A very special island is inhabited only by knights and knaves. Knights always tell the truth, and knaves always lie. You meet 6 inhabitants: David, Emma, Sebastian, Samuel, Noah, and Ella. As David put it, "Ella is a knave or Emma is a knight". According to Emma, "Sebastian is a knave and David is a knave". Sebastian expressed that If Noah is a knave then Ella is a knave. "Emma is a knave or Noah is a knave," Samuel claimed. According to Noah, "David is a knave or Samuel is a knave". "Emma is a knight" - Ella. So who is a knight and who is a knave?
David is a knight, Emma is a knave, Sebastian is a knight, Samuel is a knight, Noah is a knave, and Ella is a knave.
(1) David is a knight
(2) Emma is a knave
(3) Sebastian is a knight
(4) Samuel is a knight
(5) Noah is a knave
(6) Ella is a knave
Assume David is a knight. No contradiction is found in their claim that Ella is a knave or Emma is a knight. Assume Ella is a knight. No contradiction is found in their claim that Emma is a knight. Emma cannot be a knight, because this would contradict the claim of their own that Sebastian is a knave and David is a knave. Emma cannot be a knave, because this would contradict the claim of David that Ella is a knave or Emma is a knight. We have exhausted all possibilities for Emma, so let us go back and reconsider Ella. Assume Ella is a knave. No contradiction is found in their false claim that Emma is a knight. Emma cannot be a knight, because this would contradict the claim of their own that Sebastian is a knave and David is a knave. Assume Emma is a knave. No contradiction is found in their false claim that Sebastian is a knave and David is a knave. Assume Sebastian is a knight. No contradiction is found in their claim that If Noah is a knave then Ella is a knave. Assume Noah is a knight. No contradiction is found in their claim that David is a knave or Samuel is a knave. Samuel cannot be a knight, because this would contradict the claim of Noah that David is a knave or Samuel is a knave. Samuel cannot be a knave, because this would contradict the false claim of their own that Emma is a knave or Noah is a knave. We have exhausted all possibilities for Samuel, so let us go back and reconsider Noah. Assume Noah is a knave. No contradiction is found in their false claim that David is a knave or Samuel is a knave. Assume Samuel is a knight. No contradiction is found in their claim that Emma is a knave or Noah is a knave.