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Roger Penrose Interview, Part 2

May 16, 2016     Time: 14:45
Roger Penrose Interview, Part 2


The great physicist and mathematician weighs in on what things actually exist, the Mind/Body Problem, and the Philosophy of Mathematics. Dr. Craig has lots to say about it!

Transcript Roger Penrose Interview Part 2


KEVIN HARRIS: Welcome back to Reasonable Faith with Dr. William Lane Craig. It is Kevin Harris. We are going to get into part two of this great interview with Roger Penrose[1] Coming up next he is talking about the great mysteries of life. He discussed mystery number one last time with Dr. Craig's comments.

Before we get to these other mysteries that Penrose discusses, don't forget about the new app that we have. The Reasonable Faith app now has live streaming. You can listen to Defenders and other events live when they are streamed with the new Reasonable Faith app. So get it. You can't do without it! Go to for more.

Here is part two of the interview with Roger Penrose. Dr. Penrose begins with mystery number two.

DR. PENROSE: Mystery number two is how is it that when you have physical structures of the right kind . . . and here I am referring very specifically to living human, wakeful, healthy brains, and probably many other animals I would say also have this quality of mentality. Somehow it is evoked when the structures have the right character whatever that is. So there is mentality that seems to have this deep relation to certain kinds of physical structures.

ROBERT KUHN: That's mystery number two.

DR. PENROSE: That's mystery number two.

DR. CRAIG: Here is the problem of mind-body dualism. How is it that the mind or the mental is coordinated with these physical structures like the brain? The question here would be whether theism can shed any light on this. I think this is still an area of open exploration and mystery, but what one can say is that the existence of such minds which are coordinated with brains in the world fits into a theistic world much better than it does fit into a naturalistic world because on theism ultimate reality is mental. There is a mind who has created the universe and who has created these physical structures. These finite minds are simply an imitation on a finite level of the ultimate mind that created the world. That doesn't solve the mystery, but I think it does say that this mind-body duality fits into a theistic world much better than it does into a non-theistic world because at least you've got ultimate reality being mind and creating the physical in a certain way.

KEVIN HARRIS: Is this where the argument from consciousness comes in?

DR. CRAIG: Right. This would be an argument from consciousness, intentionality, and so forth to say that there are minds and that this fits in better with a theistic view of the world than with a naturalistic view of the world.

DR. PENROSE: Mystery number three has to do with our access to the world of mathematics. Why it is a mystery is perhaps not so clear, but it is something that you certainly can't describe in terms of purely computational activity. There is something outside of that involved in our appreciation of mathematics. Even just knowing what the natural numbers are: 0, 1, 2, 3, 4 – I can say that. And you can explain that to a child perhaps on Sesame Street and different things and they get the idea. They know what they are talking about. They know what numbers are. But yet you can't characterize simply by axiomatic procedures what the natural numbers are. Theorems and logic can say that, yet how do you know what they are if you can't describe in a finite set of rules what these numbers are? There is a mystery there, too. That is mystery number three.

DR. CRAIG: This is known as the epistemological objection to Platonism, namely, if there really are these mathematical objects which are causally unrelated to us, existing beyond time and space as Penrose says, then how in the world do we know anything about them? How do we know arithmetic or complex mathematics? We have no causal connection with this realm of mathematical objects.[2] I know no more about them than I know about what is happening in some remote village in the Himalayas in Nepal right now. This is a very common objection to Platonism – it cannot explain how we know mathematical truth or know about this mathematical realm. Here, again, I think theism could help because it could say that God has created us with a sort of mathematical ability whereby we can grasp mathematical truth. Anti-realism would help, too, because on the anti-realist view you don't have a separate realm of causally inert abstract objects that you are trying to know. I think mathematical truths can be reduced to just logical truths or to make believe in fact. So I think this mystery three is a problem for the non-theistic Platonist.

DR. PENROSE: There is another feature about this which is that in each case it is only a small part of one world which encompasses seemingly the entirety of the next world. Only a little bit of mathematics – a very subtle, beauty, and powerful part of mathematics, but there is the whole world of mathematics . . . if you look at any pure mathematical journal it is full of things that have absolutely no relevance to physical activity. OK maybe the odd thing turns out to have, but most of it seems to have no relation to physical reality. That is not the point of it. You do it because you are interested in mathematics for its own sake. So it is a small part of the mathematical world which seems to encompass the behavior of the physical world. And it is a very small part of the physical world which seems to evoke mentality. There are far more rocks and things – dead planets – around then there are conscious brains around. It is only a very small part of that. It has to be organized in a very subtle and sophisticated way to give rise to mentality whatever that is. And it is only a small part of our mental activities which relate to mathematics. I think most non-mathematicians would appreciate that. But even mathematicians most of the time are thinking about other things. So it is only a small part of our mentality. I like to draw this picture almost in a paradoxical way. Each world is a small part of it which seems to encompass the next one as you go around.

