Without Principle C of physical causality conjoined with the kinematic principle of relative motion, it is not groundless or impossible that a stationary body of fluid at rest takes the form of a sphere while a rotating body takes the form of a flattened ellipsoid

The underlying motivation for assumption \(\mathbf{C}\) of physical causality is essentially Mach’s empiricist programme, namely, Mach’s insistence on the primacy of observable facts of experience. Addressing Einstein’s formulation of Mach’s paradox, Weyl (1924b) says: Only if we conjoin the kinematic principle of relative motion with the physical assumption \(\mathbf{C}\) does it appear groundless or impossible on the basis of the kinematic principle that in the absence of any external forces a