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"Owen" wrote:
> Roberto Vescarelli wrote:
>> If you don't want to help me in developing this logic [about
>> fictional and non-existent] objects, because you are a defenser of
>> classical views, you can not help me.
> There is no help to be given, your persuit is silly.
> Clearly, non-existent things have no properties, that's it!
Oh, bullshit.
It is not at all so clear that logic should treat non-existent things
as classical logic does. Sometimes, we want to reason about fictional
characters. There is a fact of the matter about Othello's race, for
instance. Sherlock Holmes lives in 221B Baker Street. It is false
that he lives (lived?) elsewhere. And it is also false that Holmes's
address is part of the defining predicate "isHolmes". Holmes could
have lived elsewhere and still been Holmes, but the fact is he didn't
live elsewhere.
Sometimes, we want to reason counterfactually. If ether existed, what
properties must it have?
First-order logic is remarkably successful, but it does not capture
all of the ways in which people reason (and, indeed, reason
correctly).
--
"But remember, as long as one human being follows the rules of
mathematics, then mathematics as a human discipline survives.
Right now I'm that one human being, so mathematics survives."
-- James S. Harris
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