This went on, he tells us, for almost ten years, and in that time there were revealed to him things that could not be reckoned and the discussion of which could not be exhausted. He learned that the Sufis were on the true and only path to the knowledge of God; that neither intelligence nor wisdom nor science could change or improve their doctrine or their ethics. The light in which they walk is essentially the same as the light of prophecy; Muhammad was a Sufi when on his way to be a prophet. There is none other light to light any man in this world. A complete purifying of the heart from all but God is their Path; a seeking to plunge the heart completely in the thought of God, is its beginning, and its end is complete passing away in God. This last is only its end in relation to what can be entered upon and grasped by a voluntary effort; in truth, it is only the first step in the Path, the vestibule to the contemplative life. Revelations (_mukashafas_, unveilings) came to the disciples from the very beginning; while awake they see angels and souls of prophets, hear their voices and gain from them guidance. Then their State (_hal_, a Sufi technicality for a state of ecstasy) passes from the beholding of forms to stages where language fails and any attempt to express what is experienced must involve some error. They reach a nearness to God which some have fancied to be a _hulul_, fusion of being, others an _ittihad_, identification, and others a _wusul_, union; but these are all erroneous ways of indicating the thing. Al-Ghazzali notes one of his books in which he has explained wherein the error lies. But the thing itself is the true basis of all faith and the beginning of prophecy; the _karamat_ of the saints lead to the miracles of the prophets. By this means the possibility and the existence of prophecy can be proved, and then the life itself of Muhammad proves that he was a prophet. Al-Ghazzali goes on to deal with the nature of prophecy, and how the life of Muhammad shows the truth of his mission; but enough has been given to indicate his attitude and the stage at which he had himself arrived.