[FOM] Use of Ex Falso Quodlibet (EFQ)

[Paul Blain Levy]

I was referring to natural deduction, where n-ary or-elimination is

                      [A_1]    [A_n]
                        :  ...   :
A1 or ... or A_n       B        B
------------------------------------
                B

The case n=0 is

False
----------------------------------
   B

which is Ex Falso Quodlibet.

Paul


On 2015-09-02 19:45, Tennant, Neil wrote:
> Paul Levy writes:
> 
>  Or-elimination may be seen as the special case n=2 of n-ary
>  or-elimination. The case n=0 is EFQ. I can think of no philosophical
>  or ideological reason for accepting n=2 but rejecting n=0.
> 
> I must respectfully disagree. This is in error. If one were to frame
> n-ary or-elimination in Core Logic, it would be done graphically thus:
> 
>  __(i) ... __(i)
>  A1 An
>  : :
>  A1v...An B/# B/#
>  _________________________(i)
>  B/#
> 
> where this is to be understood as follows:
> 1. if # is the conclusion of every case-proof (all n of them!), then
> the main conclusion is # ;
> 2. otherwise, the main conclusion is B .
> 
> There is no case of n-ary or-elimination corresponding to n=0. What on
> earth would it look like?
> 
> Neil Tennant