What do you ask?, page-5

"If I asked you "does this door lead to the castle" would you say yes?"

Classic logic problem of determining a positive by forcing a double negative, i.e. forcing the lying guard to lie twice. Assuming the guard asked is guarding the death door:

	Question	Truthful guard	Lying guard
1	Does this door lead to the castle?	No	Yes (Lying because it doesn't)
2	Would you say 'yes'	No	No (Lying because he would say 'yes' to first question