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by adrian_b
35 days ago
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Another poster has provided a link to a definition of "proof by contradiction", which I assume that it is the one that you mean ("A proof by contradiction is a proof of a positive by refutation of the negative."). Unlike in that unambiguous definition, the words used by you are confusing, because "we reach a contradiction" is also applicable to the 2 variants of "Reductio ad absurdum" that I have described. A demonstration like "a proof of a positive by refutation of the negative" is valid only in strictly bivalent logic and invalid in any multivalent logic. The 2 variants of "Reductio ad absurdum" that I have mentioned are also valid in any multivalent logic or modal logic. |
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