LAST EDITED ON Aug-03-01 AT 10:43 PM (EDT)

>>I've found that the best way to improve my mood over a "logic" puzzle
>>in any piece of fiction is to sit down with Mates' Elementary
>>Logic and do formal proofs until one of the following happens to
>>my head:
>>3) #56 in Chapter 6: Tautologous Sentences causes neural
>>shutdown... again.
>
>Okay... what's #56? (Asks the man who doesn't have this particular
>book...)

56. ((P&Q)v(R&S))<-->(((PvR)&(PvS))&((QvR)&(QvS)))

& = both the antecedent and the consequent are true
<--> = the antecedent is true if and only if the consequent is true (and vice versa)
v = either the antecedent is true, or else the consequent is true, or both are true
The ampersand, wedge, arrow, double headed arrow, and wedge are all binary connectives; the bar is negation, and is the only unary connective in this language, and it not present in the truth of logic above (but it may be present in the proof itself).
P, Q, R, and S are all sentential variables.
The left- and right-hand parenthesis are grouping symbols.

If I remember correctly, it ends up being about a 40-70 line proof.

I think that's a pretty succinct explanation. If it isn't sufficient, please email me privately. After all, as interesting as mathematical logic is, not everyone digs it....

Juun.

doh... the negation symbol is a unary connective, not a binary connective. My mistake.