How to eliminate ''the explanatory gap''between human's conscious experiences and his brain's physiology? This is the hard problem in the area of the mind-body relationship as well as the central issue of contemporary philosophy of mind. The irreducibility of conscious experiences and qualia originates from their subjectivity, which means that they could be experienced only from the first-person perspective instead of the third-person perspective. It is the neglect of the subjectivity of conscious experiences that causes the failing of Functionalism and Representationalism. Subjectivity is the key to eliminate the mystery of consciousness. Whereas the object of my perceptual experience is intersubjectively accessible, my perceptual experience itself is only given directly to me. It is this first-personal givenness of the experience that makes it subjective. Consciousness is self-luminous. It is characterized by intentionality. Being intentionally aware of objects is simultaneously self-aware through and in itself. Its self-awareness is not due to a secondary act or reflex but is a constitutive moment of experience itself. Despite his criticism of the reflection theory, Brentano continues to speak of consciousness, taking itself as its own object, and self-awareness as a secondary object-awareness. Husserl does not deny the existence of a tacit self-awareness. But he does deny that this self-awareness can provide us with more than awareness. The actual life and lived-experiencing is of course always conscious, but it is not therefore always thematically experienced and known. According to Heidegger, any worldly experiencing is characterized by the fact that ''I am always somehow acquainted with myself''and this basic familiarity with oneself does not take the form of a reflective self-perception or a thematic self-observation, nor does it involve any kind of self-objectification. For Sartre, the conscious givenness of the experience is not simply a quality added to experience, but the very mode of being of the experience. Just as an extended object can only exist three dimensionally, an experience can only exist as self-aware.