What Irenaeus Was Fighting Against in Gnosticism?

Gnosticism was somewhat of a fight against the dualist tendencies, I imagine. Even if we don't have contemporary Gnostics presenting the same cosmogany, we still have that same dualism between matter and spirit in our world today. It's almost like it's inverted though in some ways. We've become, instead of the Gnostics who are so spiritualized, we have the focus on materialism today to the neglect of the spirit.