With respect to phenomena like mass extinction, somebody might say why worry about it because in a geological perspective mass extinctions aren't so bad, they wipe out some things and then 10 million years down the road we get new and interesting objects.But I tell you mass extinctions are really awful for folks caught in the midst of them.

If we're going to make a politically responsible and a scientifically sensible claim it should not be stop the world exactly where it is because that's not possible. It has to be to decide what kind of world do we as human beings want to live in.

If I put myself on the side of those who see the world as warming up in a bad way, who see the general march of industrial culture as something undesirable, the one thing I must be beware of doing and which my colleagues on that side don't beware of doing, we must beware of saying we've got to stop changing the environment. There is no 'the' environment which we can change, the world is changing all the time.

People who have various kinds of politics for whom it is congenial for their apriority politics to say yes, things are getting much worse. They are opposed by people who also have a priori politics saying that this is the best of all possible worlds, capitalism is the greatest thing since sliced bread and you're just alarmists and so on and they can massage the data so it fits them.

There are a whole other range of sciences that must deal with the narrative reconstruction of the inordinately complex events of history that can occur but once in their detailed glory. And for those kinds of sciences, be it cosmology, or evolutionary biology, or geology, or palaeontology, the experimental methods, simplification, quantification, prediction and repetition of the experimental sciences don't always work. You have to go with the narrative, the descriptive methods of what? Of historians.

We do have tendency, now in biology especially to make up stories, to make theoretical biology a kind of game, in fact we have game theory in biology which is meant to use the theory of games to make predictions or explain things.

In my mind the job of a natural scientist is to bend over backwards to say something which can be demonstrated to be true or at least which is not of such a nature that there's no way to demonstrate that it's false.