Gurdjieff on the topic:
ADDED: Gurdjieff himself was on a similar quest - to find out the truth of such matters. And he was well positioned to make the search in the area where he was born and grew up. He did a lot of traveling, talked to a lot of people, read a lot of books, and what he said above, recorded by Ouspensky, was the bottom line, or the end of the line of his protracted, painful, and dangerous search."Fusion, inner unity, is obtained by means of 'friction,' by the struggle between 'yes' and 'no' in man. If a man lives without inner struggle, if everything happens in him without opposition, if he goes wherever he is drawn or wherever the wind blows, he will remain such as he is.
"But if a struggle begins in him, and particularly if there is a definite line in this struggle, then, gradually, permanent traits begin to form themselves, he begins to 'crystallize.'
"But crystallization is possible on a right foundation and it is possible on a wrong foundation. 'Friction,' the struggle between 'yes' and 'no,' can easily take place on a wrong foundation. For instance, a fanatical belief in some or other idea, or the 'fear of sin,' can evoke a terribly intense struggle between 'yes' and 'no,' and a man may crystallize on these foundations. But this would be a wrong, incomplete crystallization. Such a man will not possess the possibility of further development. In order to make further development possible he must be melted down again, and this can be accomplished only through terrible suffering.
"Crystallization is possible on any foundation. Take for example a brigand, a really good, genuine brigand. I knew such brigands in the Caucasus. He will stand with a rifle behind a stone by the roadside for eight hours without stirring. Could you do this? All the time, mind you, a struggle is going on in him. He is thirsty and hot, and flies are biting him; but he stands still.
"Another is a monk; he is afraid of the devil; all night long he beats his head on the floor and prays. Thus crystallization is achieved.
"In such ways people can generate in themselves an enormous inner strength; they can endure torture; they can get what they want. This means that there is now in them something solid, something permanent. Such people can become immortal. But what is the good of it? A man of this kind becomes an 'immortal thing,' although a certain amount of consciousness is sometimes preserved in him. But even this, it must be remembered, occurs very rarely."