 Heuristically, one may view the Gödel sentence \(G_F\) as expressing its own unprovability—saying “I am not provable”—though, as was already emphasized, such claims should be taken with a grain of salt. Leon Henkin put forward the question whether the sentence expressing its own provability (“I am provable”) is true or false, and provable or not (Henkin 1952). Georg Kreisel soon pointed out that this depends vitally on how provability is expressed; with different choices, one gets opposite answers (Kreisel 1953). 