After the author of this book, J. B. Stallo, had primarily dealt with political and legal issues during the American Civil War, he turned to scientific topics after the war and wrote this book, his most famous work: "The Concepts and Theories of Modern Physics," as it was titled in the spelling of that time. It was first published in 1882 and mainly addresses the role of concepts in physical theory. Stallo argues that these concepts must be treated as provisional and that one must not succumb to the danger of confusing concepts with facts. These viewpoints make the book an early representative of modern philosophy of science. The present German translation of the work was created after Stallo's death by Ernst Mach, the renowned Austrian physicist.