I think it’s far simpler to realize that the meaning of “won’t figure out” is a bit ambiguous. The logic is sound that it won’t be a surprise on Friday, and given that, won’t be a surprise on Thursday, and given that, won’t be a surprise on Wednesday, etc. for all days. But it’s not a problem if you realize that there’s going to be a test anyway, it’s ONLY a lie about the conditions IF it happens on a Friday. The fact that it doesn’t happen on a friday allows the surprise to be consistent with the statement, WITHOUT any implication that every universe would be consistent with the statement.
The test-giver could have simply randomized among the 5 days. If it were Friday, they’d have lied about the conditions, but 80% of the time they’d have performed magic.
The test-taker can defeat it by predicting a day (psychologically, M-Th are best bets), and having a good chance of beating the game—the statement is “won’t figure out”, which is simply wrong if the taker DOES IT.
I think it’s far simpler to realize that the meaning of “won’t figure out” is a bit ambiguous. The logic is sound that it won’t be a surprise on Friday, and given that, won’t be a surprise on Thursday, and given that, won’t be a surprise on Wednesday, etc. for all days. But it’s not a problem if you realize that there’s going to be a test anyway, it’s ONLY a lie about the conditions IF it happens on a Friday. The fact that it doesn’t happen on a friday allows the surprise to be consistent with the statement, WITHOUT any implication that every universe would be consistent with the statement.
The test-giver could have simply randomized among the 5 days. If it were Friday, they’d have lied about the conditions, but 80% of the time they’d have performed magic.
The test-taker can defeat it by predicting a day (psychologically, M-Th are best bets), and having a good chance of beating the game—the statement is “won’t figure out”, which is simply wrong if the taker DOES IT.