A New religion has no theology; that develops later. It is only natural that Islam should show some influence of the older religions among which it grew up. New ideas came in with converts or through talk with men of other faiths. Muslim theology moved in a circle, and came back to its starting-point with the same ideas deeper and riper. The second and third centuries of the Hijra were the formative period, after which thought degenerated into the splitting of hairs. The religious world was in a ferment which threw out many strange ideas. Sober thinkers mostly belonged to the Mu‘tazila, who taught the freedom of the human will to free God from the responsibility for sin and evil. Others found a solution of this problem in other ways, some being forerunners of al-Ash‘ari, who in 300 A.H. deserted the Mu‘tazila and used their methods to build up the system of orthodoxy. Many of these men were not Arabs, and their writings have perished; so all that is known of their teaching comes from the works of their opponents. The earliest of these is Maḳālāt al-islāmiyyīn by al-Ash‘ari; it is also the most valuable, for it is objective and free from theological hatred. The author has done his best to report what these men taught, and his education fitted him for this. Later books are not so impartial. ‘Abd al-Ḳāhir al-Baghdādi († 429) calls each deviation from the strait path an error.