A term I once read that covers consensus terminology and when methods and theories need to overlap to enable collaboration, is "Intersubjectivity". Like agreeing that blue is the name of the colour of the sky, and "wet" means being soaked with or covered in water. And water is that stuff that falls out of the sky from time to time and makes plants grow. And plants are generally green. Darkness is black. etc.
Intersubjectivity is the only reality we can both apprehend and describe and share. So it is fallacious to talk about objectivity. We can only, like a blockchain, share the data, replicate the experiment, and add our confirmation to the chain of data. What it is may be something entirely other, but we cannot describe what we have no words for, and we cannot communicate our description unless others use the same words for experiences that are demonstrably analogous.
Once we use intersubjectivity and we agree on the terms, it is possible to form objective judgments. For instance, say we subjectively decide "wrongs" are punishable in some form. Say we both subjectively agree theft is a "wrong." We can then objectively conclude theft is punishable in some form. As long as the subjective definitions of "wrongs" as punishable offenses and theft as a "wrong" stay the same, the objective conclusion that theft is a punishable offense also remains true.
Take the brain in the vat example. You must either make the subjective decision that what you see is reality and you're not a brain in a vat or not. If you make the subjective decision that what you see is reality then you can make objective decisions about that reality - that killing yourself or others would end your or their perception of reality and that you or they would, in reality, be dead.
Objective is an absolute and that is why there is a need to make a distinction. Democracy works on a basis of consensus also, but without a cost in risk of making a false confirmation, using the blockchain analogy, it is possible to bend the consensus to your benefit. This is why the democracy in a private company is based on stake, and why stake matters here. With no "skin in the game" you can manipulate the consensus without you suffering the results of the manipulation. This cost is externalised.
Reality, by definition, has no absolutes, because you cannot measure them. Absolutes are limits in mathematics, they take infinite confirmations, infinite processing.
I refer you to of Law and equity, specifically his one "sacrifice is the measure of credibility": if you have nothing to lose, your opinion cannot be credibile. This is where the crime of perjury comes in, your evidence must be tested and if it can be shown you deliberately lie to benefit, it is a very serious crime, up there with murder and rape.
I agree. That's why I try to make clear that my "objective" ethical judgments are only "objective" within the framework I have subjectively arrived at through my own personal emotions and values. Consensus merely confirms or denies what I already hold to true within my subjective framework. In the end however if you arrive at a different subjective framework than I do, the "objective" judgments you make within that framework will be different than mine.
So essentially you are correct. Each person arriving at a differing subjective framework, might make differing objective judgments with respect to their framework. So are they really absolute? No. Not outside of their subjective framework.
The points you bring up are exactly why I disagree with Rothbard's assessment that "natural law" is the objective truth (with respect to no framework - just 100% objective and therefore absolute). Self-ownership may or may not be an objective truth (given your conclusion on the brain vat problem) but the value of the sovereignty that comes from self-ownership is a purely subjective argument.
Your points are exactly why I thought it so important to have one whole post dedicated to establishing that all ethical judgments are truly subjective at their core.
Yes, in fact, it goes so far as to the point where a central thinking problem we have in our world comes from the convenience of using absolutes when none can be grabbed onto and held in the real world. But this is not relativism, but rather, consensus building. Once enough confirmations are on the blockchain, the 'truth' is considered to have been recorded.