An interesting piece in Aeon by David Deutsch. There was a shorter version in the Guardian, but it just goes to show how even reasonably intelligent editing can mess up a piece. There were several bits in the Guardian version where I was thinking to myself: ooh, he’s missed the point a bit there, he doesn’t really get that: but on reading the full version I found those very points were ones he actually understood very well. In fact he talks a lot of sense and has some real insights.
Not that everything is perfect. Deutsch quite reasonably says that AGI, artificial general intelligence, machines that think like people, must surely be possible. We could establish that by merely pointing out that if the brain does it, then it seems natural that a machine must be able to do it: but Deutsch invokes the universality of computation, something he says he proved in the 1980s. I can’t claim to understand all this in great detail, but I think what he proved was the universality in principle of quantum computation: but the notion of computation used was avowedly broader than Turing computation. So it’s odd that he goes on to credit Babbage with discovering the idea, as a conjecture, and Turing with fully understanding it. He says of Turing:
He concluded that a computer program whose repertoire included all the distinctive attributes of the human brain — feelings, free will, consciousness and all — could be written.
That seems too sweeping to me: it’s not unlikely that Turing did believe those things, but they go far beyond his rather cautious published claims, something we were sort of talking about last time.
I’m not sure I fully grasp what people mean when they talk about the universality of computation. It seems to be that they mean any given physical state of affairs can be adequately reproduced, or at any rate emulated to any required degree of fidelity, by computational processes. This is probably true: what it perhaps overlooks is that for many commonplace entities there is no satisfactory physical description. I’m not talking about esoteric items here: think of a vehicle, or to be Wittgensteinian, a game. Being able to specify things in fine detail, down to the last atom, is simply no use in either case. There’s no set of descriptions of atom placement that defines all possible vehicles (virtually anything can be a vehicle) and certainly none for all possible games, which given the fogginess of the idea, could easily correspond with any physical state of affairs. These items are defined on a different level of description, in particular one where purposes and meanings exist and are relevant. So unless I’ve misunderstood, the claimed universality is not as universal as we might have thought.
However, Deutsch goes on to suggest, and quite rightly, I think, that what programmed AIs currently lack is a capacity for creative thought. Endowing them with this, he thinks, will require a philosophical breakthrough. At the moment he believes we still tend to believe that new insights come from induction; whereas ever since Hume there has been a problem over induction, and no-one knows how to write an algorithm which can produce genuine and reliable new inductions.
Deutsch unexpectedly believes that Popperian epistemology has the solution, but has been overlooked. Popper, of course, took the view that scientific method was not about proving a theory but about failing to disprove one: so long as your hypotheses withstood all attempts to prove them false (and so long as they were not cast in cheating ways that made them unfalsifiable) you were entitled to hang on to them.
Maybe this helps to defer the reckoning so far as induction is concerned: it sort of kicks the can down the road indefinitely. The problem, I think, is that the Popperian still has to be able to identify which hypotheses to adopt in the first place; there’s a very large if not infinite choice of possible ones for any given set of circumstances.
I think the answer is recognition: I think recognition is the basic faculty underlying nearly all of human thought. We just recognise that certain inductions, and certain events are that might be cases of cause and effect are sound examples: and our creative thought is very largely powered by recognising aspects of the world we hadn’t spotted before.
The snag is, in my view, that recognition is unformalisable and anomic – lacking in rules. I have a kind of proof of this. In order to apply rules, we have to be able to identify the entities to which the rules should be applied. This identification is a matter of recognising the entities. But recognition cannot itself be based on rules, because that would then require us to identify the entities to which those rules applied – and we’d be caught in a in a vicious circle.
It seems to follow that if no rules can be given for recognition, no algorithm can be constructed either, and so one of the basic elements of thought is just not susceptible to computation. Whether quantum computation is better at this sort of thing than Turing computation is a question I’m not competent to judge, but I’d be surprised if the idea of rule-free algorithms could be shown to make sense for any conception of computation.
So that might be why AGI has not come along very quickly. Deutsch may be right that we need a philosophical breakthrough, although one has to have doubts about whether the philosophers look likely to supply it: perhaps it might be one of those things where the practicalities come first and then the high theory is gradually constructed after the fact. At any rate Deutsch’s piece is a very interesting one, and I think many of his points are good. Perhaps if there were a book-length version I’d find that I actually agree with him completely…