A very special island is inhabited only by knights and knaves. Knights always tell the truth, and knaves always lie. You meet 6 inhabitants: Grace, Scarlett, James, Penelope, Ella, and Henry. Grace told you that If Ella is a knight then Penelope is a knave. "If James is a knave then James is a knight," Scarlett declared. James was heard saying, "Henry is a knave". "Grace is not a knight," Penelope mentioned. In a statement by Ella: "Henry is a knave". Henry stated, "Penelope is a knight or Penelope is a knave". So who is a knight and who is a knave?
Grace is a knight, Scarlett is a knave, James is a knave, Penelope is a knave, Ella is a knave, and Henry is a knight.
(1) Grace is a knight
(2) Scarlett is a knave
(3) James is a knave
(4) Penelope is a knave
(5) Ella is a knave
(6) Henry is a knight
Assume Grace is a knight. No contradiction is found in their claim that If Ella is a knight then Penelope is a knave. Assume Ella is a knight. No contradiction is found in their claim that Henry is a knave. Henry cannot be a knight, because this would contradict the claim of Ella that Henry is a knave. Henry cannot be a knave, because this would contradict the false claim of their own that Penelope is a knight or Penelope is a knave. We have exhausted all possibilities for Henry, so let us go back and reconsider Ella. Assume Ella is a knave. No contradiction is found in their false claim that Henry is a knave. Assume Henry is a knight. No contradiction is found in their claim that Penelope is a knight or Penelope is a knave. Penelope cannot be a knight, because this would contradict the claim of their own that Grace is not a knight. Assume Penelope is a knave. No contradiction is found in their false claim that Grace is not a knight. Assume Scarlett is a knight. No contradiction is found in their claim that If James is a knave then James is a knight. James cannot be a knight, because this would contradict the claim of their own that Henry is a knave. James cannot be a knave, because this would contradict the claim of Scarlett that If James is a knave then James is a knight. We have exhausted all possibilities for James, so let us go back and reconsider Scarlett. Assume Scarlett is a knave. No contradiction is found in their false claim that If James is a knave then James is a knight. James cannot be a knight, because this would contradict the false claim of Scarlett that If James is a knave then James is a knight. Assume James is a knave. No contradiction is found in their false claim that Henry is a knave.