As we have already seen (see p. 121), Irenaeus took the word hairesis (‘self-chosen opinion’), used in the latest epistles in the New Testament in the sense of ‘sect’, and reapplied it to the whole spectrum of gnostic belief. He thereby implied that he was condemning a single if many-headed movement. Progressing from speaking of sectarianism, he was popularizing a concept with a prosperous future in Christian consciousness: heresy.
