Re: reductio ad falsum versus reductio ad absurdum

"futurist" <adamgolding@xxxxxxxxxxxxxxx> writes:

> Conditional Proof:
>
> P|-Q => P->Q
>

You can use any notation you like as long as you define a precise
syntax and semantics.

> just the form you told me was called constructive reductio:
>...
> is one with no premises, and is presumably construed as a 'variety' of
> RAA.

There can be any number of premises in both constructive reductio
and indirect proof - I just left them out in the notation.

> i suppose we could simply call it the 'nonconstructive reductio' but
> 'reductio ad falsum' seems a rather good term to me--relating it to the
> link i gave before

Your "reductio ad falsum" is constructively valid, and we don't need
non-constructive reductio to prove it as a derived rule.

.

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