Re: Disjunction in propositional logic

From: Karl Weber (dudendude_at_hotmail.com)
Date: 09/10/04 

Date: Sat, 11 Sep 2004 01:48:25 +0200

Converter wrote:
 
> Both A and B are valid elementary propositions and the statement P is
> a valid disjunctive proposition, A is valid because it asserts that
> Easter will fall in March and B is valid because it asserts that
> Easter will fall in April.

Hmmm... isn't it a problem that A/B do not in any way specify _which_ Easter
will fall in March/April? Of course it should be ok if it is taken to mean
"This year, Easter ..."

> I think where the confusion comes in is that you have already come to
> the conclusion that easter will always fall within these two months
> and you haven't added it into your logic (your statement about not
> making sense wasn't symbolized within the propositional logic). So,
> the statement will always be true according to you.

I think, my problem was that the original P could be interpreted in two
different ways:

  P1 = "Every year, Easter will fall in March or in April"
  P2 = "This year, Easter falls in March or in April"

As I see it, P1 would be a statement of predicate logic, while P2 is a
statement of propositional logic... ?

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