In its beginnings, Sufism was a moral movement concerned with asceticism (zuhd) and poverty (faqr). Later, Sufism's second period, which was called "Sunnī Sufism" with problems arising from a spiritual life of which the theoretical basis is unknown, was again within the limits of a moral content. Finally came an era of maturity with the advent of Ibn al-ʿArabī and his followers, who revealed a set of metaphysical principles for moral life. In this last period, the Sufis, who have always been loyal to their own methods, instruments and (especially) to the objectives that have always aimed at the progress of morals, dealt largely with theoretical problems, interpreted the relations among God, man and the universe, expressed at times the already-discussed traditional problems in a new style, and extended the field of metaphysical thought in Islam by adding and considering new problems. In extending the domain of metaphysics, concentrating on the problem of the relations between God and man, Sufism has represented an attempt to express the intellectual heritage put forth by Islam for a period of four centuries through various philosophical-religious traditions and dialectical relations; consequently, a Sufi language or discourse has arisen that describes traditional problems by means of a renovation of terms and styles. One of the main obstacles facing the academic study of Sufism is determining the relation between this language and the theoretical discourse that has arisen within Islamic philosophy and within kalām (Islamic theology). If this obstacle can be overcome, the origins of Sufism and the degree of its contribution to the heritage of Islamic reflection as a whole will be revealed.