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Extracto de una entrevista con Sir Roger Penrose , Gresham Professor of Geometry en Londres, matemático y físico mundialmente conocido, autor de "La mente del Emperador", "La nueva mente del Emperador", "Sombras en la mente" y -aparecerá en el año 2002- "Camino a la realidad". Presentamos aquí una parte de la entrevista aparecida en el número de marzo 2001, de la Newsletter de la European Mathematical Society, realizada por Oscar Garcia-Prada.

In 1989 you published a best-selling book, "The Emperor"s New Mind". Where you"re concerned with computers and artificial intelligence, the mind, the laws of physics, and many other things. What is the central question you address in this book?

I think I mentioned earlier that I had formulated a certain view while I was a graduate student. Before that, I"d been quite sympathetic to the idea that we were all computers, but it seemed to me that Godel"s theorem tells us that there are aspects of our understanding which you cannot encompass in a computational picture. Nevertheless, I still maintain a scientific viewpoint that something in the laws of physics allows us to behave the way we do, but that the laws of physics are much deeper. My view is that we know much less about them than many people would maintain.

So I was quite prepared to believe that there was something outside computation. I"ve been interested in mathematical logic for a long time, and I"d known for a long time that there are things of a mathematical nature that are outside computation; that didn"t frighten me - it just seemed to me "all right, why not?" Then I saw a television programme where Marvin Minsky, Edward Fredkin and others were making outrageous statements about how computers were going to exceed everything we could do. What they were saying was logical if we were indeed computers - but since I didn"t believe that, it seemed to me that this was something they"d completely missed - and not only they had missed it, I"d never seen it anywhere else. So as I"d previously considered writing a popular or semi-popular book on physics - something I thought I"d do at some stage in life, but perhaps not until I retired - this provided an opportunity: `All right, let"s explain things about physics and what the world is like, as far as we know, but with a different focus: let"s explore the laws of physics to see whether there"s scope for something of a non-computational character". I"d never seen anybody put this forward as a serious viewpoint. Since it seemed to me that it needed to be put forward, that"s what I did.

So this was an attack on artificial intelligence; but you also questioned the fact that as quantum mechanics is incomplete, the understanding of physical laws has to precede understanding the functioning of the mind?

Yes, I"d felt that if there was something non-computational it needed to be outside the laws that we presently understand in physics, because they seem to have this computational character. And it also seemed to me that the biggest gap in our understanding is when quantum theory relates to large-scale objects, where the rules of quantum mechanics Live us non sense - they tell us that cats can be alive and dead at the same time, and so on, which is nonsense; we don"t see our world like that. Yet quantum theory was supposed to be so absolutely accurate, so why are we not aware of the manifestations of that theory on a large scale? It seemed to me that the theory can"t be quite accurate and that there must be some changes that take place when it gets involved with large-scale objects.

I think I"d already thought this was to do with when gravitational phenomena start to become entangled with quantum effects - that"s when the changes start to appear, and there are good reasons for believing that. So that is what I believed at the time, and still believe; but when writing The Emperor"s New Mind I didn"t really have any clear idea where in brain function quantum effects could start to become important and have an influence on large-scale effects, and where these new physical processes that should be noncomputable could come in.

So I started writing the book, expecting that by the time I"d finished I"d have some clearer ideas on this. This happened to some degree - I was very ignorant about lots of things to do with the brain when I started, and I had to study to write the chapters specifically on them, and in particular the idea of `brain plasticity", that the connections between neurons can change and that these changes can take place quickly - it seemed to me that this was very important, and that the new physics comes in to regulate these changes.

So has this given you any clue as to what changes are needed in quantum mechanics? A little, but the physical motivations are largely independent. I did, however, think about the needed changes in quantum mechanics a little more seriously than before and I changed my views between writing the two books.

You"re now referring to your second book `Shadows of the Mind". Do you pursue the same problems in this book?

