, I shake my head, I stretch out my hand, so that the difference between wakefulness and sleeping appears quite vividly); but new memories, on a second level (the vividness of this impression has often been a part of my dreams); with these memories, the vivid feeling that I am awake begins to disappear; it is replaced by the clear vision that there is no certain indication that might separate sleeping and wakefulness: a conclusion that provokes an astonishment in the meditating subject such that the indifference between sleep and wakefulness provokes the quasi certainty that one is sleeping.