Metaphysics and psychology are two of Brentano’s main areas of interest in philosophy. His first writings, the dissertation On the Several Senses of Being in Aristotle (1862) and the habilitation thesis, The Psychology of Aristotle (1867), bear witness to the duality of his concerns. As such, these works were not only significant contributions to the German Aristotelianism of the second half of the XIXth century, but they also played an important role in the development of Brentano’s later philosophy and in defining his school of thought. At the same time, the dissertation, now celebrating the sesquicentennial of its first publication, was received beyond the immediate sphere of the Brentanian school, for its reading played a significant role in young Heidegger’s thought on being, and thus in his development of a new type of phenomenology, distinct from the Husserlian one. The studies comprising this volume examine the relevance of Brentano’s dissertation, of his metaphysics and psychology for contemporary philosophical research. Generally, the papers emphasize a tendency in Brentanian research, which has become more conspicuous in the last two decades, and can be described as a gradual shift in focus from the specific problems of Brentano’s late philosophy, towards his earlier philosophy, especially his first writings and manuscripts. Taking into account both Brentano’s published works, and the manuscripts of the dissertation and the Psychology, the contributions of this volume manage to emphasise unexplored aspects of Brentano’s philosophy and stand witness to the complexity and the historical dimension of a legacy whose richness still awaits full discovery.Table of Contents: Ion Tanasescu, Foreword; Edoardo Fugali, Trendelenburg, Brentano und die Aristoteles-Renaissance in der deutschen Philosophie des 19. Jahrhunderts. Die Frage nach dem Ursprung der Kategorien; Dale Jacquette, Brentano on Aristotle s Categories: First Philosophy and the Manifold Senses of Being; Klaus Hedwig, … eine gewisse kongeniale Denkweise. Brentanos Ruckgriffe auf Thomas von Aquin in seiner Dissertation; Susan Krantz Gabriel, Heidegger’s Question and the Fundamental Sense of Being in Brentano; Ion Tanasescu, Franz Brentano’s Dissertation and the Problem of Intentionality; Josef Seifert, Uber das notwendige Dasein Gottes. Eine kritische Antwort auf Franz Brentanos Kritik des ontologischen Gottesbeweises; Paul Janssen, Die Gottesrede bei Brentano; Robin Rollinger, Brentano’s Psychology from an Empirical Standpoint: Its Background and Conception; Guillaume Frechette, Deux aspects de l’intentionnalite dans la Psychologie de Brentano; Denis Seron, The Fechner-Brentano Controversy on the Measurement of Sensation; Carlo Ierna, Brentano and Mathematics; Roberto Poli, Modes and Boundaries; Federico Boccaccini, La verite efficace. L’epistemologie de Brentano entre Evidenzphilosophie et pragmatisme; Thomas Binder, Der Nachlass Franz Brentanos. Eine historische Annaherung an einen schwierigen Fall