 Machian influences specific to the general theory of relativity appeared even more extensive. Mach’s idée fixe, that a body’s inertial mass and motion result from the influence of all other surrounding masses (thus eliminating the “monstrous” Newtonian concept of absolute space), was perhaps the strongest motivation guiding Einstein’s pursuit of a relativistic theory of gravity. In papers leading up to the definitive presentation of the general theory of relativity in 1916, Einstein made no secret of the fact that Mach was the inspiration for an epistemologically mandated attempt to generalize the principle of relativity. Holding, with Mach, that no observable facts could be associated with the notions of absolute acceleration or absolute inertia (i.e., resistance to acceleration), the generalization required that the laws of nature be completely independent of the state of motion of any chosen reference system. In fact, in striving to completely relativize inertia, Einstein conflated a valid principle of form invariance of the laws of nature (general covariance, see below) with a spurious “principle of general relativity”, according to which accelerated motions like rotations would be relative to an observer’s state of motion. In a warm obituary of Mach written within a few days of completing the definitive 1916 presentation of his theory, Einstein, quoting extensively from the famous passages in Mach’s Mechanics critical of Newton’s “absolute” concepts of space, time and motion, generously avowed that Mach’s understanding of the principles of mechanics had brought him very close to demanding a general theory of relativity a half-century earlier (1916b: 102–3). No doubt with this reference in mind, physicist Phillip Frank, later to be associated with the Vienna Circle, observed that