 Franz Brentano (1838–1917) is famous for arguing in his Psychology from an Empirical Standpoint (1874) that intentionality—being directed toward something—is the mark of the mental. Brentano used that conception not only for distinguishing mental from physical phenomena, but also for developing a classification of mental phenomena. If intentionality is a fundamental feature of any mental act, Brentano argues, differences in the way mental phenomena are directed toward something constitute differences in kind between mental acts. Judgements are one of the three basic kinds of intentional phenomena with which Brentano deals at great length in his Psychology. That is not to say, however, that Brentano’s theory of judgement is just concerned with psychological issues. Brentano also aims to show how an experience of judging, specifically the experience of judging correctly, can provide us with a basis for grasping concepts like existence, truth, and logical inference. Brentano’s investigation of the mental act of judgement promises therefore to advance logic, epistemology, and ultimately metaphysics.