Descartes, philosophy’s great sceptic, asked himself how he could be sure that he was awake. He wrote, «How often do I dream that I am here, in my robe, sitting by the fire, whereas in reality I am lying undressed in bed!» This thought led Descartes to formulate his famous doubts and finally to the sentence «I think, therefore I am». Whether awake or dreaming and whatever else might be «out there», there can be no doubt that I exist. In the meantime, this has also been confirmed by sleep researchers in the meantime. Each individual is his own fixed point of reference. He remains himself whether awake or asleep, although it is never possible to be absolutely sure what he is really doing at any given time.
From a neurophysiological point of view, this puzzle has a simple solution – it is not possible to differentiate completely between wakefulness and dreaming simply because there is no significant difference between the two. The brain does not possess a sleep module. We dream using the same areas of the brain, linked to the same networks as those we use for our everyday experiences in the real world. Our awareness of sleep and dreams is based on the same neuronal processes. The Indian neuroscientist, V. S. Ramachandran states that “we are constantly hallucinating and what we perceive to be true are simply the hallucinations that best fit the current sensual information.”