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