After its initial growth over the first three centuries of Islamic history, Sufis began to espouse a distinct cosmological and metaphysical perspective. In part, these tendencies grew out of broader speculative trends in Islamic philosophy and theology. As the social acceptability of Sufism grew, its practitioners were organized by their shaykhs and disciples into Orders, or turuq (singular: tariqa). These had a social and religious function, since they became vehicles for the passing down of knowledge and practices among distinct circles of students. The institutionalization of learning in Islamic schools, madrasas, overlapped with that of the tariqas, and the scholarly works of Sufis were part of broader educational curricula.
In the 12th and 13th centuries C.E., the Sufi scholar Ibn al-Arabi (d. 1240) was highly influential, but not without some controversy. He was called "Al-Shaykh al-Akbar," the "Greatest Shaykh." He wrote on all issues of theory and practice in Islam, not just mysticism, and he did so in ways that were so sophisticated and erudite as to be intimidating if not confusing. Due to the vast range of his work, it is not easy to make decisive statements about all of his views, and though many modern scholars have attempted to categorize his thinking, most agree that one cannot explicitly pinpoint his doctrine. Instead, Ibn al-Arabi is well known for his ability to expound at length from a multiplicity of perspectives.
Nonetheless, a number of concepts were central to his work and to subsequent Sufi thinking. One of these is wujud, which can mean "being, or existence"; this concept necessitates the disciple's realization of God's existence. Another is the understanding of God's names, of which, according to Islamic tradition, there are ninety-nine. Each name describes an attribute of God, such as "The Merciful" or "The All-Knowing." Sufis interpreted facets of their relationship to God through the lens of the ninety-nine names. For example, God as "All-Seeing" would affect the Sufi's awareness of God's omniscience and omnipresence, and have a corresponding effect on one's behavior and thought.
Ibn al-Arabi was central to the history of Sufism in the Islamic world. His teachings on the Quran (namely that every verse, word, and letter of the scripture reveals a different manifestation of God) were highly influential for other esoteric readings. Drawing on law, theology, and hadith, Ibn al-Arabi understood that shariah, or Islamic law in the broadest sense, was all the teaching brought by prophets. Secondarily, and more specifically, it refers to the teachings in the Quran and Sunna of Muhammad . Finally, and most narrowly, within the Sunna it refers to the revealed legal rulings as opposed to other anecdotal or historical reports. In his view, the purpose of obeying shariah is to die and return to God in such a way that one's eternal happiness, namely salvation, is assured.
Ibn al-Arabi is seen as pivotal in the history of Sufism because his work exemplifies a moment in which themes such as God's oneness (tawhid) or the nature of prophecy, which had previously been the purview of theologians or philosophers, shifted into Sufi writing as well. Broadly speaking, these two issues dealt with the nature of God and the nature of God's relationship with humans, respectively.
The oneness of God was a matter of tremendous discussion in the early Islamic period, especially as it related to his attributes, mentioned above. Questions arose as to whether or not God's attributes were separate from him, or a part of him. That is, did they describe God, or were they somehow co-eternal entities? This opened up many complicated philosophical and theological lines of inquiry for medieval scholars, especially because of one attribute that calls God "the One who Speaks." The answer to the question "What is God's speech?" was "The Quran." This answer inspired yet another question: If the Quran is God's speech, did it always exist (are his attributes co-eternal)? If not, was it created at a specific moment, or was it always there? In other words, is the Quran eternal or created? At first glance, it seems that these questions are about the text of the Quran but in fact they originated from discussions about God's attributes, namely his speech.
Another dimension of how God communicates is the history of prophecy—namely, how does God choose to instruct humans regarding their behavior? When prophets speak and act, is it by their authority or God's? Are they infallible because they are guided by God? Sufis did not come up with a uniform set of responses to these questions, but their engagement in such matters illustrates how much philosophy and theology came to shape Sufi thought.
Before these philosophical questions arose, Sufi works had been more concerned with the practice of morality and the nature and status of the self and the soul. After the 13th century, performative writing, especially poetry (the most famous example of which is the poetry of Jalal al-Din Rumi, who died in the 13th century), came to dominate Sufi literature. With such luminaries of mystical poetry as Farid al-Din Attar (d. 1221 C.E.), Hafiz (d. 1390 C.E.), and Amir Khusraw (d. 1325), Sufi literature took yet another turn, making the 13th century a high point for Sufi intellectual writing.