The relativity of inertia and reality of nothing
  We first see that the inertia of Newtonian mechanics is absolute and troublesome. General relativity can be viewed as Einstein's attempt to remedy, by making inertia relative, to matter---perhaps imperfectly though, as at least a couple of freedom degrees separate inertia from matter in his theory. We consider ways the relationist (for whom it is of course unwelcome) can try to overcome such undetermination, dismissing it as physically meaningless, especially by insisting on the right transformation properties. 
Alexander Afriat and Ermenegildo Caccese