What is the nature of mind ?

That which is called 'mind', which projects all thoughts, is an awesome power existing within the Self, one's real nature. If we discard all thoughts and look [to see what remains when there are no thoughts, it will be found that] there is no such entity as mind remaining separate [from those thoughts]. Therefore, thought itself is the nature of the mind. There is no such thing as 'the world' independent of thoughts. There are no thoughts in deep sleep, and there is no world. In waking and dream there are thoughts, and there is also the world. Just as a spider emits the thread of a web from within itself and withdraws it again into itself, in the same way the mind projects the world from within itself and later reabsorbs it into itself. When the mind emanates from the Self, the world appears. Consequently, when the world appears, the Self is not seen, and when the Self appears or shines, the world will not appear.

If one goes on examining the nature of the mind, it will finally be discovered that [what was taken to be] the mind is really only one's self. That which is called one's self is really Atman, one's real nature. The mind always depends for its existence on something tangible. It cannot subsist by itself. It is the mind that is called sukshma sarira [the subtle body] or jiva [the soul].

Bhagawan Ramana Maharishi