David: Can I ask about this notion whether knowledge, or truth, to use a more difficult word, in science particularly, is just a big sand heap or facts, or whether you can have a kind of knowledge and kind of truths that are more like writing: more a narrative, a story that you tell. In other words, is all the truth just contained in the individual grains of fact? What do you think?

DN: I think you have to have the story, because I can’t go into the laboratory without an idea. There’s no way in which I can test a hypothesis without there being a hypothesis, and if I can’t test a hypothesis, I don’t think I’m doing science.

David: Can a hypothesis be a metaphor? Like, you can go in to, say, are genes selfish?

DN: Well, except that that one, I’m afraid, is empty.

David: Well, all right!

DN: That one’s not even testable. But, no, much more generally, you’re right. And in fact the first thing you do is to ask, ‘How would I test this hypothesis? Is it a hypothesis that is testable?’ I think that’s the first step in a scientific experiment. Otherwise you’re just chasing after something that you can’t test.

David: So are you saying that knowledge can be more than just the individual grains of fact?

DN: It has to be. Not just that it can be, it has to be, yes. The individual grains of fact are no more than that.

David: So it’s not doing some violence to the facts of the world?

DN: No, because the facts are still there.

David: To put them into a story, to write a book?

DN: Yes, why do you write a book? Yes, exactly.

Ard: You’ve written in your book about the metaphor of the selfish gene, and whether an experiment can adjudicate between that metaphor and other metaphors for looking at life.

DN: Yes. First of all, no experiment could possibly distinguish between that metaphor and, for example, a cooperative gene. The reason for that is very simple.

Ard: Between a selfish gene and a cooperative gene? There’s no difference? You can’t distinguish…?

DN: There’s no difference empirically.

Ard: Empirically. It’s conceptual?

DN: It is a conceptual question, yes, that’s right. And I think we can illustrate this in the following way: the modern definition of a gene, and notice, incidentally, I said ‘modern’, because that was not the original definition.

The modern definition of a gene is a sequence of DNA. A sequence does not have meaning. It’s dependent on the context.

DN: Just as the words in a language… Take ‘but’ in English and make it ‘but’ in French. Exactly the same sequence means something totally different. ‘But’ to us is obvious. ‘But’ in French is a goal.

So the sequence itself cannot possibly tell you what the meaning is. So no possible experiment could tell you whether this sequence is selfish or cooperative other than in the context of the rest of the system. But then the metaphor fails because it isn’t the sequence itself that is selfish or cooperative: it is its interactions with the rest of the system. And once you’ve done that, you’ve taken the power of the metaphor – the selfish gene – away.

David: But, I mean, metaphors… You need them in science. Science seems to be littered…

DN: Absolutely.

David: And they are very useful, aren’t they?

DN: Yes. Yes, absolutely. The up and down metaphor, which…

David: Yes, we’ve been using that all morning.

DN: The body as a whole: the top, as it were, and the molecules down here. Well, my molecules are everywhere. My genes are everywhere. You know, my cells are everywhere. That is obviously a metaphor.

DN: And we wouldn’t be able to do without it. Without the concept of levels, and up and down, how could we manage? We couldn’t even talk about circular causality.

David: So using metaphor is a very powerful tool?

DN: Precisely so.

David: A metaphor isn’t a failed fact?

DN: No, exactly.

David: I mean, you… everyone… all scientists…

Ard: You can’t think without metaphors.

DN: No, that’s right. Exactly. The advice here is essentially, be careful, don’t get trapped by your metaphors.

David: Yes. If you know you’re using a metaphor, then you’re using it. If you don’t, it’s using you.

DN: Then it’s using you and you fall into the conceptual hole that’s waiting for you to go into. Yes.