@fast,
fast;158656 wrote:
I'm at a disadvantage. I don't speak that language.
I agree with that.
[~(SH and detective)] is true.
I'm almost afraid to ask, but do you think the sentence, "SH is not a detective" is cognitively meaningful? Everything you've said would lead me to think the answer is no, but stranger things have happened.
I think it has meaning, yes. So don't misrepresent what I am saying. But technically, I don't think it is
cognitively meaningful because a person who truly meant what he said would be saying something very similar to,
"George Bush is no longer the President." This is true. So in logic, the following inference is valid,
(Ex)~Px
This says, there exists something that is not a president.
If "SH is not a detective" is true, the same logical inference is valid,
(Ex)~Dx
But this says, there exists something that is not a detective. So this is true for all those existent things which are not detectives, but it is not true of Sherlock. So there is no sense in saying that "Sherlock is not a detective" anyway.
It's much better if someone said,
"It is not the case there is something that is Sherlock and is a detective."
---------- Post added 04-30-2010 at 09:49 PM ----------
fast;158656 wrote: I do not think that. I can't make heads or tails of Ds, Ex, and Dx. Sorry.
Ok, look.
If "SH is not a detective" is true, then logic says (by the rule of *existential introduction*) that it is valid to infer that something exists which does not have that property.
So, if "SH is not a detective" is true, then it is also true that,
"There exists at least one thing that is Sherlock, and that thing is not a detective."
But the proposition that
this sentence DOES express is literally false. So I don't believe it is true.
Does that make sense?