Nothing.
But the gist of Gnostic cosmology is that the material universe is ultimately illusory, the product of an ignorant, deranged, and evil demigod in which spirits are imprisoned in cages of flesh. The "knowledge" Gnosticism offers is the "knowledge" of the secret and hidden workings behind the world, to peel away the ignorance of the material and discover the realm of pure spirit--and that one's true identity isn't this flesh-and-blood creature, but a spark of the divine pleroma which has its ultimate source in the Monad. And to ultimately free oneself from the ignorance and corruption of materiality, and return to the pleroma.
The idea that the universe is all illusion, at least from the Christian perspective, is absolute heresy. The very opening phrase of the Creed, "We believe in one God, the Father, Almighty Maker of heaven and earth, of all that is seen and unseen." From the outset Christian dogma asserts the inherent goodness and legitimacy of the whole universe: This universe is real, good, and the One we worship is its Author. The material world is objectively real, and objectively good. And, hence, because it is real and truth-bearing, it can be studied and known. When I see a tree, there's actually a tree; the evidence of the material world all around us can be studied, and sought out, and we can come to real answers about the nature of the universe and its reality. Science is, therefore, an inherently noble pursuit, because truth is an inherently noble pursuit, and the truth about the universe is meaningful to be learned in and of itself.
From a Christian perspective the study of the natural world, in and of itself, can be comprehended as a form of worship of the Creator. To deny the reality of the world, or to deny the reality which scientific evidence points to, is a kind of soft heresy; a shrinking away from the world and denial of the good creation of God. That is what I mean by Gnosticism here.
-CryptoLutheran