Physics, Plato, and Parmenides are the foils for philosopher of science Weizsacker in this collection of lectures and essays produced over the last ten or fifteen years (a number unpublished). Perhaps one should say philosopher in science as well, for the formidable credentials of the German thinker--Director of the Max Planck Institute for Research into the Essentials of the Scientific Technological World (!)--include an apprenticeship with Heisenberg, and, by extension, with Heisenberg's teacher, Niels Bohr. Both men figure importantly in Weizsacker's metaphysical speculations. Like many a contemporary philosopher, Weizsacker is painstaking in his concern for meaning in language, and he devotes some time to questions of how truth-values may/may not be dependent on the particular language in which propositions are expressed. This leads to excursions into the nature of logic, proof, the theory of classes, mathematics--and, inevitably, the paradoxes inherent in self-reflecting expressions. These considerations are ancillary to Weizsacker's concept of the unity of nature. At the heart of that unity is quantum theory. In a complex and illuminating essay, Weizsacker takes up the paradoxes of ""being"" and ""oneness"" posed by the writings of Parmenides and the Platonic dialogue devoted to Parmenides. There, he provides a model in which the ""one"" of elementary particleness subsumes a manifold of states according to various mathematical/physical formulas. The totality of objects describable by quantum theory, in turn, constitutes the ""world""--but one can again raise the Platonic paradoxical question, ""for whom is this world an object?"" So the speculations go round, providing an exhilarating trip--but only for those philosopher/scientists with the classical/contemporary scholarship to pave the way.