Re: [isabelle] Kleene's Ternary Logic



I have to agree. I've never seen a convincing application of a 3-valued logic. Even LCF, with its undefined values, didn't have undefined truth values.

Larry Paulson


On 28 Aug 2013, at 07:37, "Jens-D. Doll" <jd at cococo.de> wrote:

> Hello Arthur,
> 
> afaik you will have to distinguish these cases, independent of bound state,
> 
> a) a tautology, which is always true
> b) the absurd, which is always false
> c) there is an x s.th. p(x) is true, which really depends on the bound x
> 
> Jens
> 
> -----------------------------------------------------------------------------
> 
> Is there an existing theory of Kleene's Termary Logic written is Isabelle?
> A search didn't show up anything.
> 
> I need it for representing that predicates that reference unbound variables
> are neither true nor false.
> 
> Thanks.
> -Arthur
> 





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