Yes, but Shadows of the Mind had slightly ambivalent purposes. Originally I started to write it to address some of the points that arose out of people"s criticisms and misunderstandings of The Emperor"s New Mind, and in particular my treatment of Gödel"s theorem. I just didn"t expect the kind of vehement response that I got. I was very naive, perhaps. I didn"t realise that people would feel attacked in the way they did and would therefore respond by attacking me, while misunderstanding a lot of what I was trying to say.

The main point that I was making about Gödel"s theorem was that if you have a system which you believe in and which you believe might be usable as mathematical proof, then you can produce a statement which lies beyond the scope of the system, but which you must also believe in. Now there is an assumption here that the system is consistent, something which I didn"t bother to stress particularly, because it seemed to me quite obvious that there"s no point in using the system if you don"t think it"s consistent: the proof is no proof if it"s in a system you don"t thoroughly believe in and therefore don"t trust its consistency. That seemed to me to be obvious, but I didn"t make those points strongly and so there are loopholes that people could point to, which of course they did. So I felt it necessary to address these issues with a great deal more care in Shadows. It was not meant to be a particularly long or popular book; it was just addressing these points and was quite technical and complicated in places, but in the process of writing this book, two things happened.

One of them was that I received a letter from Stuart Hameroff telling me about the cytoskeleton whose structures inside cells I was totally ignorant of: But most people who work in artificial intelligence didn"t seem to know about them either; Marvin Minsky didn"t, as he told me afterwards. But it seemed to me that here was a completely new area for which it was much more plausible that quantum effects could be important. They are much smaller structures than neurons and are much more tightly organised structures. The most relevant of these were microtubules, where one has a much more believable place for coherent quantum phenomena to take place. It is still hard to see how this takes place, because it is dif ficult to maintain quantum coherence on the large scale that one needs in order for these ideas to work. One needs to go beyond what can be done in any physics lab today, and there is no physical experiment performed today that can achieve the kind of quantum coherence at the level that I would need in order for the kind of phenomena to take place that I suspect are taking place all the time in our brains. So nature has been a lot cleverer than physics has been able to be so far, but why not? It seems to me quite plausible that this is the case. The cytoskeleton, and in particular microtubules, seem to me to be structures where quantum coherence is much more plausible. So I changed the nature of this book. I wanted to put in microtubules and the cytoskeleton, and so I needed to learn a little bit more about it and to express why I think that"s important in brain action.

The other thing which happened was that I somewhat shifted my viewpoint on quantum state reduction, in relation to gravity. The viewpoint I"d held for quite a long time, and which is expressed in The Emperor"s New Mind, is more or less that if you have too big a discrepancy between two states, then they don"t superpose and the state reduces. This discrepancy is to be measured in terms of space-time geometry; I called it the one graviton criterion. It is to do with how many gravitons come into this difference between the two states.

Now in work that I did subsequently, and also in work that had been done by others (particularly Diósi, a Hungarian, and Ghirardi in Italy) who had developed different ideas in connection with quantum state reduction, it seemed to me that I needed to modify the view that I had before. I think it"s quite a significant modification. Basically, when you have two states that are significantly different from each other, then their superposition becomes unstable, and there is a calculable time scale involved in how long it takes for the superposition to "decay" to one state or the other. The details are probably a bit too technical for here, but there is a time scale, rather than an instantaneous reduction, and this time scale produces figures that are much more plausible - also, it is easier to use and it may be much more relevant to brain action.

One can see how to use it, and these ideas I developed with Stuart Hameroff. We produced a number of suggestions about how this idea could be carried forward, but again we found a great deal of opposition. A lot of these ideas are clearly speculative, but I don"t think it is that speculative that something like this is going on. It seems to me it has got to be. Consciousness seems to be such a different phenomenon from the other things we see in the physical world that it"s got to be something very special, in physical organisation. I can"t see that it"s really just the same old physics put together in more complicated systems. It"s got to be something of quite a different character from other things that are important in the way the world operates. This new physics would be only occasionally employed in a useful way, and you have to have a very careful organisation that takes advantage of whatever is going on in state reduction and channels it in a direction which makes us operate. But it is very rarely actually taken advantage of in physical systems, where most things don"t use this phenomenon in any useful way at all.

