- #1
dobry_den
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Hi! I'm just reading Wilfrid Hodges's book Logic, chapter 24. Properties of Semantic Entailment. I'm a bit puzzled by the following paragraphs concerning the Extension Theorem:
http://i83.photobucket.com/albums/j315/dobry_den/extension_theorem.jpg
What if X contains formulae A, A->B and Y contains just B' (negation of B). Then the resulting set X,Y is semantically inconsistent and therefore the theorem isn't true.
I'm probably wrong, but I can't see where...
http://i83.photobucket.com/albums/j315/dobry_den/extension_theorem.jpg
What if X contains formulae A, A->B and Y contains just B' (negation of B). Then the resulting set X,Y is semantically inconsistent and therefore the theorem isn't true.
I'm probably wrong, but I can't see where...
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