Comment author: DuncanS 13 October 2012 10:30:19AM -1 points [-]

If anyone accepts a pascals mugging style trade off with full knowledge of the problem,

Well, it's very well known that Pascal himself accepted it, and I'm sure there are others. So, off you go and do whatever it is you wanted to do.

To be honest, your ability to come through on this threat is a classic example of the genre - it's very, very unlikely that you are able to do it, but obviously the consequences if you were able to would be, er, quite bad. In this case my judgement of the probabilities is that we are completely justified in ignoring the threat.

Comment author: DuncanS 05 October 2012 08:30:00PM 0 points [-]

Actually human Godel sentences are quite easy to construct.

For example, I can't prove that I'm not an idiot.

If I'm not an idiot, then I can perhaps make an argument that I'm not an idiot that seems reasonable to me, and that may persuade that I'm not an idiot.

However, if I am an idiot, then I can still perhaps make an argument that I'm not an idiot that seems reasonable to me.

Therefore any argument that I might make on whether I'm an idiot or not does not determine which of the two above states is the case. Whether I'm an idiot or not is therefore unprovable under my system.

You can't even help me. You might choose to inform me that I am / am not an idiot. I still have to decide whether you are a reasonable authority to decide the matter, and that question runs into the same problem - if I decide that you are, I may have decided so as an idiot, and therefore still have no definitive answer.

You cannot win, you can only say "I am what I am" and forget about it.

Comment author: ciphergoth 02 October 2012 07:50:54AM 11 points [-]

Off the top of my head, I also can't think of a philosopher who has made an explicit connection from the correspondence theory of truth to "there are causal processes producing map-territory correspondences" to "you have to look at things to draw accurate maps of them..."

OK, I defended the tweet that got this response from Eliezer as the sort of rhetorical flourish that gets people to actually click on the link. However, it looks like I also underestimated how original the sequences are - I had really expected this sort of thing to mirror work in mainstream philosophy.

Comment author: DuncanS 04 October 2012 11:02:46PM *  2 points [-]

Although I wouldn't think of this particular thing as being an invention on his part - I'm not sure I've read that particular chain of thought before, but all the elements of the chain are things I've known for years.

However I think it illustrates the strength of Eliezer's writing well. It's a perfectly legitimate sequence of thought steps that leads in a clear and obvious way to the right answer. It's not new thought, but a particularly clear way of expressing something that many people have thought and written about in a less organised way.

To clarify - there are times when Eliezer is inventive - for example his work on CEV - but this isn't one of those places. I know I'm partly arguing about the meaning of "inventive", but I don't think we're doing him a favor here by claiming this is an example of his inventiveness when there are much better candidates.

Comment author: Benquo 02 October 2012 07:46:33PM *  1 point [-]

I don't think 2 is answered even if you say that the mathematical objects are themselves real. Consider a geometry that labels "true" everything that follows from its axioms. If this geometry is consistent, then we want to say that it is true, which implies that everything it labels as "true", is. And the axioms themselves follow from the axioms, so the mathematical system says that they're true. But you can also have another valid mathematical system, where one of those axioms is negated. This is a problem because it implies that something can be both true and not true.

Because of this, the sense in which mathematical propositions can be true can't be the same sense in which "snow is white" can be true, even if the objects themselves are real. We have to be equivocating somewhere on "truth".

Comment author: DuncanS 02 October 2012 10:23:29PM 4 points [-]

It's easy to overcome that simply by being a bit more precise - you are saying that such and such a proposition is true in geometry X. Meaning that the axioms of geometry X genuinely do imply the proposition. That this proposition may not be true in geometry Y has nothing to do with it.

It is a different sense of true in that it isn't necessarily related to sensory experience - only to the interrelationships of ideas.

Comment author: Sniffnoy 02 October 2012 08:59:24AM 10 points [-]

The quantum-field-theory-and-atoms thing seems to be not very relevant, or at least not well-stated. I mean, why the focus on atoms in the first place? To someone who doesn't already know, it sounds like you're just saying "Yes, elementary particles are smaller than atoms!" or more generally "Yes, atoms are not fundamental!"; it's tempting to instead say "OK, so instead of taking a possible state of configurations of atoms, take a possible state of whatever is fundamental."

I'm guessing the problem you're getting at is that is that when you actually try to do this you encounter the problem that you quickly find that you're talking about not the state of the universe but the state of a whole notional multiverse, and you're not talking about one present state of it but its entire evolution over time as one big block, which makes our original this-universe-focused, present-focused notion a little harder to make sense of -- or if not this particular problem then something similar -- but it sounds like you're just making a stupid verbal trick.

