 The key idea is that machines can only do what we know how to order them to do (or that machines can never do anything really new, or anything that would take us by surprise). As Turing says, one way to respond to these challenges is to ask whether we can ever do anything “really new.” Suppose, for instance, that the world is deterministic, so that everything that we do is fully determined by the laws of nature and the boundary conditions of the universe. There is a sense in which nothing “really new” happens in a deterministic universe—though, of course, the universe’s being deterministic would be entirely compatible with our being surprised by events that occur within it. Moreover—as Turing goes on to point out—there are many ways in which even digital computers do things that take us by surprise; more needs to be said to make clear exactly what the nature of this suggestion is. (Yes, we might suppose, digital computers are “constrained” by their programs: they can’t do anything that is not permitted by the programs that they have. But human beings are “constrained” by their biology and their genetic inheritance in what might be argued to be just the same kind of way: they can’t do anything that is not permitted by the biology and genetic inheritance that they have. If a program were sufficiently complex—and if the processor(s) on which it ran were sufficiently fast—then it is not easy to say whether the kinds of “constraints” that would remain would necessarily differ in kind from the kinds of constraints that are imposed by biology and genetic inheritance.)