In mathematical logic, the FriedbergâMuchnik theorem is a theorem about Turing reductions that was proven independently by Albert Muchnik and Richard Friedberg in the middle of the 1950s. [1] [2] It is a more general view of the KleeneâPost theorem. The KleeneâPost theorem states that there exist incomparable languages A and B below K. The FriedbergâMuchnik theorem states that there exist incomparable, computably enumerable languages A and B. Incomparable meaning that there does not exist a Turing reduction from A to B or a Turing reduction from B to A. It is notable for its use of the priority finite injury approach. [3]