[knightoffaith]

OK, let's be completely, utterly, crystal clear about this.

1. I observe that people who do not base their actions on sensory experience do stupid things.

2. Therefore, true knowledge or justification comes primarily from sensory experience and empirical evidence.

You're telling me that 2 is a logical implication of 1? You're perfectly happy with the way I've framed this---there are no hidden premises or anything like that? 2 is a direct, logical implication of 1?

[lisper]

I am not "perfectly happy" with it, no. For starters, I don't think there actually are people who do not base their actions on sensory experiences. Evolution mitigates against that pretty strongly.

I would say that if someone doesn't base their actions on sensory experience (a very big if) then they will be totally unable to navigate reality. They will almost certainly injure themselves, possibly others, and likely even kill themselves and maybe take others down with them. It's so obvious and the consequences so severe that it would be unethical to actually conduct this experiment.

Also, 2 is not a logical implication of 1. One can never rule out the possibility that, say, all human behavior is controlled by evil demons. What I would say is that my version of 1 is very compelling evidence for 2, and one of the things that makes it compelling is that it is so obviously true that a sane person would never even contemplate it as anything other than a thought experiment.

BTW, would you have any interest in being a guest on a podcast?

[knightoffaith]

>Also, 2 is not a logical implication of 1. One can never rule out the possibility that, say, all human behavior is controlled by evil demons. What I would say is that my version of 1 is very compelling evidence for 2, and one of the things that makes it compelling is that it is so obviously true that a sane person would never even contemplate it as anything other than a thought experiment.

Oh good, ok - you see my confusion, I thought you were saying that it was a logical implication. I would still say that 2 isn't really grounded in 1 so much as it is self-evidently true. Like, if we're being controlled by evil demons, 1 isn't even relevant---the question is fundamentally whether sense-experience gives us true knowledge bar extenuating circumstances or not; I think the answer is yes, but not because we see that this belief is a useful belief, it's because 2 itself is intuitively true. I don't believe that my perception of me sitting on a chair is good grounds for the proposition that I really am sitting on a chair not because of a thought experiment about lacking that belief leading to injury---I believe it because it seems true itself. And I think this is the right solution in general for related issues, whether it's inductive inferences (I think they're rational), belief in causality, belief in the validity of sense-data, or any other typical issue for empiricism.

The "X is key for survival, so X must be true" way of thinking has never been appealing to me---this seems to miss the point of what it means for something to be true. Like, I don't believe in 1+1=2 because it's useful for economics, physics, math, or whatever---I think it's true independently of its utility. Similarly for other truths.

>podcast

I'd prefer to not publicize my real name and face, so no, unfortunately (unless you'd be OK with that; I'd be happy to chat if so).

[lisper]

> I don't believe in 1+1=2 because it's useful for economics, physics, math, or whatever---I think it's true independently of its utility.

I actually doubt that. What do you think 11+27 is? If your answer was "38" then the followup question is: suppose it is 11:00. What time will it be 27 hours from now?

The "correct" answer to "what is 11+27" depends on circumstances in the real world (and so does 1+1). There are no Platonic truths, only preferred models.

> X is key for survival, so X must be true

It's not that. It's "X is a faithful reflection of the actual state of affairs in objective reality." That's what the word "true" means.

It just so happens that the actual state of affairs in objective reality has an impact on survival, so having a faithful reflection of it in your brain is handy. That's the reason "truth" is a thing.

> I'd prefer to not publicize my real name and face

Well, a podcast is voice only, so that's not really a show-stopper.

[knightoffaith]

>There are no Platonic truths, only preferred models.

Yeah, I disagree, I think there's something mathematical truths reflect that are independent of the physical world. When we decide whether certain mathematical claims are true or not, say, Fermat's last theorem---we prove them mathematically, we don't want to appeal to their utility or lack thereof, right? My reasoning for not wanting to appeal to utility for the validity of sense-data is analogous.

>That's what the word "true" means.

I agree.

>It just so happens that the actual state of affairs in objective reality has an impact on survival, so having a faithful reflection of it in your brain is handy.

I agree.

>That's the reason "truth" is a thing.

Well, truth is a thing regardless of whether or not we evolved to be able to hold such a concept in our minds, no?

>podcast

Sure. Contact me at [e-mail]

[lisper]

> When we decide whether certain mathematical claims are true or not, say, Fermat's last theorem---we prove them mathematically, we don't want to appeal to their utility or lack thereof, right?

Well, sort of. We don't care about the utility of Fermat's last theorem per se, but the only reason we care about numbers, which is what Fermat's last theorem is about, is because numbers have utility. It turns out that, having invented numbers for their utility, they also make fun mental playthings. But they were invented to keep track of how many sheep you had.

> Well, truth is a thing regardless of whether or not we evolved to be able to hold such a concept in our minds, no?

No. Truth is a property of propositions, so it only makes sense to talk about truth in the context of something that can harbor a proposition. If such a thing does not exist then neither do propositions and hence neither does truth. It's kind of like talking about "the mass of an idea". Mass is a property of matter, so it doesn't make sense to apply it to something that isn't made of matter.

The thing that encodes propositions doesn't have to be a human brain, of course. It could be an alien brain, or a computer, perhaps even a thermostat (that one is debatable). But it has to be something.

[knightoffaith]

>Well, sort of

All that's fine---but I think you would agree that Fermat's last theorem isn't true by virtue of its utility for counting sheep or anything like that. Similarly, I don't think that the fact the physical world exists in the manner suggested by sense-data is true by virtue of its utility for preventing us from dying.

>The thing that encodes propositions doesn't have to be a human brain, of course. It could be an alien brain, or a computer, perhaps even a thermostat (that one is debatable). But it has to be something.

Are you saying that if there were no humans (or anything capable of encoding propositions) to conceive of it, the proposition "the earth is round" wouldn't be true---in other words, it would not be true that the earth is round? That seems to defy common sense.