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amcknight comments on The Useful Idea of Truth - Less Wrong
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I think this includes too much. It would includes meaningless beliefs. "Zork is Pork." True or false? Consistency seems to me to be, at best, a necessary condition, but not a sufficient one.
Could you give me an example of a belief that is consistent with reality but false?
I take "consistent" to mean roughly "does not contain a contradiction", so "a belief that is consistent with reality" would mean something like "if you take all of reality as a collection of facts, and then add this belief, as a fact, to that collection, the collection won't contain a contradiction." It seems to me, if this is a fair representation of the concept, that some beliefs about the future are consistent with reality, but false. For example:
Humanity will be mining asteroids in 2024.
This is consistent with reality: there is at least one company talking about it, there are no obvious impossibilities (there are barriers, but we recognise they can be overcome with engineering)... but it's very probably false.
I'm definitely having more trouble than I expected. Unicorns have 5 legs... does that count? You're making me doubt myself.
Cool. : )
Is "Unicorns have 5 legs" consistent with reality? I would be quite surprised to find out that it was.
Well it doesn't seem to be inconsistent with reality.
It doesn't even have any referents to reality. It's not even a statement about whatever "reality" we live in, to the best of my knowledge. If it does mean five-leggedness of unicorn creatures with the implication of the existence of possible-existence of such creatures in reality, then it is false, but it's inconsistent with what we know of reality, since there's no way such a creature would exist.
...I think, anyway. Not quite sure about that second part.
The non-existence of unicorns makes the claim that they have legs, in whatever number, inconsistent with reality.
Counterfactuals? If there's a unicorn on Mars, then I'm the president. Though it depends on what gets included in the term "reality."
Neither of those things are examples of beliefs that are consistent with reality but false. The belief "If there's a unicorn on Mars, then I'm the president" is true, consistent with reality but also utterly worthless.
Counterfactuals are also not false. (Well, except for false counterfactual claims.) A (well formed) counterfactual claim is of the type "Apply this specified modifier to reality. If that is done then this conclusion will follow.". Such claims can be true, albeit somewhat difficult to formally specify.
I didn't mean that all counterfactuals are false, I meant a specific example of a counterfactual claim that is false - e.g. If you put a unicorn on Mars, then I'll become president (which expresses the example I meant to give in the grandparent, not a logical if-then).
(Apologies for not clearly saying that)
Thankyou, I understand what you are saying now.
For what it is worth I would describe that counterfactual claim as inconsistent with reality and false. That is, when instantiating the counterfactual using the counterfactual operation as reasonably as possible it would seem that reality as I know it is not such that the modified version would result in the consequences predicted.
(Note that with my understanding of the terms in question I think it is impossible to have something consistent with reality and false so it is unsurprising that given examples would not appear to me to meet those criteria simultaneously.)
Yeah, I think I agree after thinking about it a bit - I mean, why wouldn't we define the terms that way?
Better example, maybe: the continuum hypothesis
Mutualy inconsistent statements can be consistent with known facts, eg Lady MacBeth had 2 chidren, Ldy MacBeth had 3 children...but that just exposes the problem with correspondence. if it isn't consistency...what is it?
Tell me what Zork is and i'll let you know. : )
Zork is a classic computer game (or game series, or game franchise; usage varies with context) from c.1980.