Part 9 of Turing: a natural philosopher (1997)
Of God and Extra-Sensory PerceptionCourtroom imagery runs through the paper: not only is the Turing Test an interrogation, but Turing puts himself in the dock and answers objections to his thesis. The objections differ considerably in how seriously they are set up and taken. After a sally at 'Heads in the Sand' objectors, Turing enunciates:
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.This is not an objection made or answered with seriousness, but used to make fun of Christianity, with a reference to Galileo's heresy as an analogy to his own. He wrote as he spoke: a proud atheist, in the habit of anti-church remarks. A more serious response might have been aimed not just at religious dogma, but at the more general assertions made by moral philosophy that human beings have properties (e.g. responsibility, authority) that other objects are unable to possess. As it stands, the paragraph might amuse those who already shared his views, it would convince no-one who did not. However there is a serious germ in his debating society point, made to dispose of this objection, that God could give a machine a soul. From the operational viewpoint adopted, Turing need not argue about whether or not people have 'souls'; he need only address what can be observed.
Although rooted in intellectual integrity, there is an unattractive facile gloss in Turing's dismissal of such questions. In the aftermath of the Second World War there were good reasons for anxiety about treating people as machines. In his personal attitudes Turing was fierce for liberty and honesty, qualities hard to fit into the setting of the imitation game. But ad hominem questions cause one to ask: what words of moral discourse could have been appropriate from an innocent valiant-for-truth who had lent a mastermind to the defeat of Nazism, but could never breathe a word of it? His frivolity had its own moral seriousness, the washing of hands from the evil of the 1940s. Like others of the early 1950s, Turing was impatient to see the future, having defeated Hitler's attempt to destroy it. And with its references to the place of women in Islamic theology, the cloning of human beings, and the question of animals' consciousness, one cannot accuse Turing's paper of lacking foresight for moral issues.
I now turn to the strangest passage in all Turing's writing.
The Argument from Extra-Sensory Perception. I assume that the reader is familiar with the idea of extra-sensory perception, and the meaning of the four items of it, viz. telepathy, clairvoyance, precognition and psycho-kinesis. These disturbing phenomena seem to deny all our usual scientific ideas. How we should like to discredit them! Unforunately the statistical evidence, at least for telepathy, is overwhelming. It is very difficult to rearrange one's ideas so as to fit these new facts in. Once one has accepted them it does not seem a very big step to believe in ghosts and bogies. The idea that our bodies move simply according to the known laws of physics, together with some others not yet discovered but somewhat similar, would be one of the first to go.It is not clear how serious the statements are. The exclamation mark suggests irony, the 'overwhelming' evidence sounds literal. On balance it appears he was at that time convinced by contemporary claims for observing E.S.P. There are no other passages on E.S.P. in Turing's writing or letters, although his interest in dreams and strange events was sharp. In 1930 he had a presentiment of Chistopher Morcom's death at the very moment he was taken ill, and he later wrote, 'It is not difficult to explain these things away — but, I wonder!' He wondered; it was natural wonder.
There is a point made here, though left elliptical, of more general significance: namely that the discrete state machine model rests upon the brain's operation according to 'known laws of physics, together with some others not yet discovered but somewhat similar'; we shall return to this question.
The problem of consciousnessTuring now addressed:
The Argument from Consciousness: This argument is very well expressed in Professor Jefferson's Lister Oration for 1949, from which I quote. 'Not until a machine can write a sonnet or compose a concerto because of thoughts and emotions felt, and not by the chance fall of symbols, could we agree that machine equals brain — that is, not only write it but know that it had written it. No mechanism could feel (and not merely signal, an easy contrivance) 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.' This argument appears to be a denial of the validity of our test. According to the most extreme form of this view the only way by which one could be sure that a machine thinks is to be the machine and to feel oneself thinking. One could then describe these feelings to the world, but of course no one would be justified in taking any notice. Likewise according to this view the only way to know that a man thinks is to be that particular man. It is in fact the solipsist point of view.
Jefferson's central objection is that of commonsense repugnance to the idea of machines being credited with thought; and its burden is similar to John Searle's claim of the machine lacking human 'intentionality'. It is of interest, even if anachronistic, to guess Turing's answer to Searle's parable of the Chinese Room, itself a sort of riposte to the drama of the imitation game. Searle supposes (1) That there is an algorithm for translating Chinese to English (2) That this algorithm is effected not by a machine but by one or many people in a room, working mindlessly. Then the Chinese is translated; but none of the translators has the faintest knowledge or understanding: a paradox. Turing's thesis is, I believe, that this if achieved would be no paradox at all, merely a dramatisation of the true state of affairs. It would reflect the mechanism of the brain, where the neurons have no understanding individually, but somehow the system as a whole seems to; and that appearance is all that matters. One might go further: the situation in Bletchley Park was uncannily like the Chinese Room, since for reasons of secrecy people were trained to perform the cryptanalytic algorithms without knowing their purpose. Perhaps this very sight, of good judgment emerging from mindless calculation, was what positively inspired Turing to the picture of mechanical intelligence in about 1941. The drift of Turing's views is that the definiteness of consciousness is an illusion, a quality emerging from and ultimately to be explained by great complexity. His approach would not accept 'intentionality' as any better an explanation than 'soul'. For a materialist such words are a restatement of the problem, perhaps the greatest problem of science, and not an answer to it.
At this point it is appropriate to introduce the ideas of Roger Penrose, who shares the materialist dissatisfaction with explanations through souls or intentionality, but holds consciousness to be an undeniable fact. Penrose poses a physical question about consciousness, probably similar to what Turing had in mind when referring to a paradox in trying to localise it: is the intelligence supposed to emerge when the machine is run? If so, it is not the discrete state machine alone, but that plus its physical implementation. Or is intelligence present in the abstract table of behaviour? But if so, we could choose a notation where the number 42 encodes the table of behaviour of Einstein's brain; can 42 have Einstein's intelligence? As Turing says, his own presentation leaves such mysteries unresolved.
© 1997, Andrew Hodges.