I develop two fundamental ideas about sexual difference on the basis of classical phenomenology. The first idea concerns the perceptual world and its structures. Using the phenomenological distinction between perceptual type and empirical concept, I argue that sexual identity is not one unitary objectivity but includes two different levels of objectivity: one sensuous and the other conceptual. Moreover, our concepts of man and woman do not automatically emerge from our pre-conceptual perceptions of sexed bodies but are constituted by an active focus of attention. Conversely, our critical work on concepts and forms of discourse cannot change or undo the pre-conceptual structures of perception even if it may allow a reflective distance from these structures. The second argument is based on the phenomenological account of selfhood and its temporal nature. I explain the concept of the transcendental person as a temporal unity and show how this concept helps to establish a non-naturalistic philosophy of sexual difference. Ultimately, I show that the subjects that constitute the sense of being are not sexually neutral "consciousnesses" or "humans" (Dasein) but are feminine and masculine persons with different sensual lives and lived motivations. This means that sexual difference is not just an ontological difference but is also a structure in the foundations of ontology.