From ancient times it has been averred that the Gnostics derived their basic ideas from the Greek philosophers, especially Pythagoras and Plato. For example, Irenaeus (Adv. haer. 2.14) argued that the Valentinian Gnostics borrowed their doctrines of the pleroma and kenoma from Democritus and Plato. Hippolytus (Ref. 1.11), more systematically, tried to show that the founders of the Gnostic heresies borrowed most of their ideas from Greek philosophy and religion. The Valentinian brand of gnosis, Hippolytus (Ref. 6.21–29) argues, is derived from the philosophy of Pythagoras and Plato. Tertullian (Praesc. 7) claimed that all of the heresies were based on Greek philosophy. Valentinus is stated specifically to be “of the school of Plato.” Plotinus (Enn. 2.9.6), the reputed founder of Neoplatonism, claimed in a famous tract that his doctrinal opponents, whom he did not identify but who were obviously Gnostics, based their doctrines on a misunderstanding of Plato. Porphyry's Life of Plotinus 16 provides us with more information on the Gnostic opponents of Plotinus, and refers to them as αἱρετικοὶ ἐκ τῆς παλαιᾶς ϕιλοσοϕίας (“sectarians from the ancient philosophy,” i.e., Platonism).