The volumes of the Symposium Aristotelicum have become essential reference works for the study of Aristotle. In this nineteenth volume, eleven distinguished scholars of ancient philosophy provide a running commentary on the first book of Aristotle's Physics, a central treatise of the Aristotelian corpus that aims at knowledge of the principles of physical change. Along with the general introduction, the ten chapters together comment on the entirety of the Aristotelian text and discuss the philosophical issues that are raised in it in detail. Aristotle is shown to be in dialogue with the divergent doctrines of earlier philosophers, namely with the Eleatics' monism, with Anaxagoras' theory of mixture, and finally with the Platonist dyadism that posits the two principles of Form and the Great and Small. Aristotle uses critical examination of his predecessors' views as the basis for formulating his own theory of the principles of natural things, which are fundamental for the entire Aristotelian study of the natural world. He provides his own solution to the problem of coming-to-be and passing-away by distinguishing between coming in actuality and in potentiality. Comprehensive analysis of Aristotle's doctrines and arguments, as well as critical discussion of rival interpretations, will make this volume a valuable resource for scholars of Aristotle.