This post is in english - the next will be in italian.
Avicenna (arguebly the most important philosopher in the history of Islam, born in the 11th Century BC) was a very clever man, and he knew it. Famous for his groundbreaking works in the field of philosophy and medicine, he is less famous for his modesty which was nonexistent. But he had a good reason to be boastful and he certainly hasn't become one of Iran's national heros for nothing.
His most famous thought experiment was that of the “floating man” (or “flying man” depending on what your read), which he claimed proved the existence of a soul (or a god). His thought experiment goes like this;
Imagine a man is born in adult form in complete darkness and floating in nothingness. He is without gravity, without sound nor any visual input. He cannot see anything nor feel anything, not even his own body as his fingers are splayed open, his legs apart and his arms away from his sides so there is non tactile (or visual or audial) information coming in. If a man should be born in without any sensory input would he be aware of anything? According to Avicenna despite this “sterile” ambient, he would still be aware of his own existence. And this he claims is the proof of the existence of the soul (or god).
I think the floating man would be aware of his existence not through thought (as he hasn't had any possibility to develop language) but through “proprioception” which is a sense dedicated to the awareness of our body in space. I can pick up a glass of water and bring it to my lips without having to consciously follow the pathway through visual signals, although they help. In the middle of the night I do not need to see my arm to know that it is placed folded under me. Proprioception is best understood when we have lost it. For example when you drink too much: alcohol influences and diminishes this sense, which is why (at least in Britain – I don't know about here in Italy) if a policeman thinks you have been drinking to much he will ask you to shut your eyes and bring your finger to the tip of your nose. If you can do this with relative ease you probably haven't had one to many down the pub. If you lose this sense in order to walk you would need to see your leg coming up and then down in order to know where to place it. It's totally non-verbal and I suspect involves the right (sensory) side of the brain rather than the left (linguistic – but this is I confess a very crude differentiation). By the way.....If there are any neurologists out there who could clarify this for me I would be most grateful!
I believe Avicenna's floating man would have been thinking proprioceptively through the awareness of his internal organs within his own body and through his awareness of his body in space. I think he would have had a very dominant right side of the brain. Rather than concluding that this is the proof of the existence of the soul (or god) I believe that it is the key to getting one of the former, or getting into contact with the latter in so far as, the quietening down of the our internal brain chatter and the development of the right “sensory sensitive” side of the brain brings us closer to god, peace, collective consciousness, tranquility, "being at one with the world", calm, ...call it what you will.
Sometimes when I am in the tree position I think of Avicenna's floating man – I close my eyes, distance my body from itself so the only sensory input I have is tactile through the soles of my feet and through sound. I imagine I am floating. I fine tune my proprioceptive ability. It's very calming. Try it.
Yoga is a great way to stimulate and develop the sense of proprioception.