The phenomenon of dreamless sleep and its philosophical consequences, particularly deep sleep's relevance to such issues as Self, Consciousness, Personal Identity, Unity of Subject, and Disembodied Life, are explored through a discussion, in varying detail, of certain noted doctrines and views--for example of Advaita Vedānta, Hegel, and H. D. Lewis. Finally, with a cue from Leibniz and McTaggart, the suggestion is made that at no stage during sleep is the self without some perceptions, however indeterminate. Support for this hypothesis is (...) claimed from the current psychoanalytic opinion that mental activity does not cease during any part of sleep and that human beings continue to dream even in the so-called dreamless state. (shrink)