A very special island is inhabited only by knights and knaves. Knights always tell the truth, and knaves always lie. You meet 6 inhabitants: Amelia, Riley, Grace, Evelyn, Matthew, and Ava. Amelia told you that Matthew is not a knave. According to Riley, "If Matthew is a knight then Ava is a knave". Grace remarked, "If Ava is a knight then Riley is a knave". Evelyn said that Matthew is a knight or Riley is a knight. Matthew told you that Grace is not a knave. "Amelia is not a knave" - Ava. So who is a knight and who is a knave?
Amelia is a knight, Riley is a knave, Grace is a knight, Evelyn is a knight, Matthew is a knight, and Ava is a knight.
(1) Amelia is a knight
(2) Riley is a knave
(3) Grace is a knight
(4) Evelyn is a knight
(5) Matthew is a knight
(6) Ava is a knight
Assume Amelia is a knight. No contradiction is found in their claim that Matthew is not a knave. Assume Matthew is a knight. No contradiction is found in their claim that Grace is not a knave. Assume Grace is a knight. No contradiction is found in their claim that If Ava is a knight then Riley is a knave. Assume Ava is a knight. No contradiction is found in their claim that Amelia is not a knave. Riley cannot be a knight, because this would contradict the claim of their own that If Matthew is a knight then Ava is a knave. Assume Riley is a knave. No contradiction is found in their false claim that If Matthew is a knight then Ava is a knave. Assume Evelyn is a knight. No contradiction is found in their claim that Matthew is a knight or Riley is a knight.