The book provides a careful unprecedented analysis of the Sufi-mystical treatises of Abu al-Qasim al-Junayd (d. 910), especially his Treatise on Annihilation, focusing on two central notions in his treatises, namely, the notions of annihilation and unification. It compares al-Junayd's thought with the thought of other important Sufis and seeks to correct the kind of understanding in scholarship that reflects on the Sufi tradition in terms of division and discontinuity between the earlier and the later Sufi thinkers.