A very special island is inhabited only by knights and knaves. Knights always tell the truth, and knaves always lie. You meet 6 inhabitants: Aiden, Abigail, Joseph, Jack, Mason, and David. Aiden expressed that Mason is not a knave. Abigail told you that Aiden is not a knight. Joseph said, "Mason is a knight and David is a knight." According to Jack, "Abigail is not a knight". "Joseph is a knave if and only if Jack is a knave," Mason declared. "If David is a knight then Jack is a knight," David mentioned. So who is a knight and who is a knave?
Aiden is a knight, Abigail is a knave, Joseph is a knight, Jack is a knight, Mason is a knight, and David is a knight.
(1) Aiden is a knight
(2) Abigail is a knave
(3) Joseph is a knight
(4) Jack is a knight
(5) Mason is a knight
(6) David is a knight
Assume Aiden is a knight. No contradiction is found in their claim that Mason is not a knave. Assume Mason is a knight. No contradiction is found in their claim that Joseph is a knave if and only if Jack is a knave. Assume Joseph is a knight. No contradiction is found in their claim that Mason is a knight and David is a knight. Assume David is a knight. No contradiction is found in their claim that If David is a knight then Jack is a knight. Assume Jack is a knight. No contradiction is found in their claim that Abigail is not a knight. Abigail cannot be a knight, because this would contradict the claim of their own that Aiden is not a knight. Assume Abigail is a knave. No contradiction is found in their false claim that Aiden is not a knight.