Exercises and Puzzles
I'm still doing exercises for the logic book. This is rather unpleasant because I have to use Microsoft Word. Getting back to Word after using reasonable document formats (like LaTeX) and editors (like Alpha) for a while is a very frustrating experience.
At the moment, I'm trying to find nice and simple versions of Gödel's Theorems that still leave something formal to prove (like deducing Löb's Theorem from provability properties). This turns out to be difficult because I don't have the space to introduce the concepts of representability and recursiveness.
David Chalmers quickly found the answer to the puzzle in my last posting, which apparently he didn't even find difficult:
Are you A iff you tell the truth iff "qwer" means "yes"?
He also tells me that Tomassi himself stole the sandwich inference from Smullyan. On my Google search for the origins of this inference, I came across this very nice and huge archive of puzzles. Maybe I'll steal some of those instead of the Gödel exercises. On the other hand, there don't seem to be many pure logic puzzles in there ("logic puzzle" is often used where I would rather say "elementary arithmetic puzzle").