Special relativity upended our normal conceptions of space and time by postulating that the speed of light was absolute for all observers. So rather than the absolute space and time of Newton, Einstein postulated an absolute speed of light, which by necessity leads to a malleable space and time (speed is space/time so if the speed of light is absolute space and/or time must then become non-absolute). I've never come across a good explanation of WHY the speed of light would be absolute, however, and it is obviously very counter-intuitive. All other speeds are non-absolute, so why is only the speed of light absolute? I'm curious if anyone can point me to any good philosophical/physical explanatios of Einstein's key postulate? Or if anyone has any good ideas of their own as to why the speed of light would be absolute in an ontological sense, please let me know.