"In his Science of Mechanics... Ernst Mach suspended... the classic formula of the law of inertia because he believed that... [this] had to be rethought. His famous studies of Newton's terminology (in particular... absolute space and absolute time)... led Mach to propose a new formulation in which gravitation appears as a function of the entire mass distribution of the universe. In this critical reconstruction... Mach believed that it had to be shown... that even the most firmly established concepts were merely auxiliary constructs... [which] give a provisional account of relations... between our experiences. And... we tend to forget that we were the ones who introduced our concepts... Mach demands that we... keep dissolving the most firmly established concepts and formulæ... so that we do not perceive them as something independent of ourselves and allow them to become obstacles to our knowledge."