Re: reductio ad falsum versus reductio ad absurdum

"futurist" <adamgolding@xxxxxxxxxxxxxxx> writes:

> then you should be able to prove pv~p using either rule.
>
> in the first case you assume A where A <=> ~(Pv~P)
> in the secome case you assume ~A where A <=> (Pv~P)
>
> (with <=> meaning formal equivalence here)
>
> the second form seems like the first rule with an unnecessary tilde (~)
> added in... am i missing something?

Using constructive reductio, you can only prove ~~(Pv~P).

.

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