D.J. Griffiths in his "Introduction to Electrodynamics" writes: "Some authers consider Einstein's second postulate redundant - no more than a special case of the first. They maintain that the very existence of ether would violate the principle of relativity, in the sense that it would define a unique stationary reference frame. I think this is nonsense. The existence of air as a medium for sound does not invalidate the theory of relativity. Ether is no more an absolute rest system than the water in a goldfish bowl - which is a special system, if you happen to be the goldfish, but scarcely 'absolute.'" I think Mr Griffiths' argument is not completely convincing. According to the 1st postulate of SR, the laws of physics apply in all inertial reference system. So in any inertial frame of reference, the Maxwell's equations and their direct results must be valid. In any given inertial frame of reference we can obtain the equation of a wave that propagates with speed c (which is a fundamental constant). In any other inertial reference system, the result is the same. What's your opinion? Are the "some authors" right?