 For a number of years Einstein expressed the ambition of the general theory of relativity to fully implement Mach’s program for the relativization of all inertial effects, even appending the so-called cosmological constant in an attempt to obtain a fully Machian global solution to his field equations (1917b) for this purpose. This genuine point of contact of Mach’s influence was clearly identified only in 1918, when Einstein distinguished what he baptized as Mach’s Principle —(too) strongly stated as the requirement that the metric field (responsible for gravitational-inertial properties of bodies) on the left hand side of his field equation, is completely determined by the energy-momentum tensor on the right hand side—from the principle of general relativity which he misleadingly interpreted as the principle of general covariance. Taken together with the principle of the equivalence, Einstein asserted that the three principles, were three pillars on which his theory rested, even if they could not be thought completely independent of one another. Despite Einstein’s intent, there is considerable disagreement about the extent to which, if at all, the general theory of relativity could conform to anything like Mach’s Principle. The Dutch astronomer Willem De Sitter had immediately shown in 1917 that the Einstein field equations, even as augmented with the new cosmological constant, permitted matter-free solutions. Machians still have some room for maneuver due to vagaries regarding just what such a principle actually requires. On the other hand, it remains difficult to comprehend just what physical process or mechanism might implement the principle, however interpreted. How, for instance, might a given body’s inertial mass be accounted due to the influence of all other masses in the universe? (See the discussions in Barbour &amp; Pfister 1995.)