You might find this paper interesting: A Derivation of Special Relativity from Causal Sets--http://arxiv.org/abs/1005.4172 http://arxiv.org/abs/1005.4172 It do

You might find this paper interesting: A Derivation of Special Relativity from Causal Sets--http://arxiv.org/abs/1005.4172 http://arxiv.org/abs/1005.4172 It doesn't answer why c is the value of c, but it's an interesting way to show that there must be an invariant bounding speed limit. It doesn't assume the "existence of space or time, motion, constancy of the speed of light, or the principle of relativity."