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.
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.
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.
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.
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.
What’s special about a mosquito is that it drinks blood.
Phil originally said this:
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.
Ah. That makes more sense.