Such thoughts as these threatened to shake my reason, and I sought to find an escape from them. But how? In order to disentangle the knot of this difficulty, a proof was necessary. Now a proof must be based on primary assumptions, and it was precisely these of which I was in doubt. This unhappy state lasted about two months, during which I was, not, it is true, explicitly or by profession, but morally and essentially, a thorough-going skeptic. God at last deigned to heal me of this mental malady; my mind recovered sanity and equilibrium, the primary assumptions of reason recovered with me all their stringency and force. I owed my deliverance, not to a concatenation of proofs and arguments, but to the light which God caused to penetrate into my heart—the light which illuminates the threshold of all knowledge. To suppose that certitude can be only based upon formal arguments is to limit the boundless mercy of God. Some one asked the Prophet the explanation of this passage in the Divine Book: "God opens to Islam the heart of him whom he chooses to direct." "That is spoken," replied the Prophet, "of the light which God sheds in the heart." "And how can man recognize that light?" he was asked. "By his detachment from this world of illusion and by a secret drawing toward the eternal world," the Prophet replied. On another occasion he said: "God has created his creatures in darkness, and then has shed upon them his light." It is by the help of this light that the search for truth must be carried on. As by his mercy this light descends from time to time among men, we must ceaselessly be on the watch for it. This is also corroborated by another saying of the Apostle: "God sends upon you, at certain times, breathings of his grace; be prepared for them." My object in this account is to make others understand with what earnestness we should search for truth, since it leads to results we never dreamed of. Primary assumptions have not got to be sought for, since they are always present to our minds; if we engage in such a search, we only find them persistently elude our grasp. But those who push their investigation beyond ordinary limits are safe from the suspicion of negligence in pursuing what is within their reach. _The Different Kinds of Seekers after Truth_ When God in the abundance of his mercy had healed me of this malady, I ascertained that those who are engaged in the search for truth may be divided into three groups. I. Scholastic theologians, who profess to follow theory and speculation. II. The philosophers, who profess to rely upon formal logic. III. The Sufis, who call themselves the elect of God and possessors of intuition and knowledge of the truth by means of ecstasy.