In fact, their dream experiences are indistinguishable from their waking ones. Moreover, their dream lives have the same continuity from one sleeping to another that their waking lives have from day to day. As a result, the professors have great dificulty determining whether they are awake or asleep at any given time. It should be pointed out that the professors at QUNY only dream when they are asleep. Diurnal professors are characterized by the fact that everything they believe while awake is true, while what they believe during dreams is false.
Nocturnal professors are just the reverse.
At one particular time, Prof. Chambois believed that she was diurnal. On another occasion, Prof. Concarne believed he was asleep at the time. Ny friend is quite bright, so I related the following situation to her. At time t, Prof. Vacula believed that he was diurnal and awake.