Among philosophical approaches to the notion of subject, at least three main historical stages may be distinguished: at the metaphysical stage, the structure of the subject is that of a substance; at the transcendental stage (Kant and Fichte), the subject is viewed as a unifying polarity of horizons; at the psychoanalytical stage, the subject is defined as a gap structure. The transcendental subject is a structure for the world, whereas the psychoanalytical subject needs to have a structure in itself to structure its own ontological lack. For Lacan, this ontological lack is made manifest through language. The structure of the subject is conceived as a structure of signification. The paper compares these three viewpoints and discusses what r...