A conversation

Stephen Hawking, who was diagnosed with motor neurone disease at the age of 21, shared his thoughts on death, human purpose and our chance existence in an exclusive interview with the Guardian. A belief that heaven or an afterlife awaits us is a "fairy story" for people afraid of death, Hawking said.

What is the value in knowing “Why are we here?”

The universe is governed by science. But science tells us that we can't solve the equations, directly in the abstract. We need to use the effective theory of Darwinian natural selection of those societies most likely to survive. We assign them higher value.

You've said there is no reason to invoke God to light the blue touchpaper. Is our existence all down to luck?

Science predicts that many different kinds of universe will be spontaneously created out of nothing. It is a matter of chance which we are in.

So here we are. What should we do?

We should seek the greatest value of our action.

You had a health scare and spent time in hospital in 2009. What, if anything, do you fear about death?

I have lived with the prospect of an early death for the last 49 years. I'm not afraid of death, but I'm in no hurry to die.

I have so much I want to do first. I regard the brain as a computer which will stop working when its components fail. There is no heaven or afterlife for broken down computers; that is a fairy story for people afraid of the dark.

What are the things you find most beautiful in science?

Science is beautiful when it makes simple explanations of phenomena or connections between different observations.

Examples include the double helix in biology, and the fundamental equations of physics.— © Guardian Newspapers Limited, 2011