 Cassirer, Ernst |  equivalence of mass and energy |  general relativity: early philosophical interpretations of |  geometry: in the 19th century |  Natorp, Paul |  physics: holism and nonseparability |  quantum mechanics: Copenhagen interpretation of |  quantum theory: philosophical issues in |  quantum theory: the Einstein-Podolsky-Rosen argument in |  space and time: absolute and relational space and motion, post-Newtonian theories |  space and time: conventionality of simultaneity |  space and time: inertial frames |  space and time: the hole argument |  Uncertainty Principle 