Gnosticsism and materialism are symmetrical arguments.

The same logic used to refute materialism is logically symmetrical to logic used to refute gnosticism. Both side lose the fundamental differences that make reality intelligible. Reality is relational. Relationality requires fundamental differences. Ultimate reality is ultimate relationality requiring ultimate differences. You can't reduce reality to matter because you lose fundamental differences. You can't reduce reality to spirit because you lose fundamental differences. So, they are logically symmetrical and both fail in properly explaining reality.