. At the turn of 1900, Hendrik A. Lorentz (Lorentz 1900, 1905; see Frisch 2005) and Henri Poincaré (for example, Poincaré 1904; see, Giedymin 1982, Darrigol 1995) presented the opposition between the “physics of principles“ and the “physics of models“ as commonplace. In a similar vein, Arnold Sommerfeld opposed a “physics of problems“, a style of doing physics based on concrete puzzle solving, to the “practice of principles“ defended by Max Planck (Seth 2010). Philipp Frank (1908, relying on Rey 1909) defined relativity theory as a “ conceptual theory“ based on abstract, but empirically well confirmed principles rather than on intuitive models. Probably many other examples could be find. . But however extensive his borrowings (no explicit debt was ever acknowledged), in Einstein’s hands the distinction becomes a methodological tool of impressive scope and fertility. What is puzzling, and even a bit sad, is that this most original methodological insight of Einstein’s had comparatively little impact on later philosophy of science or practice in physics. Only in recent decades, Einstein constructive-principle distinction has attracted interest in the philosophical literature, originating a still living philosophical debate on the foundation of spacetime theories (Brown 2005, Janssen 2009, Lange  2014).[4]