 To see how the claim that the Turing Test is merely criterial for the ascription of intelligence differs from the logical behaviorist claim that the Turing Test provides logically sufficient conditions for the ascription of intelligence, it suffices to consider the question of whether it is nomically possible for there to be a “hand simulation” of a Turing Test program. Many people have supposed that there is good reason to deny that Blockhead is a nomic (or physical) possibility. For example, in The Physics of Immortality, Frank Tipler provides the following argument in defence of the claim that it is physically impossible to “hand simulate” a Turing-Test-passing program: