 Turing argued that, given his various assumptions about human computers, the work of any human computer can be taken over by a Turing machine. Whatever sequence the human computer is computing, a Turing machine “can be constructed to compute the same sequence”, Turing said (1936: 77). Therefore (argument I concludes) any humanly computable number—or, more generally, sequence of symbols—is also computable by Turing machine.