wedrifid comments on The Useful Idea of Truth - Less Wrong

77 Post author: Eliezer_Yudkowsky 02 October 2012 06:16PM

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Comment author: wedrifid 04 October 2012 07:26:03PM *  1 point [-]

Could you give me an example of a belief that is consistent with reality but false?

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.

Comment author: Matt_Simpson 04 October 2012 10:04:54PM 2 points [-]

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)

Comment author: wedrifid 05 October 2012 12:04:47AM *  0 points [-]

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.)

Comment author: Matt_Simpson 05 October 2012 04:42:40AM 1 point [-]

Yeah, I think I agree after thinking about it a bit - I mean, why wouldn't we define the terms that way?