I'll take a crack at this one. I've been thinking about the same question lately, and I think I've reached a satisfactory answer. Whether I can articulate that answer briefly with any clarity whatsoever is another matter... Let's see.
First, ressentiment is basically the process by which the slave psychologically overcomes his bondage by thinking of himself as the moral better of his master. ("Yeah, you may have me under your boot, but so what -- _you_ are a totally despicable human being!"). What this leads to are the adoption of Christian values (weakness, submission, hatred of the body) that run against healthy, natural "aristocratic" virtues (strength, domination, love of the body).
N. seems to have had a lot of admiration for caste-based societies where everyone knows his proper role and that was the end of it. Much of his hatred for socialists and anarchists seems to revolve around how they're riling the groundlings up and taking them out of their happy slumber: socialism and anarchism were really very Christian in that they promoted hatred of the ruling classes simply because they _ruled_.
(If you listened to Doug's great interview with Ian Bone a few weeks ago, what was particularly striking to me was his insistence that we ought to hate the rich, not just in the abstract, but _personally_ as individuals -- there is a deeply moral component to this sentiment -- I remember thinking "ah ha! this is what N. was writing about when he was talking shit about anarchists").
Okay, how can this view at all be reconciled with an egalitarian, anti-capitalist political project? I think the answer lies in that the left seems to be divided between those who view politics as a _moral_ struggle versus those who view politics as a _power_ struggle: The moral folks see their own moral superiority as their primary advantage, and they're driven by essentially moral considerations: they're the ones who want "justice" for workers, minorities, women, etc.. Compare this stance with that of the power folks, for whom "justice" is irrelevant -- they'll make their own justice damnit: they don't need a moral imperative or any other ethereal justification to seize the means of production -- they'll do it because they _want_ to. Fuck "justice"! For the power folks, politics needn't be personal, your adversaries don't have to be rotten people -- its okay to respect your adversaries -- you just have to beat them.
So I guess N.'s notion of ressentiment is helpful to those of us on the left who view politics as a power struggle; it explains the deficiencies of having morality sit at the center of one's political engagement.
-WD
^^^ CB: Thanks , WD. My impression of ressentiment is like your summary. It also seems to me that N. does champion caste-based, aristocratic societies and aristocrats, as you say. The latter point seems to mean that this would be an ironic case of gaining insights in the class war from a spokeman for the ruling classes. This is of course possible. But it also means N. is not trying to advise the underling classes on how to change things. He seems to be trying to get the underclasses to stay under (!) Do we really need N. to know that the class struggle is a power struggle ? Seems we could figure tht out without N. When we make N. the source of our theory of power struggle, we bring in all his pro-aristocratic ideas. It just seems simpler to understand the class struggle as a power struggle without bringing in all of N's other baggage.
Also, let me mention that N. doesn't seem here to be focussed on issues beyond the main areas of concern of Marxism. Sure Marx doesn't explain everything, but Marx does explain the issues N. is concerned with here. Ressentiment seems to be directly concerned with class struggle, but from the standpoint and in favor of the ruling classes over the ruled classes, a sort of direct anatagonism with Marxism. That's why I say N. seems like an anti-Marx, not a complement to Marx.