the structural pattern Irenaeus set became the basis for the historical investigation of heresy well into the modern period: describing various texts and teachings, emphasizing their differences from one another, while at the same time... connecting them in a linear genealogy to a single origin and a single essential character.
King argues that Irenaeus's genealogical method — not any substantive doctrinal consensus — is the foundational template for the modern scholarly category of Gnosticism itself.
, What Is Gnosticism?, 2003thesis