Re: [bpfk] {ro}, existential import and De Morgan

[Alex Burka <durka42@gmail.com>]

I understand {ro broda} to be the same as {ro da poi broda}, whereas {ro lo broda} is the one that's different (= {ro da poi me lo broda}). Not to put words in your mouth, but at least once in 2002[1] you agreed.

mu'o mi'e la durka

1: https://groups.google.com/forum/#!msg/lojban/Akan3w4mnuw/9AHz8s15dNsJ

On Friday, October 17, 2014 at 9:14 PM, John Cowan wrote:

Riley Martinez-Lynch scripsit:

Which is to say, {ro} has existential import. This is the position of

classic/Aristotelian logic, but not modern logic.

As pc explained it to me, Aristotelian and Fregean (modern) logic don't

actually contradict one another in this area. However, the *translation*

from Aristotelian "All As are Bs" to Fregean "For all x, if A(x) then

B(x)" is not quite truth-preserving. "All A is B" is taken to be false

if there are no As, whereas "For all x, if A(x) then B(x)" is vacuously

true if there does not exist x such that A(x). Lojban expresses each

of these differently: the Aristotelian claim is "ro broda cu brode"

whereas the Fregean claim is "ro da poi broda cu brode".

Now these can be reconciled in their interpretation if we assume that

"ro" has existential import: then "ro broda cu brode" requires that

there are brodas, whereas "ro da poi broda cu brode" requires only that

there are das. The latter is true except in a completely empty universe,

which is not really worth talking about.

Can anyone show me where and how this problem was resolved? Failing that,

would anyone care to take this up and once and for all settle the matter?

In answer to both questions: probably not.

--

John Cowan http://www.ccil.org/~cowan cowan@ccil.org

What has four pairs of pants, lives in Philadelphia,

and it never rains but it pours?

--Rufus T. Firefly

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