Irenaeus of Lyons, Against Heresies 3.2

When they are confronted with Scripture, they turn their attack against Scripture itself, claiming it is not rightly preserved, lacks authority, contradicts itself in its varied expressions, and cannot yield truth to those who lack the tradition. For that tradition was not handed down in writing but by living voice — which is why Paul declared, "We speak wisdom among the perfect, but not the wisdom of this world" (1 Corinthians 2:6). Each of these teachers claims that this wisdom is his own private discovery, a mere invention, so that truth might be whatever suits him: one moment it appears in Valentinus, another in Marcion, then in Cerinthus, later in Basilides, even in the one who argues against the rest yet could speak nothing that saves. Every single one of them is thoroughly perverted; without shame each makes himself the rule of truth, distorting it as he preaches. But when we appeal to the tradition that comes from the Apostles — the tradition guarded through the succession of presbyters in the churches — they reject it, boasting that they have found the pure truth and are wiser not only than the presbyters but than the Apostles themselves. They allege that the Apostles mixed legal ordinances with the Savior's words, and that even the Lord Himself spoke sometimes from the Demiurge, sometimes from the middle realm, sometimes from the highest summit. Meanwhile they claim to know the hidden mystery without doubt, without stain, purely — which is nothing less than the most brazen blasphemy against their own Maker. Consequently they agree with neither Scripture nor tradition. Our struggle, dear friend, is against such men, who like slippery serpents try to wriggle free on every side. Therefore they must be resisted on every front, so that by refuting them we may confound some and lead them to the conversion of truth. For though it is not easy for a soul seized by error to recover, it is not utterly impossible to escape error when truth is applied.