Comment author: DuncanS 02 October 2012 10:08:32PM *  4 points [-]

I agree - atoms and so forth are what our universe happens to consist of. But I can't see why that's relevant to the question of what truth is at all - I'd say that the definition of truth and how to determine it are not a function of the physics of the universe one happens to inhabit. Adding physics into the mix tends therefore to distract from the main thrust of the argument - making me think about two complex things instead of just one.

Comment author: DuncanS 02 October 2012 09:39:13PM *  8 points [-]

Of course the limited amount of knowledge available to the primitive tribe doesn't rule out the existence of George, but neither does it do much to justify the theory of George. What they know is that the ground shook, but they have no reasonable explanation of why.

There are, for them, many possible explanations they could dream up to explain the shaking. Preferring any one above the others without a reason to do so is a mistake.

At their postulated level of sophistication, I don't think they can do much better than "The Earth shook. It does that sometimes." Adding the bit about George and so forth is just unnecessarily multiplying entities, as Ockham might say.

Comment author: DuncanS 02 October 2012 09:28:32PM *  2 points [-]

People usually are not mistaken about what they themselves believe - though there are certain exceptions to this rule - yet nonetheless, the map of the map is usually accurate, i.e., people are usually right about the question of what they believe:

I'm not at all sure about this part - although I don't think it matters much to your overall case. I think one of our senses is a very much simplified representation of our own internal thought state. It's only just about good enough for us to make a chain of thought - taking the substance of a finished thought and using it as input to the next thought. In animals, I suspect this sense isn't good enough to allow thought chains to be made - and so they can't make arguments. In humans it is good enough, but probably not by very much - it seems rather likely that the ability to make thought chains evolved quite recently.

I think we probably make mistakes about what we think we think all the time - but there is usually nobody who can correct us.

Comment author: mbrubeck 02 October 2012 08:31:21PM 2 points [-]

I think this one gets more complicated when you include beliefs about things like theorems of logic, e.g., "Any consistent formal system powerful enough to describe Peano arithmetic is incomplete." It seems to me that this belief is meaningful, yet independent of any sensory experience or physical law. That is, it's not really a belief about "the universe" of atoms or quantum fields or whatnot. Perhaps it would be better to talk about these "beliefs" as a separate category.

Comment author: DuncanS 02 October 2012 09:09:38PM 0 points [-]

They are truisms - in principle they are statements that are entirely redundant as one could in principle work out the truth of them without being told anything. However, principle and practice are rather different here - just because we could in principle reinvent mathematics from scratch doesn't mean that in practice we could. Consequently these beliefs are presented to us as external information rather than as the inevitable truisms they actually are.

Comment author: Eliezer_Yudkowsky 02 October 2012 05:26:28AM 5 points [-]

Koan answers here for:

What rule could restrict our beliefs to just propositions that can be meaningful, without excluding a priori anything that could in principle be true?

Comment author: DuncanS 02 October 2012 08:49:02PM 0 points [-]

Maps are models of the territory. And the usefulness of them is often that they make predictions about parts of the territory I haven't actually seen yet, and may have trouble getting to at all. The Sun will come up in the morning. There isn't a leprachaun colony living a mile beneath my house. There aren't any parts of the moon that are made of cheese.

I have no problem saying that these things are true, but they are in fact extrapolations of my current map into areas which I haven't seen and may never see. These statements don't meaningfully stand alone, they arise out of extrapolating a map that checks out in all sorts of other locations which I can check. One can then have meaningful certainty about the zones that haven't yet been seen.

How does one extrapolate a map? In principle I'd say that you should find the most compressible form - the form that describes the territory without adding extra 'information' that I've assumed from someplace else. The compressed form then leads to predictions over and above the bald facts that go into it.

The map should match the territory in the places you can check. When I then make statements that something is "true", I'm making assertions about what the world is like, based on my map. As far as English is concerned, I don't need absolute certainty to say something is true, merely reasonable likelihood.

Hence the photon. The most compressible form of our description of the universe is that the parts of space that are just beyond visibility aren't inherently different from the parts we can see. So the photon doesn't blink out over there, because we don't see any such blinking out over here.

Comment author: DuncanS 02 October 2012 07:41:42PM 4 points [-]

To summarise the argument further.

"A lot of people talk rubbish about AI. Therefore most existing predictions are not very certain."

That doesn't in itself mean that it's hard to predict AI - merely that there are many existing predictions which aren't that good. Whether we could do better if we (to take the given example) used the scientific method isn't something the argument covers.

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