For no reason at all today I recalled a conversation I had with my Logic Professor.  I was learning Derivations and I was stuck on a problem because I had to derive something, from nothing.

Prof: …so when is A or not A True?

me: if either one is true.

Prof: right, so when is A or not A true?

me: if…um…if A is true OR not A is true.

Prof:  Right.  So–when is A or not A true?

(I make a sad, puzzled face)

Prof:  Make a truth table

(I draw a truth table and fill it out)

Prof:  and…when is A or not A true?

(I stare at the truth table, then exclaim)

me: Always!

Prof: Always! And what’s that called?

me: A Tautololgy!

Prof: And what’s the opposite of a tautology?

me: A CONTRADICTION!

Prof: And what can you do with a contradiction?!!

me: ANYTHING I WAAAAAANNNNTTT.

That’s all.  Made me laugh…hysterically…all by myself in my room.  Back to my Philosophy homework.