Putnam’s thought experiment can be easily tweaked to get around that problem: suppose that on Twin Earth cats are in fact very sophisticated cat-imitating robots.
That would be an even weirder version of Earth. Well, less weird because it wouldn’t be a barren, waterless hellscape, but easier for my mind to paint.
A universe were cats were replaced with cat-imitating robots would be amazing for humans. Instead of the bronze age, we would hunt cats for their strong skeletons to use as tools and weapons. Should the skeletons be made instead of brittle epoxy of some kind, we would be able to study cat factories and bootstrap our mechanical knowledge. Should cats be self replicating with nano-machines, we would employ them as guard animals for crops bootstrapping agriculture; an artificial animal which cannot be eaten would have caused other animals to evolve not to mess with them. Should cats, somehow, manage to turn themselves edible after they die, we would still be able to look at their construction and know that they were not crafted by evolution; humanity would know that there was another race out there in the stars and that artificial life was possible. Twin-Eliezer could point to cats and say, “see, we can do this,” and all of humanity would be able to agree and put huge sums of money into AI research.
And if they are cat-robots who are indeed made of bone instead of metal, who reproduce just like cats do, who have exactly the same chemical composition as cats, and evolved here on earth in the exact same way cats do… then they’re just cats. The concept of identical-robot-cats is no different than the worthless concept of philosophical zombies. That’s the whole point of the quote.
Perhaps “cat” was a bad idea: we know too much about cats. Pick something where there are some properties that we don’t know about yet; then consider the situation where they are as the actually are, and where they’re different. The two would be indistinguishable to us, but that doesn’t mean that no experiment could ever tell them apart. See also asparisi’s comment.
I am most assuredly fighting the hypothetical (I’m familiar with and disagree with that link). As far as I can tell, that’s what Thagard is doing too.
I’m reminded of a rebuttal to that post, about how hypotheticals are used as a trap. Putnam intentionally chose to create a scientifically incoherent world. He could have chosen a jar of acid instead of an incoherent twin-earth, but he didn’t. He wanted the sort of confusion that could only come from an incoherent universe (luke links that in his quote).
I think that’s Thagard’s point. As he notes: these types of thought experiments are only expressions of our ignorance, and not deep insights about the mind.
What mileage do you think Putnam is getting here from creating this confusion? Do you think the point he’s trying to make hinges on the incoherence of the world he’s constructed?
I’m not quite sure why it matters that the world Putnam creates is “scientifically incoherent”—which I take to mean it conflicts with our current understanding of science?
As far as we know, the facts of science could have been different; hell, we could still be wrong about the ones we currently think we know. So our language ought to be able to cope with situations where the scientific facts are different than they actually are. It doesn’t matter that Putnam’s scenario can’t happen in this world: it could have happened, and thinking about what we would want to say in that situation can be illuminating. That’s all that’s being claimed here.
I wonder if the problem is referring to these kinds of things as “thought experiments”. They’re not really experiments. Imagine a non-native speaker asking you about the usage of a word, who concocts an unlikely (or maybe even impossible scenario) and then asks you whether the word would apply in that situation. That’s more like what’s going on, and it doesn’t bear a lot of resemblance to a scientific experiment!
Well you could go for something much more subtle, like using sugar of the opposite handedness on the other ‘Earth’. I don’t think it really changes the argument much whether the distinction is subtle or not.
That would be an even weirder version of Earth. Well, less weird because it wouldn’t be a barren, waterless hellscape, but easier for my mind to paint.
A universe were cats were replaced with cat-imitating robots would be amazing for humans. Instead of the bronze age, we would hunt cats for their strong skeletons to use as tools and weapons. Should the skeletons be made instead of brittle epoxy of some kind, we would be able to study cat factories and bootstrap our mechanical knowledge. Should cats be self replicating with nano-machines, we would employ them as guard animals for crops bootstrapping agriculture; an artificial animal which cannot be eaten would have caused other animals to evolve not to mess with them. Should cats, somehow, manage to turn themselves edible after they die, we would still be able to look at their construction and know that they were not crafted by evolution; humanity would know that there was another race out there in the stars and that artificial life was possible. Twin-Eliezer could point to cats and say, “see, we can do this,” and all of humanity would be able to agree and put huge sums of money into AI research.
And if they are cat-robots who are indeed made of bone instead of metal, who reproduce just like cats do, who have exactly the same chemical composition as cats, and evolved here on earth in the exact same way cats do… then they’re just cats. The concept of identical-robot-cats is no different than the worthless concept of philosophical zombies. That’s the whole point of the quote.
I feel like you’re fighting the hypothetical a bit here.
Perhaps “cat” was a bad idea: we know too much about cats. Pick something where there are some properties that we don’t know about yet; then consider the situation where they are as the actually are, and where they’re different. The two would be indistinguishable to us, but that doesn’t mean that no experiment could ever tell them apart. See also asparisi’s comment.
I am most assuredly fighting the hypothetical (I’m familiar with and disagree with that link). As far as I can tell, that’s what Thagard is doing too.
I’m reminded of a rebuttal to that post, about how hypotheticals are used as a trap. Putnam intentionally chose to create a scientifically incoherent world. He could have chosen a jar of acid instead of an incoherent twin-earth, but he didn’t. He wanted the sort of confusion that could only come from an incoherent universe (luke links that in his quote).
I think that’s Thagard’s point. As he notes: these types of thought experiments are only expressions of our ignorance, and not deep insights about the mind.
What mileage do you think Putnam is getting here from creating this confusion? Do you think the point he’s trying to make hinges on the incoherence of the world he’s constructed?
I’m not quite sure why it matters that the world Putnam creates is “scientifically incoherent”—which I take to mean it conflicts with our current understanding of science?
As far as we know, the facts of science could have been different; hell, we could still be wrong about the ones we currently think we know. So our language ought to be able to cope with situations where the scientific facts are different than they actually are. It doesn’t matter that Putnam’s scenario can’t happen in this world: it could have happened, and thinking about what we would want to say in that situation can be illuminating. That’s all that’s being claimed here.
I wonder if the problem is referring to these kinds of things as “thought experiments”. They’re not really experiments. Imagine a non-native speaker asking you about the usage of a word, who concocts an unlikely (or maybe even impossible scenario) and then asks you whether the word would apply in that situation. That’s more like what’s going on, and it doesn’t bear a lot of resemblance to a scientific experiment!
Well you could go for something much more subtle, like using sugar of the opposite handedness on the other ‘Earth’. I don’t think it really changes the argument much whether the distinction is subtle or not.