Irenaeus and "the decisive criterion of salvation"

In the introduction to his selection of readings from St Irenaeus' Adversus Haereses, Hans Urs von Balthasar lets us know why the Bishop of Lyon has a particular significance for the Church amidst the virtual spiritualities of post-modernity:

From this very general description we can see that Gnosticism is radically anti-Christian.  Irenaeus, with great perspicacity, understood this, and showed it up for what it was. For him, Christianity is about the divine and spiritual Word becoming flesh and body.  The redemption depends on the real Incarnation, the real suffering on the Cross, and the real resurrection of the flesh.  All three of these are a scandal for Gnosticism.  On their view, Mary is not really Mother of God, and Christ did not really suffer ... And so the main object of Irenaeus' anti-Gnostic polemic is the salvific character of the Incarnation of God's Son and Word ... Caro cardo salutis, the flesh is the hinge, the decisive criterion, of salvation: this well-known saying of Tertullian, upon whom Irenaeus had a lasting influence, can in fact be regarded as the very centre of Irenaeus' theology.