[1] πᾶσα διδασκαλία καὶ πᾶσα μάθησις διανοητικὴ ἐκ προϋπαρχούσης γένεται γνώσεως (Arist. _Anal. post._ i. 1, P. 71). John Philoponus, in his note on the passage, points out that emphasis is laid upon the word διανοητική, in antithesis to sensible knowledge, ἡ γὰρ αἰσθητικὴ γνῶσις οὐκ ἔχει προϋποκειμένην γνῶσιν (_Schol._ ed. Brandis, p. 196 _b_). [2] Tertullian (_adv. Valentin._ c. 5) singles out four writers of the previous generation whom he regards as standing on an equal footing: Justin, Miltiades, Irenæus, Proculus. Of these, Proculus has entirely perished; of Miltiades, only a few fragments remain; Justin survives in only a single MS. (see A. Harnack, _Texte und Untersuchungen_, Bd. i. 1, _die Ueberlieferung der griechischen Apologeten des zweiten Jahrhunderts_); and the greater part of Irenæus remains only in a Latin translation. [3] Marcion, in the sad tone of one who bitterly felt that every man’s hand was against him, addresses one of his disciples as “my partner in hate and wretchedness” (συμμισούμενον καὶ συνταλαίπωρον, Tert. _adv. Marc._ 4. 9). [4] Examples are the accounts of Basilides in Clement of Alexandria and Hippolytus, compared with those in Irenæus and Epiphanius; and the accounts of the Ophites in Hippolytus, compared with those of Irenæus and Epiphanius. The literature of the subject is considerable: see especially A. Hilgenfeld, _die Ketzergeschichte des Urchristenthums_ (e.g. p. 202); R. A. Lipsius, _zur Quellenkritik des Epiphanios_; and A. Harnack, _zur Quellenkritik der Geschichte des Gnosticismus_. [5] The very names of most of the heathen opponents are lost: Lactantius (5. 4) speaks of “plurimos et multis in locis et non modo Græcis sed etiam Latinis litteris.” But for the ordinary student, Keim’s remarkable restoration of the work of Celsus from the quotations of Origen, with its wealth of illustrative notes, compensates for many losses (Th. Keim, _Celsus’ Wahres Wort_, Zürich, 1873). [6] This was the common view of the Stoics, probably following Anaxagoras or his school; cf. Plutarch [Aetius], _de Plac. Philos._ 4. 3 (Diels, _Doxographi Græci_, p. 387). It was stated by Chrysippus, οὐδὲν ἀσώματον συμπάσχει σώματι οὐδὲ ἀσωμάτῳ σῶμα ἀλλὰ σῶμα σώματι· συμπάσχει δὲ ἡ ψυχὴ τῷ σώματι ... σῶμα ἄρα ἡ ψυχή (Chrysipp. _Fragm. ap. Nemes. de Nat. Hom._ 33); by Zeno, in _Cic. Academ._ 1. 11. 39; by their followers, Plutarch [Aetius], _de Plac. Philos._ 1. 11. 4 (Diels, p. 310), οἱ Στωικοὶ πάντα τὰ αἴτια σωματικά· πνεύματα γάρ; so by Seneca, _Epist._ 117. 2, “quicquid facit corpus est;” so among some Christian writers, e.g. Tertullian, _de Anima_, 5.