The merely conscious being does not have a preference for continued life. Perhaps while having a pleasurable experience it has a preference for that experience to continue, or while having a painful experience it has a preference for that experience to end, but it will not have any preferences for the long-term future, and the desires it has do not survive periods of sleep or temporary unconsciousness, because unlike a self-aware being, it has no conception of its own future existence after a period of sleep. Thus if we are concerned only about the thwarting of preferences, for a merely conscious being, painless killing and administering an anesthetic seem to be equivalent. Killing does not thwart any more desires than putting the being to sleep. The being will be able to continue to satisfy its preferences after it awakes, but from the being's subjective perspective it is as if a new being, with new preferences, came into existence.
Peter Singer, Practical Ethics
consciousness, ethics, utilitarianism