[FOM] Question of the Day: What is a Logic?

[Neil Tennant]

On Mon, 9 Oct 2006, Steven Obua wrote:

> So, when I do a classical proof by contradiction, assuming locally the 
> negation of what I really want to prove, am I then using in this local 
> context a paraconsistent logic?

Yes---provided you are *really using* not-P to derive absurdity (whence
you infer P by classical RAA). For, this is accommodated within the
relevant logic CR, which is paraconsistent, in that it allows for distinct
inconsistent theories. The step of RAA will of course discharge the
assumption not-P.

Neil Tennant