This book offers the first-ever English translation of Oskar Becker?s Zur Logik der Modalitäten. This essay, published in 1930, is a pioneering yet often neglected contribution in the context of prewar modal logic research in Europe. Becker?s text is complemented by an extended commentary that explains, analyzes and highlights Becker?s accomplishments and the philosophical background of his investigations.The commentary provides an in-depth analysis of all of Becker's important contributions, both from a philosophical and logical perspective, making it a very useful book for scholars in both philosophy and logic.