In this scheme there are certainly grave difficulties, philosophical and ethical. It establishes a relationship between God and the atoms; but we have already seen that relationships are subjective illusions. That, however, was in the case of the things of the world, perceived by the senses—contingent being, as they would put it. It does not hold of necessary being. God possesses a quality called Difference from originated things (_al-mukhalafa lil-hawadith_). He is not a natural cause, but a free cause; and the existence of a free cause they were compelled by their principles to admit. The ethical difficulty is perhaps greater. If there is no order of nature and no certainty, or nexus, as to causes and effects; if there is no regular development in the life, mental, moral, and physical of a man—only a series of isolated moments; how can there be any responsibility, any moral claim or duty? This difficulty seems to have been recognized more clearly than the philosophical one. It was met formally by the assertion of a certain order and regularity in the will of God. He sees to it that a man’s life is a unity, and, for details, that the will to eat and the action always coincide. But such an answer must have been felt to be inadequate and to involve grave moral dangers for the common mind. Therefore, as we have seen, the study of kalam was hedged about with difficulties and restrictions. Theologians recognized its trap-falls and doubts, even for themselves, and lamented that they were compelled by their profession to study it. The public discussion of its questions was regarded as a breach of professional etiquette. Theologians and philosophers alike strove to keep these deeper mysteries hidden from the multitude. The gap between the highly educated and the great mass—that fundamental error and greatest danger in Muslim society—comes here again to view. Further, even among theologians, there was some difference in degree of insight, and books and phrases could be read by different men in very different ways. To one, they would suggest ordinary, Qur’anic doctrines; another would see under and behind them a trail of metaphysical consequences bristling with blasphemous possibilities. Thus, Muslim science has been always of the school; it has never learned the vitalizing and disinfecting value of the fresh air of the market-place. This applies to philosophers even more than to theologians. The crowning accusation which Ibn Rushd, the great Aristotelian commentator, brought against al-Ghazzali was that he discussed such subtilties in popular books. [Sidenote: SPREAD OF ASH‘ARISM]