In examining healing and spiritual power we encountered references to Sufism, but this category includes a far broader range of phenomena than those we discussed. When scholars of Islam mention Sufism, they might mean one of two things. Many Muslims throughout the world practice one or more ways of praying and praising God, drawing on the mystical tradition of Islam called tasawwuf. They invoke God's name in recitations often called dhikr, literally “remembrance.” In this sense, Sufism refers to a set of practices based on widely accepted ideas about communication and devotion available to most Muslims.

But a Muslim might also belong to an organized Sufi group or order (tarîqa), which traces its particular set of practices back to a founder and highlights this genealogy as its grounds for sanctity. An order has a leader – a sheikh or pir – and rules about how their members worship. Some orders also structure political or economic life. Some of the larger orders (Naqshbandiyya, Qadariyya, Tijaniyyah) have spread across continents and indeed may have been one of the major vehicles for the coming of Islam to parts of Asia and Africa. Today, membership in these or other orders links some Muslims living in Muslim-majority societies with those living in Europe and North America.