"The traits which characterise the Chaos Powers are insanity, violence, ambition, greed, and others of a kind which are often felt to typify the worst of human nature. But this is not wholly the case, and Chaos Powers also exist which typify fellowship, charity, law, and other redeeming characteristics. Indeed, no Chaos Power is wholly one sided, for no human or other creature is wholly good or evil, and likewise neither are their shadow-selves. For example, along with violence and bloodshed Khorne has inherited a warrior's sense of honour and moral virtue. Nurgle may typify decay and disease, but he also embodies the human hope and energy that defies the inevitable" (Realm of Chaos: The Lost and the Damned, (1990) p.7)
The idea that Nurgle does not just represent disease and decay, but is also the embodiment of hope, defiance, and stoicism is repeated through the book. The same is true for the other Powers. The Powers of Chaos, it makes clear, are the product of the combined energies of the shadow-selves of the dead, which retain their most powerful mental traits and flow together to create whirlpools in the Realm of Chaos, and these whirlpools are the Chaos Powers.
"The four Great Powers of Chaos represent the four largest and most powerful of these many co-joined entities. They are so large that they have achieved a coherent consciousness and will, a mind formed from the collective emotions and beliefs of the countless myriads of shadow-selves that comprise it.
Other Chaos Powers sometimes achieve temporary consciousness, but their existence is less stable because they are smaller; they may be likened to slumbering gods whose dreams sometimes achieve a passing solidity and who will perhaps one day awake to full awareness."
This is much more interesting, to me, than the view of Chaos presented in WFRP2e's Tome of Corruption (2006), which answers the question of why people might worship Nurgle with the, 'Hopeless despair' - the very opposite of the human virtues that Nurgle is taken to embody in Realms of Chaos.
And consider this;
"At this time [the Great War against Chaos] many Chaos Champions took up arms alongside the daemonic forces of their Patron Powers, but others flocked to help the human defenders against the Chaos Hordes. Such is the nature of the Chaos Powers that such willful independence by Champions often amuses rather than angers them, and may even lead to a Power rewarding his Champion for providing good entertainment. In this way, Chaos Champions and their warbands fought on both sides in the Great War against Chaos, both for and against the human nations. Although the presence of Chaos Champions in their ranks may have caused the human defenders some trepidation and even mistrust, their aid was still welcomed at a time when survival hung momentarily in the balance" (Realm of Chaos: The Lost and the Damned, p. 9).