Carra de Vaux[8] thus graphically describes the process in Al Ghazzali’s mind, as he himself suggests it to us: “Religious beliefs, he reflected, are transmitted by the authority of parents; but authority is not proof. To arrive at certitude it was necessary for him to reconstruct all his knowledge from the very foundation. With a vivid feeling of this necessity, he aspired to certitude, defining it in a purely psychological fashion as a state in which the mind is so bound up with and so satisfied with a piece of knowledge that nothing might henceforth deprive him of it. This curious definition, which is applied to religious faith as well as to scientific knowledge, does not escape from being purely subjective. As one might foresee, the great desire for certitude only led him at first into a series of doubts. As he sought this state of perfect assurance, step by step he saw it recede before him. He looked for certitude in the perceptions of the senses, with the result that he could no longer trust his senses. Sight, the most powerful of the faculties of sense, for example, led him to the perception of an immovable shadow on the sun and an hour afterwards this shadow was gone. Sight showed him a star which is very small, and geometry made him recognise it to be greater than the earth. Then he turned to the first principles of reason; but the perception of the senses took its revenge in saying to him: ‘Previously you believed in me and you abandoned me when this judge reason presented itself. If this judge had remained hidden you would have continued to believe in me. Who can tell you that beyond the reason there is no other judge, which if it made itself evident, would convict reason of falsehood?’. That is a movement of thought which is dramatic enough, though perhaps a little artificial.—The thinker continued his search for the certain. He halted and concerned himself with the famous comparison of life with a dream and death with an awakening. Perhaps after that awakening he would see things in a different manner from that in which he then saw them. Mysticism thus suggested itself to him: This actual dream of death could be anticipated by the condition of ecstasy, by less than ecstasy, by a light which God pours into the heart. In this light, he saw not only the truth of the dogmas of the faith or the beauty of the moral life, but he was assured of the truth of the first principles of reason, the basis of all knowledge and all reasoning. He doubted no longer; he was cured of his pains; he had found certitude and peace.”