There are several intellectual challenges to studying and describing Sufism. First of all, Sufism is a protean phenomenon: mysticism, esotericism, spirituality, metaphysics, popular religion, occultism, philosophy, theology, asceticism – we need all these categories to discuss Sufism. Secondly, this phenomenon is not strictly distinct from Islam. A substantial and definitive definition would thus run the risk of being not only futile, but also deceptive.

The protean nature of Sufism is due to its paradoxicality, which consists in mystical knowledge based on a direct experience of God, ineffable and incommunicable, that has nonetheless been communicated, transmitted and constructed as a tradition, through religious movements with their doctrines, practices and organisational structures. Through its charismatic leaders and its adaptable organisational structures, Sufism has been able to disseminate itself throughout the Islamic world, but also beyond it. This dissemination has most often involved the conversion of new disciples to Islam–Sufism and, in rare cases, the creation of syncretic forms: non-Islamic Sufism.