1. Philosophy 4610 Philosophy of Mind Week 8: Can a Computer Think?

2. Turing and Computers  Alan Turing (1912-1954)  During World War II, Turing’s work on code-breaking was instrumental in breaking the “Enigma” code used by the German and Japanese armies  Because of this work, Turing has been called the single figure most responsible for the Allied victory in the war.

3. Turing and the Enigma  The enigma machine used a series of rotors to encode any message in a way that depended on the particular settings for that day  Turing’s task was to find a way to decode a coded message using only guesses about some of the words likely to appear in it

4.  To solve the problem, Turing’s team developed a massively complicated machine called the “Bombe” that eventually succeeded in breaking the enigma code  Although this machine was very complicated, it was not a computer in the modern sense because it had only one, fixed program.

5. Turing’s Prediction (1950)  “I believe that at the end of the century the use of words and general educated opinion will have altered so much that one will be able to speak of machines thinking without expecting to be contradicted …”

6. Computer thinking and Artificial Intelligence  Turing’s prediction from 1950 inaugurated the field of artificial intelligence. In this field, researchers are trying to build a computer or artificial system that could actually think or be intelligent.  How might we define “thinking”? “Intelligence”?  Does Turing’s prediction hold true? If it does not already, when will it hold true?

7. Artificial Intelligence: What are the Bounds?  Since 1950, tasks once thought possible only for human beings have again and again been accomplished by computers.  Are there limits to this progress? Is there anything that humans can do that computers or machines never will be able to?

8. Turing: The “Turing Test”  Turing considers the question: “Can Computers Think?”  But this question is unclear and difficult to answer. Turing suggests replacing it with another question, which he puts in the form of an “imitation game” or “test”

9. The Turing Test  A judge is connected to two subjects by teletype machine  One of the subjects is a machine and the other is a person: the judge doesn’t know which is which  If the machine can fool the judge into believing it is a person, it is actually thinking.

10. The Turing Test  “I believe that in about fifty years' time it will be possible to programme computers, with a storage capacity of about 10 9, to make them play the imitation game so well that an average interrogator will not have more than 70 per cent chance of making the right identification after five minutes of questioning.” (p. 4)  Do we agree with Turing? If a computer can pass the Turing test 70% of the time, is it actually thinking?

11. The Turing Test: Questions and Objections  Is there anything essential that a human being can do that a computer could never do? Why?  Even if a computer can pass a Turing test, how do we know it is really thinking as opposed to imitating or simulating thought?  If the Turing test is not a good test for actual thinking, is there any better test?

12. Computer Thinking: Objections 1) The Theological Objection: “Thinking is a function of man’s immortal soul. God has given an immortal soul to every man and woman, but not to any other animal or to machines. Hence no animal or machine can think.” (p. 5) Response: 1) If God can create bodies and attach souls to them, he could also attach souls to computers 2) Theological arguments are unsatisfactory for establishing scientific conclusions

13. Computer Thinking: Objections 2) The “Heads in the Sand” Objection: “The consequences of machines thinking would be too dreadful. Let’s hope and believe that they cannot do so.” (p. 6) Response: This is not really an argument at all, but just an appeal for consolation.

14. Computer Thinking: Objections 4) The Argument from Consciousness: “No machine could feel (and not merely artificially signal...) pleasure at its successes, grief when its valves fuse, be warmed by flattery, be made miserable by its mistakes, be charmed by sex, be angry or depressed when it cannot get what it wants.” (Geoffery Jefferson, 1949 (P. 6)) Response: If it is impossible to know that a machine is really conscious judging from its responses, then it is impossible to know whether any other person is really conscious as well. If the Turing test could not show that a computer is really thinking, then it is impossible for me to show that anyone else (other than myself) is really thinking.

15. Computer Thinking: Objections 5) Arguments from Various Disabilities: No computer could ever do X (where X is, e.g. “Be kind, resourceful, beautiful, friendly, have initiative, have a sense of humour, tell right from wrong, make mistakes, fall in love, enjoy strawberries and cream, make some one fall in love with it, learn from experience, use words properly, be the subject of its own thought, have as much diversity of behaviour as a man, do something really new.” (p. 8) Response: Various, but all of these seem to be based on a bad extrapolation from what we have seen before. Some of the computers we have seen cannot do these things, but that is no reason to think we could not eventually build a computer that can.

16. Computer Thinking: Objections 6) Lady Lovelace’s Objection: Computers only do what they are programmed to do, so it is impossible for a computer ever to learn something new or do something unexpected Response: Computers do “new” and surprising things all the time. It is also easily possible for us to set up a mechanism whereby a computer can modify its own program, and thereby can be said to have “learned.”

17. Computer Thinking: Minds and Machines  “The ‘skin-of-an-onion analogy is also helpful. In considering the functions of the mind or brain we find certain operations which we can explain in purely mechanical terms. This we say does not correspond to the real mind: it is a sort of skin which we must strip off to find the real mind. But then in what remains we find a further skin to be stripped off, and so on. Proceeding in this way do we ever come to the ‘real’ mind, or do we eventually come to the skin which has nothing in it? In the latter case the mind is mechanical.” (Turing, p. 12)

18. Computer Thinking: Summary  Turing suggested that computers could think and he suggested the Turing test to determine whether they can think.  If we accept the test, it will be difficult to hold onto a dualist or theological view of human consciousness  On the other hand, it is not obvious how to explain consciousness or the possibility of a physical organism giving rise to experience at all