How can a pain wake you up? You were not dreaming, nor did any bodily stimuli filter into your consciousness. You did not just wake up and realize you were in pain, as you might wake up and realize it is Saturday. You were deeply, dreamlessly asleep, and suddenly you were awake, and in pain. How is this possible? If pain exists only inasmuch as it is experienced, it seems that the pain did not exist when you were asleep, and so could not have woken you up. I shall argue that you were woken by a pain sensation that you did not know you had, so that the distinction between what is and what is known holds even for the contents of consciousness. This illuminates the relationship between consciousness and attention, and casts light on the Classical Empiricist tradition that identifies the foundations of knowledge with direct experience.