[tshaddox]

> If you believe "flat-Earth advocates don't actually care about whether the Earth is flat or not, they just want to prevent space exploration to keep us trapped on Earth" , this would pose difficulty for changing the belief "the earth isn't flat".

I’m not sure why. The normal simple tests to distinguish between a flat Earth and a ball-shaped Earth ought to still work independent of what flat-Earth advocates believe.

[joshuamorton]

The crux of the issue here is that it's not possible to know what someone else truly believes. You hear various forms of this argument all the time. Was Trump unable to string together a coherent sentence, or was his speech style a conscious choice to appeal to certain people? Are people who identify as LGBT doing so because that's what they truly feel about themselves, or because they want to be popular and fit in?

The statements being made aren't about the earth, but about people's perception of the earth. And ultimately you can't objectively determine someone else's qualia.

What GP is suggesting is that if the claimed flat-earth belief is simply a justification for a different goal (prevent space exploration), then providing contrary evidence doesn't matter, because the belief isn't core of the issue. But you can't really know that independently. And this is especially true where you get a sort of metacircularity in beliefs and belief systems. Identifying what the "real" axiom someone subscribes to is difficult.

To look at the conspiracy theory about flat earthers that GP proposed, imagine that tomorrow, suddenly, the Earth was flat. All of the historical record was the same. We have evidence and recordings that it was round, and that the Greeks agreed, but tomorrow we couldn't reproduce those experiments. The horizon suddenly looked different. A reasonable conclusion here might be that we're all suffering from a collective delusion (and that in fact the earth is still round[0]), because our prior that the earth could rearrange itself overnight is low. But, this person might believe that the collective delusion is the result of machinations of the flat earthers, trying to trick us all into stopping further space exploration by convincing us that the earth is flat. This despite there being no evidence that flat earthers were at fault, or even capable, of causing such a worldwide event.

[0]: This actually objectively doesn't make a whole lot of sense, if we're capable of being subject to a massive collective delusion at worldwide scale, it could be that we were doing so before, and that the change is the delusion wearing off, but I digress.

[tshaddox]

> The crux of the issue here is that it's not possible to know what someone else truly believes.

I don’t think there’s some process to follow to acquire knowledge with a guarantee that we haven’t made a mistake, but I don’t think that means it’s impossible to acquire knowledge. I think we can and do acquire knowledge about people’s beliefs and intentions and use that knowledge to solve problems. Obviously examples are convicting people of fraud and various crimes where the person’s intentions are relevant.

[joshuamorton]

This gets more complex in the realm of, let's call it politics, where the quest for knowledge may be adversarial, and is played over long periods. With fraud and crimes of intent, you often have very clear evidence where the person was unguarded (they said a slur as they committed the crime, making it a hate crime, for example).

I'm not saying reliably discovering intentions is always impossible. I'm saying that it is not always possible.