Abstract Leonard Peikoff and David Harriman have denounced modern physics as incompatible with Objectivist metaphysics and epistemology. Physics, they say, must return to a Newtonian viewpoint; much of relativity theory must go, along with essentially all of quantum mechanics, string theory, and modern cosmology. In their insistence on justifications in terms of “physical nature,” they cling to a macroscopic worldview that doesn't work in the high-velocity arena of relativity or the subatomic level of quantum mechanics. It is suggested that the concept of identity be widened to accommodate the probabilistic nature of quantum phenomena.