  Mach's principle is incompatible with general relativity (GR), it has not
condensed into an established theory and suffers from inconsistencies. Yet, the
problem is that Mach's principle is a consequence of Berkeley's notions, which
are as good as irrefutable for their ontological nature. Moreover, the observed
coincidence of the "preferred inertial frame" and the frame attached to the
"fixed stars" is essentially Machian, while this coincidence is anomalous to
both GR and Newtonian physics. Another issue is that GR needs dark energy to
explain the accelerating expansion of the universe, while acceleration of
receding masses is inherent to the Machian principle. So GR and Mach's
principle question each other, while neither one can be falsified easily. This
suggest that both are valid in their particular domain. A relational theory may
reconcile the two, since it can cover both.