In these books you reveal yourself to be a philosopher. How have you come to terms with the Great Mystery?

Well, there are lots of hugely unanswered questions - there"s no doubt about that. I"d certainly want to emphasize that even if everything that Stuart Hameroff and I say turns out to be absolutely correct, it would not answer these questions. I hope we are moving a little in the right direction towards answering those questions. However, I think there"s very little progress towards answering the deep questions of what is going on in mentality, who we are, what is consciousness, why are we here and why does the universe allow beings who can be aware, or is there life after death? Any questions of that nature seem to me to require us to know more about what the world is like - we really know very little.

People say, and physicists often say: we nearly have the solution to the grand theory of the universe which is just around the corner, the theory of everything. I simply just don"t believe that. I think there are major areas of which we have almost no understanding at all, and it"s quite curious that one can have a view which seems to encompass (at least in principle) most of the things that you see around you, why they behave this way and that way.

One of the major things that isn"t explained is simply ignored and just swept under the carpet by physicists generally, which is quantum state reduction. They say: quantum theory is a beautiful theory; it works perfectly well and describes how tiny particles behave. But, to put it bluntly, it gives you the wrong answer. What the theory tells us is that, for example, if you had Schrödinger"s famous cat, the cat could very easily be put into a state of being alive and dead simultaneously. That"s simply wrong; it doesn"t do that. So what is it? I mean, there is something big missing from our view of the world, it"s huge and it"s not just a tiny phenomenon which we haven"t quite got because we"ve got to get the last decimal place right and the coupling constant or something: it"s a huge aspect of the way the world behaves which we simply do not understand, and understanding it is, in my view, one small step towards understanding what mentality is. I think it must be part of it, but it is not going to answer the question of mentality. We may well know what state reduction is (and I expect we will know if we don"t destroy ourselves first); then that theory will have as part of its nature some completely different way of looking at the world from the way we have now. We"ve already seen that happen in Einstein"s general relativity, because before that we had Newton"s theory which told us how bodies attracted each other with forces and moved around and so on. It"s beautifully accurate: Newton"s theory is incredibly precise. It tells you how the planets move around in their orbits to almost complete precision - not quite, but almost. You might think it only requires a little tiny modification to that changes our whole outlook. Now what I am saying is that when we see how quantum theory is to be changed to accommodate state reduction as a phenomenon, with the measurement process as a phenomenon, we shall have to come to terms with a completely different way of looking at what matter is and what the world is like.

Are you saying that this is a step that will help us to address questions that are typically addressed, by some people at least, by religion?

Well it will, I think so. But you see I"m more... `tolerant" isn"t quite the right word ... I think I"m a little bit more supportive of religious viewpoints than many totally scientific people would be. It"s not that I believe in the dogma that is attached to any of the established religions, because I don"t. On the other hand, religions are trying to address questions which are not addressed by science, particularly moral issues. I regard morality as something with an absolute `platonic" component which is outside us. Is there really a platonic absolute notion of "the good"? I have to say I"m inclined somewhat in that direction. I think morality is not just man made, but there are things outside us which we have nothing in the way of scientific understanding of at the moment, but nevertheless they are part of a big overall picture which maybe someday will come together. So I mean these questions are nowadays considered not to be part of science, but they"re part of religion, you see. Well, as I say, I don"t believe in the dogma of religion, but I do think that religion is groping for something which we don"t know the answers to yet, and which is outside traditional science. So I suppose what I think is that the whole scientific enterprise must broaden its scope and eventually make it completely right, but that"s not what happened. Einstein produced a theory that is completely different. Its structure is utterly different from that of Newton"s theory, but it gives almost exactly the same answers. The philosophical framework of that theory is quite different. The very nature of space is warped, and ally change its character.


Director de Revistas: Javier Martínez Cortés
Editor-Coordinador:Antonio Orozco Delclós


28/07/2005 ir arriba
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