Is Moral Nihilism a Morality?

[The Grand Nudger]

I don't think that you're giving hedonists a fair shake, at all, lol.  It's not impossible for a hedonist to declare something good or beautiful or pleasurable on account of the whole over it's constituent parts.  Paint is just paint, but a painting is another animal.  More to the effect that some of the constituent parts may not be beautiful or good, and that end results being equal, it would have been better to derive whatever pleasure or betterment without that pain - if possible...

.....and have you ever read up on how some of that paint is manufactured, lol?   

There's an argument for genocide from hedonism too.  It may be that the most effective way to maximize happiness and minimize suffering is to exterminate a good portion of all life...and isn't this precisely what we've done as we rose from scavengers to spacefarers?  The confrontation of that truth is uncomfortable and unsatisying, so much so that no matter how well articulated or demonstrated the point might be, many folks (myself included) will immediately reject the course of action and insist that there is a better way.  Same as above, essentially.  

This thing you have about pluralist values and the totality of x does seem to cut to the core of your issues with particular meta-ethical positions.  I;m not sure why, though.  If the good and bad reduce to natural properties there isn't exactly a shortage of those properties to be derived from.  If the good and the bad are instrumental properties - then there's a potentially infinite set of them.    Nothing prevents a naturalist (or a hedonist) from considering the totality of some x before a moral consideration.  There's no other point to identifying and tallying up parts to be weighed against one another. Now, I don't know how many values there are, but I can say with confidence that harm and help* are among them, and also that a fully competent moral conclusion is impossible unless a person takes the nature of an act, the character of a person, and the consequences of that person committing that act into account.  No complete deontology or desert can be derived without that full accounting.  The fact that I don't require any other metrics to apply to these disparate moral theories is why I employ value monism without making a binding commitment to it. There may be more, but as some random french fucker said, I just don't need them.

*even here, help might be reducible to anti-harm, lol.

I'm not sure why you think the things you do about beauty (either that naturalism can't account for it or that idealism somehow does).  Nor do I think that your nazi example was anything more than an issue of the limitations you placed on the thought experiment.  If the world were full of nazis then the best nazis would be the most virtuous people.  They're as good as you;ve allowed them to be, how better -can- they be, and what is the silent evaluative premise informing you that this won't stand, and on what grounds of desert do you reject their classification as good people?  

On moore, I think he had some good things to say, obviously..but if his idealism was either wrong or content equivalent to naturalism (and it's one or the other, lol) then it doesn't matter if he left room for pluralism.  Humes dickery is emphatically not what you think it is nor does moore actually derive his oughts from an ideal anymore than hume avoided deriving oughts from is-es (or moore oughts from natural is-es).  His conformity to ideal is the evaluative premise, and that's judged by empiracal facts..satisfying humes conditions in the same way that any other moral theory does.  The is-ought problem is the most misquoted and overemphasized bit of ethical philosophy, imo.  It's a problem -if your evaluative premises are a problem- but I'm not aware of anyone who can competently argue that the mere presence or employment of an analytical bridge necessarrily entails a commitment to some non natural x in anything other than the novel sense of "non-natural" as thoughts.  Knowing what we do, now, about the brain and our cognitive apparatus,  I don't think that any meta-ethical position that makes that distinction is even remotely coherent.

If (if if if if..lol) what we're apprehending and communicating when we make moral distinctions are empirical properties of x, then natural realism is facially true. How many empirical properties (and which empirical properties) belong in the good and bad sets..and why, is a great convo..but if that's what we're dealing with than idealism is a non starter on every level. Value pluralism has some subtle but important meta-ethically neutral differences from moral pluralism conceptualized as methodological pluralism (some combination of many different overarching schemas) - mostly in that a person can be a value monist and a moral pluralist in that sense, and vv. Naturalism and idealism ride under the competing moral theories and ideas about value and desert ride neutrally alongside all of them. There's nothing preventing a person from picking any one from those three categories. No fundamental disparity. At least none that I'm aware of but you may have more to say on that that I hadn't considered or read.

Personally, I think that moral naturalisms biggest issue isn't in demonstrating it's fundamental premise, but in how we determine the weight given to some property in consideration relative to others - particularly in ambiguous cases, exclusively sub-optimal fields, and known unknowns.