Validity and necessary truths

Validity is defined in a couple of ways. I like to define it like this: An argument is valid iff the superconjunction1 of all the premises and the negation of the conclusion is impossible. It sounds a bit unusual at first but it is worded that way to prevent confusion about modalities. A more common…

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Truth tables and necessary truths

In the essay Validity and necessary truths I used truth tables with necessary truths and impossibilities in it. I did it like this: P □Q P→□Q T T T F T T Note that the modal operator is placed in the truth table also. It could also be done like this: P Q P→Q T…

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