One of our ancestors, somewhere around the year 1000 AD and near what is now known as Uzbekistan, had his doubts about the human soul. You may know him as 'Avicenna', but I always refer to him as 'that guy from the flying man experiment'. Well, what is the flying man experiment then? 

To prove to himself that he had a soul (one he was very attached to), Avicenna first had to figure out the origin of this phenomenon. Something he, among others, was fairly unknown with. So he first started questioning whether he needed his senses to prove the existence of his soul, as is the nowadays widely used 'empirical standard'. Was his soul something that is inherently bound to the reality where people 'come together' to interact with each other's senses? Did his soul only exist in the senses of others or might it also be possible that he, Avicenna, existed on his own? 

After some frustrating nights (I figure) he came with the answer: in pursuit of a world without sensory input, he imagined himself falling in mid-air, without any relation or physical contact to the external world. There he found himself thinking of... himself. Without any senses, one is not made of the substance that one perceives through one's senses and might therefore be a substance of its own. The soul as an independent free will so to say. Or was that a bit of a quick step to make? 

Last summer, I had these same frustrating nights as Avicenna had a thousand years ago, but nowadays we have some more resources to prove the existence of the soul: Airplanes!! Or anything else that can bring you high enough up in the sky to jump out of. In this video, I found my soul, which, paradoxically, you can read from my face.

P.S. You might know this 'floating man' idea from Avicenna better in the words "I think, therefore I am" from Descartes, who merely performed an act of translation on the idea from our old Persian friend.