The point is, the plains Shshi, who are a later evolutionary product and who live in an expansive, open-skyed land with treeless vistas, maintained an optimistic, perhaps somewhat naive view of evil. Good is the thing that is real and evil is the absence of good, the failure to project that quality. Good is innate and to fail to be good is considered unnatural. Thus the patently evil villain Mo'gri'ta'tu becomes known in lore as the Unnatural Alate and the traitorous Commander Hi'ta'fu becomes the Unnatural Warrior. (These are characters in "The Termite Queen.")
In later volumes of "The Labors of Ki'shto'ba Huge-Head" series, we get a different view of evil. There is a character named Krai'zei, an older Worker-Helper to a Warrior who joins the quest (both these characters first appear in "The Storm-Wing").
Krai'zei is a member of an ancient race, the same race as the Warrior Ju'mu whom we meet in "The War of the Stolen Mother." They are called the Yo'sho'zei -- the Old Ones -- and in fact play the role of the Centaurs in Greek myth. (Ju'mu embodies one of the functions of Cheiron, that of teacher of Warriors.) The Yo'sho'zei are a dwindling race and have been forced into a small area of the southern coast, a land of dense vegetation and rugged, rocky outcroppings and caves. Time has taught them to be pessimists. For them evil is innate, something that lives deep within the soul of everyone. They call it the "Old Absolute." Good is the conquest of this evil within ourselves.
Linguistically speaking, the Yo'sho'zei language is much closer to the original archaic Shshi speech than the speech of the Shum'za or the Da'no'no Shshi is. Thus, ses'de| is the base word, meaning both "evil" and also "cursed" and "fated." It derives from the archaic root *sesk, which yields both ses'de| (evil) and ei'ses| which means "to destine or put a fate upon." The root is still seen in the Shum'za language in sasko|, sask'zei|, and tha'sask| (to curse or damn; a cursed person; the imprecation "far-curse!")
In Yo'sho'zei "good" is ses’wa’de|, i.e. evil + not + the noun affix. So this reflects the exact opposite of the Plains Shshi's view.
There is considerable discussion of these concepts in the later volumes of the "Labors" series. I wanted to quote some examples here, but I decided they would act as a spoiler for a very important part of the plot, so I guess you'll just have to wait and read the books after they're published!
Then I did find one passage that I could quote without giving away too much. It occurs in Volume Five, where Di'fa'kro'mi and Ki'shto'ba are talkng with the venerable and learned Yo'sho'zei Alate Vai'zei'a'parn (who embodies the half of Cheiron that is a scholarly healer). They even discuss some of the points I made above:
Ki’shto’ba frequently conversed with Vai’zei’a’parn, either alone or in the company of other Yo’sho’zei or some of us Companions. At times when I was present, we often discussed topics that are not usually of interest to Warriors, like the nature of evil, considered by the Yo’sho’zei to be an all-pervasive reality – the Old Absolute, who wove itself out of a web of darkness before Creation started, behind the back of ta’ta’wa’tze| [Yo'sho'zei word for The-Highest-Mother-who-Has-No-Name] where she could not see it. It grew until she felt the pain of it pressing against her ovipositor; by then it was so strong that she could not uncreate it or remove it from the fabric of her new-made world. So she gave her children the power to overcome it in their souls if they had the will, but the struggle was fated to be both arduous and unending, and not always successful.