When we proposed climbing Everest without oxygen in 1978 people told us it wasn't possible, that we were risking our lives. They said we would lose our brains up there. When the first climbers on the Austrian expedition we joined came down, they said we shouldn't even try. It was hard: I didn't know if I'd have a chance to go back to Everest, and Everest is Everest. I was determined then to try and get as high as possible.

Climbing Everest solo without bottled oxygen in 1980 was the hardest thing I've ever done. I was alone up there, completely alone. I fell down a crevasse at night and almost gave up. Only because I had this fantasy-because for two years I had been pregnant with this fantasy of soloing Everest-was I able to continue.

When you're high on a mountain you cannot be anything but what you are. Mallory said he climbed Everest because it was there. I think we go up so we can come back down again. This coming down is a very strong experience. You come back from an inhuman place. We are not made for it, this loneliness and cold. When you come back you feel reborn, you have a new chance. The experience is so strong you want to have it again and again, but you have to suffer for it. It's addictive.

This is what I had got as a child, without even thinking: I could find a good route, understand the weather quickly, know that this rock is good, if this gully will go to the left. I had learnt the structure of the mountain.

Until I was 20 my parents helped me with my climbing. When my father realised it was going to be my life, he tried to stop me, but it was too late. And when I went to Everest in 1978 to climb it without oxygen, he would sit in his local bar and say I was crazy. When I succeeded he said: "I knew he would do it!"

My father blamed me for my brother G?nther's death, for not bringing him home. He died in an avalanche as we descended from the summit of Nanga Parbat, one of the 14 peaks over 8,000m, in 1970. G?nther and I did so much together. It was difficult for my father to understand what it was like up there.

On Nanga Parbat I understood the reality of my own death. I had not eaten or drunk anything for days, I was hallucinating, my toes were black from frostbite and my brother was lost in the avalanche.

When I lost seven of my toes on Nanga Parbat and small parts of my fingertips I knew I'd never be a great rock climber. So I specialised in high-altitude climbing. It's a totally different game. I developed a 15-year passion for it and became maybe even a little narrow-minded in my desire for 8,000m peaks. It's certainly partly my fault that today 8,000m peaks are something special. To be honest, they are not that special.

After my brother died it took me a year to recover, but I knew I could do more. I knew it must be possible to climb one of these big mountains without fixed ropes and so on, so I tried to solo Nanga Parbat in 1973. But it wasn't possible then to be up there alone, having no one to speak with, no other faces. It took me a long time to learn how to do that.

High-altitude climbing is about suffering, it's about being afraid. I don't believe anyone who says there's a lot of pleasure in climbing the biggest peaks. It's dangerous, especially if there are no Sherpas or fixed ropes and camps. If you make one mistake, you die.

I was the first man to climb the world's 14 tallest peaks without supplementary oxygen, but I never asked how high I would go, just how I would do it. Climbing is more of an art than a sport. It's the aesthetics of a mountain that compels me. The line of a route, the style of ascent. It is creative. Children have to find their own way. My way is wrong for my kids. They climb, but I'm not forcing them into it.

I was elected an MEP for the Green Party. Politics and climbing are exact opposites. But they're both games. If the world's leaders could spend a few days climbing a mountain together, then things would go better. I always take the same perspective with each new adventure. I put myself in the position of being at the end of my life looking back. Then I ask myself if what I am doing is important to me.

The Shackleton Endurance expedition was the best adventure of the last century. Though Shackleton failed, he saved all his people. Now that I'm nearing 59, I understand that failing is more important than having success.
If you look at my life, then one thing is clear. I did one activity at a time, with all my willpower, all my money and all my time. Complete commitment. (Interview by Ed Douglas in The Observer)