Alan Turing

• Born 1912, an Englishman, often called the father of digital computing and artificial intelligence.
• One of the most prominent allied code breakers in WWII.
• Pioneered many early computing techniques.
• Was convicted of homosexuality in 1952, committed suicide at the age of 41 in 1954 under the influence of the chemical castration medications that he was courtordered to take.
• In 2009, the British gov’t issued a formal apology to Turing.

• What is at stake here is a claim about what is possible in principle rather than what is currently the case or what may or may not be the case soon.
• Turing proposes a test which (he claims) would provide us with reason to say that any machine that passed it would be a thinking thing.

• Turing proposes that the machine play an imitation game. The machine is in one room, and a human is in another. The judges get to ask questions by means of something like text messages or IM. The machine’s responses to questions are supposed to be able to be such that the judges aren’t able to tell the difference between the machine and the human more than half the time.

• The kinds of “machines” that are disallowed from the competition include:
– Humans born in the usual way
– Clones of humans
– Humans made in something other than the usual way
• The difficulty is in making a rule about the kinds of machines disallowed that provides a definition of ‘machine’ that doesn’t include people (Recall the problems of vagueness that are intrinsic to language).

• While Turing does not use this word, this is the term that philosophers have applied to the kind of position that
Turing holds.
• Functionalism is a school of thought that is above all committed to multiple realizability.
• Multiple realizability is the idea that the same functions can be realized by multiple physical setups. Consider a vacuum tube radio versus a solid state radio or a digital versus an analog watch.
• According to the functionalist in this context, thinking is something that can be done by persons as well as
(someday) machines.
• So Turing’s Test is supposed to determine whether some given machine is the functional equivalent of a human mind.

• Be sure to consider which of these Searle subscribes to and which he does not, and keep track of how Turing answers them.
– Theological Argument
– The “Heads in the Sand” Objection
– The Mathematical Objection
– The Argument from Consciousness
– Arguments from various disabilities
– Lady Lovelace's Objection
– Argument from Continuity in the Nervous System
– Argument from Informality of Behavior

• Turing is not generally impressed with theological arguments, but argues that the second premise below is dubious (God can do whatever God wants)
• The argument looks something like:
– Thinking requires a soul
– Mechanical things cannot have souls
– .: Mechanical things cannot think

• This is an objection that many hold but that does not survive much scrutiny.
• Turing does not specifically refute this objection aside from pointing out that no valid argument follows from this view:
– It would be scary if computers could think
– .: computers cannot think

• Goedel’s incompleteness theorems show that no axiomatic system is self-proving (at least on axiom must always be assumed)
• This is a limitation on any discrete state machine (what remains to be shown is that such a limitation does not apply to humans)
• Turing points out that while the proponents of the prior two objections would not be interested in ANY proposed criteria for machine intelligence, while the proponent of this argument might entertain the Turing Test.

• In order to be thinking, a being must be
“conscious” where consciousness requires some form of self-awareness.
• Turing Responds:
– In that case the only way to perform an adequate test would be to BE the machine and see if you’re conscious, which applies not only to machines but other people, too. (leads to solipsism)
– If a behavioral test is allowed though, it seems the
Turing Test could well satisfy this condition (see example p. 530)

• Machines could never X (list of examples p. 530), and various forms of thinking are presumably on the list.
• This springs from a set of inductive generalizations (all machines encountered so far are “ugly, designed for a limited purpose, when required for a different purpose they are useless, the variety of behaviors of any one of them are small, etc.)
• Such generalizations (because they are inductive) do not preclude any exceptions to them.

• Thinking requires either 1) indeterminism or 2) originality.
• Turing Responds:
– 1) if indeterminism violates some law of nature, then it remains to be shown how humans violate those laws of nature
– 2) the Turing test would establish if machines could ever “surprise us”.

• This is a rather sophisticated objection.
– The human nervous system is not a discrete state machine
– No discrete state machine can mimic human nervous structures
– .: Since computers are discrete state machines, no computer can mimic human nervous structures.
• Turing points out that any discrete state machine can approximate the output of a non-discrete state machine
(like a differential analyzer) such that nobody could tell the difference only from the output. This is the point of the Turing Test; it falsifies p2 above.

• Turing summarizes the argument: “If each man had a definite set of rules of conduct by which he regulated his life he would be no better than a machine. But there are no such rules, so men cannot be machines”
• Convert this to categorical form and:
– All those with definite rules of conduct are machines
– No men are those with definite rules of conduct
– .: No men are machines

• Turing points out that the above argument is invalid due to an undistributed middle term.
• In any case, If one substitutes “laws of behavior” for “principles of conduct” the argument comes out alright, and must either show that there are no such laws of behavior for humans or that human are (at some level) machines.
• Turing points out that there can be no basis for concluding that there are no laws of behavior.

• Turning concedes that programming something to be able to pass the Turing test “out of the box” may not be the most likely approach. Instead building something with an ability to learn and teaching it like a human child might be more effective.

• Turing’s argumentative approach has two parts:
1. Present a positive account of what criteria are sufficient for thinking
2. Defend the idea that machines could be thinking things against a set of general principles that would exclude machines from the category of thinking things.