White pawn Alice

Magritte

Question: When we are dreaming and, as often happens, have a dim consciousness of the fact and try to wake, do we not say and do things which in waking life would be insane? May we not then sometimes difine insanity as an inability to distinguish which is the waking and which is the sleeping life? we often dream whithout the last suspicion of unreality: "sleep halth its own world" and it is often as lifelike as the other. 

Lewis Carroll's diary, 9 feb 1856.