Once again I've taken some time to give this some thought, and my conclusion is that I still don't know what this "Unwritten Universal Moral Principle" is, other than perhaps that which everyone intuits to be right or wrong. Is that what it is? I presume not. Because not everyone intuits the same things to be right or wrong. So therein lies my dilemma. Without knowing what this "Unwritten Universal Moral Principle" is, your argument confuses me.
I don't intend for it to be understood as a mere intuition. Rather, it's only meant to be a basic rational cognition that results in a moral recognition, kind of like how the Categorical Imperative is a rational capacity withing Kant's Deontological Ethics.
But even so, if it doesn't work for you or you don't understand what you read when I directed to those previous posts to see what the principle says,
then don't worry yourself with it. It's not something that I insist is a mandatory principle everyone needs to learn.
For example, I could ask whether it's immoral for a fifty year old man to marry and have relations with a ten year old girl. In certain times, and indeed even now in certain cultures, the answer to that question is no, it's not immoral, whereas most people in this day and age would say yes, it is immoral. So we have diverse groups of people intuiting and rationally concluding completely different answers.
Oddly enough, this still doesn't rule out the existence of objective morality, because it may simply be that people just don't understand the nature of morality. Slavery may be perfectly moral in one instance and completely immoral in another. These two things need not be contradictory, nor mutually exclusive.
How can that be?
I think you have a loose idea as to what consitutes "intuition." It's probably best to look up the Intuitionist Ethics of G.E. Moore or of moral philosophers like him to get a firmer feel by what they mean by "moral intuition," because it's not the colloquial meaning of the same term. Moral Intuition isn't simply a feeling, and kind of like how the term 'theory' doesn't retain the same low level of meaning when it's used in conjunction with science, this is the case also when "intuition" is used in tandem with Ethics and Moral Philosophy.
From my perspective, intuition is merely the first 10 seconds response of what should authomatically lead to a fuller, more rationally developed personal analysis of a moral issue or principle. We don't want to leave it at a colloquial level of "feelings" and think we've done enough to 'be moral.' Feelings don't usually cut it in the moral world.
Well, consider evolution with its own unwritten universal principle of "Survival of the Fittest". That principle holds true no matter what. It's never, ever violated. Yet that doesn't mean that what survives in one scenario will be the same thing that survives in another scenario. So while the underlying principle is never violated, the effect of that principle can and does change over time depending upon the prevailing conditions.
I think you've misunderstood Survivial of the Fittest. You're description of it is too abstracted from the actual lived experiences that take place in expanded networks among populations; survival of the fittest doesn't necessarily apply at all times to single individuals. Even so-called "Chads" who are found amongs various species can get dumped, sometimes worse.
The question then is, is the same thing true with morality, i.e. its "Unwritten Universal Moral Principle" as you put it, never changes, but the way that that principle gets expressed in any given place and time can and does change. Hence slavery may be immoral in one instance, but not in another. In both instances the principle remains the same, but the circumstances don't.
.......................that's because the principle is only one principle and isn't meant to work in isolation of all other aspects of an overall Ethical system or playing out of morality where moral complicated deliberations are at stake. Do you understand now what I mean? My claim that this UUMP exists is but one small aspect of an overall, more extensive ethics, not the whole ball of wax. It's kind of like how your nose isn't your whole face or your whole body. It's just one little part. It's not meant to address all moral problems or issues. It's not meant to serve as a complete code of conduct. It's not going to make a person realize that slavery isn't a good thing or just. It's a simple test that, when applied, will provide a moral recognition about an extreme instance, and it should do so easily enough and 'tell' a person that they're being inconsistent [irrational is the word I'm looking for] if they deny the principle.
I find this to be an interesting concept, but it also leaves me wondering, if evolution has the simple underlying principle of "Survival of the Fittest" then what's the "Unwritten Universal Moral Principle" behind morality?
So far you haven't explained it to me, and I really, really would like to know.
Where evolution is concerned, this is where I leave off with the UUMP since it's not meant to be applied to anything in the remote past. No, for me, the next step would be to invoke anthropologist, Barbara J. King, as a second consideration out of several in working toward my own Ethical Outlook of the world.
Eventually, once I've gone far enough in my education, I think I should end up with Jesus and a kind of "Ethics of Care" where I have to bother myself with going way beyond just the mere deontological or intutional level of the singole principle I've delineated above. But that's what happens when we know we
have to go beyond a mere principle about moral cognizance and move on to building or framing an extensive Ethical Outlook by which to ply our personal morality in life.