Intellectual study may last the whole of one's life; there is no end to it, and this is why the teacher does not encourage speculation. A doctrine means a separation from other doctrines. The Sufi belongs to every religion, and thus he has no special beliefs and speculations. There can for instance be one Sufi who believes in reincarnation, and another who realizes heaven and hell. The work of the Sufi is personal development. It is what one practices that is important rather than what the teacher says, though the teacher can give protection.