ROBERT KUHN: Encompass the total of the other.

DR. PENROSE: OK, there are some prejudices of mine involved in drawing the picture that way, but it seems to give you a good view . . .

ROBERT KUHN: The typical scientific response to that would say the mental world is just an expression of the physical brain and so it is an artificial phenomena. It is not real. It is just something that is evoked by the physical brain. And mathematics is very nice but it is something that human beings have invented to sort of describe the physical world. So there really is only one world; the other two are kind of derivative or imaginary.

DR. PENROSE: You could take that view, or to a mathematician you might take the mathematical world somehow as the one because somehow it has to be there. It sort of creates itself out of nothing. And it has to be there, and physical reality you might think has its source in that. Or you might say, no, no, it is mentality – that's where all our knowledge comes.

DR. CRAIG: When he says that the mathematical realm is self-created, that shouldn't be taken literally. What he really means is that it is necessary in its being. It is necessary, timeless, and uncreated in fact. I think also you can't take seriously the idea that the physical world derives from this mathematical world because, as I've said, the mathematical realm is causally impotent. It can't cause anything. So you can't derive the physical world literally from the mathematical realm. I think we are seeing here the way in which theism better incorporates all three of these realms in a synoptic coherent worldview that apart from theism tends to fall apart.

DR. PENROSE: Everything ultimately has to do with our consciousness. Everything else is then explained in terms of it.

ROBERT KUHN: So each one of the worlds can feel its own predominance over the others.

DR. CRAIG: Here the suggestion is what is called idealism, and that is that the physical world (and I suppose the mathematical world) are derived from human minds. Again, on a human level that just seems fantastic.[3] As he said, mathematics applied and were true during the Jurassic period long before we got here. Grounding mathematics in human minds is not going to explain the necessity of mathematical truth since human beings are contingent. The idea that we somehow caused the physical world to come into existence before we got here would postulate a bizarre form of backward causation that just seems utterly bizarre. So the relation between these realms of reality is incoherent on a non-theistic worldview, it seems evident to me.

DR. PENROSE: I am trying to make it look a little more symmetrical and even-handed. To a mathematician, the mathematical world has a kind of reality out there. If you like, the reality of the mathematical world, the Platonic world, is an expression of the objectivity of mathematics. It is something outside any particular individual. Mathematicians strive for that. They don't often achieve it. You can get things wrong. You can only partially appreciate what's going on. Different mathematicians have different ways of appreciating these things. But there is outside of us something there which is beyond any individual mathematician, and beyond the totality of all mathematicians.

ROBERT KUHN: When you look at these three worlds, you are obviously doing it more than metaphor, but is it just as a description of reality or is there some sense of real independent existence?

DR. PENROSE: They are not independent because each one does have this relation to the next even though each relationship I regard as a mystery. Maybe we will understand these relationships better in the future. I don't necessarily regard this as a sort of ultimate picture. I think that in some sense they are different aspects of reality. The true reality in some sense encompasses the whole thing. In fact, I tend to draw the picture deliberately in a paradoxical way. If you look at this it has a sort of a feeling of one of these impossible triangles. That is deliberate.

ROBERT KUHN: Escher-like.

DR. PENROSE: Escher-like. It is deliberately impossible; there is another mystery hiding behind there which is how all three of these worlds can somehow coexist in some deeper reality that is not expressed really in that picture.

DR. CRAIG: Was that it?

KEVIN HARRIS: That's the end.

DR. CRAIG: That ending – the incoherence of the view admitted, Escher-like (these drawings where it appears you are going up the stairs with each staircase and then you are back where you started again), an incoherent view of reality unless there is a deeper mystery behind all three of these. This is fairly crying out for theism, it seems to me. This is a wonderful interview. I think it is beautifully explained – the different aspects of reality are beautifully delineated. I think it just cries out for theism to be complete.

KEVIN HARRIS: I think that some of these anti-philosophy scientists that are so popular today should take note with Roger Penrose. Because here is a scientist who reads philosophy and he has looked into Platonism and abstract objects and these things like that.

DR. CRAIG: You are absolutely right. I am listening to this as a philosopher and failing to appreciate that this is a mathematical physicist, not a philosopher. And it is a world apart from the sort of reductionistic physicalism of people like Hawking, Krauss, Mlodinow, Dawkins, and the rest. I think you are absolutely right. They should read a good dose of Penrose[4]