Draft version, in H. Breger, J. Herbst, S. Erdner (eds.) Natur und Subjekt. Vorträge 1. Teil, Proceedings of the ninth international Leibniz Congress, Hanover 2011, p. 351-359. Guillaume Fréchette (Montréal) Leibniz and Brentano on Apperception What makes my seeing of a red patch a conscious act? Is it a second-order act or is it a build- in feature of all mental acts? Regarding the first question, we might ask further: is the second-order act itself conscious? Or are these acts unconscious acts? Higher-Order-Theories of perception and thought (HOT-theories) usually answer the first question affirmatively. In order to avoid the infinite regress of second-, third-, etc. order of conscious-making acts, they usually argue that second-order acts are not conscious. But what is then the relation between the second-order act and the first order act? If a second-order act is directed upon a first-order act in the same way as the first-order act is directed upon an object, the HOT-theorists will have to allow for cases of failure of reference in second-order act as they also appear in the case of first-order acts. This consequence seems counter- intuitive, for the possibility of failure of reference in first-order mental acts doesn’t seem to apply to second-order mental acts: my presentation of a unicorn fails to refer to an object, but there doesn’t seem to be an analogue to such cases on the level of second-order mental acts. Another difficulty of the model of consciousness advocated by HOT-theorists is the consequence of there being two distinct acts going on (two distinct existences): if the second-order act is not itself conscious, and if the first-order act needs the second to become conscious, consciousness would simply be a property which first-order acts get or lack in given conditions. However, this concept of consciousness doesn’t seem to have much to offer when it comes to elucidate the fact that conscious experiences have a phenomenal character – that they are given in some way, but also that they are given to someone – that ownership is one of their intrinsic features. These are only some of the reasons that made HOT-accounts of consciousness less attractive in the last years. In searching for alternatives or for support for their thesis, some HOT-theorists have tried to go back to Leibniz and Brentano in order to address some of the difficulties of the standard HOT-accounts 1 . Whereas Leibniz is often seen as defending a traditional HOT-theory, Brentano is often believed to be offering a viable alternative, within the framework of HOT-theories, to the assumption that first-order and second- order acts are distinct existences without compromising the core idea of HOT-theories, namely that the explanation of phenomenal consciousness to be reached rests on the cognitive level and not on the sensory level of our experience. One might, however, wonder how one single strategy concerning the explanation of consciousness relies on two philosophers who are in disagreement regarding consciousness. Brentano and Leibniz have indeed different views concerning the nature of perception as well as different views concerning the nature of consciousness and the possibility of unconscious perceptions. In this paper, I will address some of the difficulties of both these strategies by comparing Leibniz’s and Brentano’s concepts of apperception (Bewußtsein or inneres Bewußtsein in Brentano’s language). The view adopted here is quite wide. Due to shortage of space, I will have 1 As for Leibniz, see R. Gennaro, “Leibniz on Consciousness and Self-Consciousness”, in Gennaro, R., Huenemann, C. (eds.), New Essays on the Rationalists, Oxford, Oxford University Press, 1999, 353-371; L. Jorgensen, “The Principle of Continuity and Leibniz’s Theory of Consciousness,” Journal of the History of Philosophy, vol. 47 (2009), 223-248. L. Jorgensen, “Leibniz on Memory and Consciousness”, British Journal for the History of Philosophy (forthcoming). As for Brentano, see among others U. Kriegel, “Consciousness, Higher-Order Content, and the Individuation of Vehicles”, Synthese, vol. 134 (2003), 477-504; K. Hossack, “Self-Consciousness and Knowledge”, Proceedings of the Aristotelian Society, vol. 102 (2002), 163-181; A. L. Thomasson, “After Brentano: A One-Level Theory of Consciousness”, European Journal of Philosophy, vol. 8 (2001), 190–209; M. Textor, “Brentano (and some Neo- Brentanians) on inner Consciousness”, Dialectica, vol. 60, N° 4 (2006), 411-432; C. Siewert, “In Favor of (Plain) Phenomenology”, Phenomenology and the Cognitive Sciences, vol. 6, N° 2 (2007), 201-220. Thanks to Zeki Hamawand for his comment on an earlier version of this paper.