What's failing?
"what is 2+3?" has an objectively true answer.
The fact that some other creature might instead want to know the answer to the question "what is 6*7?" (which also has an objectively true answer) is irrelevant.
How does that make "what is 2+3?" less real?
Similarly, how does the fact that some other beings might care about something other than morality make questions of the form "what is moral? what should I do?" non objective?
It's nothing to do with agreement. When you ask "ought I do this?", well... to the extent that you're not speaking empty words, you're asking SOME specific question.
There is some criteria by which "oughtness" can be judged... that is, the defining criteria. It may be hard for you to articulate, it may only be implicitly encoded in your brain, but to the extent that word is a label for some concept, it means something.
I do not think you'd argue too much against this.
I make an additional claim: That that which we commonly refer to in these contexts by words like "Should", "ought" and so on is the same thing we're referring to when we say stuff like "morality".
To me "what should I do?" and "what is the moral thing to do?" are basically the same question, pretty much.
"Ought I be moral?" thus would translate to "ought I be the sort of person that does what I ought to do?"
I think the answer to that is yes.
There may be beings that agree with that completely but take the view of "but we simply don't care about whether or not we ought to do something. It is not that we disagree with your claims about whether one ought to be moral. We agree we ought to be moral. We simply place no value in doing what one 'ought' to do. Instead we value certain other things." But screw them... I mean, they don't do what they ought to do!
(EDIT: minor changes to last paragraph.)
"what is 2+3?" has an objectively true answer. The fact that some other creature might instead want to know the answer to the question "what is 6*7?" (which also has an objectively true answer) is irrelevant.
I just want to know, what is six by nine?
On Wei_Dai's complexity of values post, Toby Ord writes:
The kind of moral realist positions that apply Occam's razor to moral beliefs are a lot more extreme than most philosophers in the cited survey would sign up to, methinks. One such position that I used to have some degree of belief in is:
Strong Moral Realism: All (or perhaps just almost all) beings, human, alien or AI, when given sufficient computing power and the ability to learn science and get an accurate map-territory morphism, will agree on what physical state the universe ought to be transformed into, and therefore they will assist you in transforming it into this state.
But most modern philosophers who call themselves "realists" don't mean anything nearly this strong. They mean that that there are moral "facts", for varying definitions of "fact" that typically fade away into meaninglessness on closer examination, and actually make the same empirical predictions as antirealism.
Suppose you take up Eliezer's "realist" position. Arrangements of spacetime, matter and energy can be "good" in the sense that Eliezer has a "long-list" style definition of goodness up his sleeve, one that decides even contested object-level moral questions like whether abortion should be allowed or not, and then tests any arrangement of spacetime, matter and energy and notes to what extent it fits the criteria in Eliezer's long list, and then decrees goodness or not (possibly with a scalar rather than binary value).
This kind of "moral realism" behaves, to all extents and purposes, like antirealism.
I might compare the situation to Eliezer's blegg post: it may be that moral philosophers have a mental category for "fact" that seems to be allowed to have a value even once all of the empirically grounded surrounding concepts have been fixed. These might be concepts such as "would aliens also think this thing?", "Can it be discovered by an independent agent who hasn't communicated with you?", "Do we apply Occam's razor?", etc.
Moral beliefs might work better when they have a Grand Badge Of Authority attached to them. Once all the empirically falsifiable candidates for the Grand Badge Of Authority have been falsified, the only one left is the ungrounded category marker itself, and some people like to stick this on their object level morals and call themselves "realists".
Personally, I prefer to call a spade a spade, but I don't want to get into an argument about the value of an ungrounded category marker. Suffice it to say that for any practical matter, the only parts of the map we should argue about are parts that map-onto a part of the territory.