The ego, as our familiar sense of self, seems predicated on fear. The fear that we might not make it, that we might not get where we want to go. But deep down there is also a grain of fear that we have nothing to give or nothing to offer. I think that's the ego's justifiable anxiety about its substantiality and existence.
Ether is the only substance we are confident of in dynamics. One thing we are sure of and that is the reality and substantiality of the luminferous ether.
If there is only empty space, with no suns nor planets in it, then space loses its substantiality.