Mach's principle in general relativity

Mach's Principle is examined in the light of its recent formulation within General Relativity. It is argued that properties of geometry which Mach didn't envisage, specifically finite propagation velocity and independent field excitations, destroy the philosophic justification of Mach's Principle. What remains is a conjecture on which recent developments in cosmology throw doubt. A simpler and somewhat less Machian alternative proposed by Wheeler is also discussed briefly.