"Against Heresies" by St. Irenaeus is a significant work in early Christian theology and apologetics. Written in the late 2nd century, it addresses various Gnostic teachings and defends orthodox Christian beliefs. St. Irenaeus critiques Gnostic interpretations of Scripture and asserts the unity and authority of the Church founded on apostolic tradition. His work emphasizes the importance of doctrinal purity and the continuity of faith handed down from the apostles. "Against Heresies" remains a crucial text for understanding early Christian controversies and the development of theological thought in the early Church.