Well, on another tangent concerning duality, an interesting tidbit may be the history and mythology surrounding the subject. I’ll start with what I know of the history of absolutist moral dualism in this blog, mythology in the next. (Then I’ll get back to tying this rambling pedantry back into contemporary politics, which is our real subject matter here after all.)
Again, the following is from my eclectic reading of the subject, and I’m writing a lot from memory as opposed to going back and re-reading the sources, so I likely stand to be corrected. A History of Moral Dualism The history that I’ve read seems to place the origin of ultimate moral dualism (a god v. devil-esque cosmology) with the zoroastrianism religion in persia (iran) around 400 bc. According to who you read and believe, it then filtered from them to the jews, and hence the judeo-christian-islamic nexus of righteousness. Strangely, this is also called the alleged origins of "monotheism." As to whether it should be monotheism or dualism again gets into somewhat contradictory ideas in all these religions as to whether god really is supposedly omnipotent, or a force opposed (perhaps equally) by the devil (implying limitations to his omnipotence). The more common historical reference to a theology of ultimate moral dualism is to "manichaeism," which was more explicitly dualist than zoroastrianism. Manichaeism was founded by another persian (mani) and was very popular in the later roman empire (200-400 ad) and into india and china. I’ve read very contradictory accounts of it, but am told by encarta that manichaeism was a synthesizing religion seeing zoroaster, buddha, and christ as prophets. In Europe, manichaeism spawned more christian influenced offshoots: cathars, albigenses, and others. These were also very popular, and continued into the 1300s before finally being violently stamped out by the young roman catholic church in a series of crusades starting before and continuing after the "holy land" crusades we’re much more familiar with. Manichaean is now often used as a derogatory term for any dualistic cosmology. As much as I hate the idea of ultimate moral dualism, I think the manicheans are getting somewhat of a raw deal. The implication behind the derogatory "manichaean" term, as I’ve heard it used, is of a fanatical, exclusivist, and rigid worldview despising the physical world in favor of an idealized spiritual realm. I believe this much more closely reflects the judeo-christian-islamic worldview, especially in practice, than that of the manichaens and their european offshoots, the cathars and albigenses. I formed a positive impression of these groups based on some long ingested readings (20-plus years ago) from questionable sources. However, the core of what impressed me in what I read about them seems to be repeated in the more standard histories. (At least this is my understanding to date.) Though they had a priesthood of men and women who were to attempt to reject the physical world entirely, the attitude toward the larger communities of (non-priesthood) believers was remarkable humane and open-minded, which probably explains the various sects’ popularity when compared to what surrounded them. The larger community of believers was generally encouraged not to reproduce (in keeping with the physical world negation), but it was in a non-punitive framework which valued compassion and forgiveness as opposed to the rules-obsessed romans and judeo-christian-islamic religions. Finally, there is the non-religious and modern history of dualism in the cartesian philosophy developed by descartes. This is a similar dualism, but replaces spirit with mind, positing a mind-body division in a reductionist-scientific worldview. My understanding is that this part of descartes worldview is not generally well thought of today in academic circles. Still, I’d argue that his rationalist dualism is widely accepted (generally speaking) by most people in the west, and that this is a kind of nonreligious counterpart to the ultimate good/evil philosophy that I’m arguing against, although not as destructive.