Shake

Well, since I don't believe in either of them, the question is moot (for me).

Galan

The dualistic tendencies that we see in Christianity likely originated in Zoroastrianism, which passed them into postexilic Judaism and from there to Christianity. As already noted, the Gnostics maintained a very dualistic world-view. This is also true of the 'heretical' sects in medieval Europe -- it seems dualism was okay, as long as you didn't go _too_ far with it.

An excellent history of all this is given in "The Other God: Dualist Religions from Antiquity to the Cathar Heresy" by Yuri Stoyanov
available on Amazon: http://www.amazon.com/exec/obidos/tg...glance&s=books

There are a number of sites explaining Zoroastrianism. But for a good basic introduction, albeit from a believer's perspective, I usually recommend:
http://www.zoroastrianism.cc/index.html