<i>Newton on Matter and Activity</i> shows persuasively that while the <i>Principia</i> remains within the first two stages of inquiry (mathematical and physical) into nature Newton spent the next forty years of his life making a philosophical analysis of matter force and transmission of force. Close attention is paid to methodological issues especially Newton's move beyond inductivism and toward a reproductive theoretical schema of interpretation required to treat of attraction hardness and impenetrability. --<i>Cross Currents</i>