Sufi philosophy includes the schools of thought unique to Sufism, the mystical tradition within Islam, also termed as Tasawwuf or Faqr according to its adherents. Sufism and its philosophical tradition may be associated with both Sunni and Shia branches of Islam. It has been suggested that Sufi thought emerged from the Middle East in the eighth century CE, but adherents are now found around the world. According to Sufi Muslims, it is a part of the Islamic teaching that deals with the purification of inner self and is the way which removes all the veils between the divine and humankind. It was around 1000 CE that early Sufi literature, in the form of manuals, treatises, discourses and poetry, became the source of Sufi thinking and meditations. Sufi philosophy, like all other major philosophical traditions, has several sub-branches, including cosmology and metaphysics, as well as several unique concepts. History of Islam The emergence of Sufi thought is commonly linked to the historical developments of the Middle East in the seventh and eighth centuries CE following the life of the Islamic prophet Muhammad, and its development took place throughout the centuries after that. Between the tenth and 12th centuries, Sufism became a widely spread discipline in the Muslim world. One influential early writer on Sufi philosophy was the Muslim scholar and theologian Al-Ghazali (1058–1111). He discussed the concept of the self and the causes of its misery and happiness. Sufism in the Muslim world emerged and grew as a mystical, somewhat hidden tradition in the mainstream Sunni and Shia denominations of Islam, state Eric Hanson and Karen Armstrong, likely in reaction to "the growing worldliness of Umayyad and Abassid societies". Sufism was adopted and then grew particularly in the frontier areas of Islamic states, where the asceticism of its fakirs and dervishes appealed to populations already used to the monastic traditions of Hinduism, Buddhism, and Christianity.