A very special island is inhabited only by knights and knaves. Knights always tell the truth, and knaves always lie. You meet 6 inhabitants: David, Michael, Luke, Evelyn, Victoria, and Jackson. "Luke is not a knave" - David. Michael expressed that Jackson is a knight. As Luke put it, "Evelyn is a knave if and only if Evelyn is a knight". As Evelyn put it, "Victoria is a knave if and only if Jackson is a knave". Victoria expressed that Jackson is not a knight. According to Jackson, "If David is a knight then Luke is a knave". So who is a knight and who is a knave?
David is a knave, Michael is a knight, Luke is a knave, Evelyn is a knave, Victoria is a knave, and Jackson is a knight.
(1) David is a knave
(2) Michael is a knight
(3) Luke is a knave
(4) Evelyn is a knave
(5) Victoria is a knave
(6) Jackson is a knight
Assume David is a knight. No contradiction is found in their claim that Luke is not a knave. Luke cannot be a knight, because this would contradict the claim of their own that Evelyn is a knave if and only if Evelyn is a knight. Luke cannot be a knave, because this would contradict the claim of David that Luke is not a knave. We have exhausted all possibilities for Luke, so let us go back and reconsider David. Assume David is a knave. No contradiction is found in their false claim that Luke is not a knave. Luke cannot be a knight, because this would contradict the false claim of David that Luke is not a knave. Assume Luke is a knave. No contradiction is found in their false claim that Evelyn is a knave if and only if Evelyn is a knight. Assume Evelyn is a knight. No contradiction is found in their claim that Victoria is a knave if and only if Jackson is a knave. Assume Victoria is a knight. No contradiction is found in their claim that Jackson is not a knight. Jackson cannot be a knight, because this would contradict the claim of Victoria that Jackson is not a knight. Jackson cannot be a knave, because this would contradict the claim of Evelyn that Victoria is a knave if and only if Jackson is a knave. We have exhausted all possibilities for Jackson, so let us go back and reconsider Victoria. Assume Victoria is a knave. No contradiction is found in their false claim that Jackson is not a knight. Jackson cannot be a knight, because this would contradict the claim of Evelyn that Victoria is a knave if and only if Jackson is a knave. Jackson cannot be a knave, because this would contradict the false claim of Victoria that Jackson is not a knight. We have exhausted all possibilities for Jackson and Victoria, so let us go back and reconsider Evelyn. Assume Evelyn is a knave. No contradiction is found in their false claim that Victoria is a knave if and only if Jackson is a knave. Assume Victoria is a knight. No contradiction is found in their claim that Jackson is not a knight. Jackson cannot be a knight, because this would contradict the false claim of Evelyn that Victoria is a knave if and only if Jackson is a knave. Jackson cannot be a knave, because this would contradict the false claim of their own that If David is a knight then Luke is a knave. We have exhausted all possibilities for Jackson, so let us go back and reconsider Victoria. Assume Victoria is a knave. No contradiction is found in their false claim that Jackson is not a knight. Assume Jackson is a knight. No contradiction is found in their claim that If David is a knight then Luke is a knave. Assume Michael is a knight. No contradiction is found in their claim that Jackson is a knight.