I think often, in science, it turns out that you find yourself arguing with somebody, and then you actually realise that the argument is only about what words you want to use for what things. No, I don't think that's trivial, by any means. I mean, it can be very important what words you use for... for what things, you know. But I think it's terribly important when you're doing science and you find yourself disagreeing with somebody, to realise what kind of a disagreement is it. Is it disagreement just about the use of words, which doesn't mean it's not important, but it's a different kind of argument than an argument about what you think the world is like. And indeed, there might even be a third kind of argument, which we've touched on when talking about Bill Hamilton and your different views of the way of imaging the evolution of social behaviour. It... it may not be an argument about either words or what the word is like, but what is the easiest way of looking at the world. What's the... the clearest imaging of the world. And there, you may never be able to decide. I mean, one person may say, 'I find it easier to look at it from this side,' and somebody may say, 'But no, I find it easier to look at it from that side.' And if so, I don't think there's any way of settling it rationally, you just have to encourage the students to learn both ways and choose whichever way they like.