§ 26.4. =Sources of Information.=--Abundant as the literary productions were which assumed the name or else without the name developed the principles of Gnosticism, comparatively little of this literature has been preserved. We are thus mainly dependent upon the representations of its catholic opponents, and to them also we owe the preservation of many authentic fragments. The first church teacher who _ex professo_ deals with Gnosticism is Justin Martyr (§ 30, 9), whose controversial treatise, however, as well as that of Hegesippus (§ 31, 7), has been lost. The most important of extant treatises of this kind are those of Irenæus in five books _Adv. hæreses_, and of Hippolytus Ἔλεγχος κατὰ πασῶν αἱρέσεων, the so-called _Philosophoumena_ (§ 31, 3). The Σύνταγμα κ. π. αἱρ. of Hippolytus is no longer extant in the original; a Latin translation of it apparently exists in the _Libellus adv. omnes hæreses_, which has been attributed to Tertullian. Together with the work of Irenæus, it formed a query for the later heresiologists, Epiphanius and Philaster (§ 47, 10, 14), who were apparently unacquainted with the later written but more important and complete _Elenchus_. Besides these should be mentioned the writings of Tertullian (§ 31, 10) and Theodoret (§ 47, 9) referring to this controversy, the _Stromata_ of Clement of Alexandria, and the published discussions of Origen (§ 31, 4, 5), especially in his Commentary on John, also the five Dialogues of the Pseudo-Origen (Adamantius) against the Gnostics from the beginning of the fourth century;[39] and finally many notices in the Church History of Eusebius. The still extant fragments of the Gnostic Apocryphal historian of the Apostles afford information about the teaching and forms of worship of the later syncretic vulgar Gnosticism, and also from the very defective representations of them in the works of their Catholic opponents. § 27. THE GENTILE CHRISTIAN GNOSTICISM.