> I was thinking that in defending reproduction being our purpose that you were claiming that this is true and that people who deny this are wrong to do so---but certainly, we can make objective claims about subjective beliefs.
Yes, I don't think you're wrong for disagreeing with me.
> ... it's not feasible to bootstrap yourself Cartesian-style from "I think, therefore I am" all the way to normal, everyday truths...
Yes, I also think it's impossible to build from the bottom up like that for anything value-dependent.
>
I know what I am saying is unfalsifiable. I have no problems with that. I don't think purpose/motivation can ever really be falsified. You're still looking to purpose as a guiding principle, rather than a subjective description of what your mind is already doing. I think we look for meaning because it is already defined within us. We can't choose meaning; we can only choose to act, and then we justify our own actions. (I don't think any of that is falsifiable either.)
> I would normally say that there is a kind of objective purpose in a tool. For example, a hammer. When I talk about the objective purpose of a hammer, I'm talking about the hammer's utility qua hammer---so whether it's hard enough for nails to get driven in when hit, whether the handle is long enough for someone to grasp it, etc. A bad hammer might be one that's made out of sponge or something, so it doesn't actually move any nails. It can be repurposed to be, for example, a paperweight, and maybe do an ok job at doing that. But it's failed to fulfill its purpose as a hammer. And I think there's an analogical sense in which humans can be good qua human. I would talk about a summum bonom, a highest good, under which various virtuous activities fall under.
You're talking about language. A monkey that picks up a rock to crack open a nut is using a hammer of sorts. There is no ideal hammer; there is only an intersubjective understanding of a hammer which we might assume is ideal.
> It's interesting that you bring up hackers. I think repurposing tools to do what they're not meant to do is generally seen as a hack. And in an engineering context, this is generally seen as a bad thing in the long-term, or at least an indicator something's not right---tools should get used for the purpose for which they were designed, at least, in the long-term. (That's not to say anything bad about hackers; I love the idea of a hacker.)
Useful hacks get relabeled. The rock could be a paperweight, a hammer, a weapon etc. even if it is explicitly labeled as only one of those things. Purpose is not in the tool itself, nor is it in language; it is in our conception, based on experience and the knowledge we accept, just like morality.
> I suppose not, but I also think there can't be any physical facts if there aren't any physical things. But I don't think this means physical facts aren't objectively true; likewise, I still think moral facts are objectively true.
So a universe could exist without morals if there were no moral agents in it. That means morality is contingent on moral agents existing. Your argument is that beings would eventually end up with the same morals every time, but I don't think so.
If we met a sentient carnivorous species, we should expect its morality to be quite different to a sentient herbivorous species'. I think a carnivore would always construct a moral view that eating animals is right (or its existence would be morally wrong). A sentient herbivore would most likely come to the conclusion that carnivorism is morally wrong and all those carnivorous animals should be exterminated. A sentient parasite would most likely come to the conclusion that parasitism is morally right (that a form of slavery is morally right). Could nature itself be morally wrong for creating those things?
> I don't think that any moral truths are grounded in the bill of rights anymore than truths about Newtonian physics are grounded in Newton's Principia. What we think and say about truths is distinct from the existence of truths themselves.
> Well, I think that we have a strong intuition that it is morally impermissible to deprive one of certain rights, and from that, it logically follows that slavery (in the relevant sense---I think you know what I'm talking about) is immoral.
Okay, so you are a moral fallibilist after all; you are open to the possibility that your moral beliefs are wrong. I think our views are somewhat compatible, since we both see that we are relying on intuition, rather than something testable.
> This is because our beliefs about morals do not themselves determine what morals are, just like our beliefs about science do not themselves determine what scientific facts are---if humanity were to suddenly regress and start thinking the Earth was flat again, that wouldn't change the roundness of the Earth.
> ... when I talk about the existence of physical things. Like, maybe I tell you about the chair I'm sitting on, and you say, "Well, I see the chair you're sitting on, and I can touch it, but I don't share the intuition that that means that the chair exists physically." And if you say that, there's nothing more I can really say to you---that's just an intuition you don't share. But of course, I still believe that the chair really is there.
Language itself is learnable because of the shared basis in the senses. Morals are way more abstract than the chair existing, and even whether the world is round or not. Our experience of physical properties is more or less going to be the same, even with conditions such as blindness etc., since sight, hearing and touch all construct a model of the world that coheres. That is not the case for morality, which starts with something like a sense of pain and jumps to cultural abstractions which we inherit.
> I suspect we won't come to an agreement here either---though I do kind of suspect that you do share the same intuition. I certainly don't think you act as if morals are subjective. Like, I suspect that if you came across a culture in which people randomly chose a child every day to kill for no particular reason, you wouldn't think, "Well, that's just their culture---I find it distasteful, but if they believe it's morally right to do this, then I guess it is morally right for them."
Just because I think morals are subjective, doesn't mean I think anything goes. They are still subject to my own sense of what is sustainable long-term. I understand how they think that what they could be doing is justifiable.
If you wander into anthropology, you will see people who take a stance like what you describe: that one culture cannot morally judge another. I can sort of see where they are coming from: tribes exist because they maintain a set of shared practices. If the tribe goes out of existence, their practices failed them. Their long-term existence means their shared practices have utility. I'm well aware of the immediate problem that it requires time to see the consequences; that's why I think shared knowledge (especially of what doesn't work) is vital.
> What I'm basically saying is that we have strong intuitions that morals are true independently of what people think, and that objections like "people disagree about morals" or "people have changed their stances on morals" aren't objections to my intuitions any more than "people disagree about scientific facts" or "people have changed their stances on scientific facts" are objections to science.
Yes, and a sentient parasite would probably tell us that parasitism seems morally right independent of what people think.
> It is true that the manner in which moral truths exist are strange---it's not like you can go out and touch them. But I also think the same is true for, for example, numbers---I would say that numbers exist, even though we can't go out and touch them. Not that numbers and moral truths exist in the same sense---just providing some intuition.
I don't think morals can be true just like I don't think numbers can be true.