Sufism is an esoteric religion that overlaps with philosophy. So, we can posit Sufism is a way of being. Also, I should like to point out that Sufism in Persia (Iran) was a movement that began to transgress the exoteric-and institutionalized- Islam that was appropriated by the rulers of the region to control society. So Sufism was not only a theistic existential movement but also a political movement to escape the doctrinal and oppressive brand of Islam imposed on people in the East.
Out here in the US, Sufism has become yet another exotic way of mysticism that gets appropriate by the New Agers to fit their “desires.” You can find superficial writings about Rumi (Molavi) and Hafiz, translations of their poetry in accordance to what “sells.”
Mysticism is, of course, very sexy in privileged circles. Those who can afford it, pay lip service to Sufism. Alas, this is how it is sometimes.
As for Sufi thinkers, the first name that comes to mind is Ghazali.
He was the Persian philosopher, known in the West as al-Ghazali. Abu Hamid Muhammad al-Ghazali was born at Tus, Persia, in 450 AH (1058). He was an erudite scholar, so much so that he was appointed a professor of Islamic theology at the university in Baghdad {where the Greek knowledge was kept alive during the dark ages in the West]. A few years later, Ghazali had an emotional and spiritual crisis and came to believe that his way of life was too worldly. He left his academic post and became an ascetic, studying both the teachings and the practices of Islamic mystics. He later returned to teaching . His most important text is Deliverance from Error, which arguably constitutes Ghazali’s spiritual and intellectual autobiography.
Ghazali’s inquiry was a quest for certainty. He studied theology, but was disappointed with its intellectual achievements. His inquiry prompted him to study philosophy, but once again it seems that he was disappointed, especially with philosophy’s unfounded metaphysical claims and with the fact that many philosophers held beliefs contrary to Islamic revelation. Thinking this way, he turned to the Batiniyah, who teach that truth is attained not by reason, but by accepting the pronouncements of the infallible imam (religious leader). At the time, this teaching had important political implications since it was the official ideology of the Fatimid caliphate with its center in Cairo. However, Ghazali recognized that the teachings of the imams were quite trivial. He characterized their knowledge as “feeble” and “emaciated.” Finally he investigated and interrogated Sufism. It is among the Sufis that his restless soul found peace.
Ghazali was not satisfied with empiricism, rationalism, or skepticism. Hence, he sought to discover a source or means to knowledge that escapes the skeptic’s doubts and provides a firmer foundation than either empiricism or rationalism. He believed that he had found such a source in mystical experience, an intimate union with the “divine.”
This mystical experience is what attracts many Westerners to Sufism.
While Ghazali’s motivations were philosophical and scientific, above all, his inquiry has its impetus in a quest to know about the divine. His (creative) inquiry may reveal to us something about the limited nature of epistemological theories.
To be sure, Ghazali’s paradigmatic views are controversial (especially in the Western academy) to say the least. How could adequate knowledge be grounded in some sort of mystical experience? How do we know that mystical experience is not an illusion, just like some sense experiences?
Here’s a passage from “Deliverance from Error” that I think reveals a facet of Sufi thinking (here he is having a dialogue with sense-perception),
My reliance on sense-perception also has been destroyed. Perhaps only those intellectual truths which are first principles (or derived from first principles) are to be relied upon, such as the assertion that ten are more than three, that the same thing cannot be both affirmed and denied at one time, that one thing is not both generated in time and eternal, nor both existent and non-existent, nor both necessary and impossible.
Now, what did Ghazali think about the mystic experience of ecstasy, as understood by the Sufis? He wrote,
It may be that that state is what the Sufis claim as their special ‘state’(sc. Mystic union or ecstasy), for they consider that in their ‘states’(or ecstasies), which occur when they have withdrawn into themselves and are absent from their senses, they witness states (or circumstances) which do not tally with these principles of intellect. Perhaps that ‘state’ is death; for the Messenger of God (God bless and preserve him) says: ‘The people are dreaming; when they die, they become awake.’ So perhaps life in this world is a dream by comparison with the world to come; and when a man dies, things come to appear differently to him from what he now beholds, and at the same time the words are addressed to him: ‘We have taken off thee thy covering, and thy sight today is sharp’(Q. 50, 21).