# Talk:Exportation (logic)

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## What??

P implies Q implies R.

Does this mean

(P implies Q) implies R

or

P implies (Q implies R)

??

Which is it?? Michael Hardy (talk) 04:35, 18 February 2012 (UTC)

The latter, according to the quoted source. -- Jitse Niesen (talk) 14:53, 18 February 2012 (UTC)

## Proof

I removed the proof (reproduced below) because it seems to prove the same thing as it assumes at the start.

Proposition Derivation
$(P\rightarrow Q)\rightarrow R$ Given
$\neg(P\rightarrow Q)\or R$ Material implication
$\neg(\neg P\or Q)\or R$ Material implication
$(P\and\neg Q)\or R$ de Morgan's law
$\neg(P\and \neg Q)\rightarrow R$ Material implication
$(\neg P\or Q)\rightarrow R$ de Morgan's law
$(P\rightarrow Q)\rightarrow R$ Material implication

-- Jitse Niesen (talk) 14:53, 18 February 2012 (UTC)