The books I mentioned in my previous post by Horton and Knox clarify this. Summarizing gnosticism as "salvation by knowledge" is a bit of an over-simplification. Primitive gnosticism denied the incarnation. Contemporary gnosticism in American Evangelicalism does not deny that the Logos took on human nature; but it does deny that salvation comes to us through the vehicle of material sacraments (i.e. baptism, Eucharist, etc.). All the graces of salvation come to us, according to contemporary gnosticism, directly through the Spirit, apart from material means. For contemporary gnosticism, we are saved by the "Word", by "hearing the Word", and thus by knowledge. That Word need not be incarnate. Our bodies need no physical sacraments. "Faith comes by hearing, and hearing by the Word", and that's all we need, according to contemporary gnosticism. Salvation is all internal, all about the soul and spirit, not about the body. It is just the establishing of a personal relationship between Jesus and me. That's contemporary gnosticism.
-A8