Al-Razi's development of Kalam (Islamic scholastic theology) led to the evolution and flourishing of theology among Muslims. Razi had experienced different periods in his thinking, affected by the Ash'ari school of thought and later by al-Ghazali. Al-Razi tried to make use of elements of Muʿtazila and Falsafah, and although he had some criticisms on ibn Sina, Razi was greatly affected by him. The most important instance showing the synthesis of Razi's thought may be the problem of the eternity of the world and its relation to God. He tried to reorganize the arguments of theologians and philosophers on this subject, collected and critically examined the arguments of both sides. He considered, for the most part, the philosophers' argument for the world's eternity stronger than the theologians' position of putting emphasis on the temporal nature of the world. According to Tony Street, we should not see in Razi's theoretical life a journey from a young dialectician to a religious condition. It seems that he adopted different thoughts of diverse schools, such as those of Mutazilite and Asharite, in his exegesis, The Great Commentary.