"Think of transitional processes of various kinds: waking from sleep, emerging from a coma or from general anesthesia, a fetus developing sentience in the womb, or a lineage evolving sentience over millions of years. In all of these cases, we face the question of whether there is a sudden jump from the complete absence of phenomenal consciousness to its presence in at least minimal form – a ‘lights on’ moment – or a gradual transition with a region of borderline cases in which there is no determinant fact of the matter about whether phenomenal consciousness is present or absent. On this second view, the metaphor of the light switch is no longer appropriate (not even a dimmer switch, because a dimmer switch still has a sharp transition from off to on). The transition is more like the transition from being non-bald to bald, or young to old, where there is no sharp threshold, no single moment at which the transition happens"