A very special island is inhabited only by knights and knaves. Knights always tell the truth, and knaves always lie. You meet 6 inhabitants: Mason, Daniel, William, Sofia, Grace, and Jacob. "Sofia is a knave," Mason mentioned. Daniel stated, "Jacob is a knight or Mason is a knave". William expressed that Mason is a knave or Grace is a knave. "William is not a knight" - Sofia. Grace noted, "Sofia is a knight". Jacob told you that Grace is a knight or William is a knave. So who is a knight and who is a knave?
Mason is a knight, Daniel is a knave, William is a knight, Sofia is a knave, Grace is a knave, and Jacob is a knave.
(1) Mason is a knight
(2) Daniel is a knave
(3) William is a knight
(4) Sofia is a knave
(5) Grace is a knave
(6) Jacob is a knave
Assume Mason is a knight. No contradiction is found in their claim that Sofia is a knave. Sofia cannot be a knight, because this would contradict the claim of Mason that Sofia is a knave. Assume Sofia is a knave. No contradiction is found in their false claim that William is not a knight. Assume William is a knight. No contradiction is found in their claim that Mason is a knave or Grace is a knave. Grace cannot be a knight, because this would contradict the claim of William that Mason is a knave or Grace is a knave. Assume Grace is a knave. No contradiction is found in their false claim that Sofia is a knight. Assume Daniel is a knight. No contradiction is found in their claim that Jacob is a knight or Mason is a knave. Jacob cannot be a knight, because this would contradict the claim of their own that Grace is a knight or William is a knave. Jacob cannot be a knave, because this would contradict the claim of Daniel that Jacob is a knight or Mason is a knave. We have exhausted all possibilities for Jacob, so let us go back and reconsider Daniel. Assume Daniel is a knave. No contradiction is found in their false claim that Jacob is a knight or Mason is a knave. Jacob cannot be a knight, because this would contradict the false claim of Daniel that Jacob is a knight or Mason is a knave. Assume Jacob is a knave. No contradiction is found in their false claim that Grace is a knight or William is a knave.