It is generally accepted that the first exponent of Sufi doctrine was the Egyptian, or Nubian, _Dhu n-Nun_ (d. 245-246), a pupil of the jurist Malik b. ´Anas, who lived at the time when there was much percolation of Hellenistic influence into the Islamic world. He was indeed nearly contemporary with `Abdullah, the son of Maymum, whose work we have already noticed. Dhu n-Nun’s teaching was recorded and systematized by al-Junayd of Baghdad (d. 297), and in it appears essential doctrine of Sufism, as of all mysticism, in the teaching of _tawhid_, the final union of the soul with God, a doctrine which is expressed in a way closely resembling the neo-Platonic teaching, save that in Sufism the means whereby this union is to be attained is not by the exercise of the intuitive faculty of reason but by piety and devotion. Still the two come very close when we find in the teachings of the later philosophers that the highest exercise of reason consists in the intuitive apprehension of the eternal verities rather than in any other activity of the intellect. Al-Junayd is stated by Jami to have been a Persian, and it is chiefly in Persian hands that the doctrines of Sufism develop and turn towards pantheism. Both agnosticism and pantheism are present practically in the later neo-Platonism; agnosticism as regards the unknowable First Cause, the God from the Agent Intellect is an emanation, a doctrine which develops in the teaching of the philosophers and of the Isma`ilians and kindred sects; but Sufi teaching centres its attention upon the knowable God, which the philosopher would describe as the Agent Intellect or Logos, and this develops more usually in a pantheistic direction. The doctrines thus developed and expressed by al-Junayd were boldly preached by his pupil, _ash-Shibli_ of Kurasan (d. 335).
_Al-Husayn b. Mansur al-Hallaj_ (d. 309) was a fellow-student of ash-Shibli, and shows Sufism as allied with extremely unorthodox elements. He was of Zoroastrian descent and closely in touch with the Qarmatians, and seems to have held those doctrines which are usually associated with the _ghulat_ or extreme Shi`ites, such as transmigration, incarnation, etc. He was put to death as a heretic for declaring “I am the truth”, thus identifying himself with God. The accounts given of him show great differences of opinion: for the most part the earlier historians, approaching the subject from an orthodox stand-point, represent him as a wily conjurer who by pretended miracles gained a number of adherents, but later Sufi writers regard him as a saint and martyr who suffered because he disclosed the great secret of the union between the soul and God. The doctrine of _hulul_, or the incarnation of God in the human body, was one of the cardinal tenets of the _ghulat_. According to al-Hallaj, man is essentially divine because he was created by God in his own image, and that is why, in Qur. 2, 32, God bids the angels worship Adam. In _hulul_, which is treated as _tawhid_ taking place in this present life, the deity of God enters the human soul in the same way that the soul at birth enters the body. This teaching is a fusion of the old pre-Islamic Persian beliefs as to incarnation and the philosophical theories of neo-Platonism, of the Intellect or rational soul or spirit, as it is more commonly called by English writers, the part added to the animal soul is an emanation from the Agent Intellect, to which it will ultimately return and with which it will be united (cf. Massignon: _Kitab al-Tawasin_, Paris, 1913). This is an extremely interesting illustration of the fusion of oriental and Hellenistic elements in Sufism, and shows that the theoretical doctrines of Sufism, whatever they may have borrowed from Persia and India, receive their interpretative hypotheses from neo-Platonism. It is interesting also as shewing in the person of al-Hallaj a meeting-point between the Sufi and the philosopher of the Isma`ilian school.