" But how does one square this with the idea of rebirth, of something distinct from that which dies but which is somehow reborn and so passes from life to life? To answer this question, more or less every Buddhist school has come up with a different explanation—a fact that in itself suggests that their answers are based on speculatioṇ Most schools claim that what is reborn is some kind of consciousness. Some say that this is simply the sixth sense (manovijñāṇa); others speak of a special existence-generating mind (bhavangacitta); still others propose the presence of an underlying foundation consciousness (ālayavijñāṇa); while the tantric traditions talk of a combination of extremely subtle energy and mind. But as soon as one hypothesizes the presence of some kind of subtle stuff, no matter how sophisticated the technical term one invents to denote it, one has already reintroduced the notion of some kind of esoteric self-substance. "

― Stephen Batchelor , Secular Buddhism: Imagining the Dharma in an Uncertain World