Weyl proved a theorem showing that the inertial and causal structure of spacetime already fully determines the spacetime metric.

It should be noted, however, that Weyl’s defence of his theory implicitly addresses an important methodological consideration concerning the relation between theory and evidence. As Pauli puts it above, according to Weyl “the metric field must not be defined by means of information taken from these measuring instruments [rigid rods and ideal clocks]”. That is, Weyl rejects Einstein’s operational standpoint which gives operational significance to the metric field in terms of the observable b