David: Can I ask about… various people have mentioned to us, they’ve said there’s weak emergence and strong emergence. What are they and what’s the difference?

GE: Okay, emergence is when you put simple things together to create much more complicated things which have got behaviour which is completely different from the simple things which you put together. So new kinds of behaviours emerge at the higher level structures you create out of these simple things. And so just as an example: each of us are made out of atoms, of protons, neutrons, electrons, but what we get at the level of the body, the mind, is completely different from what you had at lower levels.

Roughly speaking, weak emergence is where new powers come in but you can explain them in terms of the lower level, and strong emergence is where you can’t.

David: Right. Which one do you believe in? You believe in strong emergence?

GE: I believe both exist. For instance, I just believe, as I have made very clear, the mind can emerge and that requires top-down causation and you can explain all of the properties of the brain in terms of the physics of the molecules, the neurons and all the rest of it, but you can’t explain the ideas in there. And so those ideas are strong emergence. And so, in my view point, it’s absolutely clear: strong emergence occurs and has physical causes.

David: And so that phrase that Rosenberg uses, where he says the physical facts fix everything?

GE: It’s not true. But, you see, what is true is once these ideas have been incorporated in the brain and we learn them, then they get built into the connection strengths in the neuron. Once that has happened, then it is reasonably plausible that a totally identical brain with totally identical strengths and totally identical excitations at that instant might experience the same thoughts. But the point is, you can’t get to that state without top-down causation.

I believe that as complexity arises, higher level rules come into being which were not implied by the lower level. Just as a very, very simple example. Physics talks about interaction between particles, forces, electromagnetic and strong and weakened direction. A little bit up, you get bacteria and amebae where the rules that come in there are Darwinian selection.

David: You’ve got life.

GE: Yes. Physics says nothing about Darwinian selection. A new principle has come into being.

David: Is that a level or emergence then?

GE: Yes.

David: So you have physics and chemistry, and then at some point they manage to create something which is then life, which has its own rules.

GE: It has its own rules, and those rules are governed by information. One of the things which comes into existence is information, which didn’t exist at the lower level. But the rules by which the information acts come into existence.

David: Right, yes, DNA, for example.

GE: And at a higher level abstract thought comes into existence, and all the possibilities that thought allows come into existence.

David: Right, so then in my world you’ve got physics and chemistry, which gets more and more complicated until it creates an emergent level of life.

GE: Yes.

David: And then natural selection is building more and more complicated things until eventually it creates minds which can see or touch that level of ideas.

GE: But these are what are called the major transitions in the evolutionary history. They’re not transitions just of… They’re transitions of quality. The quality of what happens changes completely. And I think what is very important here is the following: my scientific colleagues listen to me and say, ‘Never-the-less, I believe if you knew everything about the universe at the time of the Big Bang, you could predict everything that happens today.’

David: No, do they really say that?

GE: Well, yes.

David: I thought that went out a couple of hundred years ago. Do people really say that?

GE: I’ve had a Facebook interchange with a very, very interesting colleague who claimed this a couple of months ago.

David: But that’s untenable. Surely then he is saying the reason that you would say the answer to 2+2 is 4 has got nothing to do with mathematics. It’s because some quark and electron headed out from the Big Bang bumped, and it was always going to make you say 4.

GE: That’s right.

David: That’s crackers, isn’t it?

GE: I’m just completing this book on top-down causation in which I had some derogatory comments about this. I said it was ‘ludicrous’, or some word like that, and the reviewer of the book said, ‘How can you use the word “ludicrous”’? You’re a scientist.’

David: But it is ludicrous, don’t you think?

GE: It is ludicrous. The idea that everything that we would be saying, the idea that the theory of relativity and the Battle of Waterloo was written into the Big Bang, is just ludicrous.