Message-Id: <m0qtO7A-00005XC@xiron.pc.helsinki.fi>
Date:         Fri, 7 Oct 1994 18:48:27 EDT
Reply-To:     dave@VFL.PARAMAX.COM
Sender:       Lojban list <LOJBAN%CUVMB.bitnet@FINHUTC.hut.fi>
From:         David Matuszek <dave@VFL.PARAMAX.COM>
Subject:      Re: A couple of questions
To:           Veijo Vilva <veion@XIRON.PC.HELSINKI.FI>
In-Reply-To:  Logical Language Group's message of Fri, 7 Oct 1994 08:40:18
              -0400 <9410071257.AA28341@arbor.VFL.Paramax.COM>
Content-Length: 1273
Lines: 27

lojbab writes:

> 1. Therefore the statement "Elves have pointed ears" is false since
> there is no such thing as an elf.  Likewise definitional statements
> "Elves are humanoid" is also false even if definitional.  How can you
> describe the properties of a hypothetical but non-existent object if any
> statement about such an object is false.

Whether universal quantification has existential import has been
argued extensively by philosophers and logicians, a lot of it during
the Middle Ages when Aristotle reigned supreme.  There is no "correct"
answer.  The standard interpretation in modern formal logic is that it
does not have existential import; only the explicit existential
quantifier has that.  Again this is not "correct," merely what
logicians have decided is convenient.

However, if definitional statements can be false, then it's going to
be damned hard to ever do mathematics in Lojban.  There will be no way
to prove something doesn't exist if you cannot define it in the first
place because the definition itself is false.

I think the question is whether you want to reinvent logic, or just
accept it as it exists today and work from there.

  -- dave@vfl.paramax.com -- If my header says otherwise, it lies.

In memoriam:  The Space Age, 1969-1972.