Insanity's crescendo

“How often has it happened to me that in the night I dreamt that I found myself in this particular place, that I was dressed and seated near the fire, whilst in reality I was lying undressed in bed! At this moment it does indeed seem to me that it is with eyes awake that I am looking at this paper: that this head which I move is not asleep, that it is deliberately and set purpose that I extend my hand and perceive it: what happens in sleep does not appear so clear nor so distinct as does all this. But in thinking this over I remind myself that on many occasions I have in sleep being deceived by similar illusions, and on dwelling carefully on this reflection I see so manifestly that there are no certain indications by which we may clearly distinguish wakefulness from sleep that I am lost in astonishment. And my astonishment is so great that it is almost capable of persuading me that I now dream.” (Rene Descartes, The First Meditation)