Over the course of a career that has spanned more than fifty years, philosopher Fred Sommers has taken on the monumental task of reviving the development of Aristotelian (syllogistic) logic after it was supplanted by the predicate logic of Gottlob Frege and Bertrand Russell. The enormousness of Sommers's undertaking can be gauged by the fact that most philosophers had come to believe -- as David S. Oderberg writes in his preface -- that "Aristotelian logic was good but is now as good as dead." A revival of traditional syllogistic logic would involve not only its restatement but its refashioning into a system that could rival the elegance and deductive power of predicate logic. Building on work by medieval scholastic logicians, Leibniz, and nineteenth-century algebraic logicians, Sommers accomplished this renovation and rehabilitation of syllogistic logic with his magnum opus The Logic of Natural Language, published in 1982.In The Old New Logic, essays by a diverse group of contributors show how widely influential Sommers's work has been -- not only in logic, but in category theory and other areas. Scholars in psychology, linguistics, and computer science join philosophers and logicians in discussing aspects of Sommers's contributions to philosophy. Sommers himself provides an intellectual autobiography at the beginning and in the final chapter offers comments on the contributions. This collection should help bring to Sommers's work the attention it deserves from the wider philosophical and intellectual community.