Erich Kretschmann

German physicist whose 1917 paper, "Über den physikalischen Sinn der Relativitätspostulate..." (Annalen der Physik 53), argued that general covariance alone places no substantive physical constraint on a theory — any theory can in principle be rewritten in generally covariant form, so covariance by itself cannot be what makes general relativity distinctive.

Matters to this vault as the originator of the "Kretschmann objection," which Weatherall and Eleanor March's 2026 paper credits as the historical motivation for the whole project of "naturalizing" physical equations — defining precisely which equations transform functorially under diffeomorphisms, rather than merely asserting covariance.

References

• claim-march-weatherall-minimal-coupling-unique-up-to-isomorphism