They arose within the lands of Islam during the reign of al-Maʾmūn, and they remain few in number.
As for the Yaʿqūbiyya (Jacobites), they claim that the lāhūt (divine nature) and the nāsūt (human nature) (1) united and blended just as water mixes with milk or wine. Hence, the two became one substance (2), one hypostasis, and one nature, so that the very human nature became identical with the divine nature, and the one who was crucified (3) was, in their view, none other than the divine Himself.
The Malikiyya (Melkites) (4) maintain that the two became a single substance (5) possessing two hypostases; others report the reverse: one hypostasis possessing two substances.
The Nestorians declare (6) that there are two substances and two hypostases, joined only in will. Both of these last positions belong to those who speak of ittiḥād (union) (7).
As for ḥulūl (indwelling), some of the scholastic theologians—such as Abū al-Maʿālī (8)—mention it
(=) p.132. See the points of consensus and disagreement among these sects in al-Milal wa al-Nihal by al-Shahrastani, vol.1, pp.226–228; for their refutation and rebuttal, see al-Fasl by Ibn Hazm, vol.1, pp.50–65; and for the proper response to those who altered the religion of Christ, see Ibn Taymiyya’s The Correct Answer to Those Who Have Altered the Religion of Christ.
(1) In his Kulliyyāt, vol.4, p.173, Abu al-Baqa lists various uses of “ilahiyyat” (theology) and “nasut” (human nature): theology as the Creator and human nature as the created; theology for the spirit and human nature for the body; theology for the upper world and human nature for the lower; and, by extension, theology for cause and effect or for jinn and humans. See also The Philosophical Dictionary by Jamil Sulayba, vol.2, p.277.
(2) In the original: wahid jawhar (“one substance”); this reading is supported by manuscripts S and Ṭ and by al-Milal wa al-Nihal 1:226.
(3) In manuscript Ṭ: al-maṭlūb (“the demanded”), which is erroneous.
(4) In manuscripts S and Ṭ: al-malakāniyya.
(5) In the original: jawāhir (“substances”); supported by manuscripts S and Ṭ.
(6) In the original: “and al-Nastūr says”; in manuscript S: “and the Nestorians say.” The original reading is confirmed by manuscript Ṭ, and by Jawāb al-Ṣaḥīḥ 2:310 and Manḥat al-Qarīb al-Mujīb, p.134.
(7) In the original: bi al-ittiḥādiyya (“unionism”); supported by manuscripts S and Ṭ and consistent with the context.
(8) In al-Irshād, p.48.