QUOTE(existwhere? @ Dec 29 2007, 07:42 PM)

Ok, question:
Does the Tanya not differentiate between nefesh, ruach, neshama, chaya, yechida?
Depends where, many times it will refer to all the levels at once as just Neshamah, also most of the time they are grouped into two groups, the lower being Nefesh, Ruah and Neshamah, the higher being Chaye and yechida [Yechida being the highest]
QUOTE
My main issue throughout is zeh l'umas zeh. I'm used to thinking that there is a seeming balance of good and bad in the world, but everything is originally good or neutral and turns seemingly bad. He seems to be saying that there is essentially more evil in the world.
(Not that I understand most of it, but trying to avoid being boggled too fast. The next chapter will probably explain sichlit.)
Perhaps this may explain it for you [although I am not yet sure what exactly is your question] the word "Assur" (from the Tanya's perspective) comes from the word "Tied" as in "tied up to Kelipah" the word "Muttar" is from "untied to kelippah" therefore something that is Assur, is getting its energy (so to speak) through Kelippah.
I would note that it is explained (by others, elsewhere) that when it talks about non-jews it is NOT referring to the righteous non-jews (who keep the 7 mitzvot bnei noach etc, and who have a share in the world to come as the Rambam writes).
(as for the "Nefesh hasichlit" it is hardly mentioned at all in the the tanya)