After one has practiced these three aspects of discipline, one is able to arrive at the fourth aspect which is greater still; it is greater because by it one arrives at spiritual experiences. This discipline is practiced to free one's consciousness from one's environment. It is the experience of the adepts and they have spent much of their lives arriving at this. In the old school of the Sufis, and even today, there is a custom that when they enter or leave the room of meditation, one among them says, 'Solitude in the crowd.' The suggestion is that even when one is in the midst of the crowd one can still keep one's tranquility, one's peace, so that one is not disturbed by the surroundings. It is this which enables one to live in the midst of the world and yet progress spiritually; and it is no longer necessary to go into the wilderness, as many souls did in ancient times, in order to develop spiritually.