In this paper, I propose a reassessment of Brentano’s most important writings on consciousness. My starting point is the formulation of two theses on consciousness that Brentano expresses at the very beginning of the second chapter of the second book of his Psychology from an Empirical Standpoint, which constitute the foundation of his theory of primary and secondary objects. My working hypothesis rests on the principle of the unity of consciousness, which is the key to most problems generally associated with Brentano’s theory of consciousness. In the second part of my paper, I examine three of these problems, namely, the problem of duplication, that of infinite regress, and that of complexity. In the last part of my paper, I propose an analysis of the principle of the unity of consciousness that takes into account Brentano’s writings after the publication of his Psychology, in 1874, and I briefly appraise the impact, on the atual debates regarding Brentano’s theory of consciousness, of the modifications that Brentano has subjected his theory in several lectures and manuscripts published posthumously.
