They lacked the necessary knowledge of the subject, had no scientific basis, and were constrained eventually to fall back on authority. After study of them and their methods it became clear to al-Ghazzali that the remedy for his ailment was not in scholastic theology. [Sidenote: MATERIALISTS; DEISTS; THEISTS] Then he turned to philosophy. He had seen already that the weakness of the theologians lay in their not having made a sufficient study of primary ideas and the laws of thought. Three years he gave up to this. He was at Baghdad at the time, teaching law and writing legal treatises, and probably the three years extended from the beginning of 484 to the beginning of 487. Two years he gave, without a teacher, to the study of the writings of the different schools of philosophy, and almost another to meditating and working over his results. He felt that he was the first Muslim doctor to do this with the requisite thoroughness. And it is noteworthy that at this stage he seems to have again felt himself to be a Muslim, and in an enemy’s country when he was studying philosophy. He speaks of the necessity of understanding what is to be refuted; but this may be only a confusion between his attitude when writing after 500, and his attitude when investigating and seeking truth, fifteen years earlier. He divides the followers of philosophy in his time into three: Materialists, Deists (_Tabi‘is, i.e._ Naturalists), and Theists. The materialists reject a creator; the world exists from all eternity; the animal comes from the egg and the egg from the animal. The wonder of creation compels the deists to admit a creator, but the creature is a machine, has a certain poise (_i‘tidal_) in itself which keeps it running; its thought is a part of its nature and ends with death. They thus reject a future life, though admitting God and His attributes. He deals at much greater length with the teachings of those whom he calls theists, but through all his statements of their views his tone is not that of a seeker but that of a partisan; he turns his own experiences into a warning to others, and makes of their record a little guide to apologetics. Aristotle he regards as the final master of the Greek school; his doctrines are best represented for Arabic readers in the books of Ibn Sina and al-Farabi; the works of their predecessors on this subject are a mass of confusion. Part of these doctrines must be stamped as unbelief, part as heresy, and part as theologically indifferent. He then divides the philosophical sciences into six, mathematics, logic, physics, metaphysics, political economy, ethics; and discusses these in detail, showing what must be rejected, what is indifferent, what dangers arise from each to him who studies or to him who rejects without study.