A very special island is inhabited only by knights and knaves. Knights always tell the truth, and knaves always lie. You meet 6 inhabitants: Noah, Luke, Sofia, Emily, Ethan, and Grace. As Noah put it, "Sofia is a knight". "Emily is not a knave," Luke mentioned. As Sofia put it, "Grace is not a knight". Emily expressed that Ethan is not a knave. Ethan expressed that Noah is not a knave. As Grace put it, "Ethan is a knave if and only if Noah is a knight". So who is a knight and who is a knave?
Noah is a knight, Luke is a knight, Sofia is a knight, Emily is a knight, Ethan is a knight, and Grace is a knave.
(1) Noah is a knight
(2) Luke is a knight
(3) Sofia is a knight
(4) Emily is a knight
(5) Ethan is a knight
(6) Grace is a knave
Assume Noah is a knight. No contradiction is found in their claim that Sofia is a knight. Assume Sofia is a knight. No contradiction is found in their claim that Grace is not a knight. Grace cannot be a knight, because this would contradict the claim of Sofia that Grace is not a knight. Assume Grace is a knave. No contradiction is found in their false claim that Ethan is a knave if and only if Noah is a knight. Assume Ethan is a knight. No contradiction is found in their claim that Noah is not a knave. Assume Luke is a knight. No contradiction is found in their claim that Emily is not a knave. Assume Emily is a knight. No contradiction is found in their claim that Ethan is not a knave.