A very special island is inhabited only by knights and knaves. Knights always tell the truth, and knaves always lie. You meet 6 inhabitants: Isabella, Jackson, David, Sofia, Owen, and Elizabeth. "Jackson is a knight or David is a knave," Isabella mentioned. In Jackson's words: "If Elizabeth is a knave then David is a knave". "Jackson is a knight or Isabella is a knave," David mentioned. "Jackson is a knave and Isabella is a knave," Sofia claimed. Owen stated, "Owen is a knight if and only if Jackson is a knight". "Owen is a knave," Elizabeth mentioned. So who is a knight and who is a knave?
Isabella is a knight, Jackson is a knight, David is a knight, Sofia is a knave, Owen is a knave, and Elizabeth is a knight.
(1) Isabella is a knight
(2) Jackson is a knight
(3) David is a knight
(4) Sofia is a knave
(5) Owen is a knave
(6) Elizabeth is a knight
Assume Isabella is a knight. No contradiction is found in their claim that Jackson is a knight or David is a knave. Assume Jackson is a knight. No contradiction is found in their claim that If Elizabeth is a knave then David is a knave. Assume Elizabeth is a knight. No contradiction is found in their claim that Owen is a knave. Owen cannot be a knight, because this would contradict the claim of Elizabeth that Owen is a knave. Assume Owen is a knave. No contradiction is found in their false claim that Owen is a knight if and only if Jackson is a knight. Assume David is a knight. No contradiction is found in their claim that Jackson is a knight or Isabella is a knave. Sofia cannot be a knight, because this would contradict the claim of their own that Jackson is a knave and Isabella is a knave. Assume Sofia is a knave. No contradiction is found in their false claim that Jackson is a knave and Isabella is a knave.