Are you suggesting that something that can be externally varified like the shape of the planet is on the same level as something that is based entirely off of human opinion like morals?
No.
What I am doing with my flat earth example is criticizing the logical form of what is called the "cultural differences argument." Nothing more, nothing less. Let me explain.
When people want to argue for moral relativism (cultural relativism being the most popular kind), they often cite the fact that different cultures believe different things as far as morality goes.
Well, anyone who pays any attention to things can see that that is true. Some cultures practice the death penalty, others consider it immoral. In some places in the world FGM is practiced, while westerners tend to view it with disdain. The philosopher James Rachels began his essay,
"The Challenge of Cultural Relativism" by citing King Darius who taught the Greeks about the Callatians. When the Callatians' fathers died, their children would eat his dead body as part of the funeral ceremony. The Greeks were shocked and revolted by this. After all, the Greeks burned their dead. When King Darius shared the Greek practice of burning their dead with the Callatians, they were similarly horrified at how the Greeks carried on their funerary practices. Rachels goes on to describe the Eskimo peoples (we'd say Inuit or Yuit these days) who practiced infanticide... leaving their newborns in the snow to die.
Then Rachels explores several syllogisms:
(1) The Greeks believed it was wrong to eat the dead, whereas the Callatians believed it was right to eat the dead.
(2) Therefore, eating the dead is neither objectively right nor objectively wrong. It is merely a matter of opinion, which varies from culture to culture.
(1) The Eskimos saw nothing wrong with infanticide, whereas Americans believe that infanticide is immoral.
(2) Therefore, infanticide is neither objectively right nor objectively wrong. It is merely a matter of opinion, which varies from culture to culture.
Rachels goes on to say:
"Clearly, these arguments are variations of one fundamental idea. They are both examples of a more general argument, which says:
(1) Different cultures have different moral codes.
(2) Therefore, there is no objective truth in morality.
Right and wrong are only matters of opinion, and opinions vary from culture to culture. Let’s call this the Cultural Differences Argument. To many people, it is persuasive. But is it a good argument—is it sound? It is not. For an argument to be sound, its premises must all be true, and its conclusion must logically follow from them. Here, the problem is that the conclusion does not follow from the premise—that is, even if the premise is true, the conclusion might still be false. The premise concerns what people believe—in some societies, people believe one thing; in other societies, people believe something else. The conclusion, however, concerns what really is the case. This sort of conclusion does not follow logically from that sort of premise. In philosophical terminology, this means that the argument is invalid."
https://rintintin.colorado.edu/~vancecd/phil1100/Rachels1.pdf
My use of flat earthers was merely a shorthand rendition of what Rachels is saying.
(1) Flat Earthers think the the Earth is flat. Everyone else (including the scientific community) thinks the Earth is round.
(2) Therefore, there is no objective truth about the shape of the Earth.
The reason I chose the flat earth example is because (conveniently) we have indisputable evidence that (2) is false. But guess what? Even without such evidence
the argument gives us no reason to accept (2) as true. We can determine that by logic alone. Even if we were to present the above flat earth argument to a person in ancient times, who was skilled in logic but had no idea about the shape of the Earth, even they would agree that the argument says
nothing.
Same goes for the cultural differences argument.
It says nothing. Just like with the shape of the Earth, peoples' differences in opinion have nothing to do with the reality of the matter. No moral realist worth her salt makes the claim that everyone agrees or must agree in order for moral objectivity to be true.
The point of proving objective morality is to prove that it can be objectively observed just like the shape of the earth. So then, if morality is truly objective, why are we still having this doscussion? Where is the theoretical model for objective morality? I'd love to even see a well structured hypothesis if one exists
At no point in this thread have I presented an argument in favor of moral objectivity. I might have broached on the issue in a side discussion I had about the is/ought problem with somebody. But iirc I've only defended two positions:
1. God does not (and can not) have anything to do with objective morality.
2. The cultural differences argument (that supports cultural relativism) is not logically sound.
I'm not a convinced moral objectivist. I just like to argue on its behalf because so many people sell it short as a metaethical theory. So many folks are moral relativists. And most of those people are (you guessed it) persuaded by the cultural differences argument.
I actually used to be a cultural relativist, but I've since come to see that it isn't as well founded as I once thought it was. In fact, it's quite problematic when you get right down to it. So now I think
only two plausible theories remain:
moral realism (aka moral objectivism) or
moral antirealism (aka moral nihilism). Moral antirealists are kind of like atheists about morality. They think it is a fairy tale. Something that simply cannot be true, perhaps having its basis in our emotions (there are several kinds of moral antirealism). Moral antirealism is waaaaay more logical a position than moral relativism.
As far as I'm concerned, God either does exist or he doesn't. It's not like we've settled the matter but either one or the other of those is true. What I would consider extremely foolish is if someone thought God's existence was a matter of opinion. Someone might think he's drawn a decent "halfway view" between theism and atheism with that theory, but when you look at it closely, it's downright incoherent. Many people express different views about God's existence or nonexistence. And no one's come up with a slam dunk answer that nobody can deny. But that doesn't make it a matter of opinion.
Same goes for morality.