[lisper]

> Sounds reasonable.

Cool.

> There's nothing here about "the earth is round" needing to be conceived by someone.

Yes, there is. You can't talk about a proposition without conceiving of it. The instant you wrote “"The earth is round"” (note the nested quotes) you conceived of the proposition "the earth is round" and brought it into being. This is impossible to avoid. So this:

> There's nothing here about "the earth is round" needing to be conceived by someone.

is false.

> Propositions don't just exist insofar as they are conceived. Representations of propositions, sure, but not propositions themselves.

I already gave you the answer to this in the parent comment but you ignored it.

"Ideas are not made of atoms, they are made of information. Just like material objects, ideas do not come into existence until some information that encodes that idea arranges itself in a particular way, i.e. until they are thought of."

etc.

So that is (still) my answer: you are simply mistaken when you say that "Propositions don't just exist insofar as they are conceived."

(You're in good company. Plato got this wrong too, and he was no dummy. But he didn't have Alan Turing's shoulders to stand on.)

BTW, note that the converse is not true. You can conceive of an idea without rendering it into a representation. Indeed, you can conceive of an idea without even being able to render it into a representation. (This is actually quite common!) But what you can't do is produce a rendering of an idea into a representation without conceiving of the idea being represented. (BTW, that is not quite true. There is a tiny loophole, but I'm going to leave it as an exercise for you to figure out what it is.)

[knightoffaith]

>So this is false

In the second argument, could you tell me which of (1) and (2) are incorrect, and why?

If it's the quotes that are problematic, I'm fine to drop those.

The earth is round, regardless of whether people have this idea in their heads or not. You deny this?

>I already gave you the answer to this in the parent comment but you ignored it.

But I didn't disagree that ideas are not made of atoms. What I disagreed with is that propositions only exist insofar as they are conceived.

>(You're in good company. Plato got this wrong too, and he was no dummy. But he didn't have Alan Turing's shoulders to stand on.)

What did Turing do that proved that propositions only exist insofar as they are conceived? Or are you just talking about scientific progress in general?

[lisper]

> The earth is round, regardless of whether people have this idea in their heads or not. You deny this?

No. What I deny is that "the earth is round" and "the proposition 'the earth is round' is true" are identical propositions. The first is a proposition that makes a claim about the roundness of the earth, and the second is a proposition that makes a claim about the truth of a proposition. Those aren't the same thing.

The earth is round whether or not anyone is around to contemplate it (the earth). But "the earth is round" is not true unless someone is around to contemplate it (the proposition).

> What did Turing do that proved that propositions only exist insofar as they are conceived?

That's a long story, and I have to run to a meeting right now. If you really want to know, remind me later. I may need to write a blog post about it.

But forget about propositions for the moment. Do you think that unwritten poems exist?

[knightoffaith]

So, I think if saying "the earth is round" is true and saying the earth is round mean different things, then we haven't construed the former properly, the former should be construed as expressing the same thing as the latter. If it's just a linguistic disagreement, then I think we can set that aside, I'm not very interested in that. The original point was that we can intuit certain things as being true, e.g. that sense-data reflects something about reality, and there's no need to appeal to how useful believing this is or isn't. Like, conceivably, nuclear wars could lead to the annihilation of humanity, but I don't see why that should have any bearing on whether atomic bombs exist or not.

[lisper]

> the former should be construed as expressing the same thing as the latter. If it's just a linguistic disagreement, then I think we can set that aside

No, this is not just a linguistic disagreement. This is the crux of the matter. By saying that "the earth is round" and "the proposition 'the earth is round' is true" mean the same thing you are conflating two different ontological categories. When you do that, your reasoning is no longer sound.

Consider this:

P1: The U.S.S. Enterprise can travel faster than light.

Is P1 true? If yes, then how can that be when we know from relativity theory that nothing can travel faster than light? And if no, then what about these:

P2: The U.S.S. Enterprise is powered by a matter-anti-matter reaction controlled by dilithium crystals.

P3: The U.S.S. Enterprise is powered by squirrels running on treadmills.

---

P.S. It occurred to me that there is a TL;DR answer to the question of what Turing did that was so important: he invented general-purpose software.