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Peter_de_Blanc comments on Excluding the Supernatural - Less Wrong

37 Post author: Eliezer_Yudkowsky 12 September 2008 12:12AM

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Comment author: Peter_de_Blanc 19 December 2011 04:45:06AM *  3 points [-]

I understand that Phil was not suggesting that all non-real things are vampires. That's why my example was a mosquito that isn't real, rather than, say, a Toyota that isn't real.

Comment author: MinibearRex 19 December 2011 05:23:27AM -1 points [-]

But there's nothing particularly special about a mosquito. It's still an incorrect application of modus tollens. We have: If something is a vampire, then it is not real. From this, we can infer (from modus tollens) that if something is real, then it is not a vampire. Thus, if a certain mosquito is real, it is not a vampire. However, there is nothing here that justifies the belief that if a certain mosquito is imaginary, then it is a vampire.

Comment author: Peter_de_Blanc 19 December 2011 09:29:40AM 2 points [-]

What's special about a mosquito is that it drinks blood.

Phil originally said this:

My point was that vampires were by definition not real - or at least, not understandable - because any time we found something real and understandable that met the definition of a vampire, we would change the definition to exclude it.

Note Phil's use of the word "because" here. Phil is claiming that if vampires weren't unreal-by-definition, then the audience would not have changed their definition whenever provided with a real example of a vampire as defined. It follows that the original definition would have been acceptable had it been augmented with the "not-real" requirement, and so this is the claim I was responding to with the unreal mosquito example.

Comment author: MinibearRex 20 December 2011 07:08:37AM 0 points [-]

Ah. That makes more sense.