 The weaker form is sketched in a paper by Gerald Massey (1991). Massey suggests that ‘logic and mathematics … forfeited all claims to the honorific title sciences of necessary truth when they admitted Church’s thesis into their innersanctum’ (1991, 186). According to Church’s thesis , there is no algorithm that is more powerful than a Turing machine. Or, put differently, every function that is computable at all, is computable on a Turing machine. This thesis is presupposed in establishing very fundamental logical results. It is used, for example in order to prove Church’s theorem which says that there is no algorithmic decision procedure for first-order logic. Yet Church’s thesis is a mere hypothesis, and a hypothesis that cannot be proven true. This is because the notion of algorithm is not precisely definable; there is no limit to the variety that an algorithmic routine might assume. Thus Church’s thesis may indeed be false: someone might eventually come up with an algorithm that computes some definite function f that no Turing machine can compute (Jeffrey 1989, 132; Massey 1991, 186).