mental streams are kept from consciousness is the following: — Our conscious reflection teaches us that when exercising attention we pursue a definite course. But if that course leads us to an idea which does not hold its own with the critic, we discontinue and cease to apply our attention. Now, apparently, the stream of thought thus started and abandoned may spin on without regaining attention unless it reaches a spot of especially marked intensity which forces the return of attention. An initial rejection, perhaps consciously brought about by the judgment on the ground of incorrectness or unfitness for the actual purpose of the mental act, may therefore account for the fact that a mental process continues until the onset of sleep unnoticed by consciousness.

Let us recapitulate by saying that we call such a stream