The threshold. The intervals that transcend duality. Apparent states that challenge borders, lines, transience. Physical or mental states that, being ether, some of us have assumed them as real and tangible, while others states are dressed of air, and some others remain unknown.
Some ancient traditions recognize the threshold and cherish these states in order to transcend them. Between the sky and the earth there is a bridge that melts them. Its crossing lays in between these intervals.
The fear of uncertainty is a toll, and the courage its payment.